Refactor indentation for consistent style across codebase.

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-</project>

Buffer.cc

@@ -6,6 +6,9 @@
 #include "Buffer.h"
 #include "UndoSystem.h"
 #include "UndoTree.h"
+// For reconstructing highlighter state on copies
+#include "syntax/HighlighterRegistry.h"
+#include "syntax/NullHighlighter.h"
 
 
 Buffer::Buffer()
@@ -40,9 +43,32 @@ Buffer::Buffer(const Buffer &other)
 	mark_set_       = other.mark_set_;
 	mark_curx_      = other.mark_curx_;
 	mark_cury_      = other.mark_cury_;
+	// Copy syntax/highlighting flags
+	version_        = other.version_;
+	syntax_enabled_ = other.syntax_enabled_;
+	filetype_       = other.filetype_;
 	// Fresh undo system for the copy
 	undo_tree_ = std::make_unique<UndoTree>();
 	undo_sys_  = std::make_unique<UndoSystem>(*this, *undo_tree_);
+
+	// Recreate a highlighter engine for this copy based on filetype/syntax state
+	if (syntax_enabled_) {
+		// Allocate engine and install an appropriate highlighter
+		highlighter_ = std::make_unique<kte::HighlighterEngine>();
+		if (!filetype_.empty()) {
+			auto hl = kte::HighlighterRegistry::CreateFor(filetype_);
+			if (hl) {
+				highlighter_->SetHighlighter(std::move(hl));
+			} else {
+				// Unsupported filetype -> NullHighlighter keeps syntax pipeline active
+				highlighter_->SetHighlighter(std::make_unique<kte::NullHighlighter>());
+			}
+		} else {
+			// No filetype -> keep syntax enabled but use NullHighlighter
+			highlighter_->SetHighlighter(std::make_unique<kte::NullHighlighter>());
+		}
+		// Fresh engine has empty caches; nothing to invalidate
+	}
 }
 
 
@@ -65,9 +91,28 @@ Buffer::operator=(const Buffer &other)
 	mark_set_       = other.mark_set_;
 	mark_curx_      = other.mark_curx_;
 	mark_cury_      = other.mark_cury_;
+	version_        = other.version_;
+	syntax_enabled_ = other.syntax_enabled_;
+	filetype_       = other.filetype_;
 	// Recreate undo system for this instance
 	undo_tree_ = std::make_unique<UndoTree>();
 	undo_sys_  = std::make_unique<UndoSystem>(*this, *undo_tree_);
+
+	// Recreate highlighter engine consistent with syntax settings
+	highlighter_.reset();
+	if (syntax_enabled_) {
+		highlighter_ = std::make_unique<kte::HighlighterEngine>();
+		if (!filetype_.empty()) {
+			auto hl = kte::HighlighterRegistry::CreateFor(filetype_);
+			if (hl) {
+				highlighter_->SetHighlighter(std::move(hl));
+			} else {
+				highlighter_->SetHighlighter(std::make_unique<kte::NullHighlighter>());
+			}
+		} else {
+			highlighter_->SetHighlighter(std::make_unique<kte::NullHighlighter>());
+		}
+	}
 	return *this;
 }
 
@@ -91,6 +136,11 @@ Buffer::Buffer(Buffer &&other) noexcept
 	  undo_tree_(std::move(other.undo_tree_)),
 	  undo_sys_(std::move(other.undo_sys_))
 {
+	// Move syntax/highlighting state
+	version_        = other.version_;
+	syntax_enabled_ = other.syntax_enabled_;
+	filetype_       = std::move(other.filetype_);
+	highlighter_    = std::move(other.highlighter_);
 	// Update UndoSystem's buffer reference to point to this object
 	if (undo_sys_) {
 		undo_sys_->UpdateBufferReference(*this);
@@ -122,6 +172,12 @@ Buffer::operator=(Buffer &&other) noexcept
 	undo_tree_      = std::move(other.undo_tree_);
 	undo_sys_       = std::move(other.undo_sys_);
 
+	// Move syntax/highlighting state
+	version_        = other.version_;
+	syntax_enabled_ = other.syntax_enabled_;
+	filetype_       = std::move(other.filetype_);
+	highlighter_    = std::move(other.highlighter_);
+
 	// Update UndoSystem's buffer reference to point to this object
 	if (undo_sys_) {
 		undo_sys_->UpdateBufferReference(*this);
@@ -368,9 +424,9 @@ Buffer::insert_text(int row, int col, std::string_view text)
 		rows_[y].insert(x, seg);
 		x += seg.size();
 		// Split line at x
-  std::string tail = rows_[y].substr(x);
-  rows_[y].erase(x);
-  rows_.insert(rows_.begin() + static_cast<std::ptrdiff_t>(y + 1), Line(tail));
+		std::string tail = rows_[y].substr(x);
+		rows_[y].erase(x);
+		rows_.insert(rows_.begin() + static_cast<std::ptrdiff_t>(y + 1), Line(tail));
 		y += 1;
 		x = 0;
 		remain.erase(0, pos + 1);
@@ -430,8 +486,8 @@ Buffer::split_line(int row, const int col)
 	const auto y    = static_cast<std::size_t>(row);
 	const auto x    = std::min<std::size_t>(static_cast<std::size_t>(col), rows_[y].size());
 	const auto tail = rows_[y].substr(x);
- rows_[y].erase(x);
- rows_.insert(rows_.begin() + static_cast<std::ptrdiff_t>(y + 1), Line(tail));
+	rows_[y].erase(x);
+	rows_.insert(rows_.begin() + static_cast<std::ptrdiff_t>(y + 1), Line(tail));
 }
 
 
@@ -459,7 +515,7 @@ Buffer::insert_row(int row, const std::string_view text)
 		row = 0;
 	if (static_cast<std::size_t>(row) > rows_.size())
 		row = static_cast<int>(rows_.size());
- rows_.insert(rows_.begin() + row, Line(std::string(text)));
+	rows_.insert(rows_.begin() + row, Line(std::string(text)));
 }
 
 

Buffer.h

@@ -12,11 +12,15 @@
 
 #include "AppendBuffer.h"
 #include "UndoSystem.h"
+#include <cstdint>
+#include <memory>
+#include "syntax/HighlighterEngine.h"
+#include "Highlight.h"
 
 
 class Buffer {
 public:
-    Buffer();
+	Buffer();
 
 	Buffer(const Buffer &other);
 
@@ -262,11 +266,12 @@ public:
 		return filename_;
 	}
 
+
 	// Set a virtual (non file-backed) display name for this buffer, e.g. "+HELP+"
 	// This does not mark the buffer as file-backed.
 	void SetVirtualName(const std::string &name)
 	{
-		filename_ = name;
+		filename_       = name;
 		is_file_backed_ = false;
 	}
 
@@ -277,26 +282,29 @@ public:
 	}
 
 
- [[nodiscard]] bool Dirty() const
- {
-     return dirty_;
- }
+	[[nodiscard]] bool Dirty() const
+	{
+		return dirty_;
+	}
 
- // Read-only flag
- [[nodiscard]] bool IsReadOnly() const
- {
-     return read_only_;
- }
 
- void SetReadOnly(bool ro)
- {
-     read_only_ = ro;
- }
+	// Read-only flag
+	[[nodiscard]] bool IsReadOnly() const
+	{
+		return read_only_;
+	}
 
- void ToggleReadOnly()
- {
-     read_only_ = !read_only_;
- }
+
+	void SetReadOnly(bool ro)
+	{
+		read_only_ = ro;
+	}
+
+
+	void ToggleReadOnly()
+	{
+		read_only_ = !read_only_;
+	}
 
 
 	void SetCursor(const std::size_t x, const std::size_t y)
@@ -322,6 +330,12 @@ public:
 	void SetDirty(bool d)
 	{
 		dirty_ = d;
+		if (d) {
+			++version_;
+			if (highlighter_) {
+				highlighter_->InvalidateFrom(0);
+			}
+		}
 	}
 
 
@@ -360,6 +374,56 @@ public:
 
 	[[nodiscard]] std::string AsString() const;
 
+	// Syntax highlighting integration (per-buffer)
+	[[nodiscard]] std::uint64_t Version() const
+	{
+		return version_;
+	}
+
+
+	void SetSyntaxEnabled(bool on)
+	{
+		syntax_enabled_ = on;
+	}
+
+
+	[[nodiscard]] bool SyntaxEnabled() const
+	{
+		return syntax_enabled_;
+	}
+
+
+	void SetFiletype(const std::string &ft)
+	{
+		filetype_ = ft;
+	}
+
+
+	[[nodiscard]] const std::string &Filetype() const
+	{
+		return filetype_;
+	}
+
+
+	kte::HighlighterEngine *Highlighter()
+	{
+		return highlighter_.get();
+	}
+
+
+	const kte::HighlighterEngine *Highlighter() const
+	{
+		return highlighter_.get();
+	}
+
+
+	void EnsureHighlighter()
+	{
+		if (!highlighter_)
+			highlighter_ = std::make_unique<kte::HighlighterEngine>();
+	}
+
+
 	// Raw, low-level editing APIs used by UndoSystem apply().
 	// These must NOT trigger undo recording. They also do not move the cursor.
 	void insert_text(int row, int col, std::string_view text);
@@ -380,22 +444,28 @@ public:
 	[[nodiscard]] const UndoSystem *Undo() const;
 
 private:
-    // State mirroring original C struct (without undo_tree)
-    std::size_t curx_    = 0, cury_ = 0; // cursor position in characters
-    std::size_t rx_      = 0; // render x (tabs expanded)
-    std::size_t nrows_   = 0; // number of rows
+	// State mirroring original C struct (without undo_tree)
+	std::size_t curx_    = 0, cury_ = 0; // cursor position in characters
+	std::size_t rx_      = 0; // render x (tabs expanded)
+	std::size_t nrows_   = 0; // number of rows
 	std::size_t rowoffs_ = 0, coloffs_ = 0; // viewport offsets
 	std::vector<Line> rows_; // buffer rows (without trailing newlines)
 	std::string filename_;
- bool is_file_backed_   = false;
- bool dirty_            = false;
- bool read_only_        = false;
- bool mark_set_         = false;
- std::size_t mark_curx_ = 0, mark_cury_ = 0;
+	bool is_file_backed_   = false;
+	bool dirty_            = false;
+	bool read_only_        = false;
+	bool mark_set_         = false;
+	std::size_t mark_curx_ = 0, mark_cury_ = 0;
 
 	// Per-buffer undo state
 	std::unique_ptr<struct UndoTree> undo_tree_;
 	std::unique_ptr<UndoSystem> undo_sys_;
+
+	// Syntax/highlighting state
+	std::uint64_t version_ = 0; // increment on edits
+	bool syntax_enabled_   = true;
+	std::string filetype_;
+	std::unique_ptr<kte::HighlighterEngine> highlighter_;
 };
 
 #endif // KTE_BUFFER_H

CMakeLists.txt

@@ -4,7 +4,7 @@ project(kte)
 include(GNUInstallDirs)
 
 set(CMAKE_CXX_STANDARD 17)
-set(KTE_VERSION "1.1.0")
+set(KTE_VERSION "1.2.1")
 
 # Default to terminal-only build to avoid SDL/OpenGL dependency by default.
 # Enable with -DBUILD_GUI=ON when SDL2/OpenGL/Freetype are available.
@@ -13,35 +13,39 @@ set(BUILD_TESTS OFF CACHE BOOL "Enable building test programs.")
 option(KTE_USE_PIECE_TABLE "Use PieceTable instead of GapBuffer implementation" ON)
 set(KTE_FONT_SIZE "18.0" CACHE STRING "Default font size for GUI")
 option(KTE_UNDO_DEBUG "Enable undo instrumentation logs" OFF)
+option(KTE_ENABLE_TREESITTER "Enable optional Tree-sitter highlighter adapter" OFF)
 
 if (CMAKE_HOST_UNIX)
-    message(STATUS "Build system is POSIX.")
+	message(STATUS "Build system is POSIX.")
 else ()
-    message(STATUS "Build system is NOT POSIX.")
+	message(STATUS "Build system is NOT POSIX.")
 endif ()
 
 if (MSVC)
-    add_compile_options("/W4" "$<$<CONFIG:RELEASE>:/O2>")
+	add_compile_options("/W4" "$<$<CONFIG:RELEASE>:/O2>")
 else ()
-    add_compile_options(
-            "-Wall"
-            "-Wextra"
-            "-Werror"
-            "$<$<CONFIG:DEBUG>:-g>"
-            "$<$<CONFIG:RELEASE>:-O2>")
-    if ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "Clang")
-        add_compile_options("-stdlib=libc++")
-    else ()
-        # nothing special for gcc at the moment
-    endif ()
+	add_compile_options(
+		"-Wall"
+		"-Wextra"
+		"-Werror"
+		"$<$<CONFIG:DEBUG>:-g>"
+		"$<$<CONFIG:RELEASE>:-O2>")
+	if ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "Clang")
+		add_compile_options("-stdlib=libc++")
+	else ()
+		# nothing special for gcc at the moment
+	endif ()
 endif ()
 add_compile_definitions(KGE_PLATFORM=${CMAKE_HOST_SYSTEM_NAME})
 add_compile_definitions(KTE_VERSION_STR="v${KTE_VERSION}")
+if (KTE_ENABLE_TREESITTER)
+	add_compile_definitions(KTE_ENABLE_TREESITTER)
+endif ()
 
 message(STATUS "Build system: ${CMAKE_HOST_SYSTEM_NAME}")
 
 if (${BUILD_GUI})
-    include(cmake/imgui.cmake)
+	include(cmake/imgui.cmake)
 endif ()
 
 # NCurses for terminal mode
@@ -50,169 +54,251 @@ set(CURSES_NEED_WIDE)
 find_package(Curses REQUIRED)
 include_directories(${CURSES_INCLUDE_DIR})
 
+set(SYNTAX_SOURCES
+	syntax/GoHighlighter.cc
+	syntax/CppHighlighter.cc
+	syntax/JsonHighlighter.cc
+	syntax/ErlangHighlighter.cc
+	syntax/MarkdownHighlighter.cc
+	syntax/TreeSitterHighlighter.cc
+	syntax/LispHighlighter.cc
+	syntax/HighlighterEngine.cc
+	syntax/RustHighlighter.cc
+	syntax/HighlighterRegistry.cc
+	syntax/SqlHighlighter.cc
+	syntax/NullHighlighter.cc
+	syntax/ForthHighlighter.cc
+	syntax/PythonHighlighter.cc
+	syntax/ShellHighlighter.cc
+)
+
+if (KTE_ENABLE_TREESITTER)
+	list(APPEND SYNTAX_SOURCES
+		TreeSitterHighlighter.cc)
+endif ()
+
 set(COMMON_SOURCES
-        GapBuffer.cc
-        PieceTable.cc
-        Buffer.cc
-        Editor.cc
-        Command.cc
-        HelpText.cc
-        KKeymap.cc
-        TerminalInputHandler.cc
-        TerminalRenderer.cc
-        TerminalFrontend.cc
-        TestInputHandler.cc
-        TestRenderer.cc
-        TestFrontend.cc
-        UndoNode.cc
-        UndoTree.cc
-        UndoSystem.cc
+	GapBuffer.cc
+	PieceTable.cc
+	Buffer.cc
+	Editor.cc
+	Command.cc
+	HelpText.cc
+	KKeymap.cc
+	TerminalInputHandler.cc
+	TerminalRenderer.cc
+	TerminalFrontend.cc
+	TestInputHandler.cc
+	TestRenderer.cc
+	TestFrontend.cc
+	UndoNode.cc
+	UndoTree.cc
+	UndoSystem.cc
+
+	${SYNTAX_SOURCES}
+)
+
+
+set(SYNTAX_HEADERS
+	syntax/GoHighlighter.h
+	syntax/HighlighterEngine.h
+	syntax/ShellHighlighter.h
+	syntax/MarkdownHighlighter.h
+	syntax/LispHighlighter.h
+	syntax/SqlHighlighter.h
+	syntax/ForthHighlighter.h
+	syntax/JsonHighlighter.h
+	syntax/TreeSitterHighlighter.h
+	syntax/NullHighlighter.h
+	syntax/CppHighlighter.h
+	syntax/ErlangHighlighter.h
+	syntax/LanguageHighlighter.h
+	syntax/RustHighlighter.h
+	syntax/PythonHighlighter.h
+)
+
+if (KTE_ENABLE_TREESITTER)
+	list(APPEND THEME_HEADERS
+		TreeSitterHighlighter.h)
+endif ()
+
+set(THEME_HEADERS
+	themes/ThemeHelpers.h
+	themes/EInk.h
+	themes/Gruvbox.h
+	themes/Solarized.h
+	themes/Plan9.h
+	themes/Nord.h
 )
 
 set(COMMON_HEADERS
-        GapBuffer.h
-        PieceTable.h
-        Buffer.h
-        Editor.h
-        AppendBuffer.h
-        Command.h
-        HelpText.h
-        KKeymap.h
-        InputHandler.h
-        TerminalInputHandler.h
-        Renderer.h
-        TerminalRenderer.h
-        Frontend.h
-        TerminalFrontend.h
-        TestInputHandler.h
-        TestRenderer.h
-        TestFrontend.h
-        UndoNode.h
-        UndoTree.h
-        UndoSystem.h
+	GapBuffer.h
+	PieceTable.h
+	Buffer.h
+	Editor.h
+	AppendBuffer.h
+	Command.h
+	HelpText.h
+	KKeymap.h
+	InputHandler.h
+	TerminalInputHandler.h
+	Renderer.h
+	TerminalRenderer.h
+	Frontend.h
+	TerminalFrontend.h
+	TestInputHandler.h
+	TestRenderer.h
+	TestFrontend.h
+	UndoNode.h
+	UndoTree.h
+	UndoSystem.h
+	Highlight.h
+
+	${SYNTAX_HEADERS}
+	${THEME_HEADERS}
 )
 
 # kte (terminal-first) executable
 add_executable(kte
-        main.cc
-        ${COMMON_SOURCES}
-        ${COMMON_HEADERS}
+	main.cc
+	${COMMON_SOURCES}
+	${COMMON_HEADERS}
 )
 
 if (KTE_USE_PIECE_TABLE)
-    target_compile_definitions(kte PRIVATE KTE_USE_PIECE_TABLE=1)
+	target_compile_definitions(kte PRIVATE KTE_USE_PIECE_TABLE=1)
 endif ()
 if (KTE_UNDO_DEBUG)
-    target_compile_definitions(kte PRIVATE KTE_UNDO_DEBUG=1)
+	target_compile_definitions(kte PRIVATE KTE_UNDO_DEBUG=1)
 endif ()
 
 target_link_libraries(kte ${CURSES_LIBRARIES})
 
+if (KTE_ENABLE_TREESITTER)
+	# Users can provide their own tree-sitter include/lib via cache variables
+	set(TREESITTER_INCLUDE_DIR "" CACHE PATH "Path to tree-sitter include directory")
+	set(TREESITTER_LIBRARY "" CACHE FILEPATH "Path to tree-sitter library (.a/.dylib)")
+	if (TREESITTER_INCLUDE_DIR)
+		target_include_directories(kte PRIVATE ${TREESITTER_INCLUDE_DIR})
+	endif ()
+	if (TREESITTER_LIBRARY)
+		target_link_libraries(kte ${TREESITTER_LIBRARY})
+	endif ()
+endif ()
+
 install(TARGETS kte
-        RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR}
+	RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR}
 )
 
 # Man pages
 install(FILES docs/kte.1 DESTINATION ${CMAKE_INSTALL_MANDIR}/man1)
 
 if (BUILD_TESTS)
-    # test_undo executable for testing undo/redo system
-    add_executable(test_undo
-            test_undo.cc
-            ${COMMON_SOURCES}
-            ${COMMON_HEADERS}
-    )
+	# test_undo executable for testing undo/redo system
+	add_executable(test_undo
+		test_undo.cc
+		${COMMON_SOURCES}
+		${COMMON_HEADERS}
+	)
 
-    if (KTE_USE_PIECE_TABLE)
-        target_compile_definitions(test_undo PRIVATE KTE_USE_PIECE_TABLE=1)
-    endif ()
+	if (KTE_USE_PIECE_TABLE)
+		target_compile_definitions(test_undo PRIVATE KTE_USE_PIECE_TABLE=1)
+	endif ()
 
-    if (KTE_UNDO_DEBUG)
-        target_compile_definitions(test_undo PRIVATE KTE_UNDO_DEBUG=1)
-    endif ()
+	if (KTE_UNDO_DEBUG)
+		target_compile_definitions(test_undo PRIVATE KTE_UNDO_DEBUG=1)
+	endif ()
 
 
-    target_link_libraries(test_undo ${CURSES_LIBRARIES})
+	target_link_libraries(test_undo ${CURSES_LIBRARIES})
+	if (KTE_ENABLE_TREESITTER)
+		if (TREESITTER_INCLUDE_DIR)
+			target_include_directories(test_undo PRIVATE ${TREESITTER_INCLUDE_DIR})
+		endif ()
+		if (TREESITTER_LIBRARY)
+			target_link_libraries(test_undo ${TREESITTER_LIBRARY})
+		endif ()
+	endif ()
 endif ()
 
 if (${BUILD_GUI})
-    target_sources(kte PRIVATE
-            Font.h
-            GUIConfig.cc
-            GUIConfig.h
-            GUIRenderer.cc
-            GUIRenderer.h
-            GUIInputHandler.cc
-            GUIInputHandler.h
-            GUIFrontend.cc
-            GUIFrontend.h)
-    target_compile_definitions(kte PRIVATE KTE_BUILD_GUI=1)
-    target_link_libraries(kte imgui)
+	target_sources(kte PRIVATE
+		Font.h
+		GUIConfig.cc
+		GUIConfig.h
+		GUIRenderer.cc
+		GUIRenderer.h
+		GUIInputHandler.cc
+		GUIInputHandler.h
+		GUIFrontend.cc
+		GUIFrontend.h)
+	target_compile_definitions(kte PRIVATE KTE_BUILD_GUI=1)
+	target_link_libraries(kte imgui)
 
-    # kge (GUI-first) executable
-    add_executable(kge
-            main.cc
-            ${COMMON_SOURCES}
-            ${COMMON_HEADERS}
-            GUIConfig.cc
-            GUIConfig.h
-            GUIRenderer.cc
-            GUIRenderer.h
-            GUIInputHandler.cc
-            GUIInputHandler.h
-            GUIFrontend.cc
-            GUIFrontend.h)
-    target_compile_definitions(kge PRIVATE KTE_BUILD_GUI=1 KTE_DEFAULT_GUI=1 KTE_FONT_SIZE=${KTE_FONT_SIZE})
-    if (KTE_UNDO_DEBUG)
-        target_compile_definitions(kge PRIVATE KTE_UNDO_DEBUG=1)
-    endif ()
-    target_link_libraries(kge ${CURSES_LIBRARIES} imgui)
+	# kge (GUI-first) executable
+	add_executable(kge
+		main.cc
+		${COMMON_SOURCES}
+		${COMMON_HEADERS}
+		GUIConfig.cc
+		GUIConfig.h
+		GUIRenderer.cc
+		GUIRenderer.h
+		GUIInputHandler.cc
+		GUIInputHandler.h
+		GUIFrontend.cc
+		GUIFrontend.h)
+	target_compile_definitions(kge PRIVATE KTE_BUILD_GUI=1 KTE_DEFAULT_GUI=1 KTE_FONT_SIZE=${KTE_FONT_SIZE})
+	if (KTE_UNDO_DEBUG)
+		target_compile_definitions(kge PRIVATE KTE_UNDO_DEBUG=1)
+	endif ()
+	target_link_libraries(kge ${CURSES_LIBRARIES} imgui)
 
-    # On macOS, build kge as a proper .app bundle
-    if (APPLE)
-        # Define the icon file
-        set(MACOSX_BUNDLE_ICON_FILE kge.icns)
-        set(kge_ICON "${CMAKE_CURRENT_SOURCE_DIR}/${MACOSX_BUNDLE_ICON_FILE}")
+	# On macOS, build kge as a proper .app bundle
+	if (APPLE)
+		# Define the icon file
+		set(MACOSX_BUNDLE_ICON_FILE kge.icns)
+		set(kge_ICON "${CMAKE_CURRENT_SOURCE_DIR}/${MACOSX_BUNDLE_ICON_FILE}")
 
-        # Add icon to the target sources and mark it as a resource
-        target_sources(kge PRIVATE ${kge_ICON})
-        set_source_files_properties(${kge_ICON} PROPERTIES
-                MACOSX_PACKAGE_LOCATION Resources)
+		# Add icon to the target sources and mark it as a resource
+		target_sources(kge PRIVATE ${kge_ICON})
+		set_source_files_properties(${kge_ICON} PROPERTIES
+			MACOSX_PACKAGE_LOCATION Resources)
 
-        # Configure Info.plist with version and identifiers
-        set(KGE_BUNDLE_ID "dev.wntrmute.kge")
-        configure_file(
-                ${CMAKE_CURRENT_LIST_DIR}/cmake/Info.plist.in
-                ${CMAKE_CURRENT_BINARY_DIR}/kge-Info.plist
-                @ONLY)
+		# Configure Info.plist with version and identifiers
+		set(KGE_BUNDLE_ID "dev.wntrmute.kge")
+		configure_file(
+			${CMAKE_CURRENT_LIST_DIR}/cmake/Info.plist.in
+			${CMAKE_CURRENT_BINARY_DIR}/kge-Info.plist
+			@ONLY)
 
-        set_target_properties(kge PROPERTIES
-                MACOSX_BUNDLE TRUE
-                MACOSX_BUNDLE_GUI_IDENTIFIER ${KGE_BUNDLE_ID}
-                MACOSX_BUNDLE_BUNDLE_NAME "kge"
-                MACOSX_BUNDLE_ICON_FILE ${MACOSX_BUNDLE_ICON_FILE}
-                MACOSX_BUNDLE_INFO_PLIST "${CMAKE_CURRENT_BINARY_DIR}/kge-Info.plist")
+		set_target_properties(kge PROPERTIES
+			MACOSX_BUNDLE TRUE
+			MACOSX_BUNDLE_GUI_IDENTIFIER ${KGE_BUNDLE_ID}
+			MACOSX_BUNDLE_BUNDLE_NAME "kge"
+			MACOSX_BUNDLE_ICON_FILE ${MACOSX_BUNDLE_ICON_FILE}
+			MACOSX_BUNDLE_INFO_PLIST "${CMAKE_CURRENT_BINARY_DIR}/kge-Info.plist")
 
-        add_dependencies(kge kte)
-        add_custom_command(TARGET kge POST_BUILD
-                COMMAND ${CMAKE_COMMAND} -E copy
-                $<TARGET_FILE:kte>
-                $<TARGET_FILE_DIR:kge>/kte
-                COMMENT "Copying kte binary into kge.app bundle")
+		add_dependencies(kge kte)
+		add_custom_command(TARGET kge POST_BUILD
+			COMMAND ${CMAKE_COMMAND} -E copy
+			$<TARGET_FILE:kte>
+			$<TARGET_FILE_DIR:kge>/kte
+			COMMENT "Copying kte binary into kge.app bundle")
 
-        install(TARGETS kge
-                BUNDLE DESTINATION .
-        )
+		install(TARGETS kge
+			BUNDLE DESTINATION .
+		)
 
-        install(TARGETS kte
-                RUNTIME DESTINATION kge.app/Contents/MacOS
-        )
-    else ()
-        install(TARGETS kge
-                RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR}
-        )
-    endif ()
-    # Install kge man page only when GUI is built
-    install(FILES docs/kge.1 DESTINATION ${CMAKE_INSTALL_MANDIR}/man1)
-    install(FILES kge.png DESTINATION ${CMAKE_INSTALL_PREFIX}/share/icons)
+		install(TARGETS kte
+			RUNTIME DESTINATION kge.app/Contents/MacOS
+		)
+	else ()
+		install(TARGETS kge
+			RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR}
+		)
+	endif ()
+	# Install kge man page only when GUI is built
+	install(FILES docs/kge.1 DESTINATION ${CMAKE_INSTALL_MANDIR}/man1)
+	install(FILES kge.png DESTINATION ${CMAKE_INSTALL_PREFIX}/share/icons)
 endif ()

Command.h

@@ -69,6 +69,9 @@ enum class CommandId {
 	Redo,
 	// UI/status helpers
 	UArgStatus, // update status line during universal-argument collection
+	// Themes (GUI)
+	ThemeNext,
+	ThemePrev,
 	// Region formatting
 	IndentRegion, // indent region (C-k =)
 	UnindentRegion, // unindent region (C-k -)
@@ -86,6 +89,15 @@ enum class CommandId {
 	ShowHelp, // open +HELP+ buffer with manual text (C-k h)
 	// Meta
 	UnknownKCommand, // arg: single character that was not recognized after C-k
+	// Generic command prompt
+	CommandPromptStart, // begin generic command prompt (C-k ;)
+	// Theme by name
+	ThemeSetByName,
+	// Background mode (GUI)
+	BackgroundSet,
+	// Syntax highlighting
+	Syntax, // ":syntax on|off|reload"
+	SetOption, // generic ":set key=value" (v1: filetype=<lang>)
 };
 
 
@@ -109,6 +121,8 @@ struct Command {
 	std::string name; // stable, unique name (e.g., "save", "save-as")
 	std::string help; // short help/description
 	CommandHandler handler;
+	// Public commands are exposed in the ": " prompt (C-k ;)
+	bool isPublic = false;
 };
 
 
@@ -137,4 +151,4 @@ bool Execute(Editor &ed, CommandId id, const std::string &arg = std::string(), i
 
 bool Execute(Editor &ed, const std::string &name, const std::string &arg = std::string(), int count = 0);
 
-#endif // KTE_COMMAND_H
+#endif // KTE_COMMAND_H

Editor.cc

@@ -3,6 +3,9 @@
 #include <filesystem>
 
 #include "Editor.h"
+#include "syntax/HighlighterRegistry.h"
+#include "syntax/CppHighlighter.h"
+#include "syntax/NullHighlighter.h"
 
 
 Editor::Editor() = default;
@@ -151,7 +154,32 @@ Editor::OpenFile(const std::string &path, std::string &err)
 		const bool rows_empty        = rows.empty();
 		const bool single_empty_line = (!rows.empty() && rows.size() == 1 && rows[0].size() == 0);
 		if (unnamed && clean && (rows_empty || single_empty_line)) {
-			return cur.OpenFromFile(path, err);
+			bool ok = cur.OpenFromFile(path, err);
+			if (!ok)
+				return false;
+			// Setup highlighting using registry (extension + shebang)
+			cur.EnsureHighlighter();
+			std::string first = "";
+			const auto &rows  = cur.Rows();
+			if (!rows.empty())
+				first = static_cast<std::string>(rows[0]);
+			std::string ft = kte::HighlighterRegistry::DetectForPath(path, first);
+			if (!ft.empty()) {
+				cur.SetFiletype(ft);
+				cur.SetSyntaxEnabled(true);
+				if (auto *eng = cur.Highlighter()) {
+					eng->SetHighlighter(kte::HighlighterRegistry::CreateFor(ft));
+					eng->InvalidateFrom(0);
+				}
+			} else {
+				cur.SetFiletype("");
+				cur.SetSyntaxEnabled(true);
+				if (auto *eng = cur.Highlighter()) {
+					eng->SetHighlighter(std::make_unique<kte::NullHighlighter>());
+					eng->InvalidateFrom(0);
+				}
+			}
+			return true;
 		}
 	}
 
@@ -159,6 +187,30 @@ Editor::OpenFile(const std::string &path, std::string &err)
 	if (!b.OpenFromFile(path, err)) {
 		return false;
 	}
+	// Initialize syntax highlighting by extension + shebang via registry (v2)
+	b.EnsureHighlighter();
+	std::string first = "";
+	{
+		const auto &rows = b.Rows();
+		if (!rows.empty())
+			first = static_cast<std::string>(rows[0]);
+	}
+	std::string ft = kte::HighlighterRegistry::DetectForPath(path, first);
+	if (!ft.empty()) {
+		b.SetFiletype(ft);
+		b.SetSyntaxEnabled(true);
+		if (auto *eng = b.Highlighter()) {
+			eng->SetHighlighter(kte::HighlighterRegistry::CreateFor(ft));
+			eng->InvalidateFrom(0);
+		}
+	} else {
+		b.SetFiletype("");
+		b.SetSyntaxEnabled(true);
+		if (auto *eng = b.Highlighter()) {
+			eng->SetHighlighter(std::make_unique<kte::NullHighlighter>());
+			eng->InvalidateFrom(0);
+		}
+	}
 	// Add as a new buffer and switch to it
 	std::size_t idx = AddBuffer(std::move(b));
 	SwitchTo(idx);
@@ -173,6 +225,27 @@ Editor::SwitchTo(std::size_t index)
 		return false;
 	}
 	curbuf_ = index;
+	// Robustness: ensure a valid highlighter is installed when switching buffers
+	Buffer &b = buffers_[curbuf_];
+	if (b.SyntaxEnabled()) {
+		b.EnsureHighlighter();
+		if (auto *eng = b.Highlighter()) {
+			if (!eng->HasHighlighter()) {
+				// Try to set based on existing filetype; fall back to NullHighlighter
+				if (!b.Filetype().empty()) {
+					auto hl = kte::HighlighterRegistry::CreateFor(b.Filetype());
+					if (hl) {
+						eng->SetHighlighter(std::move(hl));
+					} else {
+						eng->SetHighlighter(std::make_unique<kte::NullHighlighter>());
+					}
+				} else {
+					eng->SetHighlighter(std::make_unique<kte::NullHighlighter>());
+				}
+				eng->InvalidateFrom(0);
+			}
+		}
+	}
 	return true;
 }
 

Editor.h

@@ -301,22 +301,23 @@ public:
 	}
 
 
- // --- Generic Prompt subsystem (for search, open-file, save-as, etc.) ---
- enum class PromptKind {
-     None = 0,
-     Search,
-     RegexSearch,
-     RegexReplaceFind,  // step 1 of Regex Search & Replace: find pattern
-     RegexReplaceWith,  // step 2 of Regex Search & Replace: replacement text
-     OpenFile,
-     SaveAs,
-     Confirm,
-     BufferSwitch,
-     GotoLine,
-     Chdir,
-     ReplaceFind,  // step 1 of Search & Replace: find what
-     ReplaceWith   // step 2 of Search & Replace: replace with
- };
+	// --- Generic Prompt subsystem (for search, open-file, save-as, etc.) ---
+	enum class PromptKind {
+		None = 0,
+		Search,
+		RegexSearch,
+		RegexReplaceFind, // step 1 of Regex Search & Replace: find pattern
+		RegexReplaceWith, // step 2 of Regex Search & Replace: replacement text
+		OpenFile,
+		SaveAs,
+		Confirm,
+		BufferSwitch,
+		GotoLine,
+		Chdir,
+		ReplaceFind, // step 1 of Search & Replace: find what
+		ReplaceWith, // step 2 of Search & Replace: replace with
+		Command // generic command prompt (": ")
+	};
 
 
 	void StartPrompt(PromptKind kind, const std::string &label, const std::string &initial)
@@ -518,20 +519,38 @@ private:
 	std::string prompt_text_;
 	std::string pending_overwrite_path_;
 
-    // GUI-only state (safe no-op in terminal builds)
-    bool file_picker_visible_ = false;
-    std::string file_picker_dir_;
+	// GUI-only state (safe no-op in terminal builds)
+	bool file_picker_visible_ = false;
+	std::string file_picker_dir_;
 
-    // Temporary state for Search & Replace flow
+	// Temporary state for Search & Replace flow
 public:
-    void SetReplaceFindTmp(const std::string &s) { replace_find_tmp_ = s; }
-    void SetReplaceWithTmp(const std::string &s) { replace_with_tmp_ = s; }
-    [[nodiscard]] const std::string &ReplaceFindTmp() const { return replace_find_tmp_; }
-    [[nodiscard]] const std::string &ReplaceWithTmp() const { return replace_with_tmp_; }
+	void SetReplaceFindTmp(const std::string &s)
+	{
+		replace_find_tmp_ = s;
+	}
+
+
+	void SetReplaceWithTmp(const std::string &s)
+	{
+		replace_with_tmp_ = s;
+	}
+
+
+	[[nodiscard]] const std::string &ReplaceFindTmp() const
+	{
+		return replace_find_tmp_;
+	}
+
+
+	[[nodiscard]] const std::string &ReplaceWithTmp() const
+	{
+		return replace_with_tmp_;
+	}
 
 private:
-    std::string replace_find_tmp_;
-    std::string replace_with_tmp_;
+	std::string replace_find_tmp_;
+	std::string replace_with_tmp_;
 };
 
 #endif // KTE_EDITOR_H

GUIConfig.cc

@@ -102,8 +102,27 @@ GUIConfig::LoadFromFile(const std::string &path)
 			if (v > 0.0f) {
 				font_size = v;
 			}
+		} else if (key == "theme") {
+			theme = val;
+		} else if (key == "background" || key == "bg") {
+			std::string v = val;
+			std::transform(v.begin(), v.end(), v.begin(), [](unsigned char c) {
+				return (char) std::tolower(c);
+			});
+			if (v == "light" || v == "dark")
+				background = v;
+		} else if (key == "syntax") {
+			std::string v = val;
+			std::transform(v.begin(), v.end(), v.begin(), [](unsigned char c) {
+				return (char) std::tolower(c);
+			});
+			if (v == "1" || v == "on" || v == "true" || v == "yes") {
+				syntax = true;
+			} else if (v == "0" || v == "off" || v == "false" || v == "no") {
+				syntax = false;
+			}
 		}
 	}
 
 	return true;
-}
+}

GUIConfig.h

@@ -12,10 +12,18 @@
 
 class GUIConfig {
 public:
-	bool fullscreen = false;
-	int columns     = 80;
-	int rows        = 42;
-	float font_size = (float) KTE_FONT_SIZE;
+	bool fullscreen   = false;
+	int columns       = 80;
+	int rows          = 42;
+	float font_size   = (float) KTE_FONT_SIZE;
+	std::string theme = "nord";
+	// Background mode for themes that support light/dark variants
+	// Values: "dark" (default), "light"
+	std::string background = "dark";
+
+	// Default syntax highlighting state for GUI (kge): on/off
+	// Accepts: on/off/true/false/yes/no/1/0 in the ini file.
+	bool syntax = true; // default: enabled
 
 	// Load from default path: $HOME/.config/kte/kge.ini
 	static GUIConfig Load();
@@ -24,4 +32,4 @@ public:
 	bool LoadFromFile(const std::string &path);
 };
 
-#endif // KTE_GUI_CONFIG_H
+#endif // KTE_GUI_CONFIG_H

GUIFrontend.cc

@@ -16,6 +16,8 @@
 #include "Font.h" // embedded default font (DefaultFontRegular)
 #include "GUIConfig.h"
 #include "GUITheme.h"
+#include "syntax/HighlighterRegistry.h"
+#include "syntax/NullHighlighter.h"
 
 
 #ifndef KTE_FONT_SIZE
@@ -32,8 +34,8 @@ GUIFrontend::Init(Editor &ed)
 		return false;
 	}
 
-	// Load GUI configuration (fullscreen, columns/rows, font size)
-	const auto [fullscreen, columns, rows, font_size] = GUIConfig::Load();
+	// Load GUI configuration (fullscreen, columns/rows, font size, theme, background)
+	GUIConfig cfg = GUIConfig::Load();
 
 	// GL attributes for core profile
 	SDL_GL_SetAttribute(SDL_GL_CONTEXT_FLAGS, 0);
@@ -47,7 +49,7 @@ GUIFrontend::Init(Editor &ed)
 	// Compute desired window size from config
 	Uint32 win_flags = SDL_WINDOW_OPENGL | SDL_WINDOW_RESIZABLE | SDL_WINDOW_ALLOW_HIGHDPI;
 
-	if (fullscreen) {
+	if (cfg.fullscreen) {
 		// "Fullscreen": fill the usable bounds of the primary display.
 		// On macOS, do NOT use true fullscreen so the menu/status bar remains visible.
 		SDL_Rect usable{};
@@ -61,8 +63,8 @@ GUIFrontend::Init(Editor &ed)
 #endif
 	} else {
 		// Windowed: width = columns * font_size, height = (rows * 2) * font_size
-		int w = static_cast<int>(columns * font_size);
-		int h = static_cast<int>((rows * 2) * font_size);
+		int w = cfg.columns * static_cast<int>(cfg.font_size);
+		int h = cfg.rows * static_cast<int>(cfg.font_size * 1.2);
 
 		// As a safety, clamp to display usable bounds if retrievable
 		SDL_Rect usable{};
@@ -86,7 +88,7 @@ GUIFrontend::Init(Editor &ed)
 	// macOS: when "fullscreen" is requested, position the window at the
 	// top-left of the usable display area to mimic fullscreen while keeping
 	// the system menu bar visible.
-	if (fullscreen) {
+	if (cfg.fullscreen) {
 		SDL_Rect usable{};
 		if (SDL_GetDisplayUsableBounds(0, &usable) == 0) {
 			SDL_SetWindowPosition(window_, usable.x, usable.y);
@@ -105,8 +107,45 @@ GUIFrontend::Init(Editor &ed)
 	ImGuiIO &io = ImGui::GetIO();
 	(void) io;
 	ImGui::StyleColorsDark();
-	// Apply a Nord-inspired theme
-	kte::ApplyNordImGuiTheme();
+
+	// Apply background mode and selected theme (default: Nord). Can be changed at runtime via commands.
+	if (cfg.background == "light")
+		kte::SetBackgroundMode(kte::BackgroundMode::Light);
+	else
+		kte::SetBackgroundMode(kte::BackgroundMode::Dark);
+	kte::ApplyThemeByName(cfg.theme);
+
+	// Apply default syntax highlighting preference from GUI config to the current buffer
+	if (Buffer *b = ed.CurrentBuffer()) {
+		if (cfg.syntax) {
+			b->SetSyntaxEnabled(true);
+			// Ensure a highlighter is available if possible
+			b->EnsureHighlighter();
+			if (auto *eng = b->Highlighter()) {
+				if (!eng->HasHighlighter()) {
+					// Try detect from filename and first line; fall back to cpp or existing filetype
+					std::string first_line;
+					const auto &rows = b->Rows();
+					if (!rows.empty())
+						first_line = static_cast<std::string>(rows[0]);
+					std::string ft = kte::HighlighterRegistry::DetectForPath(
+						b->Filename(), first_line);
+					if (!ft.empty()) {
+						eng->SetHighlighter(kte::HighlighterRegistry::CreateFor(ft));
+						b->SetFiletype(ft);
+						eng->InvalidateFrom(0);
+					} else {
+						// Unknown/unsupported -> install a null highlighter to keep syntax enabled
+						eng->SetHighlighter(std::make_unique<kte::NullHighlighter>());
+						b->SetFiletype("");
+						eng->InvalidateFrom(0);
+					}
+				}
+			}
+		} else {
+			b->SetSyntaxEnabled(false);
+		}
+	}
 
 	if (!ImGui_ImplSDL2_InitForOpenGL(window_, gl_ctx_))
 		return false;
@@ -135,7 +174,7 @@ GUIFrontend::Init(Editor &ed)
 #endif
 
 	// Initialize GUI font from embedded default (use configured size or compiled default)
-	LoadGuiFont_(nullptr, (float) font_size);
+	LoadGuiFont_(nullptr, (float) cfg.font_size);
 
 	return true;
 }
@@ -214,7 +253,7 @@ GUIFrontend::Step(Editor &ed, bool &running)
 		float avail_h = std::max(0.0f, disp_h - 2.0f * pad_y - status_h);
 
 		// Visible content rows inside the scroll child
-		std::size_t content_rows = static_cast<std::size_t>(std::floor(avail_h / line_h));
+		auto content_rows = static_cast<std::size_t>(std::floor(avail_h / line_h));
 		// Editor::Rows includes the status line; add 1 back for it.
 		std::size_t rows = std::max<std::size_t>(1, content_rows + 1);
 		std::size_t cols = static_cast<std::size_t>(std::max(1.0f, std::floor(avail_w / ch_w)));
@@ -264,11 +303,11 @@ GUIFrontend::Shutdown()
 bool
 GUIFrontend::LoadGuiFont_(const char * /*path*/, float size_px)
 {
-	ImGuiIO &io = ImGui::GetIO();
+	const ImGuiIO &io = ImGui::GetIO();
 	io.Fonts->Clear();
-	ImFont *font = io.Fonts->AddFontFromMemoryCompressedTTF(
-		(void *) DefaultFontBoldCompressedData,
-		(int) DefaultFontBoldCompressedSize,
+	const ImFont *font = io.Fonts->AddFontFromMemoryCompressedTTF(
+		DefaultFontBoldCompressedData,
+		DefaultFontBoldCompressedSize,
 		size_px);
 	if (!font) {
 		font = io.Fonts->AddFontDefault();

GUIFrontend.h

@@ -25,7 +25,7 @@ public:
 	void Shutdown() override;
 
 private:
-	bool LoadGuiFont_(const char *path, float size_px);
+	static bool LoadGuiFont_(const char *path, float size_px);
 
 	GUIInputHandler input_{};
 	GUIRenderer renderer_{};

GUIInputHandler.cc

@@ -3,6 +3,7 @@
 #include <ncurses.h>
 
 #include <SDL.h>
+#include <imgui.h>
 
 #include "GUIInputHandler.h"
 #include "KKeymap.h"
@@ -92,10 +93,14 @@ map_key(const SDL_Keycode key,
 		out = {true, CommandId::Backspace, "", 0};
 		return true;
 	case SDLK_TAB:
-		// Do not insert text on KEYDOWN; allow SDL_TEXTINPUT to deliver '\t'
-		// as printable input so that all printable characters flow via TEXTINPUT.
-		out.hasCommand = false;
-		return true;
+		// Insert a literal tab character when not interpreting a k-prefix suffix.
+		// If k-prefix is active, let the k-prefix handler below consume the key
+		// (so Tab doesn't leave k-prefix stuck).
+		if (!k_prefix) {
+			out = {true, CommandId::InsertText, std::string("\t"), 0};
+			return true;
+		}
+		break; // fall through so k-prefix handler can process
 	case SDLK_RETURN:
 	case SDLK_KP_ENTER:
 		out = {true, CommandId::Newline, "", 0};
@@ -280,6 +285,14 @@ GUIInputHandler::ProcessSDLEvent(const SDL_Event &e)
 	bool produced = false;
 	switch (e.type) {
 	case SDL_MOUSEWHEEL: {
+		// If ImGui wants to capture the mouse (e.g., hovering the File Picker list),
+		// don't translate wheel events into editor scrolling.
+		// This prevents background buffer scroll while using GUI widgets.
+		ImGuiIO &io = ImGui::GetIO();
+		if (io.WantCaptureMouse) {
+			return true; // consumed by GUI
+		}
+
 		// Map vertical wheel to line-wise cursor movement (MoveUp/MoveDown)
 		int dy = e.wheel.y;
 #ifdef SDL_MOUSEWHEEL_FLIPPED
@@ -347,6 +360,12 @@ GUIInputHandler::ProcessSDLEvent(const SDL_Event &e)
 		                   uarg_text_,
 		                   mi);
 
+		// If we inserted a TAB on KEYDOWN, suppress any subsequent SDL_TEXTINPUT
+		// for this keystroke to avoid double insertion on platforms that emit it.
+		if (produced && mi.hasCommand && mi.id == CommandId::InsertText && mi.arg == "\t") {
+			suppress_text_input_once_ = true;
+		}
+
 		// If we just consumed a universal-argument digit or '-' on KEYDOWN and emitted UArgStatus,
 		// suppress the subsequent SDL_TEXTINPUT for this keystroke to avoid duplicating the digit in status.
 		if (produced && mi.hasCommand && mi.id == CommandId::UArgStatus) {

GUIRenderer.cc

@@ -10,6 +10,8 @@
 #include <regex>
 
 #include "GUIRenderer.h"
+#include "Highlight.h"
+#include "GUITheme.h"
 #include "Buffer.h"
 #include "Command.h"
 #include "Editor.h"
@@ -44,6 +46,8 @@ GUIRenderer::Draw(Editor &ed)
 	ImGui::SetNextWindowSize(main_sz);
 
 	ImGuiWindowFlags flags = ImGuiWindowFlags_NoTitleBar
+	                         | ImGuiWindowFlags_NoScrollbar
+	                         | ImGuiWindowFlags_NoScrollWithMouse
 	                         | ImGuiWindowFlags_NoResize
 	                         | ImGuiWindowFlags_NoMove
 	                         | ImGuiWindowFlags_NoCollapse
@@ -151,15 +155,21 @@ GUIRenderer::Draw(Editor &ed)
 					last_row  = first_row + vis_rows - 1;
 				}
 			}
+			// Phase 3: prefetch visible viewport highlights and warm around in background
+			if (buf->SyntaxEnabled() && buf->Highlighter() && buf->Highlighter()->HasHighlighter()) {
+				int fr = static_cast<int>(std::max(0L, first_row));
+				int rc = static_cast<int>(std::max(1L, vis_rows));
+				buf->Highlighter()->PrefetchViewport(*buf, fr, rc, buf->Version());
+			}
 		}
-  // Handle mouse click before rendering to avoid dependent on drawn items
-  if (ImGui::IsWindowHovered() && ImGui::IsMouseClicked(ImGuiMouseButton_Left)) {
-      ImVec2 mp = ImGui::GetIO().MousePos;
-      // Compute viewport-relative row so (0) is top row of the visible area
-      float vy_f = (mp.y - list_origin.y - scroll_y) / row_h;
-      long vy    = static_cast<long>(vy_f);
-      if (vy < 0)
-          vy = 0;
+		// Handle mouse click before rendering to avoid dependent on drawn items
+		if (ImGui::IsWindowHovered() && ImGui::IsMouseClicked(ImGuiMouseButton_Left)) {
+			ImVec2 mp = ImGui::GetIO().MousePos;
+			// Compute viewport-relative row so (0) is top row of the visible area
+			float vy_f = (mp.y - list_origin.y - scroll_y) / row_h;
+			long vy    = static_cast<long>(vy_f);
+			if (vy < 0)
+				vy = 0;
 
 			// Clamp vy within visible content height to avoid huge jumps
 			ImVec2 cr_min = ImGui::GetWindowContentRegionMin();
@@ -171,163 +181,204 @@ GUIRenderer::Draw(Editor &ed)
 			if (vy >= vis_rows)
 				vy = vis_rows - 1;
 
-            // Translate viewport row to buffer row using Buffer::Rowoffs
-            std::size_t by = buf->Rowoffs() + static_cast<std::size_t>(vy);
-            if (by >= lines.size()) {
-                if (!lines.empty())
-                    by = lines.size() - 1;
-                else
-                    by = 0;
-            }
+			// Translate viewport row to buffer row using Buffer::Rowoffs
+			std::size_t by = buf->Rowoffs() + static_cast<std::size_t>(vy);
+			if (by >= lines.size()) {
+				if (!lines.empty())
+					by = lines.size() - 1;
+				else
+					by = 0;
+			}
 
-            // Compute desired pixel X inside the viewport content (subtract horizontal scroll)
-            float px = (mp.x - list_origin.x - scroll_x);
-            if (px < 0.0f)
-                px = 0.0f;
+			// Compute desired pixel X inside the viewport content (subtract horizontal scroll)
+			float px = (mp.x - list_origin.x - scroll_x);
+			if (px < 0.0f)
+				px = 0.0f;
 
-            // Empty buffer guard: if there are no lines yet, just move to 0:0
-            if (lines.empty()) {
-                Execute(ed, CommandId::MoveCursorTo, std::string("0:0"));
-            } else {
-                // Convert pixel X to a render-column target including horizontal col offset
-                // Use our own tab expansion of width 8 to match command layer logic.
-                std::string line_clicked = static_cast<std::string>(lines[by]);
-                const std::size_t tabw          = 8;
-                // We iterate source columns computing absolute rendered column (rx_abs) from 0,
-                // then translate to viewport-space by subtracting Coloffs.
-                std::size_t coloffs = buf->Coloffs();
-                std::size_t rx_abs  = 0; // absolute rendered column
-                std::size_t i       = 0; // source column iterator
+			// Empty buffer guard: if there are no lines yet, just move to 0:0
+			if (lines.empty()) {
+				Execute(ed, CommandId::MoveCursorTo, std::string("0:0"));
+			} else {
+				// Convert pixel X to a render-column target including horizontal col offset
+				// Use our own tab expansion of width 8 to match command layer logic.
+				std::string line_clicked = static_cast<std::string>(lines[by]);
+				const std::size_t tabw   = 8;
+				// We iterate source columns computing absolute rendered column (rx_abs) from 0,
+				// then translate to viewport-space by subtracting Coloffs.
+				std::size_t coloffs = buf->Coloffs();
+				std::size_t rx_abs  = 0; // absolute rendered column
+				std::size_t i       = 0; // source column iterator
 
-                // Fast-forward i until rx_abs >= coloffs to align with leftmost visible column
-                if (!line_clicked.empty() && coloffs > 0) {
-                    while (i < line_clicked.size() && rx_abs < coloffs) {
-                        if (line_clicked[i] == '\t') {
-                            rx_abs += (tabw - (rx_abs % tabw));
-                        } else {
-                            rx_abs += 1;
-                        }
-                        ++i;
-                    }
-                }
+				// Fast-forward i until rx_abs >= coloffs to align with leftmost visible column
+				if (!line_clicked.empty() && coloffs > 0) {
+					while (i < line_clicked.size() && rx_abs < coloffs) {
+						if (line_clicked[i] == '\t') {
+							rx_abs += (tabw - (rx_abs % tabw));
+						} else {
+							rx_abs += 1;
+						}
+						++i;
+					}
+				}
 
-                // Now search for closest source column to clicked px within/after viewport
-                std::size_t best_col = i; // default to first visible column
-                float best_dist      = std::numeric_limits<float>::infinity();
-                while (true) {
-                    // For i in [current..size], evaluate candidate including the implicit end position
-                    std::size_t rx_view = (rx_abs >= coloffs) ? (rx_abs - coloffs) : 0;
-                    float rx_px         = static_cast<float>(rx_view) * space_w;
-                    float dist          = std::fabs(px - rx_px);
-                    if (dist <= best_dist) {
-                        best_dist = dist;
-                        best_col  = i;
-                    }
-                    if (i == line_clicked.size())
-                        break;
-                    // advance to next source column
-                    if (line_clicked[i] == '\t') {
-                        rx_abs += (tabw - (rx_abs % tabw));
-                    } else {
-                        rx_abs += 1;
-                    }
-                    ++i;
-                }
+				// Now search for closest source column to clicked px within/after viewport
+				std::size_t best_col = i; // default to first visible column
+				float best_dist      = std::numeric_limits<float>::infinity();
+				while (true) {
+					// For i in [current..size], evaluate candidate including the implicit end position
+					std::size_t rx_view = (rx_abs >= coloffs) ? (rx_abs - coloffs) : 0;
+					float rx_px         = static_cast<float>(rx_view) * space_w;
+					float dist          = std::fabs(px - rx_px);
+					if (dist <= best_dist) {
+						best_dist = dist;
+						best_col  = i;
+					}
+					if (i == line_clicked.size())
+						break;
+					// advance to next source column
+					if (line_clicked[i] == '\t') {
+						rx_abs += (tabw - (rx_abs % tabw));
+					} else {
+						rx_abs += 1;
+					}
+					++i;
+				}
 
-                // Dispatch absolute buffer coordinates (row:col)
-                char tmp[64];
-                std::snprintf(tmp, sizeof(tmp), "%zu:%zu", by, best_col);
-                Execute(ed, CommandId::MoveCursorTo, std::string(tmp));
-            }
-        }
+				// Dispatch absolute buffer coordinates (row:col)
+				char tmp[64];
+				std::snprintf(tmp, sizeof(tmp), "%zu:%zu", by, best_col);
+				Execute(ed, CommandId::MoveCursorTo, std::string(tmp));
+			}
+		}
 		// Cache current horizontal offset in rendered columns
 		const std::size_t coloffs_now = buf->Coloffs();
-  for (std::size_t i = rowoffs; i < lines.size(); ++i) {
-            // Capture the screen position before drawing the line
-            ImVec2 line_pos         = ImGui::GetCursorScreenPos();
-            std::string line = static_cast<std::string>(lines[i]);
+		for (std::size_t i = rowoffs; i < lines.size(); ++i) {
+			// Capture the screen position before drawing the line
+			ImVec2 line_pos  = ImGui::GetCursorScreenPos();
+			std::string line = static_cast<std::string>(lines[i]);
 
-            // Expand tabs to spaces with width=8 and apply horizontal scroll offset
-            const std::size_t tabw = 8;
-            std::string expanded;
-            expanded.reserve(line.size() + 16);
-            std::size_t rx_abs_draw = 0; // rendered column for drawing
-            // Compute search highlight ranges for this line in source indices
-            bool search_mode = ed.SearchActive() && !ed.SearchQuery().empty();
-            std::vector<std::pair<std::size_t, std::size_t>> hl_src_ranges;
-            if (search_mode) {
-                // If we're in RegexSearch or RegexReplaceFind mode, compute ranges using regex; otherwise plain substring
-                if (ed.PromptActive() && (ed.CurrentPromptKind() == Editor::PromptKind::RegexSearch || ed.CurrentPromptKind() == Editor::PromptKind::RegexReplaceFind)) {
-                    try {
-                        std::regex rx(ed.SearchQuery());
-                        for (auto it = std::sregex_iterator(line.begin(), line.end(), rx);
-                             it != std::sregex_iterator(); ++it) {
-                            const auto &m = *it;
-                            std::size_t sx = static_cast<std::size_t>(m.position());
-                            std::size_t ex = sx + static_cast<std::size_t>(m.length());
-                            hl_src_ranges.emplace_back(sx, ex);
-                        }
-                    } catch (const std::regex_error &) {
-                        // ignore invalid patterns here; status line already shows the error
-                    }
-                } else {
-                    const std::string &q = ed.SearchQuery();
-                    std::size_t pos = 0;
-                    while (!q.empty() && (pos = line.find(q, pos)) != std::string::npos) {
-                        hl_src_ranges.emplace_back(pos, pos + q.size());
-                        pos += q.size();
-                    }
-                }
-            }
-            auto src_to_rx = [&](std::size_t upto_src_exclusive) -> std::size_t {
-                std::size_t rx = 0;
-                std::size_t s  = 0;
-                while (s < upto_src_exclusive && s < line.size()) {
-                    if (line[s] == '\t')
-                        rx += (tabw - (rx % tabw));
-                    else
-                        rx += 1;
-                    ++s;
-                }
-                return rx;
-            };
-            // Draw background highlights (under text)
-            if (search_mode && !hl_src_ranges.empty()) {
-                // Current match emphasis
-                bool has_current = ed.SearchMatchLen() > 0 && ed.SearchMatchY() == i;
-                std::size_t cur_x = has_current ? ed.SearchMatchX() : 0;
-                std::size_t cur_end = has_current ? (ed.SearchMatchX() + ed.SearchMatchLen()) : 0;
-                for (const auto &rg : hl_src_ranges) {
-                    std::size_t sx = rg.first, ex = rg.second;
-                    std::size_t rx_start = src_to_rx(sx);
-                    std::size_t rx_end   = src_to_rx(ex);
-                    // Apply horizontal scroll offset
-                    if (rx_end <= coloffs_now) continue; // fully left of view
-                    std::size_t vx0 = (rx_start > coloffs_now) ? (rx_start - coloffs_now) : 0;
-                    std::size_t vx1 = rx_end - coloffs_now;
-                    ImVec2 p0 = ImVec2(line_pos.x + static_cast<float>(vx0) * space_w, line_pos.y);
-                    ImVec2 p1 = ImVec2(line_pos.x + static_cast<float>(vx1) * space_w, line_pos.y + line_h);
-                    // Choose color: current match stronger
-                    bool is_current = has_current && sx == cur_x && ex == cur_end;
-                    ImU32 col = is_current ? IM_COL32(255, 220, 120, 140) : IM_COL32(200, 200, 0, 90);
-                    ImGui::GetWindowDrawList()->AddRectFilled(p0, p1, col);
-                }
-            }
-            // Emit entire line (ImGui child scrolling will handle clipping)
-            for (std::size_t src = 0; src < line.size(); ++src) {
-                char c = line[src];
-                if (c == '\t') {
-                    std::size_t adv = (tabw - (rx_abs_draw % tabw));
-                    // Emit spaces for the tab
-                    expanded.append(adv, ' ');
-                    rx_abs_draw += adv;
-                } else {
-                    expanded.push_back(c);
-                    rx_abs_draw += 1;
-                }
-            }
+			// Expand tabs to spaces with width=8 and apply horizontal scroll offset
+			const std::size_t tabw = 8;
+			std::string expanded;
+			expanded.reserve(line.size() + 16);
+			std::size_t rx_abs_draw = 0; // rendered column for drawing
+			// Compute search highlight ranges for this line in source indices
+			bool search_mode = ed.SearchActive() && !ed.SearchQuery().empty();
+			std::vector<std::pair<std::size_t, std::size_t> > hl_src_ranges;
+			if (search_mode) {
+				// If we're in RegexSearch or RegexReplaceFind mode, compute ranges using regex; otherwise plain substring
+				if (ed.PromptActive() && (
+					    ed.CurrentPromptKind() == Editor::PromptKind::RegexSearch || ed.
+					    CurrentPromptKind() == Editor::PromptKind::RegexReplaceFind)) {
+					try {
+						std::regex rx(ed.SearchQuery());
+						for (auto it = std::sregex_iterator(line.begin(), line.end(), rx);
+						     it != std::sregex_iterator(); ++it) {
+							const auto &m  = *it;
+							std::size_t sx = static_cast<std::size_t>(m.position());
+							std::size_t ex = sx + static_cast<std::size_t>(m.length());
+							hl_src_ranges.emplace_back(sx, ex);
+						}
+					} catch (const std::regex_error &) {
+						// ignore invalid patterns here; status line already shows the error
+					}
+				} else {
+					const std::string &q = ed.SearchQuery();
+					std::size_t pos      = 0;
+					while (!q.empty() && (pos = line.find(q, pos)) != std::string::npos) {
+						hl_src_ranges.emplace_back(pos, pos + q.size());
+						pos += q.size();
+					}
+				}
+			}
+			auto src_to_rx = [&](std::size_t upto_src_exclusive) -> std::size_t {
+				std::size_t rx = 0;
+				std::size_t s  = 0;
+				while (s < upto_src_exclusive && s < line.size()) {
+					if (line[s] == '\t')
+						rx += (tabw - (rx % tabw));
+					else
+						rx += 1;
+					++s;
+				}
+				return rx;
+			};
+			// Draw background highlights (under text)
+			if (search_mode && !hl_src_ranges.empty()) {
+				// Current match emphasis
+				bool has_current    = ed.SearchMatchLen() > 0 && ed.SearchMatchY() == i;
+				std::size_t cur_x   = has_current ? ed.SearchMatchX() : 0;
+				std::size_t cur_end = has_current ? (ed.SearchMatchX() + ed.SearchMatchLen()) : 0;
+				for (const auto &rg: hl_src_ranges) {
+					std::size_t sx       = rg.first, ex = rg.second;
+					std::size_t rx_start = src_to_rx(sx);
+					std::size_t rx_end   = src_to_rx(ex);
+					// Apply horizontal scroll offset
+					if (rx_end <= coloffs_now)
+						continue; // fully left of view
+					std::size_t vx0 = (rx_start > coloffs_now) ? (rx_start - coloffs_now) : 0;
+					std::size_t vx1 = rx_end - coloffs_now;
+					ImVec2 p0 = ImVec2(line_pos.x + static_cast<float>(vx0) * space_w, line_pos.y);
+					ImVec2 p1 = ImVec2(line_pos.x + static_cast<float>(vx1) * space_w,
+					                   line_pos.y + line_h);
+					// Choose color: current match stronger
+					bool is_current = has_current && sx == cur_x && ex == cur_end;
+					ImU32 col       = is_current
+						                  ? IM_COL32(255, 220, 120, 140)
+						                  : IM_COL32(200, 200, 0, 90);
+					ImGui::GetWindowDrawList()->AddRectFilled(p0, p1, col);
+				}
+			}
+			// Emit entire line to an expanded buffer (tabs -> spaces)
+			for (std::size_t src = 0; src < line.size(); ++src) {
+				char c = line[src];
+				if (c == '\t') {
+					std::size_t adv = (tabw - (rx_abs_draw % tabw));
+					expanded.append(adv, ' ');
+					rx_abs_draw += adv;
+				} else {
+					expanded.push_back(c);
+					rx_abs_draw += 1;
+				}
+			}
 
-            ImGui::TextUnformatted(expanded.c_str());
+			// Draw syntax-colored runs (text above background highlights)
+			if (buf->SyntaxEnabled() && buf->Highlighter() && buf->Highlighter()->HasHighlighter()) {
+				const kte::LineHighlight &lh = buf->Highlighter()->GetLine(
+					*buf, static_cast<int>(i), buf->Version());
+				// Helper to convert a src column to expanded rx position
+				auto src_to_rx_full = [&](std::size_t sidx) -> std::size_t {
+					std::size_t rx = 0;
+					for (std::size_t k = 0; k < sidx && k < line.size(); ++k) {
+						rx += (line[k] == '\t') ? (tabw - (rx % tabw)) : 1;
+					}
+					return rx;
+				};
+				for (const auto &sp: lh.spans) {
+					std::size_t rx_s = src_to_rx_full(
+						static_cast<std::size_t>(std::max(0, sp.col_start)));
+					std::size_t rx_e = src_to_rx_full(
+						static_cast<std::size_t>(std::max(sp.col_start, sp.col_end)));
+					if (rx_e <= coloffs_now)
+						continue;
+					std::size_t vx0 = (rx_s > coloffs_now) ? (rx_s - coloffs_now) : 0;
+					std::size_t vx1 = (rx_e > coloffs_now) ? (rx_e - coloffs_now) : 0;
+					if (vx0 >= expanded.size())
+						continue;
+					vx1 = std::min<std::size_t>(vx1, expanded.size());
+					if (vx1 <= vx0)
+						continue;
+					ImU32 col = ImGui::GetColorU32(kte::SyntaxInk(sp.kind));
+					ImVec2 p  = ImVec2(line_pos.x + static_cast<float>(vx0) * space_w, line_pos.y);
+					ImGui::GetWindowDrawList()->AddText(
+						p, col, expanded.c_str() + vx0, expanded.c_str() + vx1);
+				}
+				// We drew text via draw list (no layout advance). Manually advance the cursor to the next line.
+				ImGui::SetCursorScreenPos(ImVec2(line_pos.x, line_pos.y + line_h));
+			} else {
+				// No syntax: draw as one run
+				ImGui::TextUnformatted(expanded.c_str());
+			}
 
 			// Draw a visible cursor indicator on the current line
 			if (i == cy) {
@@ -349,207 +400,220 @@ GUIRenderer::Draw(Editor &ed)
 		}
 		ImGui::EndChild();
 
-  // Status bar spanning full width
-  ImGui::Separator();
+		// Status bar spanning full width
+		ImGui::Separator();
 
-  // Compute full content width and draw a filled background rectangle
-  ImVec2 win_pos = ImGui::GetWindowPos();
-  ImVec2 cr_min  = ImGui::GetWindowContentRegionMin();
-  ImVec2 cr_max  = ImGui::GetWindowContentRegionMax();
-  float x0       = win_pos.x + cr_min.x;
-  float x1       = win_pos.x + cr_max.x;
-  ImVec2 cursor  = ImGui::GetCursorScreenPos();
-  float bar_h    = ImGui::GetFrameHeight();
-  ImVec2 p0(x0, cursor.y);
-  ImVec2 p1(x1, cursor.y + bar_h);
-  ImU32 bg_col = ImGui::GetColorU32(ImGuiCol_HeaderActive);
-  ImGui::GetWindowDrawList()->AddRectFilled(p0, p1, bg_col);
-  // If a prompt is active, replace the entire status bar with the prompt text
-  if (ed.PromptActive()) {
-      std::string label = ed.PromptLabel();
-      std::string ptext = ed.PromptText();
-      auto kind         = ed.CurrentPromptKind();
-      if (kind == Editor::PromptKind::OpenFile || kind == Editor::PromptKind::SaveAs ||
-          kind == Editor::PromptKind::Chdir) {
-          const char *home_c = std::getenv("HOME");
-          if (home_c && *home_c) {
-              std::string home(home_c);
-              if (ptext.rfind(home, 0) == 0) {
-                  std::string rest = ptext.substr(home.size());
-                  if (rest.empty())
-                      ptext = "~";
-                  else if (!rest.empty() && (rest[0] == '/' || rest[0] == '\\'))
-                      ptext = std::string("~") + rest;
-              }
-          }
-      }
-
-      float pad = 6.f;
-      float left_x = p0.x + pad;
-      float right_x = p1.x - pad;
-      float max_px = std::max(0.0f, right_x - left_x);
-
-      std::string prefix;
-      if (!label.empty()) prefix = label + ": ";
-
-      // Compose showing right-end of filename portion when too long for space
-      std::string final_msg;
-      ImVec2 prefix_sz = ImGui::CalcTextSize(prefix.c_str());
-      float avail_px = std::max(0.0f, max_px - prefix_sz.x);
-      if ((kind == Editor::PromptKind::OpenFile || kind == Editor::PromptKind::SaveAs || kind == Editor::PromptKind::Chdir) && avail_px > 0.0f) {
-          // Trim from left until it fits by pixel width
-          std::string tail = ptext;
-          ImVec2 tail_sz = ImGui::CalcTextSize(tail.c_str());
-          if (tail_sz.x > avail_px) {
-              // Remove leading chars until it fits
-              // Use a simple loop; text lengths are small here
-              size_t start = 0;
-              // To avoid O(n^2) worst-case, remove chunks
-              while (start < tail.size()) {
-                  // Estimate how many chars to skip based on ratio
-                  float ratio = tail_sz.x / avail_px;
-                  size_t skip = ratio > 1.5f ? std::min(tail.size() - start, (size_t)std::max<size_t>(1, (size_t)(tail.size() / 4))) : 1;
-                  start += skip;
-                  std::string candidate = tail.substr(start);
-                  ImVec2 cand_sz = ImGui::CalcTextSize(candidate.c_str());
-                  if (cand_sz.x <= avail_px) {
-                      tail = candidate;
-                      tail_sz = cand_sz;
-                      break;
-                  }
-              }
-              if (ImGui::CalcTextSize(tail.c_str()).x > avail_px && !tail.empty()) {
-                  // As a last resort, ensure fit by chopping exactly
-                  // binary reduce
-                  size_t lo = 0, hi = tail.size();
-                  while (lo < hi) {
-                      size_t mid = (lo + hi) / 2;
-                      std::string cand = tail.substr(mid);
-                      if (ImGui::CalcTextSize(cand.c_str()).x <= avail_px) hi = mid; else lo = mid + 1;
-                  }
-                  tail = tail.substr(lo);
-              }
-          }
-          final_msg = prefix + tail;
-      } else {
-          final_msg = prefix + ptext;
-      }
-
-      ImVec2 msg_sz = ImGui::CalcTextSize(final_msg.c_str());
-      ImGui::PushClipRect(ImVec2(p0.x, p0.y), ImVec2(p1.x, p1.y), true);
-      ImGui::SetCursorScreenPos(ImVec2(left_x, p0.y + (bar_h - msg_sz.y) * 0.5f));
-      ImGui::TextUnformatted(final_msg.c_str());
-      ImGui::PopClipRect();
-      // Advance cursor to after the bar to keep layout consistent
-      ImGui::Dummy(ImVec2(x1 - x0, bar_h));
-  } else {
-  // Build left text
-  std::string left;
-  left.reserve(256);
-  left += "kge"; // GUI app name
-  left += " ";
-  left += KTE_VERSION_STR;
-		std::string fname;
-		try {
-			fname = ed.DisplayNameFor(*buf);
-		} catch (...) {
-			fname = buf->Filename();
-			try {
-				fname = std::filesystem::path(fname).filename().string();
-			} catch (...) {}
-		}
-		left += "  ";
-		// Insert buffer position prefix "[x/N] " before filename
-		{
-			std::size_t total = ed.BufferCount();
-			if (total > 0) {
-				std::size_t idx1 = ed.CurrentBufferIndex() + 1; // 1-based for display
-				left += "[";
-				left += std::to_string(static_cast<unsigned long long>(idx1));
-				left += "/";
-				left += std::to_string(static_cast<unsigned long long>(total));
-				left += "] ";
-			}
-		}
-		left += fname;
-		if (buf->Dirty())
-			left += " *";
-		// Append total line count as "<n>L"
-		{
-			unsigned long lcount = static_cast<unsigned long>(buf->Rows().size());
-			left += " ";
-			left += std::to_string(lcount);
-			left += "L";
-		}
-
-		// Build right text (cursor/mark)
-		int row1       = static_cast<int>(buf->Cury()) + 1;
-		int col1       = static_cast<int>(buf->Curx()) + 1;
-		bool have_mark = buf->MarkSet();
-		int mrow1      = have_mark ? static_cast<int>(buf->MarkCury()) + 1 : 0;
-		int mcol1      = have_mark ? static_cast<int>(buf->MarkCurx()) + 1 : 0;
-		char rbuf[128];
-		if (have_mark)
-			std::snprintf(rbuf, sizeof(rbuf), "%d,%d | M: %d,%d", row1, col1, mrow1, mcol1);
-		else
-			std::snprintf(rbuf, sizeof(rbuf), "%d,%d | M: not set", row1, col1);
-		std::string right = rbuf;
-
-		// Middle message: if a prompt is active, show "Label: text"; otherwise show status
-		std::string msg;
+		// Compute full content width and draw a filled background rectangle
+		ImVec2 win_pos = ImGui::GetWindowPos();
+		ImVec2 cr_min  = ImGui::GetWindowContentRegionMin();
+		ImVec2 cr_max  = ImGui::GetWindowContentRegionMax();
+		float x0       = win_pos.x + cr_min.x;
+		float x1       = win_pos.x + cr_max.x;
+		ImVec2 cursor  = ImGui::GetCursorScreenPos();
+		float bar_h    = ImGui::GetFrameHeight();
+		ImVec2 p0(x0, cursor.y);
+		ImVec2 p1(x1, cursor.y + bar_h);
+		ImU32 bg_col = ImGui::GetColorU32(ImGuiCol_HeaderActive);
+		ImGui::GetWindowDrawList()->AddRectFilled(p0, p1, bg_col);
+		// If a prompt is active, replace the entire status bar with the prompt text
 		if (ed.PromptActive()) {
-			msg = ed.PromptLabel();
-			if (!msg.empty())
-				msg += ": ";
-			msg += ed.PromptText();
-		} else {
-			msg = ed.Status();
-		}
+			std::string label = ed.PromptLabel();
+			std::string ptext = ed.PromptText();
+			auto kind         = ed.CurrentPromptKind();
+			if (kind == Editor::PromptKind::OpenFile || kind == Editor::PromptKind::SaveAs ||
+			    kind == Editor::PromptKind::Chdir) {
+				const char *home_c = std::getenv("HOME");
+				if (home_c && *home_c) {
+					std::string home(home_c);
+					if (ptext.rfind(home, 0) == 0) {
+						std::string rest = ptext.substr(home.size());
+						if (rest.empty())
+							ptext = "~";
+						else if (!rest.empty() && (rest[0] == '/' || rest[0] == '\\'))
+							ptext = std::string("~") + rest;
+					}
+				}
+			}
 
-		// Measurements
-		ImVec2 left_sz  = ImGui::CalcTextSize(left.c_str());
-		ImVec2 right_sz = ImGui::CalcTextSize(right.c_str());
-		float pad       = 6.f;
-		float left_x    = p0.x + pad;
-		float right_x   = p1.x - pad - right_sz.x;
-		if (right_x < left_x + left_sz.x + pad) {
-			// Not enough room; clip left to fit
-			float max_left = std::max(0.0f, right_x - left_x - pad);
-			if (max_left < left_sz.x && max_left > 10.0f) {
-				// Render a clipped left using a child region
+			float pad     = 6.f;
+			float left_x  = p0.x + pad;
+			float right_x = p1.x - pad;
+			float max_px  = std::max(0.0f, right_x - left_x);
+
+			std::string prefix;
+			if (kind == Editor::PromptKind::Command) {
+				prefix = ": ";
+			} else if (!label.empty()) {
+				prefix = label + ": ";
+			}
+
+			// Compose showing right-end of filename portion when too long for space
+			std::string final_msg;
+			ImVec2 prefix_sz = ImGui::CalcTextSize(prefix.c_str());
+			float avail_px   = std::max(0.0f, max_px - prefix_sz.x);
+			if ((kind == Editor::PromptKind::OpenFile || kind == Editor::PromptKind::SaveAs || kind ==
+			     Editor::PromptKind::Chdir) && avail_px > 0.0f) {
+				// Trim from left until it fits by pixel width
+				std::string tail = ptext;
+				ImVec2 tail_sz   = ImGui::CalcTextSize(tail.c_str());
+				if (tail_sz.x > avail_px) {
+					// Remove leading chars until it fits
+					// Use a simple loop; text lengths are small here
+					size_t start = 0;
+					// To avoid O(n^2) worst-case, remove chunks
+					while (start < tail.size()) {
+						// Estimate how many chars to skip based on ratio
+						float ratio = tail_sz.x / avail_px;
+						size_t skip = ratio > 1.5f
+							              ? std::min(tail.size() - start,
+								              (size_t) std::max<size_t>(
+									              1, (size_t) (tail.size() / 4)))
+							              : 1;
+						start += skip;
+						std::string candidate = tail.substr(start);
+						ImVec2 cand_sz        = ImGui::CalcTextSize(candidate.c_str());
+						if (cand_sz.x <= avail_px) {
+							tail    = candidate;
+							tail_sz = cand_sz;
+							break;
+						}
+					}
+					if (ImGui::CalcTextSize(tail.c_str()).x > avail_px && !tail.empty()) {
+						// As a last resort, ensure fit by chopping exactly
+						// binary reduce
+						size_t lo = 0, hi = tail.size();
+						while (lo < hi) {
+							size_t mid       = (lo + hi) / 2;
+							std::string cand = tail.substr(mid);
+							if (ImGui::CalcTextSize(cand.c_str()).x <= avail_px)
+								hi = mid;
+							else
+								lo = mid + 1;
+						}
+						tail = tail.substr(lo);
+					}
+				}
+				final_msg = prefix + tail;
+			} else {
+				final_msg = prefix + ptext;
+			}
+
+			ImVec2 msg_sz = ImGui::CalcTextSize(final_msg.c_str());
+			ImGui::PushClipRect(ImVec2(p0.x, p0.y), ImVec2(p1.x, p1.y), true);
+			ImGui::SetCursorScreenPos(ImVec2(left_x, p0.y + (bar_h - msg_sz.y) * 0.5f));
+			ImGui::TextUnformatted(final_msg.c_str());
+			ImGui::PopClipRect();
+			// Advance cursor to after the bar to keep layout consistent
+			ImGui::Dummy(ImVec2(x1 - x0, bar_h));
+		} else {
+			// Build left text
+			std::string left;
+			left.reserve(256);
+			left += "kge"; // GUI app name
+			left += " ";
+			left += KTE_VERSION_STR;
+			std::string fname;
+			try {
+				fname = ed.DisplayNameFor(*buf);
+			} catch (...) {
+				fname = buf->Filename();
+				try {
+					fname = std::filesystem::path(fname).filename().string();
+				} catch (...) {}
+			}
+			left += "  ";
+			// Insert buffer position prefix "[x/N] " before filename
+			{
+				std::size_t total = ed.BufferCount();
+				if (total > 0) {
+					std::size_t idx1 = ed.CurrentBufferIndex() + 1; // 1-based for display
+					left += "[";
+					left += std::to_string(static_cast<unsigned long long>(idx1));
+					left += "/";
+					left += std::to_string(static_cast<unsigned long long>(total));
+					left += "] ";
+				}
+			}
+			left += fname;
+			if (buf->Dirty())
+				left += " *";
+			// Append total line count as "<n>L"
+			{
+				unsigned long lcount = static_cast<unsigned long>(buf->Rows().size());
+				left += " ";
+				left += std::to_string(lcount);
+				left += "L";
+			}
+
+			// Build right text (cursor/mark)
+			int row1       = static_cast<int>(buf->Cury()) + 1;
+			int col1       = static_cast<int>(buf->Curx()) + 1;
+			bool have_mark = buf->MarkSet();
+			int mrow1      = have_mark ? static_cast<int>(buf->MarkCury()) + 1 : 0;
+			int mcol1      = have_mark ? static_cast<int>(buf->MarkCurx()) + 1 : 0;
+			char rbuf[128];
+			if (have_mark)
+				std::snprintf(rbuf, sizeof(rbuf), "%d,%d | M: %d,%d", row1, col1, mrow1, mcol1);
+			else
+				std::snprintf(rbuf, sizeof(rbuf), "%d,%d | M: not set", row1, col1);
+			std::string right = rbuf;
+
+			// Middle message: if a prompt is active, show "Label: text"; otherwise show status
+			std::string msg;
+			if (ed.PromptActive()) {
+				msg = ed.PromptLabel();
+				if (!msg.empty())
+					msg += ": ";
+				msg += ed.PromptText();
+			} else {
+				msg = ed.Status();
+			}
+
+			// Measurements
+			ImVec2 left_sz  = ImGui::CalcTextSize(left.c_str());
+			ImVec2 right_sz = ImGui::CalcTextSize(right.c_str());
+			float pad       = 6.f;
+			float left_x    = p0.x + pad;
+			float right_x   = p1.x - pad - right_sz.x;
+			if (right_x < left_x + left_sz.x + pad) {
+				// Not enough room; clip left to fit
+				float max_left = std::max(0.0f, right_x - left_x - pad);
+				if (max_left < left_sz.x && max_left > 10.0f) {
+					// Render a clipped left using a child region
+					ImGui::SetCursorScreenPos(ImVec2(left_x, p0.y + (bar_h - left_sz.y) * 0.5f));
+					ImGui::PushClipRect(ImVec2(left_x, p0.y), ImVec2(right_x - pad, p1.y), true);
+					ImGui::TextUnformatted(left.c_str());
+					ImGui::PopClipRect();
+				}
+			} else {
+				// Draw left normally
 				ImGui::SetCursorScreenPos(ImVec2(left_x, p0.y + (bar_h - left_sz.y) * 0.5f));
-				ImGui::PushClipRect(ImVec2(left_x, p0.y), ImVec2(right_x - pad, p1.y), true);
 				ImGui::TextUnformatted(left.c_str());
-				ImGui::PopClipRect();
 			}
-		} else {
-			// Draw left normally
-			ImGui::SetCursorScreenPos(ImVec2(left_x, p0.y + (bar_h - left_sz.y) * 0.5f));
-			ImGui::TextUnformatted(left.c_str());
-		}
 
-		// Draw right
-		ImGui::SetCursorScreenPos(ImVec2(std::max(right_x, left_x), p0.y + (bar_h - right_sz.y) * 0.5f));
-		ImGui::TextUnformatted(right.c_str());
+			// Draw right
+			ImGui::SetCursorScreenPos(ImVec2(std::max(right_x, left_x),
+			                                 p0.y + (bar_h - right_sz.y) * 0.5f));
+			ImGui::TextUnformatted(right.c_str());
 
-		// Draw middle message centered in remaining space
-		if (!msg.empty()) {
-			float mid_left  = left_x + left_sz.x + pad;
-			float mid_right = std::max(right_x - pad, mid_left);
-			float mid_w     = std::max(0.0f, mid_right - mid_left);
-			if (mid_w > 1.0f) {
-				ImVec2 msg_sz = ImGui::CalcTextSize(msg.c_str());
-				float msg_x   = mid_left + std::max(0.0f, (mid_w - msg_sz.x) * 0.5f);
-				// Clip to middle region
-				ImGui::PushClipRect(ImVec2(mid_left, p0.y), ImVec2(mid_right, p1.y), true);
-				ImGui::SetCursorScreenPos(ImVec2(msg_x, p0.y + (bar_h - msg_sz.y) * 0.5f));
-				ImGui::TextUnformatted(msg.c_str());
-				ImGui::PopClipRect();
+			// Draw middle message centered in remaining space
+			if (!msg.empty()) {
+				float mid_left  = left_x + left_sz.x + pad;
+				float mid_right = std::max(right_x - pad, mid_left);
+				float mid_w     = std::max(0.0f, mid_right - mid_left);
+				if (mid_w > 1.0f) {
+					ImVec2 msg_sz = ImGui::CalcTextSize(msg.c_str());
+					float msg_x   = mid_left + std::max(0.0f, (mid_w - msg_sz.x) * 0.5f);
+					// Clip to middle region
+					ImGui::PushClipRect(ImVec2(mid_left, p0.y), ImVec2(mid_right, p1.y), true);
+					ImGui::SetCursorScreenPos(ImVec2(msg_x, p0.y + (bar_h - msg_sz.y) * 0.5f));
+					ImGui::TextUnformatted(msg.c_str());
+					ImGui::PopClipRect();
+				}
 			}
+			// Advance cursor to after the bar to keep layout consistent
+			ImGui::Dummy(ImVec2(x1 - x0, bar_h));
 		}
-  // Advance cursor to after the bar to keep layout consistent
-  ImGui::Dummy(ImVec2(x1 - x0, bar_h));
-  }
 	}
 
 	ImGui::End();
@@ -703,4 +767,4 @@ GUIRenderer::Draw(Editor &ed)
 			ed.SetFilePickerVisible(false);
 		}
 	}
-}
+}

GUITheme.h

@@ -1,127 +1,415 @@
-// GUITheme.h - ImGui theme configuration for kte GUI
-// Provides a Nord-inspired color palette and style settings.
-
+// GUITheme.h — ImGui theming helpers and background mode
 #pragma once
 
 #include <imgui.h>
+#include <vector>
+#include <memory>
+#include <string>
+#include <cstddef>
+#include <algorithm>
+#include <cctype>
+
+#include "themes/ThemeHelpers.h"
 
 namespace kte {
-// Convert RGB hex (0xRRGGBB) to ImVec4 with optional alpha
-static inline ImVec4
-RGBA(unsigned int rgb, float a = 1.0f)
+// Background mode selection for light/dark palettes
+enum class BackgroundMode { Light, Dark };
+
+// Global background mode; default to Dark to match prior defaults
+static inline auto gBackgroundMode = BackgroundMode::Dark;
+
+// Basic theme identifier (kept minimal; some ids are aliases)
+enum class ThemeId {
+	EInk = 0,
+	GruvboxDarkMedium = 1,
+	GruvboxLightMedium = 1, // alias to unified gruvbox index
+	Nord = 2,
+	Plan9 = 3,
+	Solarized = 4,
+};
+
+// Current theme tracking
+static inline auto gCurrentTheme             = ThemeId::Nord;
+static inline std::size_t gCurrentThemeIndex = 0;
+
+// Forward declarations for helpers used below
+static size_t ThemeIndexFromId(ThemeId id);
+
+static ThemeId ThemeIdFromIndex(size_t idx);
+
+// Helpers to set/query background mode
+static void
+SetBackgroundMode(const BackgroundMode m)
 {
-	float r = ((rgb >> 16) & 0xFF) / 255.0f;
-	float g = ((rgb >> 8) & 0xFF) / 255.0f;
-	float b = ((rgb) & 0xFF) / 255.0f;
-	return ImVec4(r, g, b, a);
+	gBackgroundMode = m;
 }
 
 
-// Apply a Nord-inspired theme to the current ImGui style.
-// Safe to call after ImGui::CreateContext().
-static inline void
-ApplyNordImGuiTheme()
+static BackgroundMode
+GetBackgroundMode()
 {
-	// Nord palette
-	const ImVec4 nord0  = RGBA(0x2E3440); // darkest bg
-	const ImVec4 nord1  = RGBA(0x3B4252);
-	const ImVec4 nord2  = RGBA(0x434C5E);
-	const ImVec4 nord3  = RGBA(0x4C566A);
-	const ImVec4 nord4  = RGBA(0xD8DEE9);
-	const ImVec4 nord6  = RGBA(0xECEFF4); // lightest
-	const ImVec4 nord8  = RGBA(0x88C0D0); // cyan
-	const ImVec4 nord9  = RGBA(0x81A1C1); // blue
-	const ImVec4 nord10 = RGBA(0x5E81AC); // blue dark
-	const ImVec4 nord12 = RGBA(0xD08770); // orange
-	const ImVec4 nord13 = RGBA(0xEBCB8B); // yellow
+	return gBackgroundMode;
+}
 
-	ImGuiStyle &style = ImGui::GetStyle();
 
-	// Base style tweaks to suit Nord aesthetics
-	style.WindowPadding    = ImVec2(8.0f, 8.0f);
-	style.FramePadding     = ImVec2(6.0f, 4.0f);
-	style.CellPadding      = ImVec2(6.0f, 4.0f);
-	style.ItemSpacing      = ImVec2(6.0f, 6.0f);
-	style.ItemInnerSpacing = ImVec2(6.0f, 4.0f);
-	style.ScrollbarSize    = 14.0f;
-	style.GrabMinSize      = 10.0f;
-	style.WindowRounding   = 4.0f;
-	style.FrameRounding    = 3.0f;
-	style.PopupRounding    = 4.0f;
-	style.GrabRounding     = 3.0f;
-	style.TabRounding      = 4.0f;
-	style.WindowBorderSize = 1.0f;
-	style.FrameBorderSize  = 1.0f;
+static inline const char *
+BackgroundModeName()
+{
+	return gBackgroundMode == BackgroundMode::Light ? "light" : "dark";
+}
 
-	ImVec4 *colors = style.Colors;
 
-	colors[ImGuiCol_Text]         = nord4; // primary text
-	colors[ImGuiCol_TextDisabled] = ImVec4(nord4.x, nord4.y, nord4.z, 0.55f);
-	colors[ImGuiCol_WindowBg]     = nord10;
-	colors[ImGuiCol_ChildBg]      = nord0;
-	colors[ImGuiCol_PopupBg]      = RGBA(0x2E3440, 0.98f);
-	colors[ImGuiCol_Border]       = nord1;
-	colors[ImGuiCol_BorderShadow] = RGBA(0x000000, 0.0f);
+// Include individual theme implementations split under ./themes
+#include "themes/Nord.h"
+#include "themes/Plan9.h"
+#include "themes/Solarized.h"
+#include "themes/Gruvbox.h"
+#include "themes/EInk.h"
 
-	colors[ImGuiCol_FrameBg]        = nord2;
-	colors[ImGuiCol_FrameBgHovered] = nord3;
-	colors[ImGuiCol_FrameBgActive]  = nord10;
 
-	colors[ImGuiCol_TitleBg]          = nord1;
-	colors[ImGuiCol_TitleBgActive]    = nord3;
-	colors[ImGuiCol_TitleBgCollapsed] = nord1;
+// Theme abstraction and registry (generalized theme system)
+class Theme {
+public:
+	virtual ~Theme() = default;
 
-	colors[ImGuiCol_MenuBarBg]            = nord1;
-	colors[ImGuiCol_ScrollbarBg]          = nord0;
-	colors[ImGuiCol_ScrollbarGrab]        = nord3;
-	colors[ImGuiCol_ScrollbarGrabHovered] = nord10;
-	colors[ImGuiCol_ScrollbarGrabActive]  = nord9;
+	[[nodiscard]] virtual const char *Name() const = 0; // canonical name (e.g., "nord", "gruvbox-dark")
+	virtual void Apply() const = 0; // apply to current ImGui style
+	virtual ThemeId Id() = 0; // theme identifier
+};
 
-	colors[ImGuiCol_CheckMark]        = nord8;
-	colors[ImGuiCol_SliderGrab]       = nord8;
-	colors[ImGuiCol_SliderGrabActive] = nord9;
+namespace detail {
+struct NordTheme final : Theme {
+	[[nodiscard]] const char *Name() const override
+	{
+		return "nord";
+	}
 
-	colors[ImGuiCol_Button]        = nord3;
-	colors[ImGuiCol_ButtonHovered] = nord10;
-	colors[ImGuiCol_ButtonActive]  = nord9;
 
-	colors[ImGuiCol_Header]        = nord3;
-	colors[ImGuiCol_HeaderHovered] = nord10;
-	colors[ImGuiCol_HeaderActive]  = nord10;
+	void Apply() const override
+	{
+		ApplyNordImGuiTheme();
+	}
 
-	colors[ImGuiCol_Separator]        = nord2;
-	colors[ImGuiCol_SeparatorHovered] = nord10;
-	colors[ImGuiCol_SeparatorActive]  = nord9;
 
-	colors[ImGuiCol_ResizeGrip]        = ImVec4(nord6.x, nord6.y, nord6.z, 0.12f);
-	colors[ImGuiCol_ResizeGripHovered] = ImVec4(nord8.x, nord8.y, nord8.z, 0.67f);
-	colors[ImGuiCol_ResizeGripActive]  = nord9;
+	ThemeId Id() override
+	{
+		return ThemeId::Nord;
+	}
+};
 
-	colors[ImGuiCol_Tab]                = nord2;
-	colors[ImGuiCol_TabHovered]         = nord10;
-	colors[ImGuiCol_TabActive]          = nord3;
-	colors[ImGuiCol_TabUnfocused]       = nord2;
-	colors[ImGuiCol_TabUnfocusedActive] = nord3;
+struct GruvboxTheme final : Theme {
+	[[nodiscard]] const char *Name() const override
+	{
+		return "gruvbox";
+	}
 
-	// Docking colors are available only when docking branch is enabled; omit for compatibility
 
-	colors[ImGuiCol_TableHeaderBg]     = nord2;
-	colors[ImGuiCol_TableBorderStrong] = nord1;
-	colors[ImGuiCol_TableBorderLight]  = ImVec4(nord1.x, nord1.y, nord1.z, 0.6f);
-	colors[ImGuiCol_TableRowBg]        = ImVec4(nord1.x, nord1.y, nord1.z, 0.2f);
-	colors[ImGuiCol_TableRowBgAlt]     = ImVec4(nord1.x, nord1.y, nord1.z, 0.35f);
+	void Apply() const override
+	{
+		if (gBackgroundMode == BackgroundMode::Light)
+			ApplyGruvboxLightMediumTheme();
+		else
+			ApplyGruvboxDarkMediumTheme();
+	}
 
-	colors[ImGuiCol_TextSelectedBg]        = ImVec4(nord8.x, nord8.y, nord8.z, 0.35f);
-	colors[ImGuiCol_DragDropTarget]        = nord13;
-	colors[ImGuiCol_NavHighlight]          = nord9;
-	colors[ImGuiCol_NavWindowingHighlight] = ImVec4(nord6.x, nord6.y, nord6.z, 0.7f);
-	colors[ImGuiCol_NavWindowingDimBg]     = ImVec4(nord0.x, nord0.y, nord0.z, 0.6f);
-	colors[ImGuiCol_ModalWindowDimBg]      = ImVec4(nord0.x, nord0.y, nord0.z, 0.6f);
 
-	// Plots
-	colors[ImGuiCol_PlotLines]            = nord8;
-	colors[ImGuiCol_PlotLinesHovered]     = nord9;
-	colors[ImGuiCol_PlotHistogram]        = nord13;
-	colors[ImGuiCol_PlotHistogramHovered] = nord12;
+	ThemeId Id() override
+	{
+		// Legacy maps to dark; unified under base id GruvboxDarkMedium
+		return ThemeId::GruvboxDarkMedium;
+	}
+};
+
+struct EInkTheme final : Theme {
+	[[nodiscard]] const char *Name() const override
+	{
+		return "eink";
+	}
+
+
+	void Apply() const override
+	{
+		if (gBackgroundMode == BackgroundMode::Dark)
+			ApplyEInkDarkImGuiTheme();
+		else
+			ApplyEInkImGuiTheme();
+	}
+
+
+	ThemeId Id() override
+	{
+		return ThemeId::EInk;
+	}
+};
+
+struct SolarizedTheme final : Theme {
+	[[nodiscard]] const char *Name() const override
+	{
+		return "solarized";
+	}
+
+
+	void Apply() const override
+	{
+		if (gBackgroundMode == BackgroundMode::Light)
+			ApplySolarizedLightTheme();
+		else
+			ApplySolarizedDarkTheme();
+	}
+
+
+	ThemeId Id() override
+	{
+		return ThemeId::Solarized;
+	}
+};
+
+struct Plan9Theme final : Theme {
+	[[nodiscard]] const char *Name() const override
+	{
+		return "plan9";
+	}
+
+
+	void Apply() const override
+	{
+		ApplyPlan9Theme();
+	}
+
+
+	ThemeId Id() override
+	{
+		return ThemeId::Plan9;
+	}
+};
+} // namespace detail
+
+static const std::vector<std::unique_ptr<Theme> > &
+ThemeRegistry()
+{
+	static std::vector<std::unique_ptr<Theme> > reg;
+	if (reg.empty()) {
+		// Alphabetical by canonical name: eink, gruvbox, nord, plan9, solarized
+		reg.emplace_back(std::make_unique<detail::EInkTheme>());
+		reg.emplace_back(std::make_unique<detail::GruvboxTheme>());
+		reg.emplace_back(std::make_unique<detail::NordTheme>());
+		reg.emplace_back(std::make_unique<detail::Plan9Theme>());
+		reg.emplace_back(std::make_unique<detail::SolarizedTheme>());
+	}
+	return reg;
+}
+
+
+// Canonical theme name for a given ThemeId (via registry order)
+[[maybe_unused]] static const char *
+ThemeName(const ThemeId id)
+{
+	const auto &reg  = ThemeRegistry();
+	const size_t idx = ThemeIndexFromId(id);
+	if (idx < reg.size())
+		return reg[idx]->Name();
+	return "unknown";
+}
+
+
+// Helper to apply a theme by id and update current theme
+static void
+ApplyTheme(const ThemeId id)
+{
+	const auto &reg  = ThemeRegistry();
+	const size_t idx = ThemeIndexFromId(id);
+	if (idx < reg.size()) {
+		reg[idx]->Apply();
+		gCurrentTheme      = id;
+		gCurrentThemeIndex = idx;
+	}
+}
+
+
+[[maybe_unused]] static ThemeId
+CurrentTheme()
+{
+	return gCurrentTheme;
+}
+
+
+// Cycle helpers
+[[maybe_unused]] static ThemeId
+NextTheme()
+{
+	const auto &reg = ThemeRegistry();
+	if (reg.empty()) {
+		return gCurrentTheme;
+	}
+
+	const size_t nxt = (gCurrentThemeIndex + 1) % reg.size();
+	ApplyTheme(ThemeIdFromIndex(nxt));
+	return gCurrentTheme;
+}
+
+
+[[maybe_unused]] static ThemeId
+PrevTheme()
+{
+	const auto &reg = ThemeRegistry();
+	if (reg.empty()) {
+		return gCurrentTheme;
+	}
+
+	const size_t prv = (gCurrentThemeIndex + reg.size() - 1) % reg.size();
+	ApplyTheme(ThemeIdFromIndex(prv));
+	return gCurrentTheme;
+}
+
+
+// Name-based API
+[[maybe_unused]] static const Theme *
+GetThemeByName(const std::string &name)
+{
+	const auto &reg = ThemeRegistry();
+	for (const auto &t: reg) {
+		if (name == t->Name())
+			return t.get();
+	}
+
+	return nullptr;
+}
+
+
+[[maybe_unused]] static bool
+ApplyThemeByName(const std::string &name)
+{
+	// Handle aliases and background-specific names
+	std::string n = name;
+	// lowercase copy
+	std::transform(n.begin(), n.end(), n.begin(), [](unsigned char c) {
+		return static_cast<char>(std::tolower(c));
+	});
+
+	if (n == "gruvbox-dark") {
+		SetBackgroundMode(BackgroundMode::Dark);
+		n = "gruvbox";
+	} else if (n == "gruvbox-light") {
+		SetBackgroundMode(BackgroundMode::Light);
+		n = "gruvbox";
+	} else if (n == "solarized-dark") {
+		SetBackgroundMode(BackgroundMode::Dark);
+		n = "solarized";
+	} else if (n == "solarized-light") {
+		SetBackgroundMode(BackgroundMode::Light);
+		n = "solarized";
+	} else if (n == "eink-dark") {
+		SetBackgroundMode(BackgroundMode::Dark);
+		n = "eink";
+	} else if (n == "eink-light") {
+		SetBackgroundMode(BackgroundMode::Light);
+		n = "eink";
+	}
+
+	const auto &reg = ThemeRegistry();
+	for (size_t i = 0; i < reg.size(); ++i) {
+		if (n == reg[i]->Name()) {
+			reg[i]->Apply();
+			gCurrentThemeIndex = i;
+			gCurrentTheme      = ThemeIdFromIndex(i);
+			return true;
+		}
+	}
+
+	return false;
+}
+
+
+[[maybe_unused]] static const char *
+CurrentThemeName()
+{
+	const auto &reg = ThemeRegistry();
+	if (gCurrentThemeIndex < reg.size()) {
+		return reg[gCurrentThemeIndex]->Name();
+	}
+
+	return "unknown";
+}
+
+
+// Helpers to map between legacy ThemeId and registry index
+static size_t
+ThemeIndexFromId(const ThemeId id)
+{
+	switch (id) {
+	case ThemeId::EInk:
+		return 0;
+	case ThemeId::GruvboxDarkMedium:
+		return 1;
+	case ThemeId::Nord:
+		return 2;
+	case ThemeId::Plan9:
+		return 3;
+	case ThemeId::Solarized:
+		return 4;
+	}
+	return 0;
+}
+
+
+static ThemeId
+ThemeIdFromIndex(const size_t idx)
+{
+	switch (idx) {
+	default:
+	case 0:
+		return ThemeId::EInk;
+	case 1:
+		return ThemeId::GruvboxDarkMedium; // unified gruvbox
+	case 2:
+		return ThemeId::Nord;
+	case 3:
+		return ThemeId::Plan9;
+	case 4:
+		return ThemeId::Solarized;
+	}
+}
+
+
+// --- Syntax palette (v1): map TokenKind to ink color per current theme/background ---
+[[maybe_unused]] static ImVec4
+SyntaxInk(const TokenKind k)
+{
+	// Basic palettes for dark/light backgrounds; tuned for Nord-ish defaults
+	const bool dark = (GetBackgroundMode() == BackgroundMode::Dark);
+	// Base text
+	const ImVec4 def = dark ? RGBA(0xD8DEE9) : RGBA(0x2E3440);
+	switch (k) {
+	case TokenKind::Keyword:
+		return dark ? RGBA(0x81A1C1) : RGBA(0x5E81AC);
+	case TokenKind::Type:
+		return dark ? RGBA(0x8FBCBB) : RGBA(0x4C566A);
+	case TokenKind::String:
+		return dark ? RGBA(0xA3BE8C) : RGBA(0x6C8E5E);
+	case TokenKind::Char:
+		return dark ? RGBA(0xA3BE8C) : RGBA(0x6C8E5E);
+	case TokenKind::Comment:
+		return dark ? RGBA(0x616E88) : RGBA(0x7A869A);
+	case TokenKind::Number:
+		return dark ? RGBA(0xEBCB8B) : RGBA(0xB58900);
+	case TokenKind::Preproc:
+		return dark ? RGBA(0xD08770) : RGBA(0xAF3A03);
+	case TokenKind::Constant:
+		return dark ? RGBA(0xB48EAD) : RGBA(0x7B4B7F);
+	case TokenKind::Function:
+		return dark ? RGBA(0x88C0D0) : RGBA(0x3465A4);
+	case TokenKind::Operator:
+		return dark ? RGBA(0xECEFF4) : RGBA(0x2E3440);
+	case TokenKind::Punctuation:
+		return dark ? RGBA(0xECEFF4) : RGBA(0x2E3440);
+	case TokenKind::Identifier:
+		return def;
+	case TokenKind::Whitespace:
+		return def;
+	case TokenKind::Error:
+		return dark ? RGBA(0xBF616A) : RGBA(0xCC0000);
+	case TokenKind::Default: default:
+		return def;
+	}
 }
 } // namespace kte

HelpText.cc

@@ -15,24 +15,26 @@ HelpText::Text()
 	return std::string(
 		"KTE - Kyle's Text Editor\n\n"
 		"About:\n"
-		"  kte is Kyle's Text Editor and is probably ill-suited to everyone else. It was\n"
-		"  inspired by Antirez' kilo text editor by way of someone's writeup of the\n"
-		"  process of writing a text editor from scratch. It has keybindings inspired by\n"
-		"  VDE (and the Wordstar family) and emacs; its spiritual parent is mg(1).\n"
+		"  kte is Kyle's Text Editor. It keeps a small, fast core and uses a\n"
+		"  WordStar/VDE-style command model with some emacs influences.\n"
 		"\n"
-		"Core keybindings:\n"
+		"K-commands (prefix C-k):\n"
 		"  C-k '        Toggle read-only\n"
-		"  C-k -        Unindent region\n"
-		"  C-k =        Indent region\n"
+		"  C-k -        Unindent region (mark required)\n"
+		"  C-k =        Indent region (mark required)\n"
+		"  C-k ;        Command prompt (:\\ )\n"
 		"  C-k C-d      Kill entire line\n"
 		"  C-k C-q      Quit now (no confirm)\n"
-		"  C-k a        Mark all and jump to end\n"
+		"  C-k C-x      Save and quit\n"
+		"  C-k a        Mark start of file, jump to end\n"
 		"  C-k b        Switch buffer\n"
 		"  C-k c        Close current buffer\n"
 		"  C-k d        Kill to end of line\n"
 		"  C-k e        Open file (prompt)\n"
+		"  C-k f        Flush kill ring\n"
 		"  C-k g        Jump to line\n"
 		"  C-k h        Show this help\n"
+		"  C-k j        Jump to mark\n"
 		"  C-k l        Reload buffer from disk\n"
 		"  C-k n        Previous buffer\n"
 		"  C-k o        Change working directory (prompt)\n"
@@ -44,12 +46,36 @@ HelpText::Text()
 		"  C-k v        Toggle visual file picker (GUI)\n"
 		"  C-k w        Show working directory\n"
 		"  C-k x        Save and quit\n"
+		"  C-k y        Yank\n"
 		"\n"
 		"ESC/Alt commands:\n"
+		"  ESC <        Go to beginning of file\n"
+		"  ESC >        Go to end of file\n"
+		"  ESC m        Toggle mark\n"
+		"  ESC w        Copy region to kill ring (Alt-w)\n"
+		"  ESC b        Previous word\n"
+		"  ESC f        Next word\n"
+		"  ESC d        Delete next word (Alt-d)\n"
+		"  ESC BACKSPACE Delete previous word (Alt-Backspace)\n"
 		"  ESC q        Reflow paragraph\n"
-		"  ESC BACKSPACE Delete previous word\n"
-		"  ESC d        Delete next word\n"
-		"  Alt-w        Copy region to kill ring\n\n"
-		"Buffers:\n  +HELP+ is read-only. Press C-k ' to toggle if you need to edit; C-k h restores it.\n"
+		"\n"
+		"Control keys:\n"
+		"  C-a C-e      Line start / end\n"
+		"  C-b C-f      Move left / right\n"
+		"  C-n C-p      Move down / up\n"
+		"  C-d          Delete char\n"
+		"  C-w / C-y    Kill region / Yank\n"
+		"  C-s          Incremental find\n"
+		"  C-r          Regex search\n"
+		"  C-t          Regex search & replace\n"
+		"  C-h          Search & replace\n"
+		"  C-l / C-g    Refresh / Cancel\n"
+		"  C-u [digits] Universal argument (repeat count)\n"
+		"\n"
+		"Buffers:\n  +HELP+ is read-only. Press C-k ' to toggle; C-k h restores it.\n"
+		"\n"
+		"GUI appearance (command prompt):\n"
+		"  : theme NAME         Set GUI theme (eink, gruvbox, nord, plan9, solarized)\n"
+		"  : background MODE    Set background: light | dark (affects eink, gruvbox, solarized)\n"
 	);
 }

HelpText.h

@@ -8,10 +8,10 @@
 
 class HelpText {
 public:
-    // Returns the embedded help text as a single string with newlines.
-    // Project maintainers can customize the returned string below
-    // (in HelpText.cc) without touching the help command logic.
-    static std::string Text();
+	// Returns the embedded help text as a single string with newlines.
+	// Project maintainers can customize the returned string below
+	// (in HelpText.cc) without touching the help command logic.
+	static std::string Text();
 };
 
 #endif // KTE_HELPTEXT_H

Highlight.h

@@ -0,0 +1,37 @@
+// Highlight.h - core syntax highlighting types for kte
+#pragma once
+
+#include <cstdint>
+#include <vector>
+
+namespace kte {
+// Token kinds shared between renderers and highlighters
+enum class TokenKind {
+	Default,
+	Keyword,
+	Type,
+	String,
+	Char,
+	Comment,
+	Number,
+	Preproc,
+	Constant,
+	Function,
+	Operator,
+	Punctuation,
+	Identifier,
+	Whitespace,
+	Error
+};
+
+struct HighlightSpan {
+	int col_start{0}; // inclusive, 0-based columns in buffer indices
+	int col_end{0}; // exclusive
+	TokenKind kind{TokenKind::Default};
+};
+
+struct LineHighlight {
+	std::vector<HighlightSpan> spans;
+	std::uint64_t version{0}; // buffer version used for this line
+};
+} // namespace kte

KKeymap.cc

@@ -33,10 +33,10 @@ KLookupKCommand(const int ascii_key, const bool ctrl, CommandId &out) -> bool
 		out = CommandId::Redo; // C-k r (redo)
 		return true;
 	}
-    if (ascii_key == '\'') {
-        out = CommandId::ToggleReadOnly; // C-k ' (toggle read-only)
-        return true;
-    }
+	if (ascii_key == '\'') {
+		out = CommandId::ToggleReadOnly; // C-k ' (toggle read-only)
+		return true;
+	}
 
 	switch (k_lower) {
 	case 'a':
@@ -108,6 +108,9 @@ KLookupKCommand(const int ascii_key, const bool ctrl, CommandId &out) -> bool
 	case '=':
 		out = CommandId::IndentRegion;
 		return true;
+	case ';':
+		out = CommandId::CommandPromptStart; // C-k ; : generic command prompt
+		return true;
 	default:
 		break;
 	}
@@ -121,7 +124,7 @@ auto
 KLookupCtrlCommand(const int ascii_key, CommandId &out) -> bool
 {
 	const int k = KLowerAscii(ascii_key);
- switch (k) {
+	switch (k) {
 	case 'w':
 		out = CommandId::KillRegion; // C-w
 		return true;
@@ -152,12 +155,12 @@ KLookupCtrlCommand(const int ascii_key, CommandId &out) -> bool
 	case 's':
 		out = CommandId::FindStart;
 		return true;
- case 'r':
-        out = CommandId::RegexFindStart; // C-r regex search
-        return true;
-    case 't':
-        out = CommandId::RegexpReplace; // C-t regex search & replace
-        return true;
+	case 'r':
+		out = CommandId::RegexFindStart; // C-r regex search
+		return true;
+	case 't':
+		out = CommandId::RegexpReplace; // C-t regex search & replace
+		return true;
 	case 'h':
 		out = CommandId::SearchReplace; // C-h: search & replace
 		return true;

ROADMAP.md

@@ -2,9 +2,11 @@ ROADMAP / TODO:
 
 - [x] Search + Replace
 - [x] Regex search + replace
-- [ ] The undo system should actually work
 - [x] Able to mark buffers as read-only
 - [x] Built-in help text
 - [x] Shorten paths in the homedir with ~
 - [x] When the filename is longer than the message window, scoot left to
   keep it in view
+- [x] Syntax highlighting
+- [ ] The undo system should actually work
+- [ ] LSP integration

TerminalRenderer.cc

@@ -9,6 +9,7 @@
 #include "TerminalRenderer.h"
 #include "Buffer.h"
 #include "Editor.h"
+#include "Highlight.h"
 
 // Version string expected to be provided by build system as KTE_VERSION_STR
 #ifndef KTE_VERSION_STR
@@ -41,140 +42,230 @@ TerminalRenderer::Draw(Editor &ed)
 		std::size_t coloffs = buf->Coloffs();
 
 		const int tabw = 8;
-  for (int r = 0; r < content_rows; ++r) {
-            move(r, 0);
-            std::size_t li = rowoffs + static_cast<std::size_t>(r);
-            std::size_t render_col = 0;
-            std::size_t src_i = 0;
-            // Compute matches for this line if search highlighting is active
-            bool search_mode = ed.SearchActive() && !ed.SearchQuery().empty();
-            std::vector<std::pair<std::size_t, std::size_t>> ranges; // [start, end)
-            if (search_mode && li < lines.size()) {
-                std::string sline = static_cast<std::string>(lines[li]);
-                // If regex search prompt is active (RegexSearch or RegexReplaceFind), use regex to compute highlight ranges
-                if (ed.PromptActive() && (ed.CurrentPromptKind() == Editor::PromptKind::RegexSearch || ed.CurrentPromptKind() == Editor::PromptKind::RegexReplaceFind)) {
-                    try {
-                        std::regex rx(ed.SearchQuery());
-                        for (auto it = std::sregex_iterator(sline.begin(), sline.end(), rx);
-                             it != std::sregex_iterator(); ++it) {
-                            const auto &m = *it;
-                            std::size_t sx = static_cast<std::size_t>(m.position());
-                            std::size_t ex = sx + static_cast<std::size_t>(m.length());
-                            ranges.emplace_back(sx, ex);
-                        }
-                    } catch (const std::regex_error &) {
-                        // ignore invalid patterns here; status shows error
-                    }
-                } else {
-                    const std::string &q = ed.SearchQuery();
-                    std::size_t pos      = 0;
-                    while (!q.empty() && (pos = sline.find(q, pos)) != std::string::npos) {
-                        ranges.emplace_back(pos, pos + q.size());
-                        pos += q.size();
-                    }
-                }
-            }
-            auto is_src_in_hl = [&](std::size_t si) -> bool {
-                if (ranges.empty()) return false;
-                // ranges are non-overlapping and ordered by construction
-                // linear scan is fine for now
-                for (const auto &rg : ranges) {
-                    if (si < rg.first) break;
-                    if (si >= rg.first && si < rg.second) return true;
-                }
-                return false;
-            };
-            // Track current-match to optionally emphasize
-            const bool has_current = ed.SearchActive() && ed.SearchMatchLen() > 0;
-            const std::size_t cur_mx = has_current ? ed.SearchMatchX() : 0;
-            const std::size_t cur_my = has_current ? ed.SearchMatchY() : 0;
-            const std::size_t cur_mend = has_current ? (ed.SearchMatchX() + ed.SearchMatchLen()) : 0;
-            bool hl_on = false;
-            bool cur_on = false;
-            int written = 0;
-            if (li < lines.size()) {
-                std::string line = static_cast<std::string>(lines[li]);
-                src_i                   = 0;
-                render_col              = 0;
-                while (written < cols) {
-                    char ch       = ' ';
-                    bool from_src = false;
-                    if (src_i < line.size()) {
-                        unsigned char c = static_cast<unsigned char>(line[src_i]);
-                        if (c == '\t') {
-                            std::size_t next_tab = tabw - (render_col % tabw);
-                            if (render_col + next_tab <= coloffs) {
-                                render_col += next_tab;
-                                ++src_i;
-                                continue;
-                            }
-                            // Emit spaces for tab
-                            if (render_col < coloffs) {
-                                // skip to coloffs
-                                std::size_t to_skip = std::min<std::size_t>(
-                                    next_tab, coloffs - render_col);
-                                render_col += to_skip;
-                                next_tab -= to_skip;
-                            }
-                            // Now render visible spaces
-                            while (next_tab > 0 && written < cols) {
-                                bool in_hl = search_mode && is_src_in_hl(src_i);
-                                bool in_cur = has_current && li == cur_my && src_i >= cur_mx && src_i < cur_mend;
-                                // Toggle highlight attributes
-                                int attr = 0;
-                                if (in_hl) attr |= A_STANDOUT;
-                                if (in_cur) attr |= A_BOLD;
-                                if ((attr & A_STANDOUT) && !hl_on) { attron(A_STANDOUT); hl_on = true; }
-                                if (!(attr & A_STANDOUT) && hl_on) { attroff(A_STANDOUT); hl_on = false; }
-                                if ((attr & A_BOLD) && !cur_on) { attron(A_BOLD); cur_on = true; }
-                                if (!(attr & A_BOLD) && cur_on) { attroff(A_BOLD); cur_on = false; }
-                                addch(' ');
-                                ++written;
-                                ++render_col;
-                                --next_tab;
-                            }
-                            ++src_i;
-                            continue;
-                        } else {
-                            // normal char
-                            if (render_col < coloffs) {
-                                ++render_col;
-                                ++src_i;
-                                continue;
-                            }
-                            ch       = static_cast<char>(c);
-                            from_src = true;
-                        }
-                    } else {
-                        // beyond EOL, fill spaces
-                        ch       = ' ';
-                        from_src = false;
-                    }
-                    bool in_hl = search_mode && from_src && is_src_in_hl(src_i);
-                    bool in_cur = has_current && li == cur_my && from_src && src_i >= cur_mx && src_i < cur_mend;
-                    if (in_hl && !hl_on) { attron(A_STANDOUT); hl_on = true; }
-                    if (!in_hl && hl_on) { attroff(A_STANDOUT); hl_on = false; }
-                    if (in_cur && !cur_on) { attron(A_BOLD); cur_on = true; }
-                    if (!in_cur && cur_on) { attroff(A_BOLD); cur_on = false; }
-                    addch(static_cast<unsigned char>(ch));
-                    ++written;
-                    ++render_col;
-                    if (from_src)
-                        ++src_i;
-                    if (src_i >= line.size() && written >= cols)
-                        break;
-                }
-            }
-            if (hl_on) {
-                attroff(A_STANDOUT);
-                hl_on = false;
-            }
-            if (cur_on) {
-                attroff(A_BOLD);
-                cur_on = false;
-            }
-            clrtoeol();
-        }
+		// Phase 3: prefetch visible viewport highlights (current terminal area)
+		if (buf->SyntaxEnabled() && buf->Highlighter() && buf->Highlighter()->HasHighlighter()) {
+			int fr = static_cast<int>(rowoffs);
+			int rc = std::max(0, content_rows);
+			buf->Highlighter()->PrefetchViewport(*buf, fr, rc, buf->Version());
+		}
+
+		for (int r = 0; r < content_rows; ++r) {
+			move(r, 0);
+			std::size_t li         = rowoffs + static_cast<std::size_t>(r);
+			std::size_t render_col = 0;
+			std::size_t src_i      = 0;
+			// Compute matches for this line if search highlighting is active
+			bool search_mode = ed.SearchActive() && !ed.SearchQuery().empty();
+			std::vector<std::pair<std::size_t, std::size_t> > ranges; // [start, end)
+			if (search_mode && li < lines.size()) {
+				std::string sline = static_cast<std::string>(lines[li]);
+				// If regex search prompt is active (RegexSearch or RegexReplaceFind), use regex to compute highlight ranges
+				if (ed.PromptActive() && (
+					    ed.CurrentPromptKind() == Editor::PromptKind::RegexSearch || ed.
+					    CurrentPromptKind() == Editor::PromptKind::RegexReplaceFind)) {
+					try {
+						std::regex rx(ed.SearchQuery());
+						for (auto it = std::sregex_iterator(sline.begin(), sline.end(), rx);
+						     it != std::sregex_iterator(); ++it) {
+							const auto &m  = *it;
+							std::size_t sx = static_cast<std::size_t>(m.position());
+							std::size_t ex = sx + static_cast<std::size_t>(m.length());
+							ranges.emplace_back(sx, ex);
+						}
+					} catch (const std::regex_error &) {
+						// ignore invalid patterns here; status shows error
+					}
+				} else {
+					const std::string &q = ed.SearchQuery();
+					std::size_t pos      = 0;
+					while (!q.empty() && (pos = sline.find(q, pos)) != std::string::npos) {
+						ranges.emplace_back(pos, pos + q.size());
+						pos += q.size();
+					}
+				}
+			}
+			auto is_src_in_hl = [&](std::size_t si) -> bool {
+				if (ranges.empty())
+					return false;
+				// ranges are non-overlapping and ordered by construction
+				// linear scan is fine for now
+				for (const auto &rg: ranges) {
+					if (si < rg.first)
+						break;
+					if (si >= rg.first && si < rg.second)
+						return true;
+				}
+				return false;
+			};
+			// Track current-match to optionally emphasize
+			const bool has_current     = ed.SearchActive() && ed.SearchMatchLen() > 0;
+			const std::size_t cur_mx   = has_current ? ed.SearchMatchX() : 0;
+			const std::size_t cur_my   = has_current ? ed.SearchMatchY() : 0;
+			const std::size_t cur_mend = has_current ? (ed.SearchMatchX() + ed.SearchMatchLen()) : 0;
+			bool hl_on                 = false;
+			bool cur_on                = false;
+			int written                = 0;
+			if (li < lines.size()) {
+				std::string line = static_cast<std::string>(lines[li]);
+				src_i            = 0;
+				render_col       = 0;
+				// Syntax highlighting: fetch per-line spans
+				const kte::LineHighlight *lh_ptr = nullptr;
+				if (buf->SyntaxEnabled() && buf->Highlighter() && buf->Highlighter()->
+				    HasHighlighter()) {
+					lh_ptr = &buf->Highlighter()->GetLine(
+						*buf, static_cast<int>(li), buf->Version());
+				}
+				auto token_at = [&](std::size_t src_index) -> kte::TokenKind {
+					if (!lh_ptr)
+						return kte::TokenKind::Default;
+					for (const auto &sp: lh_ptr->spans) {
+						if (static_cast<int>(src_index) >= sp.col_start && static_cast<int>(
+							    src_index) < sp.col_end)
+							return sp.kind;
+					}
+					return kte::TokenKind::Default;
+				};
+				auto apply_token_attr = [&](kte::TokenKind k) {
+					// Map to simple attributes; search highlight uses A_STANDOUT which takes precedence below
+					attrset(A_NORMAL);
+					switch (k) {
+					case kte::TokenKind::Keyword:
+					case kte::TokenKind::Type:
+					case kte::TokenKind::Constant:
+					case kte::TokenKind::Function:
+						attron(A_BOLD);
+						break;
+					case kte::TokenKind::Comment:
+						attron(A_DIM);
+						break;
+					case kte::TokenKind::String:
+					case kte::TokenKind::Char:
+					case kte::TokenKind::Number:
+						// standout a bit using A_UNDERLINE if available
+						attron(A_UNDERLINE);
+						break;
+					default:
+						break;
+					}
+				};
+				while (written < cols) {
+					char ch       = ' ';
+					bool from_src = false;
+					if (src_i < line.size()) {
+						unsigned char c = static_cast<unsigned char>(line[src_i]);
+						if (c == '\t') {
+							std::size_t next_tab = tabw - (render_col % tabw);
+							if (render_col + next_tab <= coloffs) {
+								render_col += next_tab;
+								++src_i;
+								continue;
+							}
+							// Emit spaces for tab
+							if (render_col < coloffs) {
+								// skip to coloffs
+								std::size_t to_skip = std::min<std::size_t>(
+									next_tab, coloffs - render_col);
+								render_col += to_skip;
+								next_tab -= to_skip;
+							}
+							// Now render visible spaces
+							while (next_tab > 0 && written < cols) {
+								bool in_hl  = search_mode && is_src_in_hl(src_i);
+								bool in_cur =
+									has_current && li == cur_my && src_i >= cur_mx
+									&& src_i < cur_mend;
+								// Toggle highlight attributes
+								int attr = 0;
+								if (in_hl)
+									attr |= A_STANDOUT;
+								if (in_cur)
+									attr |= A_BOLD;
+								if ((attr & A_STANDOUT) && !hl_on) {
+									attron(A_STANDOUT);
+									hl_on = true;
+								}
+								if (!(attr & A_STANDOUT) && hl_on) {
+									attroff(A_STANDOUT);
+									hl_on = false;
+								}
+								if ((attr & A_BOLD) && !cur_on) {
+									attron(A_BOLD);
+									cur_on = true;
+								}
+								if (!(attr & A_BOLD) && cur_on) {
+									attroff(A_BOLD);
+									cur_on = false;
+								}
+								// Apply syntax attribute only if not in search highlight
+								if (!in_hl) {
+									apply_token_attr(token_at(src_i));
+								}
+								addch(' ');
+								++written;
+								++render_col;
+								--next_tab;
+							}
+							++src_i;
+							continue;
+						} else {
+							// normal char
+							if (render_col < coloffs) {
+								++render_col;
+								++src_i;
+								continue;
+							}
+							ch       = static_cast<char>(c);
+							from_src = true;
+						}
+					} else {
+						// beyond EOL, fill spaces
+						ch       = ' ';
+						from_src = false;
+					}
+					bool in_hl  = search_mode && from_src && is_src_in_hl(src_i);
+					bool in_cur =
+						has_current && li == cur_my && from_src && src_i >= cur_mx && src_i <
+						cur_mend;
+					if (in_hl && !hl_on) {
+						attron(A_STANDOUT);
+						hl_on = true;
+					}
+					if (!in_hl && hl_on) {
+						attroff(A_STANDOUT);
+						hl_on = false;
+					}
+					if (in_cur && !cur_on) {
+						attron(A_BOLD);
+						cur_on = true;
+					}
+					if (!in_cur && cur_on) {
+						attroff(A_BOLD);
+						cur_on = false;
+					}
+					if (!in_hl && from_src) {
+						apply_token_attr(token_at(src_i));
+					}
+					addch(static_cast<unsigned char>(ch));
+					++written;
+					++render_col;
+					if (from_src)
+						++src_i;
+					if (src_i >= line.size() && written >= cols)
+						break;
+				}
+			}
+			if (hl_on) {
+				attroff(A_STANDOUT);
+				hl_on = false;
+			}
+			if (cur_on) {
+				attroff(A_BOLD);
+				cur_on = false;
+			}
+			attrset(A_NORMAL);
+			clrtoeol();
+		}
 
 		// Place terminal cursor at logical position accounting for tabs and coloffs
 		std::size_t cy = buf->Cury();
@@ -191,71 +282,74 @@ TerminalRenderer::Draw(Editor &ed)
 		mvaddstr(0, 0, "[no buffer]");
 	}
 
- // Status line (inverse)
- move(rows - 1, 0);
- attron(A_REVERSE);
+	// Status line (inverse)
+	move(rows - 1, 0);
+	attron(A_REVERSE);
 
- // Fill the status line with spaces first
- for (int i = 0; i < cols; ++i)
-     addch(' ');
+	// Fill the status line with spaces first
+	for (int i = 0; i < cols; ++i)
+		addch(' ');
 
- // If a prompt is active, replace the status bar with the full prompt text
- if (ed.PromptActive()) {
-     // Build prompt text: "Label: text" and shorten HOME path for file-related prompts
-     std::string label = ed.PromptLabel();
-     std::string ptext = ed.PromptText();
-     auto kind         = ed.CurrentPromptKind();
-     if (kind == Editor::PromptKind::OpenFile || kind == Editor::PromptKind::SaveAs ||
-         kind == Editor::PromptKind::Chdir) {
-         const char *home_c = std::getenv("HOME");
-         if (home_c && *home_c) {
-             std::string home(home_c);
-             // Ensure we match only at the start
-             if (ptext.rfind(home, 0) == 0) {
-                 std::string rest = ptext.substr(home.size());
-                 if (rest.empty())
-                     ptext = "~";
-                 else if (rest[0] == '/' || rest[0] == '\\')
-                     ptext = std::string("~") + rest;
-             }
-         }
-     }
-     // Prefer keeping the tail of the filename visible when it exceeds the window
-     std::string msg;
-     if (!label.empty()) {
-         msg = label + ": ";
-     }
-     // When dealing with file-related prompts, left-trim the filename text so the tail stays visible
-     if ((kind == Editor::PromptKind::OpenFile || kind == Editor::PromptKind::SaveAs || kind == Editor::PromptKind::Chdir) && cols > 0) {
-         int avail = cols - static_cast<int>(msg.size());
-         if (avail <= 0) {
-             // No room for label; fall back to showing the rightmost portion of the whole string
-             std::string whole = msg + ptext;
-             if ((int)whole.size() > cols)
-                 whole = whole.substr(whole.size() - cols);
-             msg = whole;
-         } else {
-             if ((int)ptext.size() > avail) {
-                 ptext = ptext.substr(ptext.size() - avail);
-             }
-             msg += ptext;
-         }
-     } else {
-         // Non-file prompts: simple concatenation and clip by terminal
-         msg += ptext;
-     }
+	// If a prompt is active, replace the status bar with the full prompt text
+	if (ed.PromptActive()) {
+		// Build prompt text: "Label: text" and shorten HOME path for file-related prompts
+		std::string label = ed.PromptLabel();
+		std::string ptext = ed.PromptText();
+		auto kind         = ed.CurrentPromptKind();
+		if (kind == Editor::PromptKind::OpenFile || kind == Editor::PromptKind::SaveAs ||
+		    kind == Editor::PromptKind::Chdir) {
+			const char *home_c = std::getenv("HOME");
+			if (home_c && *home_c) {
+				std::string home(home_c);
+				// Ensure we match only at the start
+				if (ptext.rfind(home, 0) == 0) {
+					std::string rest = ptext.substr(home.size());
+					if (rest.empty())
+						ptext = "~";
+					else if (rest[0] == '/' || rest[0] == '\\')
+						ptext = std::string("~") + rest;
+				}
+			}
+		}
+		// Prefer keeping the tail of the filename visible when it exceeds the window
+		std::string msg;
+		if (kind == Editor::PromptKind::Command) {
+			msg = ": ";
+		} else if (!label.empty()) {
+			msg = label + ": ";
+		}
+		// When dealing with file-related prompts, left-trim the filename text so the tail stays visible
+		if ((kind == Editor::PromptKind::OpenFile || kind == Editor::PromptKind::SaveAs || kind ==
+		     Editor::PromptKind::Chdir) && cols > 0) {
+			int avail = cols - static_cast<int>(msg.size());
+			if (avail <= 0) {
+				// No room for label; fall back to showing the rightmost portion of the whole string
+				std::string whole = msg + ptext;
+				if ((int) whole.size() > cols)
+					whole = whole.substr(whole.size() - cols);
+				msg = whole;
+			} else {
+				if ((int) ptext.size() > avail) {
+					ptext = ptext.substr(ptext.size() - avail);
+				}
+				msg += ptext;
+			}
+		} else {
+			// Non-file prompts: simple concatenation and clip by terminal
+			msg += ptext;
+		}
 
-     // Draw left-aligned, clipped to width
-     if (!msg.empty())
-         mvaddnstr(rows - 1, 0, msg.c_str(), std::max(0, cols));
+		// Draw left-aligned, clipped to width
+		if (!msg.empty())
+			mvaddnstr(rows - 1, 0, msg.c_str(), std::max(0, cols));
 
-     // End status rendering for prompt mode
-     attroff(A_REVERSE);
-     // Restore logical cursor position in content area
-     if (saved_cur_y >= 0 && saved_cur_x >= 0)
-         move(saved_cur_y, saved_cur_x);
-     return;
- }
+		// End status rendering for prompt mode
+		attroff(A_REVERSE);
+		// Restore logical cursor position in content area
+		if (saved_cur_y >= 0 && saved_cur_x >= 0)
+			move(saved_cur_y, saved_cur_x);
+		return;
+	}
 
 	// Build left segment
 	std::string left;
@@ -346,10 +440,10 @@ TerminalRenderer::Draw(Editor &ed)
 	if (llen > 0)
 		mvaddnstr(rows - 1, 0, left.c_str(), llen);
 
- // Draw right, flush to end
- int rstart = std::max(0, cols - rlen);
- if (rlen > 0)
-     mvaddnstr(rows - 1, rstart, right.c_str(), rlen);
+	// Draw right, flush to end
+	int rstart = std::max(0, cols - rlen);
+	if (rlen > 0)
+		mvaddnstr(rows - 1, rstart, right.c_str(), rlen);
 
 	// Middle message
 	const std::string &msg = ed.Status();
@@ -365,7 +459,7 @@ TerminalRenderer::Draw(Editor &ed)
 		}
 	}
 
- attroff(A_REVERSE);
+	attroff(A_REVERSE);
 
 	// Restore terminal cursor to the content position so a visible caret
 	// remains in the editing area (not on the status line).
@@ -374,4 +468,4 @@ TerminalRenderer::Draw(Editor &ed)
 	}
 
 	refresh();
-}
+}

UndoSystem.cc

@@ -5,79 +5,79 @@
 
 
 UndoSystem::UndoSystem(Buffer &owner, UndoTree &tree)
-    : buf_(&owner), tree_(tree) {}
+	: buf_(&owner), tree_(tree) {}
 
 
 void
 UndoSystem::Begin(UndoType type)
 {
 #ifdef KTE_UNDO_DEBUG
-    debug_log("Begin");
+	debug_log("Begin");
 #endif
-    // Reuse pending if batching conditions are met
-    const int row = static_cast<int>(buf_->Cury());
-    const int col = static_cast<int>(buf_->Curx());
-    if (tree_.pending && tree_.pending->type == type && tree_.pending->row == row) {
-        if (type == UndoType::Delete) {
-            // Support batching both forward deletes (DeleteChar) and backspace (prepend case)
-            // Forward delete: cursor stays at anchor col; keep batching when col == anchor
-            const auto anchor = static_cast<std::size_t>(tree_.pending->col);
-            if (anchor == static_cast<std::size_t>(col)) {
-                pending_prepend_ = false;
-                return; // keep batching forward delete
-            }
-            // Backspace: cursor moved left by exactly one position relative to current anchor.
-            // Extend batch by shifting anchor left and prepending the deleted byte.
-            if (static_cast<std::size_t>(col) + 1 == anchor) {
-                tree_.pending->col = col;
-                pending_prepend_   = true;
-                return;
-            }
-        } else {
-            std::size_t expected = static_cast<std::size_t>(tree_.pending->col) + tree_.pending->text.
-                                   size();
-            if (expected == static_cast<std::size_t>(col)) {
-                pending_prepend_ = false;
-                return; // keep batching
-            }
-        }
-    }
-    // Otherwise commit any existing batch and start a new node
-    commit();
-    auto *node       = new UndoNode();
-    node->type       = type;
-    node->row        = row;
-    node->col        = col;
-    node->child      = nullptr;
-    node->next       = nullptr;
-    tree_.pending    = node;
-    pending_prepend_ = false;
+	// Reuse pending if batching conditions are met
+	const int row = static_cast<int>(buf_->Cury());
+	const int col = static_cast<int>(buf_->Curx());
+	if (tree_.pending && tree_.pending->type == type && tree_.pending->row == row) {
+		if (type == UndoType::Delete) {
+			// Support batching both forward deletes (DeleteChar) and backspace (prepend case)
+			// Forward delete: cursor stays at anchor col; keep batching when col == anchor
+			const auto anchor = static_cast<std::size_t>(tree_.pending->col);
+			if (anchor == static_cast<std::size_t>(col)) {
+				pending_prepend_ = false;
+				return; // keep batching forward delete
+			}
+			// Backspace: cursor moved left by exactly one position relative to current anchor.
+			// Extend batch by shifting anchor left and prepending the deleted byte.
+			if (static_cast<std::size_t>(col) + 1 == anchor) {
+				tree_.pending->col = col;
+				pending_prepend_   = true;
+				return;
+			}
+		} else {
+			std::size_t expected = static_cast<std::size_t>(tree_.pending->col) + tree_.pending->text.
+			                       size();
+			if (expected == static_cast<std::size_t>(col)) {
+				pending_prepend_ = false;
+				return; // keep batching
+			}
+		}
+	}
+	// Otherwise commit any existing batch and start a new node
+	commit();
+	auto *node       = new UndoNode();
+	node->type       = type;
+	node->row        = row;
+	node->col        = col;
+	node->child      = nullptr;
+	node->next       = nullptr;
+	tree_.pending    = node;
+	pending_prepend_ = false;
 
 #ifdef KTE_UNDO_DEBUG
-    debug_log("Begin:new");
+	debug_log("Begin:new");
 #endif
-    // Assert pending is detached from the tree
-    assert(tree_.pending && "pending must exist after Begin");
-    assert(tree_.pending != tree_.root);
-    assert(tree_.pending != tree_.current);
-    assert(tree_.pending != tree_.saved);
-    assert(!is_descendant(tree_.root, tree_.pending));
+	// Assert pending is detached from the tree
+	assert(tree_.pending && "pending must exist after Begin");
+	assert(tree_.pending != tree_.root);
+	assert(tree_.pending != tree_.current);
+	assert(tree_.pending != tree_.saved);
+	assert(!is_descendant(tree_.root, tree_.pending));
 }
 
 
 void
 UndoSystem::Append(char ch)
 {
-    if (!tree_.pending)
-        return;
-    if (pending_prepend_ && tree_.pending->type == UndoType::Delete) {
-        // Prepend for backspace so that text is in increasing column order
-        tree_.pending->text.insert(tree_.pending->text.begin(), ch);
-    } else {
-        tree_.pending->text.push_back(ch);
-    }
+	if (!tree_.pending)
+		return;
+	if (pending_prepend_ && tree_.pending->type == UndoType::Delete) {
+		// Prepend for backspace so that text is in increasing column order
+		tree_.pending->text.insert(tree_.pending->text.begin(), ch);
+	} else {
+		tree_.pending->text.push_back(ch);
+	}
 #ifdef KTE_UNDO_DEBUG
-    debug_log("Append:ch");
+	debug_log("Append:ch");
 #endif
 }
 
@@ -85,11 +85,11 @@ UndoSystem::Append(char ch)
 void
 UndoSystem::Append(std::string_view text)
 {
-    if (!tree_.pending)
-        return;
-    tree_.pending->text.append(text.data(), text.size());
+	if (!tree_.pending)
+		return;
+	tree_.pending->text.append(text.data(), text.size());
 #ifdef KTE_UNDO_DEBUG
-    debug_log("Append:sv");
+	debug_log("Append:sv");
 #endif
 }
 
@@ -98,10 +98,10 @@ void
 UndoSystem::commit()
 {
 #ifdef KTE_UNDO_DEBUG
-    debug_log("commit:enter");
+	debug_log("commit:enter");
 #endif
-    if (!tree_.pending)
-        return;
+	if (!tree_.pending)
+		return;
 
 	// If we have redo branches from current, discard them (non-linear behavior)
 	if (tree_.current && tree_.current->child) {
@@ -127,31 +127,31 @@ UndoSystem::commit()
 		tree_.current->child = tree_.pending;
 		tree_.current        = tree_.pending;
 	}
-    tree_.pending = nullptr;
-    update_dirty_flag();
+	tree_.pending = nullptr;
+	update_dirty_flag();
 #ifdef KTE_UNDO_DEBUG
-    debug_log("commit:done");
+	debug_log("commit:done");
 #endif
-    // post-conditions
-    assert(tree_.pending == nullptr && "pending must be cleared after commit");
+	// post-conditions
+	assert(tree_.pending == nullptr && "pending must be cleared after commit");
 }
 
 
 void
 UndoSystem::undo()
 {
-    // Close any pending batch
-    commit();
-    if (!tree_.current)
-        return;
-    UndoNode *parent = find_parent(tree_.root, tree_.current);
-    UndoNode *node   = tree_.current;
-    // Apply inverse of current node
-    apply(node, -1);
-    tree_.current = parent;
-    update_dirty_flag();
+	// Close any pending batch
+	commit();
+	if (!tree_.current)
+		return;
+	UndoNode *parent = find_parent(tree_.root, tree_.current);
+	UndoNode *node   = tree_.current;
+	// Apply inverse of current node
+	apply(node, -1);
+	tree_.current = parent;
+	update_dirty_flag();
 #ifdef KTE_UNDO_DEBUG
-    debug_log("undo");
+	debug_log("undo");
 #endif
 }
 
@@ -159,24 +159,24 @@ UndoSystem::undo()
 void
 UndoSystem::redo()
 {
-    // Redo next child along current timeline
-    if (tree_.pending) {
-        // If app added pending edits, finalize them before redo chain
-        commit();
-    }
-    UndoNode *next = nullptr;
-    if (!tree_.current) {
-        next = tree_.root; // if nothing yet, try applying first node
-    } else {
-        next = tree_.current->child;
-    }
-    if (!next)
-        return;
-    apply(next, +1);
-    tree_.current = next;
-    update_dirty_flag();
+	// Redo next child along current timeline
+	if (tree_.pending) {
+		// If app added pending edits, finalize them before redo chain
+		commit();
+	}
+	UndoNode *next = nullptr;
+	if (!tree_.current) {
+		next = tree_.root; // if nothing yet, try applying first node
+	} else {
+		next = tree_.current->child;
+	}
+	if (!next)
+		return;
+	apply(next, +1);
+	tree_.current = next;
+	update_dirty_flag();
 #ifdef KTE_UNDO_DEBUG
-    debug_log("redo");
+	debug_log("redo");
 #endif
 }
 
@@ -184,10 +184,10 @@ UndoSystem::redo()
 void
 UndoSystem::mark_saved()
 {
-    tree_.saved = tree_.current;
-    update_dirty_flag();
+	tree_.saved = tree_.current;
+	update_dirty_flag();
 #ifdef KTE_UNDO_DEBUG
-    debug_log("mark_saved");
+	debug_log("mark_saved");
 #endif
 }
 
@@ -195,12 +195,12 @@ UndoSystem::mark_saved()
 void
 UndoSystem::discard_pending()
 {
-    if (tree_.pending) {
-        delete tree_.pending;
-        tree_.pending = nullptr;
-    }
+	if (tree_.pending) {
+		delete tree_.pending;
+		tree_.pending = nullptr;
+	}
 #ifdef KTE_UNDO_DEBUG
-    debug_log("discard_pending");
+	debug_log("discard_pending");
 #endif
 }
 
@@ -208,16 +208,16 @@ UndoSystem::discard_pending()
 void
 UndoSystem::clear()
 {
-    if (tree_.root) {
-        free_node(tree_.root);
-    }
-    if (tree_.pending) {
-        delete tree_.pending;
-    }
-    tree_.root = tree_.current = tree_.saved = tree_.pending = nullptr;
-    update_dirty_flag();
+	if (tree_.root) {
+		free_node(tree_.root);
+	}
+	if (tree_.pending) {
+		delete tree_.pending;
+	}
+	tree_.root = tree_.current = tree_.saved = tree_.pending = nullptr;
+	update_dirty_flag();
 #ifdef KTE_UNDO_DEBUG
-    debug_log("clear");
+	debug_log("clear");
 #endif
 }
 
@@ -326,62 +326,73 @@ UndoSystem::find_parent(UndoNode *from, UndoNode *target)
 void
 UndoSystem::update_dirty_flag()
 {
-    // dirty if current != saved
-    bool dirty = (tree_.current != tree_.saved);
-    buf_->SetDirty(dirty);
+	// dirty if current != saved
+	bool dirty = (tree_.current != tree_.saved);
+	buf_->SetDirty(dirty);
 }
 
 
 void
 UndoSystem::UpdateBufferReference(Buffer &new_buf)
 {
-    buf_ = &new_buf;
+	buf_ = &new_buf;
 }
 
+
 // ---- Debug helpers ----
 const char *
 UndoSystem::type_str(UndoType t)
 {
-    switch (t) {
-    case UndoType::Insert: return "Insert";
-    case UndoType::Delete: return "Delete";
-    case UndoType::Paste: return "Paste";
-    case UndoType::Newline: return "Newline";
-    case UndoType::DeleteRow: return "DeleteRow";
-    }
-    return "?";
+	switch (t) {
+	case UndoType::Insert:
+		return "Insert";
+	case UndoType::Delete:
+		return "Delete";
+	case UndoType::Paste:
+		return "Paste";
+	case UndoType::Newline:
+		return "Newline";
+	case UndoType::DeleteRow:
+		return "DeleteRow";
+	}
+	return "?";
 }
 
+
 bool
 UndoSystem::is_descendant(UndoNode *root, const UndoNode *target)
 {
-    if (!root || !target) return false;
-    if (root == target) return true;
-    for (UndoNode *child = root->child; child != nullptr; child = child->next) {
-        if (is_descendant(child, target)) return true;
-    }
-    return false;
+	if (!root || !target)
+		return false;
+	if (root == target)
+		return true;
+	for (UndoNode *child = root->child; child != nullptr; child = child->next) {
+		if (is_descendant(child, target))
+			return true;
+	}
+	return false;
 }
 
+
 void
 UndoSystem::debug_log(const char *op) const
 {
 #ifdef KTE_UNDO_DEBUG
-    int row = static_cast<int>(buf_->Cury());
-    int col = static_cast<int>(buf_->Curx());
-    const UndoNode *p = tree_.pending;
-    std::fprintf(stderr,
-                 "[UNDO] %s cur=(%d,%d) pending=%p t=%s r=%d c=%d nlen=%zu current=%p saved=%p\n",
-                 op,
-                 row, col,
-                 (const void*)p,
-                 p ? type_str(p->type) : "-",
-                 p ? p->row : -1,
-                 p ? p->col : -1,
-                 p ? p->text.size() : 0,
-                 (void*)tree_.current,
-                 (void*)tree_.saved);
+	int row           = static_cast<int>(buf_->Cury());
+	int col           = static_cast<int>(buf_->Curx());
+	const UndoNode *p = tree_.pending;
+	std::fprintf(stderr,
+	             "[UNDO] %s cur=(%d,%d) pending=%p t=%s r=%d c=%d nlen=%zu current=%p saved=%p\n",
+	             op,
+	             row, col,
+	             (const void *) p,
+	             p ? type_str(p->type) : "-",
+	             p ? p->row : -1,
+	             p ? p->col : -1,
+	             p ? p->text.size() : 0,
+	             (void *) tree_.current,
+	             (void *) tree_.saved);
 #else
-    (void)op;
+	(void) op;
 #endif
 }

UndoSystem.h

@@ -12,7 +12,7 @@ class Buffer;
 
 class UndoSystem {
 public:
-    explicit UndoSystem(Buffer &owner, UndoTree &tree);
+	explicit UndoSystem(Buffer &owner, UndoTree &tree);
 
 	void Begin(UndoType type);
 
@@ -30,28 +30,30 @@ public:
 
 	void discard_pending();
 
- void clear();
+	void clear();
 
- void UpdateBufferReference(Buffer &new_buf);
+	void UpdateBufferReference(Buffer &new_buf);
 
 private:
-    void apply(const UndoNode *node, int direction); // +1 redo, -1 undo
-    void free_node(UndoNode *node);
+	void apply(const UndoNode *node, int direction); // +1 redo, -1 undo
+	void free_node(UndoNode *node);
 
-    void free_branch(UndoNode *node); // frees redo siblings only
-    UndoNode *find_parent(UndoNode *from, UndoNode *target);
+	void free_branch(UndoNode *node); // frees redo siblings only
+	UndoNode *find_parent(UndoNode *from, UndoNode *target);
 
-    // Debug helpers (compiled only when KTE_UNDO_DEBUG is defined)
-    void debug_log(const char *op) const;
-    static const char *type_str(UndoType t);
-    static bool is_descendant(UndoNode *root, const UndoNode *target);
+	// Debug helpers (compiled only when KTE_UNDO_DEBUG is defined)
+	void debug_log(const char *op) const;
 
-    void update_dirty_flag();
+	static const char *type_str(UndoType t);
+
+	static bool is_descendant(UndoNode *root, const UndoNode *target);
+
+	void update_dirty_flag();
 
 	Buffer *buf_;
 	UndoTree &tree_;
-    // Internal hint for Delete batching: whether next Append() should prepend
-    bool pending_prepend_ = false;
+	// Internal hint for Delete batching: whether next Append() should prepend
+	bool pending_prepend_ = false;
 };
 
 #endif // KTE_UNDOSYSTEM_H

docs/kge.1

@@ -1,7 +1,7 @@
 .\" kge(1) — Kyle's Graphical Editor (GUI-first)
 .\"
 .\" Project homepage: https://github.com/wntrmute/kte
-.TH KGE 1 "2025-11-30" "kte 0.1.0" "User Commands"
+.TH KGE 1 "2025-12-01" "kte 0.1.0" "User Commands"
 .SH NAME
 kge \- Kyle's Graphical Editor (GUI-first)
 .SH SYNOPSIS
@@ -52,11 +52,8 @@ tree for the canonical reference and notes:
 .PP
 Enter K-command mode with Ctrl-K. Exit K-command mode with ESC or Ctrl-G.
 .TP
-.B C-k BACKSPACE
-Delete from the cursor to the beginning of the line.
-.TP
-.B C-k SPACE
-Toggle the mark.
+.B C-k '
+Toggle read-only for the current buffer.
 .TP
 .B C-k -
 If the mark is set, unindent the region.
@@ -64,6 +61,9 @@ If the mark is set, unindent the region.
 .B C-k =
 If the mark is set, indent the region.
 .TP
+.B C-k ;
+Open the generic command prompt (": ").
+.TP
 .B C-k a
 Set the mark at the beginning of the file, then jump to the end of the file.
 .TP
@@ -80,7 +80,7 @@ Delete from the cursor to the end of the line.
 Delete the entire line.
 .TP
 .B C-k e
-Edit a new file.
+Edit (open) a new file.
 .TP
 .B C-k f
 Flush the kill ring.
@@ -88,14 +88,20 @@ Flush the kill ring.
 .B C-k g
 Go to a specific line.
 .TP
+.B C-k h
+Show the built-in help (+HELP+ buffer).
+.TP
 .B C-k j
 Jump to the mark.
 .TP
 .B C-k l
 Reload the current buffer from disk.
 .TP
-.B C-k m
-Run make(1), reporting success or failure.
+.B C-k n
+Switch to the previous buffer.
+.TP
+.B C-k o
+Change working directory (prompt).
 .TP
 .B C-k p
 Switch to the next buffer.
@@ -106,14 +112,20 @@ Exit the editor. If the file has unsaved changes, a warning will be printed; a s
 .B C-k C-q
 Immediately exit the editor.
 .TP
+.B C-k r
+Redo changes.
+.TP
 .B C-k s
 Save the file, prompting for a filename if needed.
 .TP
 .B C-k u
 Undo.
 .TP
-.B C-k r
-Redo changes.
+.B C-k v
+Toggle visual file picker (GUI).
+.TP
+.B C-k w
+Show the current working directory.
 .TP
 .B C-k x
 Save the file and exit. Also C-k C-x.
@@ -121,23 +133,50 @@ Save the file and exit. Also C-k C-x.
 .B C-k y
 Yank the kill ring.
 .TP
-.B C-k \e
-Dump core.
+.B C-k C-x
+Save the file and exit.
 
 .SS Other keybindings
 .TP
 .B C-g
 Cancel the current operation.
 .TP
+.B C-a
+Move to the beginning of the line.
+.TP
+.B C-e
+Move to the end of the line.
+.TP
+.B C-b
+Move left.
+.TP
+.B C-f
+Move right.
+.TP
+.B C-n
+Move down.
+.TP
+.B C-p
+Move up.
+.TP
 .B C-l
 Refresh the display.
 .TP
+.B C-d
+Delete the character at the cursor.
+.TP
 .B C-r
 Regex search.
 .TP
 .B C-s
 Incremental find.
 .TP
+.B C-t
+Regex search and replace.
+.TP
+.B C-h
+Search and replace.
+.TP
 .B C-u
 Universal argument. C-u followed by numbers will repeat an operation n times.
 .TP
@@ -147,6 +186,15 @@ Kill the region if the mark is set.
 .B C-y
 Yank the kill ring.
 .TP
+.B ESC <
+Move to the beginning of the file.
+.TP
+.B ESC >
+Move to the end of the file.
+.TP
+.B ESC m
+Toggle the mark.
+.TP
 .B ESC BACKSPACE
 Delete the previous word.
 .TP

docs/kte.1

@@ -1,7 +1,7 @@
 .\" kte(1) — Kyle's Text Editor (terminal-first)
 .\"
 .\" Project homepage: https://github.com/wntrmute/kte
-.TH KTE 1 "2025-11-30" "kte 0.1.0" "User Commands"
+.TH KTE 1 "2025-12-01" "kte 0.1.0" "User Commands"
 .SH NAME
 kte \- Kyle's Text Editor (terminal-first)
 .SH SYNOPSIS
@@ -57,11 +57,8 @@ in the source tree for the canonical reference and notes.
 .PP
 Enter K-command mode with Ctrl-K. Exit K-command mode with ESC or Ctrl-G.
 .TP
-.B C-k BACKSPACE
-Delete from the cursor to the beginning of the line.
-.TP
-.B C-k SPACE
-Toggle the mark.
+.B C-k '
+Toggle read-only for the current buffer.
 .TP
 .B C-k -
 If the mark is set, unindent the region.
@@ -69,6 +66,9 @@ If the mark is set, unindent the region.
 .B C-k =
 If the mark is set, indent the region.
 .TP
+.B C-k ;
+Open the generic command prompt (": ").
+.TP
 .B C-k a
 Set the mark at the beginning of the file, then jump to the end of the file.
 .TP
@@ -85,7 +85,7 @@ Delete from the cursor to the end of the line.
 Delete the entire line.
 .TP
 .B C-k e
-Edit a new file.
+Edit (open) a new file.
 .TP
 .B C-k f
 Flush the kill ring.
@@ -93,14 +93,20 @@ Flush the kill ring.
 .B C-k g
 Go to a specific line.
 .TP
+.B C-k h
+Show the built-in help (+HELP+ buffer).
+.TP
 .B C-k j
 Jump to the mark.
 .TP
 .B C-k l
 Reload the current buffer from disk.
 .TP
-.B C-k m
-Run make(1), reporting success or failure.
+.B C-k n
+Switch to the previous buffer.
+.TP
+.B C-k o
+Change working directory (prompt).
 .TP
 .B C-k p
 Switch to the next buffer.
@@ -111,14 +117,20 @@ Exit the editor. If the file has unsaved changes, a warning will be printed; a s
 .B C-k C-q
 Immediately exit the editor.
 .TP
+.B C-k r
+Redo changes.
+.TP
 .B C-k s
 Save the file, prompting for a filename if needed.
 .TP
 .B C-k u
 Undo.
 .TP
-.B C-k r
-Redo changes.
+.B C-k v
+Toggle visual file picker (GUI).
+.TP
+.B C-k w
+Show the current working directory.
 .TP
 .B C-k x
 Save the file and exit. Also C-k C-x.
@@ -126,23 +138,76 @@ Save the file and exit. Also C-k C-x.
 .B C-k y
 Yank the kill ring.
 .TP
-.B C-k \e
-Dump core.
+.B C-k C-x
+Save the file and exit.
+
+.SH GUI APPEARANCE
+When running the GUI frontend, you can control appearance via the generic
+command prompt (type "C-k ;" then enter commands):
+.TP
+.B : theme NAME
+Set the GUI theme. Available names: "nord", "gruvbox", "plan9", "solarized", "eink".
+Compatibility aliases are also accepted: "gruvbox-dark", "gruvbox-light",
+"solarized-dark", "solarized-light", "eink-dark", "eink-light".
+.TP
+.B : background MODE
+Set background mode for supported themes. MODE is either "light" or "dark".
+Themes that respond to background: eink, gruvbox, solarized. The
+"nord" and "plan9" themes do not vary with background.
+
+.SH CONFIGURATION
+The GUI reads a simple configuration file at
+~/.config/kte/kge.ini. Recognized keys include:
+.IP "fullscreen=on|off"
+.IP "columns=NUM"
+.IP "rows=NUM"
+.IP "font_size=NUM"
+.IP "theme=NAME"
+.IP "background=light|dark"
+The theme name accepts the values listed above. The background key controls
+light/dark variants when the selected theme supports it.
 
 .SS Other keybindings
 .TP
 .B C-g
 Cancel the current operation.
 .TP
+.B C-a
+Move to the beginning of the line.
+.TP
+.B C-e
+Move to the end of the line.
+.TP
+.B C-b
+Move left.
+.TP
+.B C-f
+Move right.
+.TP
+.B C-n
+Move down.
+.TP
+.B C-p
+Move up.
+.TP
 .B C-l
 Refresh the display.
 .TP
+.B C-d
+Delete the character at the cursor.
+.TP
 .B C-r
 Regex search.
 .TP
 .B C-s
 Incremental find.
 .TP
+.B C-t
+Regex search and replace.
+.TP
+.B C-h
+Search and replace.
+.TP
 .B C-u
 Universal argument. C-u followed by numbers will repeat an operation n times.
 .TP
@@ -152,6 +217,15 @@ Kill the region if the mark is set.
 .B C-y
 Yank the kill ring.
 .TP
+.B ESC <
+Move to the beginning of the file.
+.TP
+.B ESC >
+Move to the end of the file.
+.TP
+.B ESC m
+Toggle the mark.
+.TP
 .B ESC BACKSPACE
 Delete the previous word.
 .TP

docs/lsp plan.md

@@ -0,0 +1,525 @@
+# LSP Support Implementation Plan for kte
+
+## Executive Summary
+
+This plan outlines a comprehensive approach to integrating Language Server Protocol (LSP) support into kte while
+respecting its core architectural principles: **frontend/backend separation**, **testability**, and **dual terminal/GUI
+support**.
+
+---
+
+## 1. Core Architecture
+
+### 1.1 LSP Client Module Structure
+
+```c++
+// LspClient.h - Core LSP client abstraction
+class LspClient {
+public:
+    virtual ~LspClient() = default;
+    
+    // Lifecycle
+    virtual bool initialize(const std::string& rootPath) = 0;
+    virtual void shutdown() = 0;
+    
+    // Document Synchronization
+    virtual void didOpen(const std::string& uri, const std::string& languageId, 
+                         int version, const std::string& text) = 0;
+    virtual void didChange(const std::string& uri, int version, 
+                           const std::vector<TextDocumentContentChangeEvent>& changes) = 0;
+    virtual void didClose(const std::string& uri) = 0;
+    virtual void didSave(const std::string& uri) = 0;
+    
+    // Language Features
+    virtual void completion(const std::string& uri, Position pos, 
+                           CompletionCallback callback) = 0;
+    virtual void hover(const std::string& uri, Position pos, 
+                      HoverCallback callback) = 0;
+    virtual void definition(const std::string& uri, Position pos, 
+                           LocationCallback callback) = 0;
+    virtual void references(const std::string& uri, Position pos, 
+                           LocationsCallback callback) = 0;
+    virtual void diagnostics(DiagnosticsCallback callback) = 0;
+    
+    // Process Management
+    virtual bool isRunning() const = 0;
+    virtual std::string getServerName() const = 0;
+};
+```
+
+### 1.2 Process-based LSP Implementation
+
+```c++
+// LspProcessClient.h - Manages LSP server subprocess
+class LspProcessClient : public LspClient {
+private:
+    std::string serverCommand_;
+    std::vector<std::string> serverArgs_;
+    std::unique_ptr<Process> process_;
+    std::unique_ptr<JsonRpcTransport> transport_;
+    std::unordered_map<int, PendingRequest> pendingRequests_;
+    int nextRequestId_ = 1;
+    
+    // Async I/O handling
+    std::thread readerThread_;
+    std::mutex mutex_;
+    std::condition_variable cv_;
+    
+public:
+    LspProcessClient(const std::string& command, 
+                     const std::vector<std::string>& args);
+    // ... implementation of LspClient interface
+};
+```
+
+### 1.3 JSON-RPC Transport Layer
+
+```c++
+// JsonRpcTransport.h
+class JsonRpcTransport {
+public:
+    // Send a request and get the request ID
+    int sendRequest(const std::string& method, const nlohmann::json& params);
+    
+    // Send a notification (no response expected)
+    void sendNotification(const std::string& method, const nlohmann::json& params);
+    
+    // Read next message (blocking)
+    std::optional<JsonRpcMessage> readMessage();
+    
+private:
+    void writeMessage(const nlohmann::json& message);
+    std::string readContentLength();
+    
+    int fdIn_;   // stdin to server
+    int fdOut_;  // stdout from server
+};
+```
+
+---
+
+## 2. Incremental Document Updates
+
+### 2.1 Change Tracking in Buffer
+
+The key to efficient LSP integration is tracking changes incrementally. This integrates with the existing `Buffer`
+class:
+
+```c++
+// TextDocumentContentChangeEvent.h
+struct TextDocumentContentChangeEvent {
+    std::optional<Range> range;     // If nullopt, entire document changed
+    std::optional<int> rangeLength; // Deprecated but some servers use it
+    std::string text;
+};
+
+// BufferChangeTracker.h - Integrates with Buffer to track changes
+class BufferChangeTracker {
+public:
+    explicit BufferChangeTracker(Buffer* buffer);
+    
+    // Called by Buffer on each edit operation
+    void recordInsertion(Position pos, const std::string& text);
+    void recordDeletion(Range range, const std::string& deletedText);
+    
+    // Get accumulated changes since last sync
+    std::vector<TextDocumentContentChangeEvent> getChanges();
+    
+    // Clear changes after sending to LSP
+    void clearChanges();
+    
+    // Get current document version
+    int getVersion() const { return version_; }
+    
+private:
+    Buffer* buffer_;
+    int version_ = 0;
+    std::vector<TextDocumentContentChangeEvent> pendingChanges_;
+    
+    // Optional: Coalesce adjacent changes
+    void coalesceChanges();
+};
+```
+
+### 2.2 Integration with Buffer Operations
+
+```c++
+// Buffer.h additions
+class Buffer {
+    // ... existing code ...
+    
+    // LSP integration
+    void setChangeTracker(std::unique_ptr<BufferChangeTracker> tracker);
+    BufferChangeTracker* getChangeTracker() { return changeTracker_.get(); }
+    
+    // These methods should call tracker when present
+    void insertText(Position pos, const std::string& text);
+    void deleteRange(Range range);
+    
+private:
+    std::unique_ptr<BufferChangeTracker> changeTracker_;
+};
+```
+
+### 2.3 Sync Strategy Selection
+
+```c++
+// LspSyncMode.h
+enum class LspSyncMode {
+    None,        // No sync
+    Full,        // Send full document on each change
+    Incremental  // Send only changes (preferred)
+};
+
+// Determined during server capability negotiation
+LspSyncMode negotiateSyncMode(const ServerCapabilities& caps);
+```
+
+---
+
+## 3. Diagnostics Display System
+
+### 3.1 Diagnostic Data Model
+
+```c++
+// Diagnostic.h
+enum class DiagnosticSeverity {
+    Error = 1,
+    Warning = 2,
+    Information = 3,
+    Hint = 4
+};
+
+struct Diagnostic {
+    Range range;
+    DiagnosticSeverity severity;
+    std::optional<std::string> code;
+    std::optional<std::string> source;
+    std::string message;
+    std::vector<DiagnosticRelatedInformation> relatedInfo;
+};
+
+// DiagnosticStore.h - Central storage for diagnostics
+class DiagnosticStore {
+public:
+    void setDiagnostics(const std::string& uri, 
+                        std::vector<Diagnostic> diagnostics);
+    const std::vector<Diagnostic>& getDiagnostics(const std::string& uri) const;
+    std::vector<Diagnostic> getDiagnosticsAtLine(const std::string& uri, 
+                                                  int line) const;
+    std::optional<Diagnostic> getDiagnosticAtPosition(const std::string& uri,
+                                                       Position pos) const;
+    void clear(const std::string& uri);
+    void clearAll();
+    
+    // Statistics
+    int getErrorCount(const std::string& uri) const;
+    int getWarningCount(const std::string& uri) const;
+    
+private:
+    std::unordered_map<std::string, std::vector<Diagnostic>> diagnostics_;
+};
+```
+
+### 3.2 Frontend-Agnostic Diagnostic Display Interface
+
+Following kte's existing abstraction pattern with `Frontend`, `Renderer`, and `InputHandler`:
+
+```c++
+// DiagnosticDisplay.h - Abstract interface for showing diagnostics
+class DiagnosticDisplay {
+public:
+    virtual ~DiagnosticDisplay() = default;
+    
+    // Update the diagnostic indicators for a buffer
+    virtual void updateDiagnostics(const std::string& uri, 
+                                   const std::vector<Diagnostic>& diagnostics) = 0;
+    
+    // Show inline diagnostic at cursor position
+    virtual void showInlineDiagnostic(const Diagnostic& diagnostic) = 0;
+    
+    // Show diagnostic list/panel
+    virtual void showDiagnosticList(const std::vector<Diagnostic>& diagnostics) = 0;
+    virtual void hideDiagnosticList() = 0;
+    
+    // Status bar summary
+    virtual void updateStatusBar(int errorCount, int warningCount) = 0;
+};
+```
+
+### 3.3 Terminal Diagnostic Display
+
+```c++
+// TerminalDiagnosticDisplay.h
+class TerminalDiagnosticDisplay : public DiagnosticDisplay {
+public:
+    explicit TerminalDiagnosticDisplay(TerminalRenderer* renderer);
+    
+    void updateDiagnostics(const std::string& uri, 
+                          const std::vector<Diagnostic>& diagnostics) override;
+    void showInlineDiagnostic(const Diagnostic& diagnostic) override;
+    void showDiagnosticList(const std::vector<Diagnostic>& diagnostics) override;
+    void hideDiagnosticList() override;
+    void updateStatusBar(int errorCount, int warningCount) override;
+    
+private:
+    TerminalRenderer* renderer_;
+    
+    // Terminal-specific display strategies
+    void renderGutterMarkers(const std::vector<Diagnostic>& diagnostics);
+    void renderUnderlines(const std::vector<Diagnostic>& diagnostics);
+    void renderVirtualText(const Diagnostic& diagnostic);
+};
+```
+
+**Terminal Display Strategies:**
+
+1. **Gutter markers**: Show `E` (error), `W` (warning), `I` (info), `H` (hint) in left gutter
+2. **Underlines**: Use terminal underline/curly underline capabilities (where supported)
+3. **Virtual text**: Display diagnostic message at end of line (configurable)
+4. **Status line**: `[E:3 W:5]` summary
+5. **Message line**: Full diagnostic on cursor line shown in bottom bar
+
+```
+1 │ fn main() {
+E 2 │     let x: i32 = "hello";
+  3 │ }                        
+──────────────────────────────────────
+error[E0308]: mismatched types       
+expected `i32`, found `&str`         
+[E:1 W:0] main.rs
+```
+
+### 3.4 GUI Diagnostic Display
+
+```c++
+// GUIDiagnosticDisplay.h
+class GUIDiagnosticDisplay : public DiagnosticDisplay {
+public:
+    explicit GUIDiagnosticDisplay(GUIRenderer* renderer, GUITheme* theme);
+    
+    void updateDiagnostics(const std::string& uri, 
+                          const std::vector<Diagnostic>& diagnostics) override;
+    void showInlineDiagnostic(const Diagnostic& diagnostic) override;
+    void showDiagnosticList(const std::vector<Diagnostic>& diagnostics) override;
+    void hideDiagnosticList() override;
+    void updateStatusBar(int errorCount, int warningCount) override;
+    
+private:
+    GUIRenderer* renderer_;
+    GUITheme* theme_;
+    
+    // GUI-specific display
+    void renderWavyUnderlines(const std::vector<Diagnostic>& diagnostics);
+    void renderTooltip(Position pos, const Diagnostic& diagnostic);
+    void renderDiagnosticPanel();
+};
+```
+
+**GUI Display Features:**
+
+1. **Wavy underlines**: Classic IDE-style (red for errors, yellow for warnings, etc.)
+2. **Gutter icons**: Colored icons/dots in the gutter
+3. **Hover tooltips**: Rich tooltips on hover showing full diagnostic
+4. **Diagnostic panel**: Bottom panel with clickable diagnostic list
+5. **Minimap markers**: Colored marks on the minimap (if present)
+
+---
+
+## 4. LspManager - Central Coordination
+
+```c++
+// LspManager.h
+class LspManager {
+public:
+    explicit LspManager(Editor* editor, DiagnosticDisplay* display);
+    
+    // Server management
+    void registerServer(const std::string& languageId, 
+                       const LspServerConfig& config);
+    bool startServerForBuffer(Buffer* buffer);
+    void stopServer(const std::string& languageId);
+    void stopAllServers();
+    
+    // Document sync
+    void onBufferOpened(Buffer* buffer);
+    void onBufferChanged(Buffer* buffer);
+    void onBufferClosed(Buffer* buffer);
+    void onBufferSaved(Buffer* buffer);
+    
+    // Feature requests
+    void requestCompletion(Buffer* buffer, Position pos, 
+                          CompletionCallback callback);
+    void requestHover(Buffer* buffer, Position pos, 
+                     HoverCallback callback);
+    void requestDefinition(Buffer* buffer, Position pos, 
+                          LocationCallback callback);
+    
+    // Configuration
+    void setDebugLogging(bool enabled);
+    
+private:
+    Editor* editor_;
+    DiagnosticDisplay* display_;
+    DiagnosticStore diagnosticStore_;
+    std::unordered_map<std::string, std::unique_ptr<LspClient>> servers_;
+    std::unordered_map<std::string, LspServerConfig> serverConfigs_;
+    
+    void handleDiagnostics(const std::string& uri, 
+                          const std::vector<Diagnostic>& diagnostics);
+    std::string getLanguageId(Buffer* buffer);
+    std::string getUri(Buffer* buffer);
+};
+```
+
+---
+
+## 5. Configuration
+
+```c++
+// LspServerConfig.h
+struct LspServerConfig {
+    std::string command;
+    std::vector<std::string> args;
+    std::vector<std::string> filePatterns;  // e.g., {"*.rs", "*.toml"}
+    std::string rootPatterns;               // e.g., "Cargo.toml"
+    LspSyncMode preferredSyncMode = LspSyncMode::Incremental;
+    bool autostart = true;
+    std::unordered_map<std::string, nlohmann::json> initializationOptions;
+    std::unordered_map<std::string, nlohmann::json> settings;
+};
+
+// Default configurations
+std::vector<LspServerConfig> getDefaultServerConfigs() {
+    return {
+        {
+            .command = "rust-analyzer",
+            .filePatterns = {"*.rs"},
+            .rootPatterns = "Cargo.toml"
+        },
+        {
+            .command = "clangd",
+            .args = {"--background-index"},
+            .filePatterns = {"*.c", "*.cc", "*.cpp", "*.h", "*.hpp"},
+            .rootPatterns = "compile_commands.json"
+        },
+        {
+            .command = "gopls",
+            .filePatterns = {"*.go"},
+            .rootPatterns = "go.mod"
+        },
+        // ... more servers
+    };
+}
+```
+
+---
+
+## 6. Implementation Phases
+
+### Phase 1: Foundation (2-3 weeks)
+
+- [ ] JSON-RPC transport layer
+- [ ] Process management for LSP servers
+- [ ] Basic `LspClient` with initialize/shutdown
+- [ ] `textDocument/didOpen`, `textDocument/didClose` (full sync)
+
+### Phase 2: Incremental Sync (1-2 weeks)
+
+- [ ] `BufferChangeTracker` integration with `Buffer`
+- [ ] `textDocument/didChange` with incremental updates
+- [ ] Change coalescing for rapid edits
+- [ ] Version tracking
+
+### Phase 3: Diagnostics (2-3 weeks)
+
+- [ ] `DiagnosticStore` implementation
+- [ ] `TerminalDiagnosticDisplay` with gutter markers & status line
+- [ ] `GUIDiagnosticDisplay` with wavy underlines & tooltips
+- [ ] `textDocument/publishDiagnostics` handling
+
+### Phase 4: Language Features (3-4 weeks)
+
+- [ ] Completion (`textDocument/completion`)
+- [ ] Hover (`textDocument/hover`)
+- [ ] Go to definition (`textDocument/definition`)
+- [ ] Find references (`textDocument/references`)
+- [ ] Code actions (`textDocument/codeAction`)
+
+### Phase 5: Polish & Advanced Features (2-3 weeks)
+
+- [ ] Multiple server support
+- [ ] Server auto-detection
+- [ ] Configuration file support
+- [ ] Workspace symbol search
+- [ ] Rename refactoring
+
+---
+
+## 7. Alignment with kte Core Principles
+
+### 7.1 Frontend/Backend Separation
+
+- LSP logic is completely separate from display
+- `DiagnosticDisplay` interface allows identical behavior across Terminal/GUI
+- Follows existing pattern: `Renderer`, `InputHandler`, `Frontend`
+
+### 7.2 Testability
+
+- `LspClient` is abstract, enabling `MockLspClient` for testing
+- `DiagnosticDisplay` can be mocked for testing diagnostic flow
+- Change tracking can be unit tested in isolation
+
+### 7.3 Performance
+
+- Incremental sync minimizes data sent to LSP servers
+- Async message handling doesn't block UI
+- Diagnostic rendering is batched
+
+### 7.4 Simplicity
+
+- Minimal dependencies (nlohmann/json for JSON handling)
+- Self-contained process management
+- Clear separation of concerns
+
+---
+
+## 8. File Organization
+
+```
+kte/
+├── lsp/
+│   ├── LspClient.h
+│   ├── LspProcessClient.h
+│   ├── LspProcessClient.cc
+│   ├── LspManager.h
+│   ├── LspManager.cc
+│   ├── LspServerConfig.h
+│   ├── JsonRpcTransport.h
+│   ├── JsonRpcTransport.cc
+│   ├── LspTypes.h           # Position, Range, Location, etc.
+│   ├── Diagnostic.h
+│   ├── DiagnosticStore.h
+│   ├── DiagnosticStore.cc
+│   └── BufferChangeTracker.h
+├── diagnostic/
+│   ├── DiagnosticDisplay.h
+│   ├── TerminalDiagnosticDisplay.h
+│   ├── TerminalDiagnosticDisplay.cc
+│   ├── GUIDiagnosticDisplay.h
+│   └── GUIDiagnosticDisplay.cc
+```
+
+---
+
+## 9. Dependencies
+
+- **nlohmann/json**: JSON parsing/serialization (header-only)
+- **POSIX/Windows process APIs**: For spawning LSP servers
+- Existing kte infrastructure: `Buffer`, `Renderer`, `Frontend`, etc.
+
+---
+
+This plan provides a solid foundation for LSP support while maintaining kte's clean architecture. The key insight is
+that LSP is fundamentally a backend feature that should be displayed through the existing frontend abstraction layer,
+ensuring consistent behavior across terminal and GUI modes.

docs/syntax on.md

@@ -0,0 +1,102 @@
+### Objective
+Introduce fast, minimal‑dependency syntax highlighting to kte, consistent with current architecture (Editor/Buffer + GUI/Terminal renderers), preserving ke UX and performance.
+
+### Guiding principles
+- Keep core small and fast; no heavy deps (C++17 only). 
+- Start simple (stateless line regex), evolve incrementally (stateful, caching). 
+- Work in both Terminal (ncurses) and GUI (ImGui) with consistent token classes and theme mapping. 
+- Integrate without disrupting existing search highlight, selection, or cursor rendering.
+
+### Scope of v1
+- Languages: plain text (off), C/C++ minimal set (keywords, types, strings, chars, comments, numbers, preprocessor). 
+- Stateless per‑line highlighting; handle single‑line comments and strings; defer multi‑line state to v2. 
+- Toggle: `:syntax on|off` and per‑buffer filetype selection.
+
+### Architecture
+1. Core types (new):
+   - `enum class TokenKind { Default, Keyword, Type, String, Char, Comment, Number, Preproc, Constant, Function, Operator, Punctuation, Identifier, Whitespace, Error };`
+   - `struct HighlightSpan { int col_start; int col_end; TokenKind kind; };`  // 0‑based columns in buffer indices per rendered line
+   - `struct LineHighlight { std::vector<HighlightSpan> spans; uint64_t version; };`
+
+2. Interfaces (new):
+   - `class LanguageHighlighter { public: virtual ~LanguageHighlighter() = default; virtual void HighlightLine(const Buffer& buf, int row, std::vector<HighlightSpan>& out) const = 0; virtual bool Stateful() const { return false; } };`
+   - `class HighlighterEngine { public: void SetHighlighter(std::unique_ptr<LanguageHighlighter>); const LineHighlight& GetLine(const Buffer&, int row, uint64_t buf_version); void InvalidateFrom(int row); };`
+   - `class HighlighterRegistry { public: static const LanguageHighlighter& ForFiletype(std::string_view ft); static std::string DetectForPath(std::string_view path, std::string_view first_line); };`
+
+3. Editor/Buffer integration:
+   - Per‑Buffer settings: `bool syntax_enabled; std::string filetype; std::unique_ptr<HighlighterEngine> highlighter;`
+   - Buffer emits a monotonically increasing `version` on edit; renderers request line highlights by `(row, version)`. 
+   - Invalidate cache minimally on edits (v1: current line only; v2: from current line down when stateful constructs present).
+
+### Rendering integration
+- TerminalRenderer/GUIRenderer changes:
+  - During line rendering, query `Editor.CurrentBuffer()->highlighter->GetLine(buf, row, buf_version)` to obtain spans.
+  - Apply token styles while drawing glyph runs. 
+- Z‑order and blending:
+  1) Backgrounds (e.g., selection, search highlight rectangles) 
+  2) Text with syntax colors 
+  3) Cursor/IME decorations
+- Search highlights must remain visible over syntax colors:
+  - Terminal: combine color/attr with reverse/bold for search; if color conflicts, prefer search. 
+  - GUI: draw semi‑transparent rects behind text (already present); keep syntax color for text.
+
+### Theme and color mapping
+- Extend `GUITheme.h` with a `SyntaxPalette` mapping `TokenKind -> ImVec4 ink` (and optional background tint for comments/strings disabled by default). Provide default Light/Dark palettes. 
+- Terminal: map `TokenKind` to ncurses color pairs where available; degrade gracefully on 8/16‑color terminals (e.g., comments=dim, keywords=bold, strings=yellow/green if available). 
+
+### Language detection
+- v1: by file extension; allow manual `:set filetype=<lang>`. 
+- v2: add shebang detection for scripts, simple modelines (optional).
+
+### Commands/UX
+- `:syntax on|off` — global default; buffer inherits on open. 
+- `:set filetype=<lang>` — per‑buffer override. 
+- `:syntax reload` — rebuild patterns/themes. 
+- Status line shows filetype and syntax state when changed.
+
+### Implementation plan (phased)
+1. Phase 1 — Minimal regex highlighter for C/C++
+   - Implement `CppRegexHighlighter : LanguageHighlighter` with precompiled `std::regex` (or hand‑rolled simple scanners to avoid regex backtracking). Classes: line comment `//…`, block comment start `/*` (no state), string `"…"`, char `'…'` (no multiline), numbers, keywords/types, preprocessor `^\s*#\w+`. 
+   - Add `HighlighterEngine` with a simple per‑row cache keyed by `(row, buf_version)`; no background worker. 
+   - Integrate into both renderers; add palette to `GUITheme.h`; add terminal color selection. 
+   - Add commands. 
+
+2. Phase 2 — Stateful constructs and more languages
+   - Add state machine for multiline comments `/*…*/` and multiline strings (C++11 raw strings), with invalidation from edit line downward until state stabilizes. 
+   - Add simple highlighters: JSON (strings, numbers, booleans, null, punctuation), Markdown (headers/emphasis/code fences), Shell (comments, strings, keywords), Go (types, constants, keywords), Python (strings, comments, keywords), Rust (strings, comments, keywords), Lisp (comments, strings, keywords),. 
+   - Filetype detection by extension + shebang. 
+
+3. Phase 3 — Performance and caching
+   - Viewport‑first highlighting: compute only visible rows each frame; background task warms cache around viewport. 
+   - Reuse span buffers, avoid allocations; small‑vector optimization if needed. 
+   - Bench with large files; ensure O(n_visible) cost per frame.
+
+4. Phase 4 — Extensibility
+   - Public registration API for external highlighters. 
+   - Optional Tree‑sitter adapter behind a compile flag (off by default) to keep dependencies minimal. 
+
+### Data flow (per frame)
+- Renderer asks Editor for Buffer and viewport rows. 
+- For each row: `engine.GetLine(buf, row, buf.version)` → spans. 
+- Renderer emits runs with style from `SyntaxPalette[kind]`. 
+- Search highlights are applied as separate background rectangles (GUI) or attribute toggles (Terminal), not overriding text color.
+
+### Testing
+- Unit tests for tokenization per language: golden inputs → spans. 
+- Fuzz/edge cases: escaped quotes, numeric literals, preprocessor lines. 
+- Renderer tests with `TestRenderer` asserting the sequence of style changes for a line. 
+- Performance tests: highlight 1k visible lines repeatedly; assert time under threshold.
+
+### Risks and mitigations
+- Regex backtracking/perf: prefer linear scans; precompute keyword tables; avoid nested regex. 
+- Terminal color limitations: feature‑detect colors; provide bold/dim fallbacks. 
+- Stateful correctness: invalidate conservatively (from edit line downward) and cap work per frame.
+
+### Deliverables
+- New files: `Highlight.h/.cc`, `HighlighterEngine.h/.cc`, `LanguageHighlighter.h`, `CppHighlighter.h/.cc`, optional `HighlighterRegistry.h/.cc`. 
+- Renderer updates: `GUIRenderer.cc`, `TerminalRenderer.cc` to consume spans. 
+- Theming: `GUITheme.h` additions for syntax colors. 
+- Editor/Buffer: per‑buffer syntax settings and highlighter handle. 
+- Commands in `Command.cc` and help text updates. 
+- Docs: README/ROADMAP update and a brief `docs/syntax.md`. 
+- Tests: unit and renderer golden tests.

docs/syntax.md

@@ -0,0 +1,70 @@
+Syntax highlighting in kte
+==========================
+
+Overview
+--------
+
+kte provides lightweight syntax highlighting with a pluggable highlighter interface. The initial implementation targets C/C++ and focuses on speed and responsiveness.
+
+Core types
+----------
+
+- `TokenKind` — token categories (keywords, types, strings, comments, numbers, preprocessor, operators, punctuation, identifiers, whitespace, etc.).
+- `HighlightSpan` — a half-open column range `[col_start, col_end)` with a `TokenKind`.
+- `LineHighlight` — a vector of `HighlightSpan` and the buffer `version` used to compute it.
+
+Engine and caching
+------------------
+
+- `HighlighterEngine` maintains a per-line cache of `LineHighlight` keyed by row and buffer version.
+- Cache invalidation occurs when the buffer version changes or when the buffer calls `InvalidateFrom(row)`, which clears cached lines and line states from `row` downward.
+- The engine supports both stateless and stateful highlighters. For stateful highlighters, it memoizes a simple per-line state and computes lines sequentially when necessary.
+
+Stateful highlighters
+---------------------
+
+- `LanguageHighlighter` is the base interface for stateless per-line tokenization.
+- `StatefulHighlighter` extends it with a `LineState` and the method `HighlightLineStateful(buf, row, prev_state, out)`.
+- The engine detects `StatefulHighlighter` via dynamic_cast and feeds each line the previous line’s state, caching the resulting state per line.
+
+C/C++ highlighter
+-----------------
+
+- `CppHighlighter` implements `StatefulHighlighter`.
+- Stateless constructs: line comments `//`, strings `"..."`, chars `'...'`, numbers, identifiers (keywords/types), preprocessor at beginning of line after leading whitespace, operators/punctuation, and whitespace.
+- Stateful constructs (v2):
+  - Multi-line block comments `/* ... */` — the state records whether the next line continues a comment.
+  - Raw strings `R"delim(... )delim"` — the state tracks whether we are inside a raw string and its delimiter `delim` until the closing sequence appears.
+
+Limitations and TODOs
+---------------------
+
+- Raw string detection is intentionally simple and does not handle all corner cases of the C++ standard.
+- Preprocessor handling is line-based; continuation lines with `\\` are not yet tracked.
+- No semantic analysis; identifiers are classified via small keyword/type sets.
+- Additional languages (JSON, Markdown, Shell, Python, Go, Rust, Lisp, …) are planned.
+- Terminal color mapping is conservative to support 8/16-color terminals. Rich color-pair themes can be added later.
+
+Renderer integration
+--------------------
+
+- Terminal and GUI renderers request line spans via `Highlighter()->GetLine(buf, row, buf.Version())`.
+- Search highlight and cursor overlays take precedence over syntax colors.
+
+Extensibility (Phase 4)
+-----------------------
+
+- Public registration API: external code can register custom highlighters by filetype.
+  - Use `HighlighterRegistry::Register("mylang", []{ return std::make_unique<MyHighlighter>(); });`
+  - Registered factories are preferred over built-ins for the same filetype key.
+  - Filetype keys are normalized via `HighlighterRegistry::Normalize()`.
+- Optional Tree-sitter adapter: disabled by default to keep dependencies minimal.
+  - Enable with CMake option `-DKTE_ENABLE_TREESITTER=ON` and provide
+    `-DTREESITTER_INCLUDE_DIR=...` and `-DTREESITTER_LIBRARY=...` if needed.
+  - Register a Tree-sitter-backed highlighter for a language (example assumes you link a grammar):
+    ```c++
+    extern "C" const TSLanguage* tree_sitter_c();
+    kte::HighlighterRegistry::RegisterTreeSitter("c", &tree_sitter_c);
+    ```
+  - Current adapter is a stub scaffold; it compiles and integrates cleanly when enabled, but
+    intentionally emits no spans until Tree-sitter node-to-token mapping is implemented.

kte-cloc

@@ -1,3 +1,9 @@
 #!/usr/bin/env bash
 
-ls -1 *.cc *.h | grep -v '^Font.h$' | xargs cloc -fmt 3
+fmt_arg=""
+if [ "${V}" = "1" ]
+then
+	fmt_args="-fmt 3"
+fi
+
+ls -1 *.cc *.h | grep -v '^Font.h$' | xargs cloc ${fmt_args}

syntax/CppHighlighter.cc

@@ -0,0 +1,279 @@
+#include "CppHighlighter.h"
+#include "../Buffer.h"
+#include <cctype>
+
+namespace kte {
+static bool
+is_digit(char c)
+{
+	return c >= '0' && c <= '9';
+}
+
+
+CppHighlighter::CppHighlighter()
+{
+	const char *kw[] = {
+		"if", "else", "for", "while", "do", "switch", "case", "default", "break", "continue",
+		"return", "goto", "struct", "class", "namespace", "using", "template", "typename",
+		"public", "private", "protected", "virtual", "override", "const", "constexpr", "auto",
+		"static", "inline", "operator", "new", "delete", "try", "catch", "throw", "friend",
+		"enum", "union", "extern", "volatile", "mutable", "noexcept", "sizeof", "this"
+	};
+	for (auto s: kw)
+		keywords_.insert(s);
+	const char *types[] = {
+		"int", "long", "short", "char", "signed", "unsigned", "float", "double", "void",
+		"bool", "wchar_t", "size_t", "ptrdiff_t", "uint8_t", "uint16_t", "uint32_t", "uint64_t",
+		"int8_t", "int16_t", "int32_t", "int64_t"
+	};
+	for (auto s: types)
+		types_.insert(s);
+}
+
+
+bool
+CppHighlighter::is_ident_start(char c)
+{
+	return std::isalpha(static_cast<unsigned char>(c)) || c == '_';
+}
+
+
+bool
+CppHighlighter::is_ident_char(char c)
+{
+	return std::isalnum(static_cast<unsigned char>(c)) || c == '_';
+}
+
+
+void
+CppHighlighter::HighlightLine(const Buffer &buf, int row, std::vector<HighlightSpan> &out) const
+{
+	// Stateless entry simply delegates to stateful with a clean previous state
+	StatefulHighlighter::LineState prev;
+	(void) HighlightLineStateful(buf, row, prev, out);
+}
+
+
+StatefulHighlighter::LineState
+CppHighlighter::HighlightLineStateful(const Buffer &buf,
+                                      int row,
+                                      const LineState &prev,
+                                      std::vector<HighlightSpan> &out) const
+{
+	const auto &rows                     = buf.Rows();
+	StatefulHighlighter::LineState state = prev;
+	if (row < 0 || static_cast<std::size_t>(row) >= rows.size())
+		return state;
+	std::string s = static_cast<std::string>(rows[static_cast<std::size_t>(row)]);
+	if (s.empty())
+		return state;
+
+	auto push = [&](int a, int b, TokenKind k) {
+		if (b > a)
+			out.push_back({a, b, k});
+	};
+	int n   = static_cast<int>(s.size());
+	int bol = 0;
+	while (bol < n && (s[bol] == ' ' || s[bol] == '\t'))
+		++bol;
+	int i = 0;
+
+	// Continue multi-line raw string from previous line
+	if (state.in_raw_string) {
+		std::string needle = ")" + state.raw_delim + "\"";
+		auto pos           = s.find(needle);
+		if (pos == std::string::npos) {
+			push(0, n, TokenKind::String);
+			state.in_raw_string = true;
+			return state;
+		} else {
+			int end = static_cast<int>(pos + needle.size());
+			push(0, end, TokenKind::String);
+			i                   = end;
+			state.in_raw_string = false;
+			state.raw_delim.clear();
+		}
+	}
+
+	// Continue multi-line block comment from previous line
+	if (state.in_block_comment) {
+		int j = i;
+		while (i + 1 < n) {
+			if (s[i] == '*' && s[i + 1] == '/') {
+				i += 2;
+				push(j, i, TokenKind::Comment);
+				state.in_block_comment = false;
+				break;
+			}
+			++i;
+		}
+		if (state.in_block_comment) {
+			push(j, n, TokenKind::Comment);
+			return state;
+		}
+	}
+
+	while (i < n) {
+		char c = s[i];
+		// Preprocessor at beginning of line (after leading whitespace)
+		if (i == bol && c == '#') {
+			push(0, n, TokenKind::Preproc);
+			break;
+		}
+
+		// Whitespace
+		if (c == ' ' || c == '\t') {
+			int j = i + 1;
+			while (j < n && (s[j] == ' ' || s[j] == '\t'))
+				++j;
+			push(i, j, TokenKind::Whitespace);
+			i = j;
+			continue;
+		}
+
+		// Line comment
+		if (c == '/' && i + 1 < n && s[i + 1] == '/') {
+			push(i, n, TokenKind::Comment);
+			break;
+		}
+
+		// Block comment
+		if (c == '/' && i + 1 < n && s[i + 1] == '*') {
+			int j       = i + 2;
+			bool closed = false;
+			while (j + 1 <= n) {
+				if (j + 1 < n && s[j] == '*' && s[j + 1] == '/') {
+					j += 2;
+					closed = true;
+					break;
+				}
+				++j;
+			}
+			if (closed) {
+				push(i, j, TokenKind::Comment);
+				i = j;
+				continue;
+			}
+			// Spill to next lines
+			push(i, n, TokenKind::Comment);
+			state.in_block_comment = true;
+			return state;
+		}
+
+		// Raw string start: very simple detection: R"delim(
+		if (c == 'R' && i + 1 < n && s[i + 1] == '"') {
+			int k = i + 2;
+			std::string delim;
+			while (k < n && s[k] != '(') {
+				delim.push_back(s[k]);
+				++k;
+			}
+			if (k < n && s[k] == '(') {
+				int body_start     = k + 1;
+				std::string needle = ")" + delim + "\"";
+				auto pos           = s.find(needle, static_cast<std::size_t>(body_start));
+				if (pos == std::string::npos) {
+					push(i, n, TokenKind::String);
+					state.in_raw_string = true;
+					state.raw_delim     = delim;
+					return state;
+				} else {
+					int end = static_cast<int>(pos + needle.size());
+					push(i, end, TokenKind::String);
+					i = end;
+					continue;
+				}
+			}
+			// If malformed, just treat 'R' as identifier fallback
+		}
+
+		// Regular string literal
+		if (c == '"') {
+			int j    = i + 1;
+			bool esc = false;
+			while (j < n) {
+				char d = s[j++];
+				if (esc) {
+					esc = false;
+					continue;
+				}
+				if (d == '\\') {
+					esc = true;
+					continue;
+				}
+				if (d == '"')
+					break;
+			}
+			push(i, j, TokenKind::String);
+			i = j;
+			continue;
+		}
+
+		// Char literal
+		if (c == '\'') {
+			int j    = i + 1;
+			bool esc = false;
+			while (j < n) {
+				char d = s[j++];
+				if (esc) {
+					esc = false;
+					continue;
+				}
+				if (d == '\\') {
+					esc = true;
+					continue;
+				}
+				if (d == '\'')
+					break;
+			}
+			push(i, j, TokenKind::Char);
+			i = j;
+			continue;
+		}
+
+		// Number literal (simple)
+		if (is_digit(c) || (c == '.' && i + 1 < n && is_digit(s[i + 1]))) {
+			int j = i + 1;
+			while (j < n && (std::isalnum(static_cast<unsigned char>(s[j])) || s[j] == '.' || s[j] == 'x' ||
+			                 s[j] == 'X' || s[j] == 'b' || s[j] == 'B' || s[j] == '_'))
+				++j;
+			push(i, j, TokenKind::Number);
+			i = j;
+			continue;
+		}
+
+		// Identifier / keyword / type
+		if (is_ident_start(c)) {
+			int j = i + 1;
+			while (j < n && is_ident_char(s[j]))
+				++j;
+			std::string id = s.substr(i, j - i);
+			TokenKind k    = TokenKind::Identifier;
+			if (keywords_.count(id))
+				k = TokenKind::Keyword;
+			else if (types_.count(id))
+				k = TokenKind::Type;
+			push(i, j, k);
+			i = j;
+			continue;
+		}
+
+		// Operators and punctuation (single char for now)
+		TokenKind kind = TokenKind::Operator;
+		if (std::ispunct(static_cast<unsigned char>(c)) && c != '_' && c != '#') {
+			if (c == ';' || c == ',' || c == '(' || c == ')' || c == '{' || c == '}' || c == '[' || c ==
+			    ']')
+				kind = TokenKind::Punctuation;
+			push(i, i + 1, kind);
+			++i;
+			continue;
+		}
+
+		// Fallback
+		push(i, i + 1, TokenKind::Default);
+		++i;
+	}
+
+	return state;
+}
+} // namespace kte

syntax/CppHighlighter.h

@@ -0,0 +1,35 @@
+// CppHighlighter.h - minimal stateless C/C++ line highlighter
+#pragma once
+
+#include <regex>
+#include <string>
+#include <unordered_set>
+#include <vector>
+
+#include "LanguageHighlighter.h"
+
+class Buffer;
+
+namespace kte {
+class CppHighlighter final : public StatefulHighlighter {
+public:
+	CppHighlighter();
+
+	~CppHighlighter() override = default;
+
+	void HighlightLine(const Buffer &buf, int row, std::vector<HighlightSpan> &out) const override;
+
+	LineState HighlightLineStateful(const Buffer &buf,
+	                                int row,
+	                                const LineState &prev,
+	                                std::vector<HighlightSpan> &out) const override;
+
+private:
+	std::unordered_set<std::string> keywords_;
+	std::unordered_set<std::string> types_;
+
+	static bool is_ident_start(char c);
+
+	static bool is_ident_char(char c);
+};
+} // namespace kte

syntax/ErlangHighlighter.cc

@@ -0,0 +1,159 @@
+#include "ErlangHighlighter.h"
+#include "../Buffer.h"
+#include <cctype>
+
+namespace kte {
+static void
+push(std::vector<HighlightSpan> &out, int a, int b, TokenKind k)
+{
+	if (b > a)
+		out.push_back({a, b, k});
+}
+
+
+static bool
+is_ident_start(char c)
+{
+	return std::isalpha(static_cast<unsigned char>(c)) || c == '_' || c == '\'';
+}
+
+
+static bool
+is_ident_char(char c)
+{
+	return std::isalnum(static_cast<unsigned char>(c)) || c == '_' || c == '@' || c == ':' || c == '?';
+}
+
+
+ErlangHighlighter::ErlangHighlighter()
+{
+	const char *kw[] = {
+		"after", "begin", "case", "catch", "cond", "div", "end", "fun", "if", "let", "of",
+		"receive", "when", "try", "rem", "and", "andalso", "orelse", "not", "band", "bor", "bxor",
+		"bnot", "xor", "module", "export", "import", "record", "define", "undef", "include", "include_lib"
+	};
+	for (auto s: kw)
+		kws_.insert(s);
+}
+
+
+void
+ErlangHighlighter::HighlightLine(const Buffer &buf, int row, std::vector<HighlightSpan> &out) const
+{
+	const auto &rows = buf.Rows();
+	if (row < 0 || static_cast<std::size_t>(row) >= rows.size())
+		return;
+	std::string s = static_cast<std::string>(rows[static_cast<std::size_t>(row)]);
+	int n         = static_cast<int>(s.size());
+	int i         = 0;
+
+	while (i < n) {
+		char c = s[i];
+		if (c == ' ' || c == '\t') {
+			int j = i + 1;
+			while (j < n && (s[j] == ' ' || s[j] == '\t'))
+				++j;
+			push(out, i, j, TokenKind::Whitespace);
+			i = j;
+			continue;
+		}
+		// comment
+		if (c == '%') {
+			push(out, i, n, TokenKind::Comment);
+			break;
+		}
+		// strings
+		if (c == '"') {
+			int j    = i + 1;
+			bool esc = false;
+			while (j < n) {
+				char d = s[j++];
+				if (esc) {
+					esc = false;
+					continue;
+				}
+				if (d == '\\') {
+					esc = true;
+					continue;
+				}
+				if (d == '"')
+					break;
+			}
+			push(out, i, j, TokenKind::String);
+			i = j;
+			continue;
+		}
+		// char literal $X
+		if (c == '$') {
+			int j = i + 1;
+			if (j < n && s[j] == '\\' && j + 1 < n)
+				j += 2;
+			else if (j < n)
+				++j;
+			push(out, i, j, TokenKind::Char);
+			i = j;
+			continue;
+		}
+		// numbers
+		if (std::isdigit(static_cast<unsigned char>(c))) {
+			int j = i + 1;
+			while (j < n && (std::isalnum(static_cast<unsigned char>(s[j])) || s[j] == '#' || s[j] == '.' ||
+			                 s[j] == '_'))
+				++j;
+			push(out, i, j, TokenKind::Number);
+			i = j;
+			continue;
+		}
+		// atoms/variables/identifiers (including quoted atoms)
+		if (is_ident_start(c)) {
+			// quoted atom: '...'
+			if (c == '\'') {
+				int j    = i + 1;
+				bool esc = false;
+				while (j < n) {
+					char d = s[j++];
+					if (d == '\'') {
+						if (j < n && s[j] == '\'') {
+							++j;
+							continue;
+						}
+						break;
+					}
+					if (d == '\\')
+						esc = !esc;
+				}
+				push(out, i, j, TokenKind::Identifier);
+				i = j;
+				continue;
+			}
+			int j = i + 1;
+			while (j < n && is_ident_char(s[j]))
+				++j;
+			std::string id = s.substr(i, j - i);
+			// lowercase leading -> atom/function/module; uppercase or '_' -> variable
+			TokenKind k = TokenKind::Identifier;
+			// keyword check (lowercase)
+			std::string lower;
+			lower.reserve(id.size());
+			for (char ch: id)
+				lower.push_back(static_cast<char>(std::tolower(static_cast<unsigned char>(ch))));
+			if (kws_.count(lower))
+				k = TokenKind::Keyword;
+			push(out, i, j, k);
+			i = j;
+			continue;
+		}
+		if (std::ispunct(static_cast<unsigned char>(c))) {
+			TokenKind k = TokenKind::Operator;
+			if (c == ',' || c == ';' || c == '(' || c == ')' || c == '[' || c == ']' || c == '{' || c ==
+			    '}')
+				k = TokenKind::Punctuation;
+			push(out, i, i + 1, k);
+			++i;
+			continue;
+		}
+		push(out, i, i + 1, TokenKind::Default);
+		++i;
+	}
+}
+} // namespace kte

syntax/ErlangHighlighter.h

@@ -0,0 +1,17 @@
+// ErlangHighlighter.h - simple Erlang highlighter
+#pragma once
+
+#include "LanguageHighlighter.h"
+#include <unordered_set>
+
+namespace kte {
+class ErlangHighlighter final : public LanguageHighlighter {
+public:
+	ErlangHighlighter();
+
+	void HighlightLine(const Buffer &buf, int row, std::vector<HighlightSpan> &out) const override;
+
+private:
+	std::unordered_set<std::string> kws_;
+};
+} // namespace kte

syntax/ForthHighlighter.cc

@@ -0,0 +1,121 @@
+#include "ForthHighlighter.h"
+#include "../Buffer.h"
+#include <cctype>
+
+namespace kte {
+static void
+push(std::vector<HighlightSpan> &out, int a, int b, TokenKind k)
+{
+	if (b > a)
+		out.push_back({a, b, k});
+}
+
+
+static bool
+is_word_char(char c)
+{
+	return std::isalnum(static_cast<unsigned char>(c)) || c == '_' || c == '>' || c == '<' || c == '?';
+}
+
+
+ForthHighlighter::ForthHighlighter()
+{
+	const char *kw[] = {
+		":", ";", "if", "else", "then", "begin", "until", "while", "repeat",
+		"do", "loop", "+loop", "leave", "again", "case", "of", "endof", "endcase",
+		".", ".r", ".s", ".\"", ",", "cr", "emit", "type", "key",
+		"+", "-", "*", "/", "mod", "/mod", "+-", "abs", "min", "max",
+		"dup", "drop", "swap", "over", "rot", "-rot", "nip", "tuck", "pick", "roll",
+		"and", "or", "xor", "invert", "lshift", "rshift",
+		"variable", "constant", "value", "to", "create", "does>", "allot", ",",
+		"cells", "cell+", "chars", "char+",
+		"[", "]", "immediate",
+		"s\"", ".\""
+	};
+	for (auto s: kw)
+		kws_.insert(s);
+}
+
+
+void
+ForthHighlighter::HighlightLine(const Buffer &buf, int row, std::vector<HighlightSpan> &out) const
+{
+	const auto &rows = buf.Rows();
+	if (row < 0 || static_cast<std::size_t>(row) >= rows.size())
+		return;
+	std::string s = static_cast<std::string>(rows[static_cast<std::size_t>(row)]);
+	int n         = static_cast<int>(s.size());
+	int i         = 0;
+
+	while (i < n) {
+		char c = s[i];
+		if (c == ' ' || c == '\t') {
+			int j = i + 1;
+			while (j < n && (s[j] == ' ' || s[j] == '\t'))
+				++j;
+			push(out, i, j, TokenKind::Whitespace);
+			i = j;
+			continue;
+		}
+		// backslash comment to end of line
+		if (c == '\\') {
+			push(out, i, n, TokenKind::Comment);
+			break;
+		}
+		// parenthesis comment ( ... ) if at word boundary
+		if (c == '(') {
+			int j = i + 1;
+			while (j < n && s[j] != ')')
+				++j;
+			if (j < n)
+				++j;
+			push(out, i, j, TokenKind::Comment);
+			i = j;
+			continue;
+		}
+		// strings: ." ... " and S" ... " and raw "..."
+		if (c == '"') {
+			int j = i + 1;
+			while (j < n && s[j] != '"')
+				++j;
+			if (j < n)
+				++j;
+			push(out, i, j, TokenKind::String);
+			i = j;
+			continue;
+		}
+		if (std::isdigit(static_cast<unsigned char>(c))) {
+			int j = i + 1;
+			while (j < n && (std::isalnum(static_cast<unsigned char>(s[j])) || s[j] == '.' || s[j] == '#'))
+				++j;
+			push(out, i, j, TokenKind::Number);
+			i = j;
+			continue;
+		}
+		// word/identifier
+		if (std::isalpha(static_cast<unsigned char>(c)) || std::ispunct(static_cast<unsigned char>(c))) {
+			int j = i + 1;
+			while (j < n && is_word_char(s[j]))
+				++j;
+			std::string w = s.substr(i, j - i);
+			// normalize to lowercase for keyword compare (Forth is case-insensitive typically)
+			std::string lower;
+			lower.reserve(w.size());
+			for (char ch: w)
+				lower.push_back(static_cast<char>(std::tolower(static_cast<unsigned char>(ch))));
+			TokenKind k = kws_.count(lower) ? TokenKind::Keyword : TokenKind::Identifier;
+			// Single-char punctuation fallback
+			if (w.size() == 1 && std::ispunct(static_cast<unsigned char>(w[0])) && !kws_.count(lower)) {
+				k = (w[0] == '(' || w[0] == ')' || w[0] == ',')
+					    ? TokenKind::Punctuation
+					    : TokenKind::Operator;
+			}
+			push(out, i, j, k);
+			i = j;
+			continue;
+		}
+		push(out, i, i + 1, TokenKind::Default);
+		++i;
+	}
+}
+} // namespace kte

syntax/ForthHighlighter.h

@@ -0,0 +1,17 @@
+// ForthHighlighter.h - simple Forth highlighter
+#pragma once
+
+#include "LanguageHighlighter.h"
+#include <unordered_set>
+
+namespace kte {
+class ForthHighlighter final : public LanguageHighlighter {
+public:
+	ForthHighlighter();
+
+	void HighlightLine(const Buffer &buf, int row, std::vector<HighlightSpan> &out) const override;
+
+private:
+	std::unordered_set<std::string> kws_;
+};
+} // namespace kte

syntax/GoHighlighter.cc

@@ -0,0 +1,157 @@
+#include "GoHighlighter.h"
+#include "../Buffer.h"
+#include <cctype>
+
+namespace kte {
+static void
+push(std::vector<HighlightSpan> &out, int a, int b, TokenKind k)
+{
+	if (b > a)
+		out.push_back({a, b, k});
+}
+
+
+static bool
+is_ident_start(char c)
+{
+	return std::isalpha(static_cast<unsigned char>(c)) || c == '_';
+}
+
+
+static bool
+is_ident_char(char c)
+{
+	return std::isalnum(static_cast<unsigned char>(c)) || c == '_';
+}
+
+
+GoHighlighter::GoHighlighter()
+{
+	const char *kw[] = {
+		"break", "case", "chan", "const", "continue", "default", "defer", "else", "fallthrough", "for", "func",
+		"go", "goto", "if", "import", "interface", "map", "package", "range", "return", "select", "struct",
+		"switch", "type", "var"
+	};
+	for (auto s: kw)
+		kws_.insert(s);
+	const char *tp[] = {
+		"bool", "byte", "complex64", "complex128", "error", "float32", "float64", "int", "int8", "int16",
+		"int32", "int64", "rune", "string", "uint", "uint8", "uint16", "uint32", "uint64", "uintptr"
+	};
+	for (auto s: tp)
+		types_.insert(s);
+}
+
+
+void
+GoHighlighter::HighlightLine(const Buffer &buf, int row, std::vector<HighlightSpan> &out) const
+{
+	const auto &rows = buf.Rows();
+	if (row < 0 || static_cast<std::size_t>(row) >= rows.size())
+		return;
+	std::string s = static_cast<std::string>(rows[static_cast<std::size_t>(row)]);
+	int n         = static_cast<int>(s.size());
+	int i         = 0;
+	int bol       = 0;
+	while (bol < n && (s[bol] == ' ' || s[bol] == '\t'))
+		++bol;
+	// line comment
+	while (i < n) {
+		char c = s[i];
+		if (c == ' ' || c == '\t') {
+			int j = i + 1;
+			while (j < n && (s[j] == ' ' || s[j] == '\t'))
+				++j;
+			push(out, i, j, TokenKind::Whitespace);
+			i = j;
+			continue;
+		}
+		if (c == '/' && i + 1 < n && s[i + 1] == '/') {
+			push(out, i, n, TokenKind::Comment);
+			break;
+		}
+		if (c == '/' && i + 1 < n && s[i + 1] == '*') {
+			int j       = i + 2;
+			bool closed = false;
+			while (j + 1 <= n) {
+				if (j + 1 < n && s[j] == '*' && s[j + 1] == '/') {
+					j += 2;
+					closed = true;
+					break;
+				}
+				++j;
+			}
+			if (!closed) {
+				push(out, i, n, TokenKind::Comment);
+				break;
+			} else {
+				push(out, i, j, TokenKind::Comment);
+				i = j;
+				continue;
+			}
+		}
+		if (c == '"' || c == '`') {
+			char q   = c;
+			int j    = i + 1;
+			bool esc = false;
+			if (q == '`') {
+				while (j < n && s[j] != '`')
+					++j;
+				if (j < n)
+					++j;
+			} else {
+				while (j < n) {
+					char d = s[j++];
+					if (esc) {
+						esc = false;
+						continue;
+					}
+					if (d == '\\') {
+						esc = true;
+						continue;
+					}
+					if (d == '"')
+						break;
+				}
+			}
+			push(out, i, j, TokenKind::String);
+			i = j;
+			continue;
+		}
+		if (std::isdigit(static_cast<unsigned char>(c))) {
+			int j = i + 1;
+			while (j < n && (std::isalnum(static_cast<unsigned char>(s[j])) || s[j] == '.' || s[j] == 'x' ||
+			                 s[j] == 'X' || s[j] == '_'))
+				++j;
+			push(out, i, j, TokenKind::Number);
+			i = j;
+			continue;
+		}
+		if (is_ident_start(c)) {
+			int j = i + 1;
+			while (j < n && is_ident_char(s[j]))
+				++j;
+			std::string id = s.substr(i, j - i);
+			TokenKind k    = TokenKind::Identifier;
+			if (kws_.count(id))
+				k = TokenKind::Keyword;
+			else if (types_.count(id))
+				k = TokenKind::Type;
+			push(out, i, j, k);
+			i = j;
+			continue;
+		}
+		if (std::ispunct(static_cast<unsigned char>(c))) {
+			TokenKind k = TokenKind::Operator;
+			if (c == ';' || c == ',' || c == '(' || c == ')' || c == '{' || c == '}' || c == '[' || c ==
+			    ']')
+				k = TokenKind::Punctuation;
+			push(out, i, i + 1, k);
+			++i;
+			continue;
+		}
+		push(out, i, i + 1, TokenKind::Default);
+		++i;
+	}
+}
+} // namespace kte

syntax/GoHighlighter.h

@@ -0,0 +1,18 @@
+// GoHighlighter.h - simple Go highlighter
+#pragma once
+
+#include "LanguageHighlighter.h"
+#include <unordered_set>
+
+namespace kte {
+class GoHighlighter final : public LanguageHighlighter {
+public:
+	GoHighlighter();
+
+	void HighlightLine(const Buffer &buf, int row, std::vector<HighlightSpan> &out) const override;
+
+private:
+	std::unordered_set<std::string> kws_;
+	std::unordered_set<std::string> types_;
+};
+} // namespace kte

syntax/HighlighterEngine.cc

@@ -0,0 +1,209 @@
+#include "HighlighterEngine.h"
+#include "../Buffer.h"
+#include "LanguageHighlighter.h"
+#include <thread>
+
+namespace kte {
+HighlighterEngine::HighlighterEngine() = default;
+
+
+HighlighterEngine::~HighlighterEngine()
+{
+	// stop background worker
+	if (worker_running_.load()) {
+		{
+			std::lock_guard<std::mutex> lock(mtx_);
+			worker_running_.store(false);
+			has_request_ = true; // wake it up to exit
+		}
+		cv_.notify_one();
+		if (worker_.joinable())
+			worker_.join();
+	}
+}
+
+
+void
+HighlighterEngine::SetHighlighter(std::unique_ptr<LanguageHighlighter> hl)
+{
+	std::lock_guard<std::mutex> lock(mtx_);
+	hl_ = std::move(hl);
+	cache_.clear();
+	state_cache_.clear();
+	state_last_contig_.clear();
+}
+
+
+const LineHighlight &
+HighlighterEngine::GetLine(const Buffer &buf, int row, std::uint64_t buf_version) const
+{
+	std::unique_lock<std::mutex> lock(mtx_);
+	auto it = cache_.find(row);
+	if (it != cache_.end() && it->second.version == buf_version) {
+		return it->second;
+	}
+
+	// Prepare destination slot to reuse its capacity and avoid allocations
+	LineHighlight &slot = cache_[row];
+	slot.version        = buf_version;
+	slot.spans.clear();
+
+	if (!hl_) {
+		return slot;
+	}
+
+	// Copy shared_ptr-like raw pointer for use outside critical sections
+	LanguageHighlighter *hl_ptr = hl_.get();
+	bool is_stateful            = dynamic_cast<StatefulHighlighter *>(hl_ptr) != nullptr;
+
+	if (!is_stateful) {
+		// Stateless fast path: we can release the lock while computing to reduce contention
+		auto &out = slot.spans;
+		lock.unlock();
+		hl_ptr->HighlightLine(buf, row, out);
+		return cache_.at(row);
+	}
+
+	// Stateful path: we need to walk from a known previous state. Keep lock while consulting caches,
+	// but release during heavy computation.
+	auto *stateful = static_cast<StatefulHighlighter *>(hl_ptr);
+
+	StatefulHighlighter::LineState prev_state;
+	int start_row = -1;
+	if (!state_cache_.empty()) {
+		// linear search over map (unordered), track best candidate
+		int best = -1;
+		for (const auto &kv: state_cache_) {
+			int r = kv.first;
+			if (r <= row - 1 && kv.second.version == buf_version) {
+				if (r > best)
+					best = r;
+			}
+		}
+		if (best >= 0) {
+			start_row  = best;
+			prev_state = state_cache_.at(best).state;
+		}
+	}
+
+	// We'll compute states and the target line's spans without holding the lock for most of the work.
+	// Create a local copy of prev_state and iterate rows; we will update caches under lock.
+	lock.unlock();
+	StatefulHighlighter::LineState cur_state = prev_state;
+	for (int r = start_row + 1; r <= row; ++r) {
+		std::vector<HighlightSpan> tmp;
+		std::vector<HighlightSpan> &out = (r == row) ? slot.spans : tmp;
+		auto next_state                 = stateful->HighlightLineStateful(buf, r, cur_state, out);
+		// Update state cache for r
+		std::lock_guard<std::mutex> gl(mtx_);
+		StateEntry se;
+		se.version      = buf_version;
+		se.state        = next_state;
+		state_cache_[r] = se;
+		cur_state       = next_state;
+	}
+
+	// Return reference under lock to ensure slot's address stability in map
+	lock.lock();
+	return cache_.at(row);
+}
+
+
+void
+HighlighterEngine::InvalidateFrom(int row)
+{
+	std::lock_guard<std::mutex> lock(mtx_);
+	if (cache_.empty())
+		return;
+	// Simple implementation: erase all rows >= row
+	for (auto it = cache_.begin(); it != cache_.end();) {
+		if (it->first >= row)
+			it = cache_.erase(it);
+		else
+			++it;
+	}
+	if (!state_cache_.empty()) {
+		for (auto it = state_cache_.begin(); it != state_cache_.end();) {
+			if (it->first >= row)
+				it = state_cache_.erase(it);
+			else
+				++it;
+		}
+	}
+}
+
+
+void
+HighlighterEngine::ensure_worker_started() const
+{
+	if (worker_running_.load())
+		return;
+	worker_running_.store(true);
+	worker_ = std::thread([this]() {
+		this->worker_loop();
+	});
+}
+
+
+void
+HighlighterEngine::worker_loop() const
+{
+	std::unique_lock<std::mutex> lock(mtx_);
+	while (worker_running_.load()) {
+		cv_.wait(lock, [this]() {
+			return has_request_ || !worker_running_.load();
+		});
+		if (!worker_running_.load())
+			break;
+		WarmRequest req = pending_;
+		has_request_    = false;
+		// Copy locals then release lock while computing
+		lock.unlock();
+		if (req.buf) {
+			int start = std::max(0, req.start_row);
+			int end   = std::max(start, req.end_row);
+			for (int r = start; r <= end; ++r) {
+				// Re-check version staleness quickly by peeking cache version; not strictly necessary
+				// Compute line; GetLine is thread-safe
+				(void) this->GetLine(*req.buf, r, req.version);
+			}
+		}
+		lock.lock();
+	}
+}
+
+
+void
+HighlighterEngine::PrefetchViewport(const Buffer &buf, int first_row, int row_count, std::uint64_t buf_version,
+                                    int warm_margin) const
+{
+	if (row_count <= 0)
+		return;
+	// Synchronously compute visible rows to ensure cache hits during draw
+	int start    = std::max(0, first_row);
+	int end      = start + row_count - 1;
+	int max_rows = static_cast<int>(buf.Nrows());
+	if (start >= max_rows)
+		return;
+	if (end >= max_rows)
+		end = max_rows - 1;
+
+	for (int r = start; r <= end; ++r) {
+		(void) GetLine(buf, r, buf_version);
+	}
+
+	// Enqueue background warm-around
+	int warm_start = std::max(0, start - warm_margin);
+	int warm_end   = std::min(max_rows - 1, end + warm_margin);
+	{
+		std::lock_guard<std::mutex> lock(mtx_);
+		pending_.buf       = &buf;
+		pending_.version   = buf_version;
+		pending_.start_row = warm_start;
+		pending_.end_row   = warm_end;
+		has_request_       = true;
+	}
+	ensure_worker_started();
+	cv_.notify_one();
+}
+} // namespace kte

syntax/HighlighterEngine.h

@@ -0,0 +1,85 @@
+// HighlighterEngine.h - caching layer for per-line highlights
+#pragma once
+
+#include <cstdint>
+#include <memory>
+#include <unordered_map>
+#include <vector>
+#include <mutex>
+#include <condition_variable>
+#include <atomic>
+#include <thread>
+
+#include "../Highlight.h"
+#include "LanguageHighlighter.h"
+
+class Buffer;
+
+namespace kte {
+class HighlighterEngine {
+public:
+	HighlighterEngine();
+
+	~HighlighterEngine();
+
+	void SetHighlighter(std::unique_ptr<LanguageHighlighter> hl);
+
+	// Retrieve highlights for a given line and buffer version.
+	// If cache is stale, recompute using the current highlighter.
+	const LineHighlight &GetLine(const Buffer &buf, int row, std::uint64_t buf_version) const;
+
+	// Invalidate cached lines from row (inclusive)
+	void InvalidateFrom(int row);
+
+
+	bool HasHighlighter() const
+	{
+		return static_cast<bool>(hl_);
+	}
+
+
+	// Phase 3: viewport-first prefetch and background warming
+	// Compute only the visible range now, and enqueue a background warm-around task.
+	// warm_margin: how many extra lines above/below to warm in the background.
+	void PrefetchViewport(const Buffer &buf, int first_row, int row_count, std::uint64_t buf_version,
+	                      int warm_margin = 200) const;
+
+private:
+	std::unique_ptr<LanguageHighlighter> hl_;
+	// Simple cache by row index (mutable to allow caching in const GetLine)
+	mutable std::unordered_map<int, LineHighlight> cache_;
+
+	// For stateful highlighters, remember per-line state (state after finishing that row)
+	struct StateEntry {
+		std::uint64_t version{0};
+		// Using the interface type; forward-declare via header
+		StatefulHighlighter::LineState state;
+	};
+
+	mutable std::unordered_map<int, StateEntry> state_cache_;
+
+	// Track best known contiguous state row for a given version to avoid O(n) scans
+	mutable std::unordered_map<std::uint64_t, int> state_last_contig_;
+
+	// Thread-safety for caches and background worker state
+	mutable std::mutex mtx_;
+
+	// Background warmer
+	struct WarmRequest {
+		const Buffer *buf{nullptr};
+		std::uint64_t version{0};
+		int start_row{0};
+		int end_row{0}; // inclusive
+	};
+
+	mutable std::condition_variable cv_;
+	mutable std::thread worker_;
+	mutable std::atomic<bool> worker_running_{false};
+	mutable bool has_request_{false};
+	mutable WarmRequest pending_{};
+
+	void ensure_worker_started() const;
+
+	void worker_loop() const;
+};
+} // namespace kte

syntax/HighlighterRegistry.cc

@@ -0,0 +1,247 @@
+#include "HighlighterRegistry.h"
+#include "CppHighlighter.h"
+
+#include <algorithm>
+#include <filesystem>
+#include <vector>
+#include <cctype>
+
+// Forward declare simple highlighters implemented in this project
+namespace kte {
+// Registration storage
+struct RegEntry {
+	std::string ft; // normalized
+	HighlighterRegistry::Factory factory;
+};
+
+
+static std::vector<RegEntry> &
+registry()
+{
+	static std::vector<RegEntry> reg;
+	return reg;
+}
+
+
+class JSONHighlighter;
+class MarkdownHighlighter;
+class ShellHighlighter;
+class GoHighlighter;
+class PythonHighlighter;
+class RustHighlighter;
+class LispHighlighter;
+class SqlHighlighter;
+class ErlangHighlighter;
+class ForthHighlighter;
+}
+
+// Headers for the above
+#include "JsonHighlighter.h"
+#include "MarkdownHighlighter.h"
+#include "ShellHighlighter.h"
+#include "GoHighlighter.h"
+#include "PythonHighlighter.h"
+#include "RustHighlighter.h"
+#include "LispHighlighter.h"
+#include "SqlHighlighter.h"
+#include "ErlangHighlighter.h"
+#include "ForthHighlighter.h"
+
+namespace kte {
+static std::string
+to_lower(std::string_view s)
+{
+	std::string r(s);
+	std::transform(r.begin(), r.end(), r.begin(), [](unsigned char c) {
+		return static_cast<char>(std::tolower(c));
+	});
+	return r;
+}
+
+
+std::string
+HighlighterRegistry::Normalize(std::string_view ft)
+{
+	std::string f = to_lower(ft);
+	if (f == "c" || f == "c++" || f == "cc" || f == "hpp" || f == "hh" || f == "h" || f == "cxx")
+		return "cpp";
+	if (f == "cpp")
+		return "cpp";
+	if (f == "json")
+		return "json";
+	if (f == "markdown" || f == "md" || f == "mkd" || f == "mdown")
+		return "markdown";
+	if (f == "shell" || f == "sh" || f == "bash" || f == "zsh" || f == "ksh" || f == "fish")
+		return "shell";
+	if (f == "go" || f == "golang")
+		return "go";
+	if (f == "py" || f == "python")
+		return "python";
+	if (f == "rs" || f == "rust")
+		return "rust";
+	if (f == "lisp" || f == "scheme" || f == "scm" || f == "rkt" || f == "el" || f == "clj" || f == "cljc" || f ==
+	    "cl")
+		return "lisp";
+	if (f == "sql" || f == "sqlite" || f == "sqlite3")
+		return "sql";
+	if (f == "erlang" || f == "erl" || f == "hrl")
+		return "erlang";
+	if (f == "forth" || f == "fth" || f == "4th" || f == "fs")
+		return "forth";
+	return f;
+}
+
+
+std::unique_ptr<LanguageHighlighter>
+HighlighterRegistry::CreateFor(std::string_view filetype)
+{
+	std::string ft = Normalize(filetype);
+	// Prefer externally registered factories
+	for (const auto &e: registry()) {
+		if (e.ft == ft && e.factory)
+			return e.factory();
+	}
+	if (ft == "cpp")
+		return std::make_unique<CppHighlighter>();
+	if (ft == "json")
+		return std::make_unique<JSONHighlighter>();
+	if (ft == "markdown")
+		return std::make_unique<MarkdownHighlighter>();
+	if (ft == "shell")
+		return std::make_unique<ShellHighlighter>();
+	if (ft == "go")
+		return std::make_unique<GoHighlighter>();
+	if (ft == "python")
+		return std::make_unique<PythonHighlighter>();
+	if (ft == "rust")
+		return std::make_unique<RustHighlighter>();
+	if (ft == "lisp")
+		return std::make_unique<LispHighlighter>();
+	if (ft == "sql")
+		return std::make_unique<SqlHighlighter>();
+	if (ft == "erlang")
+		return std::make_unique<ErlangHighlighter>();
+	if (ft == "forth")
+		return std::make_unique<ForthHighlighter>();
+	return nullptr;
+}
+
+
+static std::string
+shebang_to_ft(std::string_view first_line)
+{
+	if (first_line.size() < 2 || first_line.substr(0, 2) != "#!")
+		return "";
+	std::string low = to_lower(first_line);
+	if (low.find("python") != std::string::npos)
+		return "python";
+	if (low.find("bash") != std::string::npos)
+		return "shell";
+	if (low.find("sh") != std::string::npos)
+		return "shell";
+	if (low.find("zsh") != std::string::npos)
+		return "shell";
+	if (low.find("fish") != std::string::npos)
+		return "shell";
+	if (low.find("scheme") != std::string::npos || low.find("racket") != std::string::npos || low.find("guile") !=
+	    std::string::npos)
+		return "lisp";
+	return "";
+}
+
+
+std::string
+HighlighterRegistry::DetectForPath(std::string_view path, std::string_view first_line)
+{
+	// Extension
+	std::string p(path);
+	std::error_code ec;
+	std::string ext = std::filesystem::path(p).extension().string();
+	for (auto &ch: ext)
+		ch = static_cast<char>(std::tolower(static_cast<unsigned char>(ch)));
+	if (!ext.empty()) {
+		if (ext == ".c" || ext == ".cc" || ext == ".cpp" || ext == ".cxx" || ext == ".h" || ext == ".hpp" || ext
+		    == ".hh")
+			return "cpp";
+		if (ext == ".json")
+			return "json";
+		if (ext == ".md" || ext == ".markdown" || ext == ".mkd")
+			return "markdown";
+		if (ext == ".sh" || ext == ".bash" || ext == ".zsh" || ext == ".ksh" || ext == ".fish")
+			return "shell";
+		if (ext == ".go")
+			return "go";
+		if (ext == ".py")
+			return "python";
+		if (ext == ".rs")
+			return "rust";
+		if (ext == ".lisp" || ext == ".scm" || ext == ".rkt" || ext == ".el" || ext == ".clj" || ext == ".cljc"
+		    || ext == ".cl")
+			return "lisp";
+		if (ext == ".sql" || ext == ".sqlite")
+			return "sql";
+		if (ext == ".erl" || ext == ".hrl")
+			return "erlang";
+		if (ext == ".forth" || ext == ".fth" || ext == ".4th" || ext == ".fs")
+			return "forth";
+	}
+	// Shebang
+	std::string ft = shebang_to_ft(first_line);
+	return ft;
+}
+} // namespace kte
+
+// Extensibility API implementations
+namespace kte {
+void
+HighlighterRegistry::Register(std::string_view filetype, Factory factory, bool override_existing)
+{
+	std::string ft = Normalize(filetype);
+	for (auto &e: registry()) {
+		if (e.ft == ft) {
+			if (override_existing)
+				e.factory = std::move(factory);
+			return;
+		}
+	}
+	registry().push_back(RegEntry{ft, std::move(factory)});
+}
+
+
+bool
+HighlighterRegistry::IsRegistered(std::string_view filetype)
+{
+	std::string ft = Normalize(filetype);
+	for (const auto &e: registry())
+		if (e.ft == ft)
+			return true;
+	return false;
+}
+
+
+std::vector<std::string>
+HighlighterRegistry::RegisteredFiletypes()
+{
+	std::vector<std::string> out;
+	out.reserve(registry().size());
+	for (const auto &e: registry())
+		out.push_back(e.ft);
+	return out;
+}
+
+#ifdef KTE_ENABLE_TREESITTER
+// Forward declare adapter factory
+std::unique_ptr<LanguageHighlighter> CreateTreeSitterHighlighter(const char *filetype,
+                                                                 const void * (*get_lang)());
+
+void
+HighlighterRegistry::RegisterTreeSitter(std::string_view filetype,
+                                        const TSLanguage * (*get_language)())
+{
+	std::string ft = Normalize(filetype);
+	Register(ft, [ft, get_language]() {
+		return CreateTreeSitterHighlighter(ft.c_str(), reinterpret_cast<const void* (*)()>(get_language));
+	}, /*override_existing=*/true);
+}
+#endif
+} // namespace kte

syntax/HighlighterRegistry.h

@@ -0,0 +1,47 @@
+// HighlighterRegistry.h - create/detect language highlighters and allow external registration
+#pragma once
+
+#include <functional>
+#include <memory>
+#include <string>
+#include <string_view>
+#include <vector>
+
+#include "LanguageHighlighter.h"
+
+namespace kte {
+class HighlighterRegistry {
+public:
+	using Factory = std::function<std::unique_ptr<LanguageHighlighter>()>;
+
+	// Create a highlighter for normalized filetype id (e.g., "cpp", "json", "markdown", "shell", "go", "python", "rust", "lisp").
+	static std::unique_ptr<LanguageHighlighter> CreateFor(std::string_view filetype);
+
+	// Detect filetype by path extension and shebang (first line).
+	// Returns normalized id or empty string if unknown.
+	static std::string DetectForPath(std::string_view path, std::string_view first_line);
+
+	// Normalize various aliases/extensions to canonical ids.
+	static std::string Normalize(std::string_view ft);
+
+	// Extensibility: allow external code to register highlighters at runtime.
+	// The filetype key is normalized via Normalize(). If a factory is already registered for the
+	// normalized key and override=false, the existing factory is kept.
+	static void Register(std::string_view filetype, Factory factory, bool override_existing = true);
+
+	// Returns true if a factory is registered for the (normalized) filetype.
+	static bool IsRegistered(std::string_view filetype);
+
+	// Return a list of currently registered (normalized) filetypes. Primarily for diagnostics/tests.
+	static std::vector<std::string> RegisteredFiletypes();
+
+#ifdef KTE_ENABLE_TREESITTER
+	// Forward declaration to avoid hard dependency when disabled.
+	struct TSLanguage;
+	// Convenience: register a Tree-sitter-backed highlighter for a filetype.
+	// The getter should return a non-null language pointer for the grammar.
+	static void RegisterTreeSitter(std::string_view filetype,
+	                               const TSLanguage * (*get_language)());
+#endif
+};
+} // namespace kte

syntax/JsonHighlighter.cc

@@ -0,0 +1,90 @@
+#include "JsonHighlighter.h"
+#include "../Buffer.h"
+#include <cctype>
+
+namespace kte {
+static bool
+is_digit(char c)
+{
+	return c >= '0' && c <= '9';
+}
+
+
+void
+JSONHighlighter::HighlightLine(const Buffer &buf, int row, std::vector<HighlightSpan> &out) const
+{
+	const auto &rows = buf.Rows();
+	if (row < 0 || static_cast<std::size_t>(row) >= rows.size())
+		return;
+	std::string s = static_cast<std::string>(rows[static_cast<std::size_t>(row)]);
+	int n         = static_cast<int>(s.size());
+	auto push     = [&](int a, int b, TokenKind k) {
+		if (b > a)
+			out.push_back({a, b, k});
+	};
+
+	int i = 0;
+	while (i < n) {
+		char c = s[i];
+		if (c == ' ' || c == '\t') {
+			int j = i + 1;
+			while (j < n && (s[j] == ' ' || s[j] == '\t'))
+				++j;
+			push(i, j, TokenKind::Whitespace);
+			i = j;
+			continue;
+		}
+		if (c == '"') {
+			int j    = i + 1;
+			bool esc = false;
+			while (j < n) {
+				char d = s[j++];
+				if (esc) {
+					esc = false;
+					continue;
+				}
+				if (d == '\\') {
+					esc = true;
+					continue;
+				}
+				if (d == '"')
+					break;
+			}
+			push(i, j, TokenKind::String);
+			i = j;
+			continue;
+		}
+		if (is_digit(c) || (c == '-' && i + 1 < n && is_digit(s[i + 1]))) {
+			int j = i + 1;
+			while (j < n && (std::isdigit(static_cast<unsigned char>(s[j])) || s[j] == '.' || s[j] == 'e' ||
+			                 s[j] == 'E' || s[j] == '+' || s[j] == '-' || s[j] == '_'))
+				++j;
+			push(i, j, TokenKind::Number);
+			i = j;
+			continue;
+		}
+		// booleans/null
+		if (std::isalpha(static_cast<unsigned char>(c))) {
+			int j = i + 1;
+			while (j < n && std::isalpha(static_cast<unsigned char>(s[j])))
+				++j;
+			std::string id = s.substr(i, j - i);
+			if (id == "true" || id == "false" || id == "null")
+				push(i, j, TokenKind::Constant);
+			else
+				push(i, j, TokenKind::Identifier);
+			i = j;
+			continue;
+		}
+		// punctuation
+		if (c == '{' || c == '}' || c == '[' || c == ']' || c == ',' || c == ':') {
+			push(i, i + 1, TokenKind::Punctuation);
+			++i;
+			continue;
+		}
+		// fallback
+		push(i, i + 1, TokenKind::Default);
+		++i;
+	}
+}
+} // namespace kte

syntax/JsonHighlighter.h

@@ -0,0 +1,12 @@
+// JsonHighlighter.h - simple JSON line highlighter
+#pragma once
+
+#include "LanguageHighlighter.h"
+#include <vector>
+
+namespace kte {
+class JSONHighlighter final : public LanguageHighlighter {
+public:
+	void HighlightLine(const Buffer &buf, int row, std::vector<HighlightSpan> &out) const override;
+};
+} // namespace kte

syntax/LanguageHighlighter.h

@@ -0,0 +1,51 @@
+// LanguageHighlighter.h - interface for line-based highlighters
+#pragma once
+
+#include <memory>
+#include <vector>
+#include <string>
+
+#include "../Highlight.h"
+
+class Buffer;
+
+namespace kte {
+class LanguageHighlighter {
+public:
+	virtual ~LanguageHighlighter() = default;
+
+	// Produce highlight spans for a given buffer row. Implementations should append to out.
+	virtual void HighlightLine(const Buffer &buf, int row, std::vector<HighlightSpan> &out) const = 0;
+
+
+	virtual bool Stateful() const
+	{
+		return false;
+	}
+};
+
+// Optional extension for stateful highlighters (e.g., multi-line comments/strings).
+// Engines may detect and use this via dynamic_cast without breaking stateless impls.
+class StatefulHighlighter : public LanguageHighlighter {
+public:
+	struct LineState {
+		bool in_block_comment{false};
+		bool in_raw_string{false};
+		// For raw strings, remember the delimiter between the opening R"delim( and closing )delim"
+		std::string raw_delim;
+	};
+
+	// Highlight one line given the previous line state; return the resulting state after this line.
+	// Implementations should append spans for this line to out and compute the next state.
+	virtual LineState HighlightLineStateful(const Buffer &buf,
+	                                        int row,
+	                                        const LineState &prev,
+	                                        std::vector<HighlightSpan> &out) const = 0;
+
+
+	bool Stateful() const override
+	{
+		return true;
+	}
+};
+} // namespace kte

syntax/LispHighlighter.cc

@@ -0,0 +1,107 @@
+#include "LispHighlighter.h"
+#include "../Buffer.h"
+#include <cctype>
+
+namespace kte {
+static void
+push(std::vector<HighlightSpan> &out, int a, int b, TokenKind k)
+{
+	if (b > a)
+		out.push_back({a, b, k});
+}
+
+
+LispHighlighter::LispHighlighter()
+{
+	const char *kw[] = {
+		"defun", "lambda", "let", "let*", "define", "set!", "if", "cond", "begin", "quote", "quasiquote",
+		"unquote", "unquote-splicing", "loop", "do", "and", "or", "not"
+	};
+	for (auto s: kw)
+		kws_.insert(s);
+}
+
+
+void
+LispHighlighter::HighlightLine(const Buffer &buf, int row, std::vector<HighlightSpan> &out) const
+{
+	const auto &rows = buf.Rows();
+	if (row < 0 || static_cast<std::size_t>(row) >= rows.size())
+		return;
+	std::string s = static_cast<std::string>(rows[static_cast<std::size_t>(row)]);
+	int n         = static_cast<int>(s.size());
+	int i         = 0;
+	int bol       = 0;
+	while (bol < n && (s[bol] == ' ' || s[bol] == '\t'))
+		++bol;
+	if (bol < n && s[bol] == ';') {
+		push(out, bol, n, TokenKind::Comment);
+		if (bol > 0)
+			push(out, 0, bol, TokenKind::Whitespace);
+		return;
+	}
+	while (i < n) {
+		char c = s[i];
+		if (c == ' ' || c == '\t') {
+			int j = i + 1;
+			while (j < n && (s[j] == ' ' || s[j] == '\t'))
+				++j;
+			push(out, i, j, TokenKind::Whitespace);
+			i = j;
+			continue;
+		}
+		if (c == ';') {
+			push(out, i, n, TokenKind::Comment);
+			break;
+		}
+		if (c == '"') {
+			int j    = i + 1;
+			bool esc = false;
+			while (j < n) {
+				char d = s[j++];
+				if (esc) {
+					esc = false;
+					continue;
+				}
+				if (d == '\\') {
+					esc = true;
+					continue;
+				}
+				if (d == '"')
+					break;
+			}
+			push(out, i, j, TokenKind::String);
+			i = j;
+			continue;
+		}
+		if (std::isalpha(static_cast<unsigned char>(c)) || c == '*' || c == '-' || c == '+' || c == '/' || c ==
+		    '_') {
+			int j = i + 1;
+			while (j < n && (std::isalnum(static_cast<unsigned char>(s[j])) || s[j] == '*' || s[j] == '-' ||
+			                 s[j] == '+' || s[j] == '/' || s[j] == '_' || s[j] == '!'))
+				++j;
+			std::string id = s.substr(i, j - i);
+			TokenKind k    = kws_.count(id) ? TokenKind::Keyword : TokenKind::Identifier;
+			push(out, i, j, k);
+			i = j;
+			continue;
+		}
+		if (std::isdigit(static_cast<unsigned char>(c))) {
+			int j = i + 1;
+			while (j < n && (std::isdigit(static_cast<unsigned char>(s[j])) || s[j] == '.'))
+				++j;
+			push(out, i, j, TokenKind::Number);
+			i = j;
+			continue;
+		}
+		if (std::ispunct(static_cast<unsigned char>(c))) {
+			TokenKind k = TokenKind::Punctuation;
+			push(out, i, i + 1, k);
+			++i;
+			continue;
+		}
+		push(out, i, i + 1, TokenKind::Default);
+		++i;
+	}
+}
+} // namespace kte

syntax/LispHighlighter.h

@@ -0,0 +1,17 @@
+// LispHighlighter.h - simple Lisp/Scheme family highlighter
+#pragma once
+
+#include "LanguageHighlighter.h"
+#include <unordered_set>
+
+namespace kte {
+class LispHighlighter final : public LanguageHighlighter {
+public:
+	LispHighlighter();
+
+	void HighlightLine(const Buffer &buf, int row, std::vector<HighlightSpan> &out) const override;
+
+private:
+	std::unordered_set<std::string> kws_;
+};
+} // namespace kte

syntax/MarkdownHighlighter.cc

@@ -0,0 +1,132 @@
+#include "MarkdownHighlighter.h"
+#include "../Buffer.h"
+#include <cctype>
+
+namespace kte {
+static void
+push_span(std::vector<HighlightSpan> &out, int a, int b, TokenKind k)
+{
+	if (b > a)
+		out.push_back({a, b, k});
+}
+
+
+void
+MarkdownHighlighter::HighlightLine(const Buffer &buf, int row, std::vector<HighlightSpan> &out) const
+{
+	LineState st; // not used in stateless entry
+	(void) HighlightLineStateful(buf, row, st, out);
+}
+
+
+StatefulHighlighter::LineState
+MarkdownHighlighter::HighlightLineStateful(const Buffer &buf, int row, const LineState &prev,
+                                           std::vector<HighlightSpan> &out) const
+{
+	StatefulHighlighter::LineState state = prev;
+	const auto &rows                     = buf.Rows();
+	if (row < 0 || static_cast<std::size_t>(row) >= rows.size())
+		return state;
+	std::string s = static_cast<std::string>(rows[static_cast<std::size_t>(row)]);
+	int n         = static_cast<int>(s.size());
+
+	// Reuse in_block_comment flag as "in fenced code" state.
+	if (state.in_block_comment) {
+		// If line contains closing fence ``` then close after it
+		auto pos = s.find("```");
+		if (pos == std::string::npos) {
+			push_span(out, 0, n, TokenKind::String);
+			state.in_block_comment = true;
+			return state;
+		} else {
+			int end = static_cast<int>(pos + 3);
+			push_span(out, 0, end, TokenKind::String);
+			// rest of line processed normally after fence
+			int i = end;
+			// whitespace
+			if (i < n)
+				push_span(out, i, n, TokenKind::Default);
+			state.in_block_comment = false;
+			return state;
+		}
+	}
+
+	// Detect fenced code block start at beginning (allow leading spaces)
+	int bol = 0;
+	while (bol < n && (s[bol] == ' ' || s[bol] == '\t'))
+		++bol;
+	if (bol + 3 <= n && s.compare(bol, 3, "```") == 0) {
+		push_span(out, bol, n, TokenKind::String);
+		state.in_block_comment = true; // enter fenced mode
+		return state;
+	}
+
+	// Headings: lines starting with 1-6 '#'
+	if (bol < n && s[bol] == '#') {
+		int j = bol;
+		while (j < n && s[j] == '#')
+			++j; // hashes
+		// include following space and text as Keyword to stand out
+		push_span(out, bol, n, TokenKind::Keyword);
+		return state;
+	}
+
+	// Process inline: emphasis and code spans
+	int i = 0;
+	while (i < n) {
+		char c = s[i];
+		if (c == '`') {
+			int j = i + 1;
+			while (j < n && s[j] != '`')
+				++j;
+			if (j < n)
+				++j;
+			push_span(out, i, j, TokenKind::String);
+			i = j;
+			continue;
+		}
+		if (c == '*' || c == '_') {
+			// bold/italic markers: treat the marker and until next same marker as Type to highlight
+			char m = c;
+			int j  = i + 1;
+			while (j < n && s[j] != m)
+				++j;
+			if (j < n)
+				++j;
+			push_span(out, i, j, TokenKind::Type);
+			i = j;
+			continue;
+		}
+		// links []() minimal: treat [text](url) as Function
+		if (c == '[') {
+			int j = i + 1;
+			while (j < n && s[j] != ']')
+				++j;
+			if (j < n)
+				++j; // include ]
+			if (j < n && s[j] == '(') {
+				while (j < n && s[j] != ')')
+					++j;
+				if (j < n)
+					++j;
+			}
+			push_span(out, i, j, TokenKind::Function);
+			i = j;
+			continue;
+		}
+		// whitespace
+		if (c == ' ' || c == '\t') {
+			int j = i + 1;
+			while (j < n && (s[j] == ' ' || s[j] == '\t'))
+				++j;
+			push_span(out, i, j, TokenKind::Whitespace);
+			i = j;
+			continue;
+		}
+		// fallback: default single char
+		push_span(out, i, i + 1, TokenKind::Default);
+		++i;
+	}
+	return state;
+}
+} // namespace kte

syntax/MarkdownHighlighter.h

@@ -0,0 +1,14 @@
+// MarkdownHighlighter.h - simple Markdown highlighter
+#pragma once
+
+#include "LanguageHighlighter.h"
+
+namespace kte {
+class MarkdownHighlighter final : public StatefulHighlighter {
+public:
+	void HighlightLine(const Buffer &buf, int row, std::vector<HighlightSpan> &out) const override;
+
+	LineState HighlightLineStateful(const Buffer &buf, int row, const LineState &prev,
+	                                std::vector<HighlightSpan> &out) const override;
+};
+} // namespace kte

syntax/NullHighlighter.cc

@@ -0,0 +1,17 @@
+#include "NullHighlighter.h"
+#include "../Buffer.h"
+
+namespace kte {
+void
+NullHighlighter::HighlightLine(const Buffer &buf, int row, std::vector<HighlightSpan> &out) const
+{
+	const auto &rows = buf.Rows();
+	if (row < 0 || static_cast<std::size_t>(row) >= rows.size())
+		return;
+	std::string s = static_cast<std::string>(rows[static_cast<std::size_t>(row)]);
+	int n         = static_cast<int>(s.size());
+	if (n <= 0)
+		return;
+	out.push_back({0, n, TokenKind::Default});
+}
+} // namespace kte

syntax/NullHighlighter.h

@@ -0,0 +1,11 @@
+// NullHighlighter.h - default highlighter that emits a single Default span per line
+#pragma once
+
+#include "LanguageHighlighter.h"
+
+namespace kte {
+class NullHighlighter final : public LanguageHighlighter {
+public:
+	void HighlightLine(const Buffer &buf, int row, std::vector<HighlightSpan> &out) const override;
+};
+} // namespace kte

syntax/PythonHighlighter.cc

@@ -0,0 +1,172 @@
+#include "PythonHighlighter.h"
+#include "../Buffer.h"
+#include <cctype>
+
+namespace kte {
+static void
+push(std::vector<HighlightSpan> &out, int a, int b, TokenKind k)
+{
+	if (b > a)
+		out.push_back({a, b, k});
+}
+
+
+static bool
+is_ident_start(char c)
+{
+	return std::isalpha(static_cast<unsigned char>(c)) || c == '_';
+}
+
+
+static bool
+is_ident_char(char c)
+{
+	return std::isalnum(static_cast<unsigned char>(c)) || c == '_';
+}
+
+
+PythonHighlighter::PythonHighlighter()
+{
+	const char *kw[] = {
+		"and", "as", "assert", "break", "class", "continue", "def", "del", "elif", "else", "except", "False",
+		"finally", "for", "from", "global", "if", "import", "in", "is", "lambda", "None", "nonlocal", "not",
+		"or", "pass", "raise", "return", "True", "try", "while", "with", "yield"
+	};
+	for (auto s: kw)
+		kws_.insert(s);
+}
+
+
+void
+PythonHighlighter::HighlightLine(const Buffer &buf, int row, std::vector<HighlightSpan> &out) const
+{
+	LineState st;
+	(void) HighlightLineStateful(buf, row, st, out);
+}
+
+
+StatefulHighlighter::LineState
+PythonHighlighter::HighlightLineStateful(const Buffer &buf, int row, const LineState &prev,
+                                         std::vector<HighlightSpan> &out) const
+{
+	StatefulHighlighter::LineState state = prev;
+	const auto &rows                     = buf.Rows();
+	if (row < 0 || static_cast<std::size_t>(row) >= rows.size())
+		return state;
+	std::string s = static_cast<std::string>(rows[static_cast<std::size_t>(row)]);
+	int n         = static_cast<int>(s.size());
+
+	// Triple-quoted string continuation uses in_raw_string with raw_delim either "'''" or "\"\"\""
+	if (state.in_raw_string && (state.raw_delim == "'''" || state.raw_delim == "\"\"\"")) {
+		auto pos = s.find(state.raw_delim);
+		if (pos == std::string::npos) {
+			push(out, 0, n, TokenKind::String);
+			return state; // still inside
+		} else {
+			int end = static_cast<int>(pos + static_cast<int>(state.raw_delim.size()));
+			push(out, 0, end, TokenKind::String);
+			// remainder processed normally
+			s                   = s.substr(end);
+			n                   = static_cast<int>(s.size());
+			state.in_raw_string = false;
+			state.raw_delim.clear();
+			// Continue parsing remainder as a separate small loop
+			int base = end;
+			// original offset, but we already emitted to 'out' with base=0; following spans should be from 'end'
+			// For simplicity, mark rest as Default
+			if (n > 0)
+				push(out, base, base + n, TokenKind::Default);
+			return state;
+		}
+	}
+
+	int i = 0;
+	// Detect comment start '#', ignoring inside strings
+	while (i < n) {
+		char c = s[i];
+		if (c == ' ' || c == '\t') {
+			int j = i + 1;
+			while (j < n && (s[j] == ' ' || s[j] == '\t'))
+				++j;
+			push(out, i, j, TokenKind::Whitespace);
+			i = j;
+			continue;
+		}
+		if (c == '#') {
+			push(out, i, n, TokenKind::Comment);
+			break;
+		}
+		// Strings: triple quotes and single-line
+		if (c == '"' || c == '\'') {
+			char q = c;
+			// triple?
+			if (i + 2 < n && s[i + 1] == q && s[i + 2] == q) {
+				std::string delim(3, q);
+				int j    = i + 3; // search for closing triple
+				auto pos = s.find(delim, static_cast<std::size_t>(j));
+				if (pos == std::string::npos) {
+					push(out, i, n, TokenKind::String);
+					state.in_raw_string = true;
+					state.raw_delim     = delim;
+					return state;
+				} else {
+					int end = static_cast<int>(pos + 3);
+					push(out, i, end, TokenKind::String);
+					i = end;
+					continue;
+				}
+			} else {
+				int j    = i + 1;
+				bool esc = false;
+				while (j < n) {
+					char d = s[j++];
+					if (esc) {
+						esc = false;
+						continue;
+					}
+					if (d == '\\') {
+						esc = true;
+						continue;
+					}
+					if (d == q)
+						break;
+				}
+				push(out, i, j, TokenKind::String);
+				i = j;
+				continue;
+			}
+		}
+		if (std::isdigit(static_cast<unsigned char>(c))) {
+			int j = i + 1;
+			while (j < n && (std::isalnum(static_cast<unsigned char>(s[j])) || s[j] == '.' || s[j] == '_'))
+				++j;
+			push(out, i, j, TokenKind::Number);
+			i = j;
+			continue;
+		}
+		if (is_ident_start(c)) {
+			int j = i + 1;
+			while (j < n && is_ident_char(s[j]))
+				++j;
+			std::string id = s.substr(i, j - i);
+			TokenKind k    = TokenKind::Identifier;
+			if (kws_.count(id))
+				k = TokenKind::Keyword;
+			push(out, i, j, k);
+			i = j;
+			continue;
+		}
+		if (std::ispunct(static_cast<unsigned char>(c))) {
+			TokenKind k = TokenKind::Operator;
+			if (c == ':' || c == ',' || c == '(' || c == ')' || c == '[' || c == ']')
+				k = TokenKind::Punctuation;
+			push(out, i, i + 1, k);
+			++i;
+			continue;
+		}
+		push(out, i, i + 1, TokenKind::Default);
+		++i;
+	}
+	return state;
+}
+} // namespace kte

syntax/PythonHighlighter.h

@@ -0,0 +1,20 @@
+// PythonHighlighter.h - simple Python highlighter with triple-quote state
+#pragma once
+
+#include "LanguageHighlighter.h"
+#include <unordered_set>
+
+namespace kte {
+class PythonHighlighter final : public StatefulHighlighter {
+public:
+	PythonHighlighter();
+
+	void HighlightLine(const Buffer &buf, int row, std::vector<HighlightSpan> &out) const override;
+
+	LineState HighlightLineStateful(const Buffer &buf, int row, const LineState &prev,
+	                                std::vector<HighlightSpan> &out) const override;
+
+private:
+	std::unordered_set<std::string> kws_;
+};
+} // namespace kte

syntax/RustHighlighter.cc

@@ -0,0 +1,145 @@
+#include "RustHighlighter.h"
+#include "../Buffer.h"
+#include <cctype>
+
+namespace kte {
+static void
+push(std::vector<HighlightSpan> &out, int a, int b, TokenKind k)
+{
+	if (b > a)
+		out.push_back({a, b, k});
+}
+
+
+static bool
+is_ident_start(char c)
+{
+	return std::isalpha(static_cast<unsigned char>(c)) || c == '_';
+}
+
+
+static bool
+is_ident_char(char c)
+{
+	return std::isalnum(static_cast<unsigned char>(c)) || c == '_';
+}
+
+
+RustHighlighter::RustHighlighter()
+{
+	const char *kw[] = {
+		"as", "break", "const", "continue", "crate", "else", "enum", "extern", "false", "fn", "for", "if",
+		"impl", "in", "let", "loop", "match", "mod", "move", "mut", "pub", "ref", "return", "self", "Self",
+		"static", "struct", "super", "trait", "true", "type", "unsafe", "use", "where", "while", "dyn", "async",
+		"await", "try"
+	};
+	for (auto s: kw)
+		kws_.insert(s);
+	const char *tp[] = {
+		"u8", "u16", "u32", "u64", "u128", "usize", "i8", "i16", "i32", "i64", "i128", "isize", "f32", "f64",
+		"bool", "char", "str"
+	};
+	for (auto s: tp)
+		types_.insert(s);
+}
+
+
+void
+RustHighlighter::HighlightLine(const Buffer &buf, int row, std::vector<HighlightSpan> &out) const
+{
+	const auto &rows = buf.Rows();
+	if (row < 0 || static_cast<std::size_t>(row) >= rows.size())
+		return;
+	std::string s = static_cast<std::string>(rows[static_cast<std::size_t>(row)]);
+	int n         = static_cast<int>(s.size());
+	int i         = 0;
+	while (i < n) {
+		char c = s[i];
+		if (c == ' ' || c == '\t') {
+			int j = i + 1;
+			while (j < n && (s[j] == ' ' || s[j] == '\t'))
+				++j;
+			push(out, i, j, TokenKind::Whitespace);
+			i = j;
+			continue;
+		}
+		if (c == '/' && i + 1 < n && s[i + 1] == '/') {
+			push(out, i, n, TokenKind::Comment);
+			break;
+		}
+		if (c == '/' && i + 1 < n && s[i + 1] == '*') {
+			int j       = i + 2;
+			bool closed = false;
+			while (j + 1 <= n) {
+				if (j + 1 < n && s[j] == '*' && s[j + 1] == '/') {
+					j += 2;
+					closed = true;
+					break;
+				}
+				++j;
+			}
+			if (!closed) {
+				push(out, i, n, TokenKind::Comment);
+				break;
+			} else {
+				push(out, i, j, TokenKind::Comment);
+				i = j;
+				continue;
+			}
+		}
+		if (c == '"') {
+			int j    = i + 1;
+			bool esc = false;
+			while (j < n) {
+				char d = s[j++];
+				if (esc) {
+					esc = false;
+					continue;
+				}
+				if (d == '\\') {
+					esc = true;
+					continue;
+				}
+				if (d == '"')
+					break;
+			}
+			push(out, i, j, TokenKind::String);
+			i = j;
+			continue;
+		}
+		if (std::isdigit(static_cast<unsigned char>(c))) {
+			int j = i + 1;
+			while (j < n && (std::isalnum(static_cast<unsigned char>(s[j])) || s[j] == '.' || s[j] == '_'))
+				++j;
+			push(out, i, j, TokenKind::Number);
+			i = j;
+			continue;
+		}
+		if (is_ident_start(c)) {
+			int j = i + 1;
+			while (j < n && is_ident_char(s[j]))
+				++j;
+			std::string id = s.substr(i, j - i);
+			TokenKind k    = TokenKind::Identifier;
+			if (kws_.count(id))
+				k = TokenKind::Keyword;
+			else if (types_.count(id))
+				k = TokenKind::Type;
+			push(out, i, j, k);
+			i = j;
+			continue;
+		}
+		if (std::ispunct(static_cast<unsigned char>(c))) {
+			TokenKind k = TokenKind::Operator;
+			if (c == ';' || c == ',' || c == '(' || c == ')' || c == '{' || c == '}' || c == '[' || c ==
+			    ']')
+				k = TokenKind::Punctuation;
+			push(out, i, i + 1, k);
+			++i;
+			continue;
+		}
+		push(out, i, i + 1, TokenKind::Default);
+		++i;
+	}
+}
+} // namespace kte

syntax/RustHighlighter.h

@@ -0,0 +1,18 @@
+// RustHighlighter.h - simple Rust highlighter
+#pragma once
+
+#include "LanguageHighlighter.h"
+#include <unordered_set>
+
+namespace kte {
+class RustHighlighter final : public LanguageHighlighter {
+public:
+	RustHighlighter();
+
+	void HighlightLine(const Buffer &buf, int row, std::vector<HighlightSpan> &out) const override;
+
+private:
+	std::unordered_set<std::string> kws_;
+	std::unordered_set<std::string> types_;
+};
+} // namespace kte

syntax/ShellHighlighter.cc

@@ -0,0 +1,105 @@
+#include "ShellHighlighter.h"
+#include "../Buffer.h"
+#include <cctype>
+
+namespace kte {
+static void
+push(std::vector<HighlightSpan> &out, int a, int b, TokenKind k)
+{
+	if (b > a)
+		out.push_back({a, b, k});
+}
+
+
+void
+ShellHighlighter::HighlightLine(const Buffer &buf, int row, std::vector<HighlightSpan> &out) const
+{
+	const auto &rows = buf.Rows();
+	if (row < 0 || static_cast<std::size_t>(row) >= rows.size())
+		return;
+	std::string s = static_cast<std::string>(rows[static_cast<std::size_t>(row)]);
+	int n         = static_cast<int>(s.size());
+	int i         = 0;
+	// if first non-space is '#', whole line is comment
+	int bol = 0;
+	while (bol < n && (s[bol] == ' ' || s[bol] == '\t'))
+		++bol;
+	if (bol < n && s[bol] == '#') {
+		push(out, bol, n, TokenKind::Comment);
+		if (bol > 0)
+			push(out, 0, bol, TokenKind::Whitespace);
+		return;
+	}
+	while (i < n) {
+		char c = s[i];
+		if (c == ' ' || c == '\t') {
+			int j = i + 1;
+			while (j < n && (s[j] == ' ' || s[j] == '\t'))
+				++j;
+			push(out, i, j, TokenKind::Whitespace);
+			i = j;
+			continue;
+		}
+		if (c == '#') {
+			push(out, i, n, TokenKind::Comment);
+			break;
+		}
+		if (c == '\'' || c == '"') {
+			char q   = c;
+			int j    = i + 1;
+			bool esc = false;
+			while (j < n) {
+				char d = s[j++];
+				if (q == '"') {
+					if (esc) {
+						esc = false;
+						continue;
+					}
+					if (d == '\\') {
+						esc = true;
+						continue;
+					}
+					if (d == '"')
+						break;
+				} else {
+					if (d == '\'')
+						break;
+				}
+			}
+			push(out, i, j, TokenKind::String);
+			i = j;
+			continue;
+		}
+		// simple keywords
+		if (std::isalpha(static_cast<unsigned char>(c))) {
+			int j = i + 1;
+			while (j < n && (std::isalnum(static_cast<unsigned char>(s[j])) || s[j] == '_'))
+				++j;
+			std::string id           = s.substr(i, j - i);
+			static const char *kws[] = {
+				"if", "then", "fi", "for", "in", "do", "done", "case", "esac", "while", "function",
+				"elif", "else"
+			};
+			bool kw = false;
+			for (auto k: kws)
+				if (id == k) {
+					kw = true;
+					break;
+				}
+			push(out, i, j, kw ? TokenKind::Keyword : TokenKind::Identifier);
+			i = j;
+			continue;
+		}
+		if (std::ispunct(static_cast<unsigned char>(c))) {
+			TokenKind k = TokenKind::Operator;
+			if (c == '(' || c == ')' || c == '{' || c == '}' || c == ',' || c == ';')
+				k = TokenKind::Punctuation;
+			push(out, i, i + 1, k);
+			++i;
+			continue;
+		}
+		push(out, i, i + 1, TokenKind::Default);
+		++i;
+	}
+}
+} // namespace kte

syntax/ShellHighlighter.h

@@ -0,0 +1,11 @@
+// ShellHighlighter.h - simple POSIX shell highlighter
+#pragma once
+
+#include "LanguageHighlighter.h"
+
+namespace kte {
+class ShellHighlighter final : public LanguageHighlighter {
+public:
+	void HighlightLine(const Buffer &buf, int row, std::vector<HighlightSpan> &out) const override;
+};
+} // namespace kte

syntax/SqlHighlighter.cc

@@ -0,0 +1,156 @@
+#include "SqlHighlighter.h"
+#include "../Buffer.h"
+#include <cctype>
+
+namespace kte {
+static void
+push(std::vector<HighlightSpan> &out, int a, int b, TokenKind k)
+{
+	if (b > a)
+		out.push_back({a, b, k});
+}
+
+
+static bool
+is_ident_start(char c)
+{
+	return std::isalpha(static_cast<unsigned char>(c)) || c == '_';
+}
+
+
+static bool
+is_ident_char(char c)
+{
+	return std::isalnum(static_cast<unsigned char>(c)) || c == '_' || c == '$';
+}
+
+
+SqlHighlighter::SqlHighlighter()
+{
+	const char *kw[] = {
+		"select", "insert", "update", "delete", "from", "where", "group", "by", "order", "limit",
+		"offset", "values", "into", "create", "table", "index", "unique", "on", "as", "and", "or",
+		"not", "null", "is", "primary", "key", "constraint", "foreign", "references", "drop", "alter",
+		"add", "column", "rename", "to", "if", "exists", "join", "left", "right", "inner", "outer",
+		"cross", "using", "set", "distinct", "having", "union", "all", "case", "when", "then", "else",
+		"end", "pragma", "transaction", "begin", "commit", "rollback", "replace"
+	};
+	for (auto s: kw)
+		kws_.insert(s);
+
+	const char *types[] = {"integer", "real", "text", "blob", "numeric", "boolean", "date", "datetime"};
+	for (auto s: types)
+		types_.insert(s);
+}
+
+
+void
+SqlHighlighter::HighlightLine(const Buffer &buf, int row, std::vector<HighlightSpan> &out) const
+{
+	const auto &rows = buf.Rows();
+	if (row < 0 || static_cast<std::size_t>(row) >= rows.size())
+		return;
+	std::string s = static_cast<std::string>(rows[static_cast<std::size_t>(row)]);
+	int n         = static_cast<int>(s.size());
+	int i         = 0;
+
+	while (i < n) {
+		char c = s[i];
+		if (c == ' ' || c == '\t') {
+			int j = i + 1;
+			while (j < n && (s[j] == ' ' || s[j] == '\t'))
+				++j;
+			push(out, i, j, TokenKind::Whitespace);
+			i = j;
+			continue;
+		}
+		// line comments: -- ...
+		if (c == '-' && i + 1 < n && s[i + 1] == '-') {
+			push(out, i, n, TokenKind::Comment);
+			break;
+		}
+		// simple block comment on same line: /* ... */
+		if (c == '/' && i + 1 < n && s[i + 1] == '*') {
+			int j       = i + 2;
+			bool closed = false;
+			while (j + 1 <= n) {
+				if (j + 1 < n && s[j] == '*' && s[j + 1] == '/') {
+					j += 2;
+					closed = true;
+					break;
+				}
+				++j;
+			}
+			if (!closed) {
+				push(out, i, n, TokenKind::Comment);
+				break;
+			} else {
+				push(out, i, j, TokenKind::Comment);
+				i = j;
+				continue;
+			}
+		}
+		// strings: '...' or "..."
+		if (c == '\'' || c == '"') {
+			char q   = c;
+			int j    = i + 1;
+			bool esc = false;
+			while (j < n) {
+				char d = s[j++];
+				if (d == q) {
+					// Handle doubled quote escaping for SQL single quotes
+					if (q == '\'' && j < n && s[j] == '\'') {
+						++j;
+						continue;
+					}
+					break;
+				}
+				if (d == '\\') {
+					esc = !esc;
+				} else {
+					esc = false;
+				}
+			}
+			push(out, i, j, TokenKind::String);
+			i = j;
+			continue;
+		}
+		if (std::isdigit(static_cast<unsigned char>(c))) {
+			int j = i + 1;
+			while (j < n && (std::isalnum(static_cast<unsigned char>(s[j])) || s[j] == '.' || s[j] == '_'))
+				++j;
+			push(out, i, j, TokenKind::Number);
+			i = j;
+			continue;
+		}
+		if (is_ident_start(c)) {
+			int j = i + 1;
+			while (j < n && is_ident_char(s[j]))
+				++j;
+			std::string id = s.substr(i, j - i);
+			std::string lower;
+			lower.reserve(id.size());
+			for (char ch: id)
+				lower.push_back(static_cast<char>(std::tolower(static_cast<unsigned char>(ch))));
+			TokenKind k = TokenKind::Identifier;
+			if (kws_.count(lower))
+				k = TokenKind::Keyword;
+			else if (types_.count(lower))
+				k = TokenKind::Type;
+			push(out, i, j, k);
+			i = j;
+			continue;
+		}
+		if (std::ispunct(static_cast<unsigned char>(c))) {
+			TokenKind k = TokenKind::Operator;
+			if (c == ',' || c == ';' || c == '(' || c == ')')
+				k = TokenKind::Punctuation;
+			push(out, i, i + 1, k);
+			++i;
+			continue;
+		}
+		push(out, i, i + 1, TokenKind::Default);
+		++i;
+	}
+}
+} // namespace kte

syntax/SqlHighlighter.h

@@ -0,0 +1,18 @@
+// SqlHighlighter.h - simple SQL/SQLite highlighter
+#pragma once
+
+#include "LanguageHighlighter.h"
+#include <unordered_set>
+
+namespace kte {
+class SqlHighlighter final : public LanguageHighlighter {
+public:
+	SqlHighlighter();
+
+	void HighlightLine(const Buffer &buf, int row, std::vector<HighlightSpan> &out) const override;
+
+private:
+	std::unordered_set<std::string> kws_;
+	std::unordered_set<std::string> types_;
+};
+} // namespace kte

syntax/TreeSitterHighlighter.cc

@@ -0,0 +1,51 @@
+#include "TreeSitterHighlighter.h"
+
+#ifdef KTE_ENABLE_TREESITTER
+
+#include "Buffer.h"
+#include <utility>
+
+namespace kte {
+TreeSitterHighlighter::TreeSitterHighlighter(const TSLanguage *lang, std::string filetype)
+	: language_(lang), filetype_(std::move(filetype)) {}
+
+
+TreeSitterHighlighter::~TreeSitterHighlighter()
+{
+	disposeParser();
+}
+
+
+void
+TreeSitterHighlighter::ensureParsed(const Buffer & /*buf*/) const
+{
+	// Intentionally a stub to avoid pulling the Tree-sitter API and library by default.
+	// In future, when linking against tree-sitter, initialize parser_, set language_,
+	// and build tree_ from the buffer contents.
+}
+
+
+void
+TreeSitterHighlighter::disposeParser() const
+{
+	// Stub; nothing to dispose when not actually creating parser/tree
+}
+
+
+void
+TreeSitterHighlighter::HighlightLine(const Buffer &/*buf*/, int /*row*/, std::vector<HighlightSpan> &/*out*/) const
+{
+	// For now, no-op. When tree-sitter is wired, map nodes to TokenKind spans per line.
+}
+
+
+std::unique_ptr<LanguageHighlighter>
+CreateTreeSitterHighlighter(const char *filetype,
+                            const void * (*get_lang)())
+{
+	const auto *lang = reinterpret_cast<const TSLanguage *>(get_lang ? get_lang() : nullptr);
+	return std::make_unique < TreeSitterHighlighter > (lang, filetype ? std::string(filetype) : std::string());
+}
+} // namespace kte
+
+#endif // KTE_ENABLE_TREESITTER

syntax/TreeSitterHighlighter.h

@@ -0,0 +1,48 @@
+// TreeSitterHighlighter.h - optional adapter for Tree-sitter (behind KTE_ENABLE_TREESITTER)
+#pragma once
+
+#ifdef KTE_ENABLE_TREESITTER
+
+#include <memory>
+#include <string>
+#include <vector>
+
+#include "LanguageHighlighter.h"
+
+// Forward-declare Tree-sitter C API to avoid hard coupling in headers if includes are not present
+extern "C" {
+struct TSLanguage;
+struct TSParser;
+struct TSTree;
+}
+
+namespace kte {
+// A minimal adapter that uses Tree-sitter to parse the whole buffer and then, for now,
+// does very limited token classification. This acts as a scaffold for future richer
+// queries. If no queries are provided, it currently produces no spans (safe fallback).
+class TreeSitterHighlighter : public LanguageHighlighter {
+public:
+	explicit TreeSitterHighlighter(const TSLanguage *lang, std::string filetype);
+
+	~TreeSitterHighlighter() override;
+
+	void HighlightLine(const Buffer &buf, int row, std::vector<HighlightSpan> &out) const override;
+
+private:
+	const TSLanguage *language_{nullptr};
+	std::string filetype_;
+	// Lazy parser to avoid startup cost; mutable to allow creation in const method
+	mutable TSParser *parser_{nullptr};
+	mutable TSTree *tree_{nullptr};
+
+	void ensureParsed(const Buffer &buf) const;
+
+	void disposeParser() const;
+};
+
+// Factory used by HighlighterRegistry when registering via RegisterTreeSitter.
+std::unique_ptr<LanguageHighlighter> CreateTreeSitterHighlighter(const char *filetype,
+                                                                 const void * (*get_lang)());
+} // namespace kte
+
+#endif // KTE_ENABLE_TREESITTER

test_undo.cc

@@ -47,14 +47,14 @@ main()
 	// Initialize cursor to (0,0) explicitly
 	buf->SetCursor(0, 0);
 
- std::cout << "test_undo: Testing undo/redo system\n";
- std::cout << "====================================\n\n";
+	std::cout << "test_undo: Testing undo/redo system\n";
+	std::cout << "====================================\n\n";
 
 	bool running = true;
 
- // Test 1: Insert text and verify buffer contains expected text
- std::cout << "Test 1: Insert text 'Hello'\n";
- frontend.Input().QueueText("Hello");
+	// Test 1: Insert text and verify buffer contains expected text
+	std::cout << "Test 1: Insert text 'Hello'\n";
+	frontend.Input().QueueText("Hello");
 
 	while (!frontend.Input().IsEmpty() && running) {
 		frontend.Step(editor, running);
@@ -66,9 +66,9 @@ main()
 	std::cout << "  Buffer content: '" << line_after_insert << "'\n";
 	std::cout << "  ✓ Text insertion verified\n\n";
 
- // Test 2: Undo insertion - text should be removed
- std::cout << "Test 2: Undo insertion\n";
- frontend.Input().QueueCommand(CommandId::Undo);
+	// Test 2: Undo insertion - text should be removed
+	std::cout << "Test 2: Undo insertion\n";
+	frontend.Input().QueueCommand(CommandId::Undo);
 
 	while (!frontend.Input().IsEmpty() && running) {
 		frontend.Step(editor, running);
@@ -80,9 +80,9 @@ main()
 	std::cout << "  Buffer content: '" << line_after_undo << "'\n";
 	std::cout << "  ✓ Undo successful - text removed\n\n";
 
- // Test 3: Redo insertion - text should be restored
- std::cout << "Test 3: Redo insertion\n";
- frontend.Input().QueueCommand(CommandId::Redo);
+	// Test 3: Redo insertion - text should be restored
+	std::cout << "Test 3: Redo insertion\n";
+	frontend.Input().QueueCommand(CommandId::Redo);
 
 	while (!frontend.Input().IsEmpty() && running) {
 		frontend.Step(editor, running);
@@ -94,242 +94,242 @@ main()
 	std::cout << "  Buffer content: '" << line_after_redo << "'\n";
 	std::cout << "  ✓ Redo successful - text restored\n\n";
 
- // Test 4: Branching behavior – redo is discarded after new edits
- std::cout << "Test 4: Branching behavior (redo discarded after new edits)\n";
- // Reset to empty by undoing the last redo and the original insert, then reinsert 'abc'
- // Ensure buffer is empty before starting this scenario
- frontend.Input().QueueCommand(CommandId::Undo); // undo Hello
- while (!frontend.Input().IsEmpty() && running) {
-     frontend.Step(editor, running);
- }
- assert(std::string(buf->Rows()[0]) == "");
+	// Test 4: Branching behavior – redo is discarded after new edits
+	std::cout << "Test 4: Branching behavior (redo discarded after new edits)\n";
+	// Reset to empty by undoing the last redo and the original insert, then reinsert 'abc'
+	// Ensure buffer is empty before starting this scenario
+	frontend.Input().QueueCommand(CommandId::Undo); // undo Hello
+	while (!frontend.Input().IsEmpty() && running) {
+		frontend.Step(editor, running);
+	}
+	assert(std::string(buf->Rows()[0]) == "");
 
- // Type a contiguous word 'abc' (single batch)
- frontend.Input().QueueText("abc");
- while (!frontend.Input().IsEmpty() && running) {
-     frontend.Step(editor, running);
- }
- assert(std::string(buf->Rows()[0]) == "abc");
+	// Type a contiguous word 'abc' (single batch)
+	frontend.Input().QueueText("abc");
+	while (!frontend.Input().IsEmpty() && running) {
+		frontend.Step(editor, running);
+	}
+	assert(std::string(buf->Rows()[0]) == "abc");
 
- // Undo once – should remove the whole batch and leave empty
- frontend.Input().QueueCommand(CommandId::Undo);
- while (!frontend.Input().IsEmpty() && running) {
-     frontend.Step(editor, running);
- }
- assert(std::string(buf->Rows()[0]) == "");
+	// Undo once – should remove the whole batch and leave empty
+	frontend.Input().QueueCommand(CommandId::Undo);
+	while (!frontend.Input().IsEmpty() && running) {
+		frontend.Step(editor, running);
+	}
+	assert(std::string(buf->Rows()[0]) == "");
 
- // Now type new text 'X' – this should create a new branch and discard old redo chain
- frontend.Input().QueueText("X");
- while (!frontend.Input().IsEmpty() && running) {
-     frontend.Step(editor, running);
- }
- assert(std::string(buf->Rows()[0]) == "X");
+	// Now type new text 'X' – this should create a new branch and discard old redo chain
+	frontend.Input().QueueText("X");
+	while (!frontend.Input().IsEmpty() && running) {
+		frontend.Step(editor, running);
+	}
+	assert(std::string(buf->Rows()[0]) == "X");
 
- // Attempt Redo – should be a no-op (redo branch was discarded by new edit)
- frontend.Input().QueueCommand(CommandId::Redo);
- while (!frontend.Input().IsEmpty() && running) {
-     frontend.Step(editor, running);
- }
- assert(std::string(buf->Rows()[0]) == "X");
- // Undo and Redo along the new branch should still work
- frontend.Input().QueueCommand(CommandId::Undo);
- frontend.Input().QueueCommand(CommandId::Redo);
- while (!frontend.Input().IsEmpty() && running) {
-     frontend.Step(editor, running);
- }
- assert(std::string(buf->Rows()[0]) == "X");
- std::cout << "  ✓ Redo discarded after new edit; new branch undo/redo works\n\n";
+	// Attempt Redo – should be a no-op (redo branch was discarded by new edit)
+	frontend.Input().QueueCommand(CommandId::Redo);
+	while (!frontend.Input().IsEmpty() && running) {
+		frontend.Step(editor, running);
+	}
+	assert(std::string(buf->Rows()[0]) == "X");
+	// Undo and Redo along the new branch should still work
+	frontend.Input().QueueCommand(CommandId::Undo);
+	frontend.Input().QueueCommand(CommandId::Redo);
+	while (!frontend.Input().IsEmpty() && running) {
+		frontend.Step(editor, running);
+	}
+	assert(std::string(buf->Rows()[0]) == "X");
+	std::cout << "  ✓ Redo discarded after new edit; new branch undo/redo works\n\n";
 
- // Clear buffer state for next tests: undo to empty if needed
- frontend.Input().QueueCommand(CommandId::Undo);
- while (!frontend.Input().IsEmpty() && running) {
-     frontend.Step(editor, running);
- }
- assert(std::string(buf->Rows()[0]) == "");
+	// Clear buffer state for next tests: undo to empty if needed
+	frontend.Input().QueueCommand(CommandId::Undo);
+	while (!frontend.Input().IsEmpty() && running) {
+		frontend.Step(editor, running);
+	}
+	assert(std::string(buf->Rows()[0]) == "");
 
- // Test 5: UTF-8 insertion and undo/redo round-trip
- std::cout << "Test 5: UTF-8 insertion 'é漢' and undo/redo\n";
- const std::string utf8_text = "é漢"; // multi-byte UTF-8 (2 bytes + 3 bytes)
- frontend.Input().QueueText(utf8_text);
- while (!frontend.Input().IsEmpty() && running) {
-     frontend.Step(editor, running);
- }
- assert(std::string(buf->Rows()[0]) == utf8_text);
- // Undo should remove the entire contiguous insertion batch
- frontend.Input().QueueCommand(CommandId::Undo);
- while (!frontend.Input().IsEmpty() && running) {
-     frontend.Step(editor, running);
- }
- assert(std::string(buf->Rows()[0]) == "");
- // Redo restores it
- frontend.Input().QueueCommand(CommandId::Redo);
- while (!frontend.Input().IsEmpty() && running) {
-     frontend.Step(editor, running);
- }
- assert(std::string(buf->Rows()[0]) == utf8_text);
- std::cout << "  ✓ UTF-8 insert round-trips with undo/redo\n\n";
+	// Test 5: UTF-8 insertion and undo/redo round-trip
+	std::cout << "Test 5: UTF-8 insertion 'é漢' and undo/redo\n";
+	const std::string utf8_text = "é漢"; // multi-byte UTF-8 (2 bytes + 3 bytes)
+	frontend.Input().QueueText(utf8_text);
+	while (!frontend.Input().IsEmpty() && running) {
+		frontend.Step(editor, running);
+	}
+	assert(std::string(buf->Rows()[0]) == utf8_text);
+	// Undo should remove the entire contiguous insertion batch
+	frontend.Input().QueueCommand(CommandId::Undo);
+	while (!frontend.Input().IsEmpty() && running) {
+		frontend.Step(editor, running);
+	}
+	assert(std::string(buf->Rows()[0]) == "");
+	// Redo restores it
+	frontend.Input().QueueCommand(CommandId::Redo);
+	while (!frontend.Input().IsEmpty() && running) {
+		frontend.Step(editor, running);
+	}
+	assert(std::string(buf->Rows()[0]) == utf8_text);
+	std::cout << "  ✓ UTF-8 insert round-trips with undo/redo\n\n";
 
- // Clear for next test
- frontend.Input().QueueCommand(CommandId::Undo);
- while (!frontend.Input().IsEmpty() && running) {
-     frontend.Step(editor, running);
- }
- assert(std::string(buf->Rows()[0]) == "");
+	// Clear for next test
+	frontend.Input().QueueCommand(CommandId::Undo);
+	while (!frontend.Input().IsEmpty() && running) {
+		frontend.Step(editor, running);
+	}
+	assert(std::string(buf->Rows()[0]) == "");
 
- // Test 6: Multi-line operations (newline split and join via backspace at BOL)
- std::cout << "Test 6: Newline split and join via backspace at BOL\n";
- // Insert "ab" then newline then "cd" → expect two lines
- frontend.Input().QueueText("ab");
- frontend.Input().QueueCommand(CommandId::Newline);
- frontend.Input().QueueText("cd");
- while (!frontend.Input().IsEmpty() && running) {
-     frontend.Step(editor, running);
- }
- assert(buf->Rows().size() >= 2);
- assert(std::string(buf->Rows()[0]) == "ab");
- assert(std::string(buf->Rows()[1]) == "cd");
- std::cout << "  ✓ Split into two lines\n";
+	// Test 6: Multi-line operations (newline split and join via backspace at BOL)
+	std::cout << "Test 6: Newline split and join via backspace at BOL\n";
+	// Insert "ab" then newline then "cd" → expect two lines
+	frontend.Input().QueueText("ab");
+	frontend.Input().QueueCommand(CommandId::Newline);
+	frontend.Input().QueueText("cd");
+	while (!frontend.Input().IsEmpty() && running) {
+		frontend.Step(editor, running);
+	}
+	assert(buf->Rows().size() >= 2);
+	assert(std::string(buf->Rows()[0]) == "ab");
+	assert(std::string(buf->Rows()[1]) == "cd");
+	std::cout << "  ✓ Split into two lines\n";
 
- // Undo once – should remove "cd" insertion leaving two lines ["ab", ""] or join depending on commit
- frontend.Input().QueueCommand(CommandId::Undo);
- while (!frontend.Input().IsEmpty() && running) {
-     frontend.Step(editor, running);
- }
- // Current design batches typing on the second line; after undo, the second line should exist but be empty
- assert(buf->Rows().size() >= 2);
- assert(std::string(buf->Rows()[0]) == "ab");
- assert(std::string(buf->Rows()[1]) == "");
+	// Undo once – should remove "cd" insertion leaving two lines ["ab", ""] or join depending on commit
+	frontend.Input().QueueCommand(CommandId::Undo);
+	while (!frontend.Input().IsEmpty() && running) {
+		frontend.Step(editor, running);
+	}
+	// Current design batches typing on the second line; after undo, the second line should exist but be empty
+	assert(buf->Rows().size() >= 2);
+	assert(std::string(buf->Rows()[0]) == "ab");
+	assert(std::string(buf->Rows()[1]) == "");
 
- // Undo the newline – should rejoin to a single line "ab"
- frontend.Input().QueueCommand(CommandId::Undo);
- while (!frontend.Input().IsEmpty() && running) {
-     frontend.Step(editor, running);
- }
- assert(buf->Rows().size() >= 1);
- assert(std::string(buf->Rows()[0]) == "ab");
+	// Undo the newline – should rejoin to a single line "ab"
+	frontend.Input().QueueCommand(CommandId::Undo);
+	while (!frontend.Input().IsEmpty() && running) {
+		frontend.Step(editor, running);
+	}
+	assert(buf->Rows().size() >= 1);
+	assert(std::string(buf->Rows()[0]) == "ab");
 
- // Redo twice to get back to ["ab","cd"]
- frontend.Input().QueueCommand(CommandId::Redo);
- frontend.Input().QueueCommand(CommandId::Redo);
- while (!frontend.Input().IsEmpty() && running) {
-     frontend.Step(editor, running);
- }
- assert(std::string(buf->Rows()[0]) == "ab");
- assert(std::string(buf->Rows()[1]) == "cd");
- std::cout << "  ✓ Newline undo/redo round-trip\n";
+	// Redo twice to get back to ["ab","cd"]
+	frontend.Input().QueueCommand(CommandId::Redo);
+	frontend.Input().QueueCommand(CommandId::Redo);
+	while (!frontend.Input().IsEmpty() && running) {
+		frontend.Step(editor, running);
+	}
+	assert(std::string(buf->Rows()[0]) == "ab");
+	assert(std::string(buf->Rows()[1]) == "cd");
+	std::cout << "  ✓ Newline undo/redo round-trip\n";
 
- // Now join via Backspace at beginning of second line
- frontend.Input().QueueCommand(CommandId::MoveDown); // ensure we're on the second line
- frontend.Input().QueueCommand(CommandId::MoveHome); // go to BOL on second line
- frontend.Input().QueueCommand(CommandId::Backspace); // join with previous line
- while (!frontend.Input().IsEmpty() && running) {
-     frontend.Step(editor, running);
- }
- assert(buf->Rows().size() >= 1);
- assert(std::string(buf->Rows()[0]) == "abcd");
- std::cout << "  ✓ Backspace at BOL joins lines\n";
+	// Now join via Backspace at beginning of second line
+	frontend.Input().QueueCommand(CommandId::MoveDown); // ensure we're on the second line
+	frontend.Input().QueueCommand(CommandId::MoveHome); // go to BOL on second line
+	frontend.Input().QueueCommand(CommandId::Backspace); // join with previous line
+	while (!frontend.Input().IsEmpty() && running) {
+		frontend.Step(editor, running);
+	}
+	assert(buf->Rows().size() >= 1);
+	assert(std::string(buf->Rows()[0]) == "abcd");
+	std::cout << "  ✓ Backspace at BOL joins lines\n";
 
- // Undo/Redo the join
- frontend.Input().QueueCommand(CommandId::Undo);
- frontend.Input().QueueCommand(CommandId::Redo);
- while (!frontend.Input().IsEmpty() && running) {
-     frontend.Step(editor, running);
- }
- assert(buf->Rows().size() >= 1);
- assert(std::string(buf->Rows()[0]) == "abcd");
- std::cout << "  ✓ Join undo/redo round-trip\n\n";
+	// Undo/Redo the join
+	frontend.Input().QueueCommand(CommandId::Undo);
+	frontend.Input().QueueCommand(CommandId::Redo);
+	while (!frontend.Input().IsEmpty() && running) {
+		frontend.Step(editor, running);
+	}
+	assert(buf->Rows().size() >= 1);
+	assert(std::string(buf->Rows()[0]) == "abcd");
+	std::cout << "  ✓ Join undo/redo round-trip\n\n";
 
- // Test 7: Typing batching – a contiguous word undone in one step
- std::cout << "Test 7: Typing batching (single undo removes whole word)\n";
- // Clear current line first
- frontend.Input().QueueCommand(CommandId::MoveHome);
- frontend.Input().QueueCommand(CommandId::KillToEOL);
- while (!frontend.Input().IsEmpty() && running) {
-     frontend.Step(editor, running);
- }
- assert(std::string(buf->Rows()[0]).empty());
- // Type a word and verify one undo clears it
- frontend.Input().QueueText("hello");
- while (!frontend.Input().IsEmpty() && running) {
-     frontend.Step(editor, running);
- }
- assert(std::string(buf->Rows()[0]) == "hello");
- frontend.Input().QueueCommand(CommandId::Undo);
- while (!frontend.Input().IsEmpty() && running) {
-     frontend.Step(editor, running);
- }
- assert(std::string(buf->Rows()[0]).empty());
- frontend.Input().QueueCommand(CommandId::Redo);
- while (!frontend.Input().IsEmpty() && running) {
-     frontend.Step(editor, running);
- }
- assert(std::string(buf->Rows()[0]) == "hello");
- std::cout << "  ✓ Contiguous typing batched into single undo step\n\n";
+	// Test 7: Typing batching – a contiguous word undone in one step
+	std::cout << "Test 7: Typing batching (single undo removes whole word)\n";
+	// Clear current line first
+	frontend.Input().QueueCommand(CommandId::MoveHome);
+	frontend.Input().QueueCommand(CommandId::KillToEOL);
+	while (!frontend.Input().IsEmpty() && running) {
+		frontend.Step(editor, running);
+	}
+	assert(std::string(buf->Rows()[0]).empty());
+	// Type a word and verify one undo clears it
+	frontend.Input().QueueText("hello");
+	while (!frontend.Input().IsEmpty() && running) {
+		frontend.Step(editor, running);
+	}
+	assert(std::string(buf->Rows()[0]) == "hello");
+	frontend.Input().QueueCommand(CommandId::Undo);
+	while (!frontend.Input().IsEmpty() && running) {
+		frontend.Step(editor, running);
+	}
+	assert(std::string(buf->Rows()[0]).empty());
+	frontend.Input().QueueCommand(CommandId::Redo);
+	while (!frontend.Input().IsEmpty() && running) {
+		frontend.Step(editor, running);
+	}
+	assert(std::string(buf->Rows()[0]) == "hello");
+	std::cout << "  ✓ Contiguous typing batched into single undo step\n\n";
 
- // Test 8: Forward delete batching at a fixed anchor column
- std::cout << "Test 8: Forward delete batching at fixed anchor (DeleteChar)\n";
- // Prepare line content
- frontend.Input().QueueCommand(CommandId::MoveHome);
- frontend.Input().QueueCommand(CommandId::KillToEOL);
- while (!frontend.Input().IsEmpty() && running) {
-     frontend.Step(editor, running);
- }
- frontend.Input().QueueText("abcdef");
- while (!frontend.Input().IsEmpty() && running) {
-     frontend.Step(editor, running);
- }
- // Ensure cursor at anchor column 0
- frontend.Input().QueueCommand(CommandId::MoveHome);
- // Delete three chars at cursor; should batch into one Delete node
- frontend.Input().QueueCommand(CommandId::DeleteChar, "", 3);
- while (!frontend.Input().IsEmpty() && running) {
-     frontend.Step(editor, running);
- }
- assert(std::string(buf->Rows()[0]) == "def");
- // Single undo should restore the entire deleted run
- frontend.Input().QueueCommand(CommandId::Undo);
- while (!frontend.Input().IsEmpty() && running) {
-     frontend.Step(editor, running);
- }
- assert(std::string(buf->Rows()[0]) == "abcdef");
- // Redo should remove the same run again
- frontend.Input().QueueCommand(CommandId::Redo);
- while (!frontend.Input().IsEmpty() && running) {
-     frontend.Step(editor, running);
- }
- assert(std::string(buf->Rows()[0]) == "def");
- std::cout << "  ✓ Forward delete batched and undo/redo round-trips\n\n";
+	// Test 8: Forward delete batching at a fixed anchor column
+	std::cout << "Test 8: Forward delete batching at fixed anchor (DeleteChar)\n";
+	// Prepare line content
+	frontend.Input().QueueCommand(CommandId::MoveHome);
+	frontend.Input().QueueCommand(CommandId::KillToEOL);
+	while (!frontend.Input().IsEmpty() && running) {
+		frontend.Step(editor, running);
+	}
+	frontend.Input().QueueText("abcdef");
+	while (!frontend.Input().IsEmpty() && running) {
+		frontend.Step(editor, running);
+	}
+	// Ensure cursor at anchor column 0
+	frontend.Input().QueueCommand(CommandId::MoveHome);
+	// Delete three chars at cursor; should batch into one Delete node
+	frontend.Input().QueueCommand(CommandId::DeleteChar, "", 3);
+	while (!frontend.Input().IsEmpty() && running) {
+		frontend.Step(editor, running);
+	}
+	assert(std::string(buf->Rows()[0]) == "def");
+	// Single undo should restore the entire deleted run
+	frontend.Input().QueueCommand(CommandId::Undo);
+	while (!frontend.Input().IsEmpty() && running) {
+		frontend.Step(editor, running);
+	}
+	assert(std::string(buf->Rows()[0]) == "abcdef");
+	// Redo should remove the same run again
+	frontend.Input().QueueCommand(CommandId::Redo);
+	while (!frontend.Input().IsEmpty() && running) {
+		frontend.Step(editor, running);
+	}
+	assert(std::string(buf->Rows()[0]) == "def");
+	std::cout << "  ✓ Forward delete batched and undo/redo round-trips\n\n";
 
- // Test 9: Backspace batching with prepend rule (cursor moves left)
- std::cout << "Test 9: Backspace batching with prepend rule\n";
- // Restore to full string then backspace a run
- frontend.Input().QueueCommand(CommandId::Undo); // bring back to "abcdef"
- while (!frontend.Input().IsEmpty() && running) {
-     frontend.Step(editor, running);
- }
- assert(std::string(buf->Rows()[0]) == "abcdef");
- // Move to end and backspace three characters; should batch into one Delete node
- frontend.Input().QueueCommand(CommandId::MoveEnd);
- frontend.Input().QueueCommand(CommandId::Backspace, "", 3);
- while (!frontend.Input().IsEmpty() && running) {
-     frontend.Step(editor, running);
- }
- assert(std::string(buf->Rows()[0]) == "abc");
- // Single undo restores the deleted run
- frontend.Input().QueueCommand(CommandId::Undo);
- while (!frontend.Input().IsEmpty() && running) {
-     frontend.Step(editor, running);
- }
- assert(std::string(buf->Rows()[0]) == "abcdef");
- // Redo removes it again
- frontend.Input().QueueCommand(CommandId::Redo);
- while (!frontend.Input().IsEmpty() && running) {
-     frontend.Step(editor, running);
- }
- assert(std::string(buf->Rows()[0]) == "abc");
- std::cout << "  ✓ Backspace run batched and undo/redo round-trips\n\n";
+	// Test 9: Backspace batching with prepend rule (cursor moves left)
+	std::cout << "Test 9: Backspace batching with prepend rule\n";
+	// Restore to full string then backspace a run
+	frontend.Input().QueueCommand(CommandId::Undo); // bring back to "abcdef"
+	while (!frontend.Input().IsEmpty() && running) {
+		frontend.Step(editor, running);
+	}
+	assert(std::string(buf->Rows()[0]) == "abcdef");
+	// Move to end and backspace three characters; should batch into one Delete node
+	frontend.Input().QueueCommand(CommandId::MoveEnd);
+	frontend.Input().QueueCommand(CommandId::Backspace, "", 3);
+	while (!frontend.Input().IsEmpty() && running) {
+		frontend.Step(editor, running);
+	}
+	assert(std::string(buf->Rows()[0]) == "abc");
+	// Single undo restores the deleted run
+	frontend.Input().QueueCommand(CommandId::Undo);
+	while (!frontend.Input().IsEmpty() && running) {
+		frontend.Step(editor, running);
+	}
+	assert(std::string(buf->Rows()[0]) == "abcdef");
+	// Redo removes it again
+	frontend.Input().QueueCommand(CommandId::Redo);
+	while (!frontend.Input().IsEmpty() && running) {
+		frontend.Step(editor, running);
+	}
+	assert(std::string(buf->Rows()[0]) == "abc");
+	std::cout << "  ✓ Backspace run batched and undo/redo round-trips\n\n";
 
- frontend.Shutdown();
+	frontend.Shutdown();
 
 	std::cout << "====================================\n";
 	std::cout << "All tests passed!\n";

themes/EInk.h

@@ -0,0 +1,177 @@
+// themes/EInk.h — Monochrome e-ink inspired ImGui themes (header-only)
+#pragma once
+#include "imgui.h"
+#include "ThemeHelpers.h"
+
+// Expects to be included from GUITheme.h after <imgui.h> and RGBA() helper
+
+static void
+ApplyEInkImGuiTheme()
+{
+	// E-Ink grayscale palette (light background)
+	const ImVec4 paper  = RGBA(0xF2F2EE); // light paper
+	const ImVec4 bg1    = RGBA(0xE6E6E2);
+	const ImVec4 bg2    = RGBA(0xDADAD5);
+	const ImVec4 bg3    = RGBA(0xCFCFCA);
+	const ImVec4 ink    = RGBA(0x111111); // primary text (near black)
+	const ImVec4 dim    = RGBA(0x666666); // disabled text
+	const ImVec4 border = RGBA(0xB8B8B3);
+	const ImVec4 accent = RGBA(0x222222); // controls/active
+
+	ImGuiStyle &style      = ImGui::GetStyle();
+	style.WindowPadding    = ImVec2(8.0f, 8.0f);
+	style.FramePadding     = ImVec2(6.0f, 4.0f);
+	style.CellPadding      = ImVec2(6.0f, 4.0f);
+	style.ItemSpacing      = ImVec2(6.0f, 6.0f);
+	style.ItemInnerSpacing = ImVec2(6.0f, 4.0f);
+	style.ScrollbarSize    = 14.0f;
+	style.GrabMinSize      = 10.0f;
+	style.WindowRounding   = 0.0f;
+	style.FrameRounding    = 0.0f;
+	style.PopupRounding    = 0.0f;
+	style.GrabRounding     = 0.0f;
+	style.TabRounding      = 0.0f;
+	style.WindowBorderSize = 1.0f;
+	style.FrameBorderSize  = 1.0f;
+
+	ImVec4 *colors                         = style.Colors;
+	colors[ImGuiCol_Text]                  = ink;
+	colors[ImGuiCol_TextDisabled]          = ImVec4(dim.x, dim.y, dim.z, 1.0f);
+	colors[ImGuiCol_WindowBg]              = paper;
+	colors[ImGuiCol_ChildBg]               = paper;
+	colors[ImGuiCol_PopupBg]               = ImVec4(bg1.x, bg1.y, bg1.z, 0.98f);
+	colors[ImGuiCol_Border]                = border;
+	colors[ImGuiCol_BorderShadow]          = RGBA(0x000000, 0.0f);
+	colors[ImGuiCol_FrameBg]               = bg2;
+	colors[ImGuiCol_FrameBgHovered]        = bg3;
+	colors[ImGuiCol_FrameBgActive]         = bg1;
+	colors[ImGuiCol_TitleBg]               = bg1;
+	colors[ImGuiCol_TitleBgActive]         = bg2;
+	colors[ImGuiCol_TitleBgCollapsed]      = bg1;
+	colors[ImGuiCol_MenuBarBg]             = bg1;
+	colors[ImGuiCol_ScrollbarBg]           = paper;
+	colors[ImGuiCol_ScrollbarGrab]         = bg3;
+	colors[ImGuiCol_ScrollbarGrabHovered]  = bg2;
+	colors[ImGuiCol_ScrollbarGrabActive]   = bg1;
+	colors[ImGuiCol_CheckMark]             = accent;
+	colors[ImGuiCol_SliderGrab]            = accent;
+	colors[ImGuiCol_SliderGrabActive]      = ink;
+	colors[ImGuiCol_Button]                = bg3;
+	colors[ImGuiCol_ButtonHovered]         = bg2;
+	colors[ImGuiCol_ButtonActive]          = bg1;
+	colors[ImGuiCol_Header]                = bg3;
+	colors[ImGuiCol_HeaderHovered]         = bg2;
+	colors[ImGuiCol_HeaderActive]          = bg2;
+	colors[ImGuiCol_Separator]             = border;
+	colors[ImGuiCol_SeparatorHovered]      = bg2;
+	colors[ImGuiCol_SeparatorActive]       = accent;
+	colors[ImGuiCol_ResizeGrip]            = ImVec4(ink.x, ink.y, ink.z, 0.12f);
+	colors[ImGuiCol_ResizeGripHovered]     = ImVec4(accent.x, accent.y, accent.z, 0.50f);
+	colors[ImGuiCol_ResizeGripActive]      = ink;
+	colors[ImGuiCol_Tab]                   = bg2;
+	colors[ImGuiCol_TabHovered]            = bg1;
+	colors[ImGuiCol_TabActive]             = bg3;
+	colors[ImGuiCol_TabUnfocused]          = bg2;
+	colors[ImGuiCol_TabUnfocusedActive]    = bg3;
+	colors[ImGuiCol_TableHeaderBg]         = bg2;
+	colors[ImGuiCol_TableBorderStrong]     = bg1;
+	colors[ImGuiCol_TableBorderLight]      = ImVec4(bg1.x, bg1.y, bg1.z, 0.6f);
+	colors[ImGuiCol_TableRowBg]            = ImVec4(bg1.x, bg1.y, bg1.z, 0.2f);
+	colors[ImGuiCol_TableRowBgAlt]         = ImVec4(bg1.x, bg1.y, bg1.z, 0.35f);
+	colors[ImGuiCol_TextSelectedBg]        = ImVec4(accent.x, accent.y, accent.z, 0.30f);
+	colors[ImGuiCol_DragDropTarget]        = accent;
+	colors[ImGuiCol_NavHighlight]          = accent;
+	colors[ImGuiCol_NavWindowingHighlight] = ImVec4(ink.x, ink.y, ink.z, 0.70f);
+	colors[ImGuiCol_NavWindowingDimBg]     = ImVec4(0.0f, 0.0f, 0.0f, 0.45f);
+	colors[ImGuiCol_ModalWindowDimBg]      = ImVec4(0.0f, 0.0f, 0.0f, 0.45f);
+	colors[ImGuiCol_PlotLines]             = accent;
+	colors[ImGuiCol_PlotLinesHovered]      = ink;
+	colors[ImGuiCol_PlotHistogram]         = accent;
+	colors[ImGuiCol_PlotHistogramHovered]  = ink;
+}
+
+
+static inline void
+ApplyEInkDarkImGuiTheme()
+{
+	// E-Ink dark variant (dark background, light ink)
+	const ImVec4 paper  = RGBA(0x1A1A1A);
+	const ImVec4 bg1    = RGBA(0x222222);
+	const ImVec4 bg2    = RGBA(0x2B2B2B);
+	const ImVec4 bg3    = RGBA(0x343434);
+	const ImVec4 ink    = RGBA(0xEDEDEA);
+	const ImVec4 dim    = RGBA(0xB5B5B3);
+	const ImVec4 border = RGBA(0x444444);
+	const ImVec4 accent = RGBA(0xDDDDDD);
+
+	ImGuiStyle &style      = ImGui::GetStyle();
+	style.WindowPadding    = ImVec2(8.0f, 8.0f);
+	style.FramePadding     = ImVec2(6.0f, 4.0f);
+	style.CellPadding      = ImVec2(6.0f, 4.0f);
+	style.ItemSpacing      = ImVec2(6.0f, 6.0f);
+	style.ItemInnerSpacing = ImVec2(6.0f, 4.0f);
+	style.ScrollbarSize    = 14.0f;
+	style.GrabMinSize      = 10.0f;
+	style.WindowRounding   = 0.0f;
+	style.FrameRounding    = 0.0f;
+	style.PopupRounding    = 0.0f;
+	style.GrabRounding     = 0.0f;
+	style.TabRounding      = 0.0f;
+	style.WindowBorderSize = 1.0f;
+	style.FrameBorderSize  = 1.0f;
+
+	ImVec4 *colors                         = style.Colors;
+	colors[ImGuiCol_Text]                  = ink;
+	colors[ImGuiCol_TextDisabled]          = ImVec4(dim.x, dim.y, dim.z, 1.0f);
+	colors[ImGuiCol_WindowBg]              = paper;
+	colors[ImGuiCol_ChildBg]               = paper;
+	colors[ImGuiCol_PopupBg]               = ImVec4(bg1.x, bg1.y, bg1.z, 0.98f);
+	colors[ImGuiCol_Border]                = border;
+	colors[ImGuiCol_BorderShadow]          = RGBA(0x000000, 0.0f);
+	colors[ImGuiCol_FrameBg]               = bg2;
+	colors[ImGuiCol_FrameBgHovered]        = bg3;
+	colors[ImGuiCol_FrameBgActive]         = bg1;
+	colors[ImGuiCol_TitleBg]               = bg1;
+	colors[ImGuiCol_TitleBgActive]         = bg2;
+	colors[ImGuiCol_TitleBgCollapsed]      = bg1;
+	colors[ImGuiCol_MenuBarBg]             = bg1;
+	colors[ImGuiCol_ScrollbarBg]           = paper;
+	colors[ImGuiCol_ScrollbarGrab]         = bg3;
+	colors[ImGuiCol_ScrollbarGrabHovered]  = bg2;
+	colors[ImGuiCol_ScrollbarGrabActive]   = bg1;
+	colors[ImGuiCol_CheckMark]             = accent;
+	colors[ImGuiCol_SliderGrab]            = accent;
+	colors[ImGuiCol_SliderGrabActive]      = ink;
+	colors[ImGuiCol_Button]                = bg3;
+	colors[ImGuiCol_ButtonHovered]         = bg2;
+	colors[ImGuiCol_ButtonActive]          = bg1;
+	colors[ImGuiCol_Header]                = bg3;
+	colors[ImGuiCol_HeaderHovered]         = bg2;
+	colors[ImGuiCol_HeaderActive]          = bg2;
+	colors[ImGuiCol_Separator]             = border;
+	colors[ImGuiCol_SeparatorHovered]      = bg2;
+	colors[ImGuiCol_SeparatorActive]       = accent;
+	colors[ImGuiCol_ResizeGrip]            = ImVec4(ink.x, ink.y, ink.z, 0.12f);
+	colors[ImGuiCol_ResizeGripHovered]     = ImVec4(accent.x, accent.y, accent.z, 0.50f);
+	colors[ImGuiCol_ResizeGripActive]      = ink;
+	colors[ImGuiCol_Tab]                   = bg2;
+	colors[ImGuiCol_TabHovered]            = bg1;
+	colors[ImGuiCol_TabActive]             = bg3;
+	colors[ImGuiCol_TabUnfocused]          = bg2;
+	colors[ImGuiCol_TabUnfocusedActive]    = bg3;
+	colors[ImGuiCol_TableHeaderBg]         = bg2;
+	colors[ImGuiCol_TableBorderStrong]     = bg1;
+	colors[ImGuiCol_TableBorderLight]      = ImVec4(bg1.x, bg1.y, bg1.z, 0.6f);
+	colors[ImGuiCol_TableRowBg]            = ImVec4(bg1.x, bg1.y, bg1.z, 0.2f);
+	colors[ImGuiCol_TableRowBgAlt]         = ImVec4(bg1.x, bg1.y, bg1.z, 0.35f);
+	colors[ImGuiCol_TextSelectedBg]        = ImVec4(accent.x, accent.y, accent.z, 0.30f);
+	colors[ImGuiCol_DragDropTarget]        = accent;
+	colors[ImGuiCol_NavHighlight]          = accent;
+	colors[ImGuiCol_NavWindowingHighlight] = ImVec4(ink.x, ink.y, ink.z, 0.70f);
+	colors[ImGuiCol_NavWindowingDimBg]     = ImVec4(0.0f, 0.0f, 0.0f, 0.45f);
+	colors[ImGuiCol_ModalWindowDimBg]      = ImVec4(0.0f, 0.0f, 0.0f, 0.45f);
+	colors[ImGuiCol_PlotLines]             = accent;
+	colors[ImGuiCol_PlotLinesHovered]      = ink;
+	colors[ImGuiCol_PlotHistogram]         = accent;
+	colors[ImGuiCol_PlotHistogramHovered]  = ink;
+}

themes/Gruvbox.h

@@ -0,0 +1,204 @@
+// themes/Gruvbox.h — Gruvbox Dark/Light (medium) ImGui themes (header-only)
+#pragma once
+#include "ThemeHelpers.h"
+
+// Expects to be included from GUITheme.h after <imgui.h> and RGBA() helper
+
+static void
+ApplyGruvboxDarkMediumTheme()
+{
+	// Gruvbox (dark, medium) palette
+	const ImVec4 bg0 = RGBA(0x282828); // dark0
+	const ImVec4 bg1 = RGBA(0x3C3836); // dark1
+	const ImVec4 bg2 = RGBA(0x504945); // dark2
+	const ImVec4 bg3 = RGBA(0x665C54); // dark3
+	const ImVec4 fg1 = RGBA(0xEBDBB2); // light1
+	const ImVec4 fg0 = RGBA(0xFBF1C7); // light0
+	// accent colors
+	const ImVec4 yellow = RGBA(0xFABD2F);
+	const ImVec4 blue   = RGBA(0x83A598);
+	const ImVec4 aqua   = RGBA(0x8EC07C);
+	const ImVec4 orange = RGBA(0xFE8019);
+
+	ImGuiStyle &style      = ImGui::GetStyle();
+	style.WindowPadding    = ImVec2(8.0f, 8.0f);
+	style.FramePadding     = ImVec2(6.0f, 4.0f);
+	style.CellPadding      = ImVec2(6.0f, 4.0f);
+	style.ItemSpacing      = ImVec2(6.0f, 6.0f);
+	style.ItemInnerSpacing = ImVec2(6.0f, 4.0f);
+	style.ScrollbarSize    = 14.0f;
+	style.GrabMinSize      = 10.0f;
+	style.WindowRounding   = 4.0f;
+	style.FrameRounding    = 3.0f;
+	style.PopupRounding    = 4.0f;
+	style.GrabRounding     = 3.0f;
+	style.TabRounding      = 4.0f;
+	style.WindowBorderSize = 1.0f;
+	style.FrameBorderSize  = 1.0f;
+
+	ImVec4 *colors                = style.Colors;
+	colors[ImGuiCol_Text]         = fg1;
+	colors[ImGuiCol_TextDisabled] = ImVec4(fg1.x, fg1.y, fg1.z, 0.55f);
+	colors[ImGuiCol_WindowBg]     = bg0;
+	colors[ImGuiCol_ChildBg]      = bg0;
+	colors[ImGuiCol_PopupBg]      = ImVec4(bg1.x, bg1.y, bg1.z, 0.98f);
+	colors[ImGuiCol_Border]       = bg2;
+	colors[ImGuiCol_BorderShadow] = RGBA(0x000000, 0.0f);
+
+	colors[ImGuiCol_FrameBg]        = bg2;
+	colors[ImGuiCol_FrameBgHovered] = bg3;
+	colors[ImGuiCol_FrameBgActive]  = bg1;
+
+	colors[ImGuiCol_TitleBg]          = bg1;
+	colors[ImGuiCol_TitleBgActive]    = bg2;
+	colors[ImGuiCol_TitleBgCollapsed] = bg1;
+
+	colors[ImGuiCol_MenuBarBg]            = bg1;
+	colors[ImGuiCol_ScrollbarBg]          = bg0;
+	colors[ImGuiCol_ScrollbarGrab]        = bg3;
+	colors[ImGuiCol_ScrollbarGrabHovered] = bg2;
+	colors[ImGuiCol_ScrollbarGrabActive]  = bg1;
+
+	colors[ImGuiCol_CheckMark]        = aqua;
+	colors[ImGuiCol_SliderGrab]       = aqua;
+	colors[ImGuiCol_SliderGrabActive] = blue;
+
+	colors[ImGuiCol_Button]        = bg3;
+	colors[ImGuiCol_ButtonHovered] = bg2;
+	colors[ImGuiCol_ButtonActive]  = bg1;
+
+	colors[ImGuiCol_Header]        = bg3;
+	colors[ImGuiCol_HeaderHovered] = bg2;
+	colors[ImGuiCol_HeaderActive]  = bg2;
+
+	colors[ImGuiCol_Separator]        = bg2;
+	colors[ImGuiCol_SeparatorHovered] = bg1;
+	colors[ImGuiCol_SeparatorActive]  = blue;
+
+	colors[ImGuiCol_ResizeGrip]        = ImVec4(fg0.x, fg0.y, fg0.z, 0.12f);
+	colors[ImGuiCol_ResizeGripHovered] = ImVec4(aqua.x, aqua.y, aqua.z, 0.67f);
+	colors[ImGuiCol_ResizeGripActive]  = blue;
+
+	colors[ImGuiCol_Tab]                = bg2;
+	colors[ImGuiCol_TabHovered]         = bg1;
+	colors[ImGuiCol_TabActive]          = bg3;
+	colors[ImGuiCol_TabUnfocused]       = bg2;
+	colors[ImGuiCol_TabUnfocusedActive] = bg3;
+
+	colors[ImGuiCol_TableHeaderBg]     = bg2;
+	colors[ImGuiCol_TableBorderStrong] = bg1;
+	colors[ImGuiCol_TableBorderLight]  = ImVec4(bg1.x, bg1.y, bg1.z, 0.6f);
+	colors[ImGuiCol_TableRowBg]        = ImVec4(bg1.x, bg1.y, bg1.z, 0.2f);
+	colors[ImGuiCol_TableRowBgAlt]     = ImVec4(bg1.x, bg1.y, bg1.z, 0.35f);
+
+	colors[ImGuiCol_TextSelectedBg]        = ImVec4(orange.x, orange.y, orange.z, 0.30f);
+	colors[ImGuiCol_DragDropTarget]        = orange;
+	colors[ImGuiCol_NavHighlight]          = orange;
+	colors[ImGuiCol_NavWindowingHighlight] = ImVec4(fg0.x, fg0.y, fg0.z, 0.70f);
+	colors[ImGuiCol_NavWindowingDimBg]     = ImVec4(0.0f, 0.0f, 0.0f, 0.45f);
+	colors[ImGuiCol_ModalWindowDimBg]      = ImVec4(0.0f, 0.0f, 0.0f, 0.45f);
+	colors[ImGuiCol_PlotLines]             = aqua;
+	colors[ImGuiCol_PlotLinesHovered]      = blue;
+	colors[ImGuiCol_PlotHistogram]         = yellow;
+	colors[ImGuiCol_PlotHistogramHovered]  = orange;
+}
+
+
+static inline void
+ApplyGruvboxLightMediumTheme()
+{
+	// Gruvbox (light, medium) palette
+	const ImVec4 bg0 = RGBA(0xFBF1C7); // light0
+	const ImVec4 bg1 = RGBA(0xEBDBB2); // light1
+	const ImVec4 bg2 = RGBA(0xD5C4A1); // light2
+	const ImVec4 bg3 = RGBA(0xBDAE93); // light3
+	const ImVec4 fg1 = RGBA(0x3C3836); // dark1
+	const ImVec4 fg0 = RGBA(0x282828); // dark0
+	// accents
+	const ImVec4 yellow = RGBA(0xB57614);
+	const ImVec4 blue   = RGBA(0x076678);
+	const ImVec4 aqua   = RGBA(0x427B58);
+	const ImVec4 orange = RGBA(0xAF3A03);
+
+	ImGuiStyle &style      = ImGui::GetStyle();
+	style.WindowPadding    = ImVec2(8.0f, 8.0f);
+	style.FramePadding     = ImVec2(6.0f, 4.0f);
+	style.CellPadding      = ImVec2(6.0f, 4.0f);
+	style.ItemSpacing      = ImVec2(6.0f, 6.0f);
+	style.ItemInnerSpacing = ImVec2(6.0f, 4.0f);
+	style.ScrollbarSize    = 14.0f;
+	style.GrabMinSize      = 10.0f;
+	style.WindowRounding   = 4.0f;
+	style.FrameRounding    = 3.0f;
+	style.PopupRounding    = 4.0f;
+	style.GrabRounding     = 3.0f;
+	style.TabRounding      = 4.0f;
+	style.WindowBorderSize = 1.0f;
+	style.FrameBorderSize  = 1.0f;
+
+	ImVec4 *colors                = style.Colors;
+	colors[ImGuiCol_Text]         = fg1;
+	colors[ImGuiCol_TextDisabled] = ImVec4(fg1.x, fg1.y, fg1.z, 0.55f);
+	colors[ImGuiCol_WindowBg]     = bg0;
+	colors[ImGuiCol_ChildBg]      = bg0;
+	colors[ImGuiCol_PopupBg]      = ImVec4(bg1.x, bg1.y, bg1.z, 0.98f);
+	colors[ImGuiCol_Border]       = bg2;
+	colors[ImGuiCol_BorderShadow] = RGBA(0x000000, 0.0f);
+
+	colors[ImGuiCol_FrameBg]        = bg2;
+	colors[ImGuiCol_FrameBgHovered] = bg3;
+	colors[ImGuiCol_FrameBgActive]  = bg1;
+
+	colors[ImGuiCol_TitleBg]          = bg1;
+	colors[ImGuiCol_TitleBgActive]    = bg2;
+	colors[ImGuiCol_TitleBgCollapsed] = bg1;
+
+	colors[ImGuiCol_MenuBarBg]            = bg1;
+	colors[ImGuiCol_ScrollbarBg]          = bg0;
+	colors[ImGuiCol_ScrollbarGrab]        = bg3;
+	colors[ImGuiCol_ScrollbarGrabHovered] = bg2;
+	colors[ImGuiCol_ScrollbarGrabActive]  = bg1;
+
+	colors[ImGuiCol_CheckMark]        = aqua;
+	colors[ImGuiCol_SliderGrab]       = aqua;
+	colors[ImGuiCol_SliderGrabActive] = blue;
+
+	colors[ImGuiCol_Button]        = bg3;
+	colors[ImGuiCol_ButtonHovered] = bg2;
+	colors[ImGuiCol_ButtonActive]  = bg1;
+
+	colors[ImGuiCol_Header]        = bg3;
+	colors[ImGuiCol_HeaderHovered] = bg2;
+	colors[ImGuiCol_HeaderActive]  = bg2;
+
+	colors[ImGuiCol_Separator]        = bg2;
+	colors[ImGuiCol_SeparatorHovered] = bg1;
+	colors[ImGuiCol_SeparatorActive]  = blue;
+
+	colors[ImGuiCol_ResizeGrip]        = ImVec4(fg0.x, fg0.y, fg0.z, 0.12f);
+	colors[ImGuiCol_ResizeGripHovered] = ImVec4(aqua.x, aqua.y, aqua.z, 0.67f);
+	colors[ImGuiCol_ResizeGripActive]  = blue;
+
+	colors[ImGuiCol_Tab]                = bg2;
+	colors[ImGuiCol_TabHovered]         = bg1;
+	colors[ImGuiCol_TabActive]          = bg3;
+	colors[ImGuiCol_TabUnfocused]       = bg2;
+	colors[ImGuiCol_TabUnfocusedActive] = bg3;
+
+	colors[ImGuiCol_TableHeaderBg]     = bg2;
+	colors[ImGuiCol_TableBorderStrong] = bg1;
+	colors[ImGuiCol_TableBorderLight]  = ImVec4(bg1.x, bg1.y, bg1.z, 0.6f);
+	colors[ImGuiCol_TableRowBg]        = ImVec4(bg1.x, bg1.y, bg1.z, 0.2f);
+	colors[ImGuiCol_TableRowBgAlt]     = ImVec4(bg1.x, bg1.y, bg1.z, 0.35f);
+
+	colors[ImGuiCol_TextSelectedBg]        = ImVec4(orange.x, orange.y, orange.z, 0.30f);
+	colors[ImGuiCol_DragDropTarget]        = orange;
+	colors[ImGuiCol_NavHighlight]          = orange;
+	colors[ImGuiCol_NavWindowingHighlight] = ImVec4(fg0.x, fg0.y, fg0.z, 0.70f);
+	colors[ImGuiCol_NavWindowingDimBg]     = ImVec4(0.0f, 0.0f, 0.0f, 0.45f);
+	colors[ImGuiCol_ModalWindowDimBg]      = ImVec4(0.0f, 0.0f, 0.0f, 0.45f);
+	colors[ImGuiCol_PlotLines]             = aqua;
+	colors[ImGuiCol_PlotLinesHovered]      = blue;
+	colors[ImGuiCol_PlotHistogram]         = yellow;
+	colors[ImGuiCol_PlotHistogramHovered]  = orange;
+}

themes/Nord.h

@@ -0,0 +1,111 @@
+// themes/Nord.h — Nord-inspired ImGui theme (header-only)
+#pragma once
+#include "ThemeHelpers.h"
+
+// Expects to be included from GUITheme.h after <imgui.h> and RGBA() helper
+
+static void
+ApplyNordImGuiTheme()
+{
+	// Nord palette
+	const ImVec4 nord0  = RGBA(0x2E3440); // darkest bg
+	const ImVec4 nord1  = RGBA(0x3B4252);
+	const ImVec4 nord2  = RGBA(0x434C5E);
+	const ImVec4 nord3  = RGBA(0x4C566A);
+	const ImVec4 nord4  = RGBA(0xD8DEE9);
+	const ImVec4 nord6  = RGBA(0xECEFF4); // lightest
+	const ImVec4 nord8  = RGBA(0x88C0D0); // cyan
+	const ImVec4 nord9  = RGBA(0x81A1C1); // blue
+	const ImVec4 nord10 = RGBA(0x5E81AC); // blue dark
+	const ImVec4 nord12 = RGBA(0xD08770); // orange
+	const ImVec4 nord13 = RGBA(0xEBCB8B); // yellow
+
+	ImGuiStyle &style = ImGui::GetStyle();
+
+	// Base style tweaks to suit Nord aesthetics
+	style.WindowPadding    = ImVec2(8.0f, 8.0f);
+	style.FramePadding     = ImVec2(6.0f, 4.0f);
+	style.CellPadding      = ImVec2(6.0f, 4.0f);
+	style.ItemSpacing      = ImVec2(6.0f, 6.0f);
+	style.ItemInnerSpacing = ImVec2(6.0f, 4.0f);
+	style.ScrollbarSize    = 14.0f;
+	style.GrabMinSize      = 10.0f;
+	style.WindowRounding   = 4.0f;
+	style.FrameRounding    = 3.0f;
+	style.PopupRounding    = 4.0f;
+	style.GrabRounding     = 3.0f;
+	style.TabRounding      = 4.0f;
+	style.WindowBorderSize = 1.0f;
+	style.FrameBorderSize  = 1.0f;
+
+	ImVec4 *colors = style.Colors;
+
+	colors[ImGuiCol_Text]         = nord4; // primary text
+	colors[ImGuiCol_TextDisabled] = ImVec4(nord4.x, nord4.y, nord4.z, 0.55f);
+	colors[ImGuiCol_WindowBg]     = nord0;
+	colors[ImGuiCol_ChildBg]      = nord0;
+	colors[ImGuiCol_PopupBg]      = ImVec4(nord1.x, nord1.y, nord1.z, 0.98f);
+	colors[ImGuiCol_Border]       = nord2;
+	colors[ImGuiCol_BorderShadow] = RGBA(0x000000, 0.0f);
+
+	colors[ImGuiCol_FrameBg]        = nord2;
+	colors[ImGuiCol_FrameBgHovered] = nord3;
+	colors[ImGuiCol_FrameBgActive]  = nord1;
+
+	colors[ImGuiCol_TitleBg]          = nord1;
+	colors[ImGuiCol_TitleBgActive]    = nord2;
+	colors[ImGuiCol_TitleBgCollapsed] = nord1;
+
+	colors[ImGuiCol_MenuBarBg]            = nord1;
+	colors[ImGuiCol_ScrollbarBg]          = nord10;
+	colors[ImGuiCol_ScrollbarGrab]        = nord3;
+	colors[ImGuiCol_ScrollbarGrabHovered] = nord2;
+	colors[ImGuiCol_ScrollbarGrabActive]  = nord1;
+
+	colors[ImGuiCol_CheckMark]        = nord8;
+	colors[ImGuiCol_SliderGrab]       = nord8;
+	colors[ImGuiCol_SliderGrabActive] = nord9;
+
+	colors[ImGuiCol_Button]        = nord3;
+	colors[ImGuiCol_ButtonHovered] = nord2;
+	colors[ImGuiCol_ButtonActive]  = nord1;
+
+	colors[ImGuiCol_Header]        = nord3;
+	colors[ImGuiCol_HeaderHovered] = nord10;
+	colors[ImGuiCol_HeaderActive]  = nord10;
+
+	colors[ImGuiCol_Separator]        = nord2;
+	colors[ImGuiCol_SeparatorHovered] = nord10;
+	colors[ImGuiCol_SeparatorActive]  = nord9;
+
+	colors[ImGuiCol_ResizeGrip]        = ImVec4(nord6.x, nord6.y, nord6.z, 0.12f);
+	colors[ImGuiCol_ResizeGripHovered] = ImVec4(nord8.x, nord8.y, nord8.z, 0.67f);
+	colors[ImGuiCol_ResizeGripActive]  = nord9;
+
+	colors[ImGuiCol_Tab]                = nord2;
+	colors[ImGuiCol_TabHovered]         = nord10;
+	colors[ImGuiCol_TabActive]          = nord3;
+	colors[ImGuiCol_TabUnfocused]       = nord2;
+	colors[ImGuiCol_TabUnfocusedActive] = nord3;
+
+	// Docking colors omitted for compatibility
+
+	colors[ImGuiCol_TableHeaderBg]     = nord2;
+	colors[ImGuiCol_TableBorderStrong] = nord1;
+	colors[ImGuiCol_TableBorderLight]  = ImVec4(nord1.x, nord1.y, nord1.z, 0.6f);
+	colors[ImGuiCol_TableRowBg]        = ImVec4(nord1.x, nord1.y, nord1.z, 0.2f);
+	colors[ImGuiCol_TableRowBgAlt]     = ImVec4(nord1.x, nord1.y, nord1.z, 0.35f);
+
+	colors[ImGuiCol_TextSelectedBg]        = ImVec4(nord8.x, nord8.y, nord8.z, 0.35f);
+	colors[ImGuiCol_DragDropTarget]        = nord13;
+	colors[ImGuiCol_NavHighlight]          = nord9;
+	colors[ImGuiCol_NavWindowingHighlight] = ImVec4(nord6.x, nord6.y, nord6.z, 0.7f);
+	colors[ImGuiCol_NavWindowingDimBg]     = ImVec4(nord0.x, nord0.y, nord0.z, 0.6f);
+	colors[ImGuiCol_ModalWindowDimBg]      = ImVec4(nord0.x, nord0.y, nord0.z, 0.6f);
+
+	// Plots
+	colors[ImGuiCol_PlotLines]            = nord8;
+	colors[ImGuiCol_PlotLinesHovered]     = nord9;
+	colors[ImGuiCol_PlotHistogram]        = nord13;
+	colors[ImGuiCol_PlotHistogramHovered] = nord12;
+}

themes/Plan9.h

@@ -0,0 +1,89 @@
+// themes/Plan9.h — Plan 9 acme-inspired ImGui theme (header-only)
+#pragma once
+#include "ThemeHelpers.h"
+
+// Expects to be included from GUITheme.h after <imgui.h> and RGBA() helper
+
+static void
+ApplyPlan9Theme()
+{
+	// Acme-like colors
+	const ImVec4 paper  = RGBA(0xFFFFE8); // pale yellow paper
+	const ImVec4 pane   = RGBA(0xFFF4C1); // slightly deeper for frames
+	const ImVec4 ink    = RGBA(0x000000); // black text
+	constexpr auto dim  = ImVec4(0, 0, 0, 0.60f);
+	const ImVec4 border = RGBA(0x000000); // 1px black
+	const ImVec4 blue   = RGBA(0x0064FF); // acme-ish blue accents
+	const ImVec4 blueH  = RGBA(0x4C8DFF); // hover/active
+
+	ImGuiStyle &style      = ImGui::GetStyle();
+	style.WindowPadding    = ImVec2(6.0f, 6.0f);
+	style.FramePadding     = ImVec2(5.0f, 3.0f);
+	style.CellPadding      = ImVec2(5.0f, 3.0f);
+	style.ItemSpacing      = ImVec2(6.0f, 6.0f);
+	style.ItemInnerSpacing = ImVec2(6.0f, 4.0f);
+	style.ScrollbarSize    = 14.0f;
+	style.GrabMinSize      = 10.0f;
+	style.WindowRounding   = 0.0f;
+	style.FrameRounding    = 0.0f;
+	style.PopupRounding    = 0.0f;
+	style.GrabRounding     = 0.0f;
+	style.TabRounding      = 0.0f;
+	style.WindowBorderSize = 1.0f;
+	style.FrameBorderSize  = 1.0f;
+
+	ImVec4 *c                         = style.Colors;
+	c[ImGuiCol_Text]                  = ink;
+	c[ImGuiCol_TextDisabled]          = dim;
+	c[ImGuiCol_WindowBg]              = paper;
+	c[ImGuiCol_ChildBg]               = paper;
+	c[ImGuiCol_PopupBg]               = ImVec4(pane.x, pane.y, pane.z, 0.98f);
+	c[ImGuiCol_Border]                = border;
+	c[ImGuiCol_BorderShadow]          = RGBA(0x000000, 0.0f);
+	c[ImGuiCol_FrameBg]               = pane;
+	c[ImGuiCol_FrameBgHovered]        = RGBA(0xFFEBA0);
+	c[ImGuiCol_FrameBgActive]         = RGBA(0xFFE387);
+	c[ImGuiCol_TitleBg]               = pane;
+	c[ImGuiCol_TitleBgActive]         = RGBA(0xFFE8A6);
+	c[ImGuiCol_TitleBgCollapsed]      = pane;
+	c[ImGuiCol_MenuBarBg]             = pane;
+	c[ImGuiCol_ScrollbarBg]           = paper;
+	c[ImGuiCol_ScrollbarGrab]         = RGBA(0xEADFA5);
+	c[ImGuiCol_ScrollbarGrabHovered]  = RGBA(0xE2D37F);
+	c[ImGuiCol_ScrollbarGrabActive]   = RGBA(0xD8C757);
+	c[ImGuiCol_CheckMark]             = blue;
+	c[ImGuiCol_SliderGrab]            = blue;
+	c[ImGuiCol_SliderGrabActive]      = blueH;
+	c[ImGuiCol_Button]                = RGBA(0xFFF1B0);
+	c[ImGuiCol_ButtonHovered]         = RGBA(0xFFE892);
+	c[ImGuiCol_ButtonActive]          = RGBA(0xFFE072);
+	c[ImGuiCol_Header]                = RGBA(0xFFF1B0);
+	c[ImGuiCol_HeaderHovered]         = RGBA(0xFFE892);
+	c[ImGuiCol_HeaderActive]          = RGBA(0xFFE072);
+	c[ImGuiCol_Separator]             = border;
+	c[ImGuiCol_SeparatorHovered]      = blue;
+	c[ImGuiCol_SeparatorActive]       = blueH;
+	c[ImGuiCol_ResizeGrip]            = ImVec4(0, 0, 0, 0.12f);
+	c[ImGuiCol_ResizeGripHovered]     = ImVec4(blue.x, blue.y, blue.z, 0.67f);
+	c[ImGuiCol_ResizeGripActive]      = blueH;
+	c[ImGuiCol_Tab]                   = RGBA(0xFFE8A6);
+	c[ImGuiCol_TabHovered]            = RGBA(0xFFE072);
+	c[ImGuiCol_TabActive]             = RGBA(0xFFD859);
+	c[ImGuiCol_TabUnfocused]          = RGBA(0xFFE8A6);
+	c[ImGuiCol_TabUnfocusedActive]    = RGBA(0xFFD859);
+	c[ImGuiCol_TableHeaderBg]         = RGBA(0xFFE8A6);
+	c[ImGuiCol_TableBorderStrong]     = border;
+	c[ImGuiCol_TableBorderLight]      = ImVec4(0, 0, 0, 0.35f);
+	c[ImGuiCol_TableRowBg]            = ImVec4(0, 0, 0, 0.04f);
+	c[ImGuiCol_TableRowBgAlt]         = ImVec4(0, 0, 0, 0.08f);
+	c[ImGuiCol_TextSelectedBg]        = ImVec4(blueH.x, blueH.y, blueH.z, 0.35f);
+	c[ImGuiCol_DragDropTarget]        = blue;
+	c[ImGuiCol_NavHighlight]          = blue;
+	c[ImGuiCol_NavWindowingHighlight] = ImVec4(0, 0, 0, 0.20f);
+	c[ImGuiCol_NavWindowingDimBg]     = ImVec4(0, 0, 0, 0.20f);
+	c[ImGuiCol_ModalWindowDimBg]      = ImVec4(0, 0, 0, 0.20f);
+	c[ImGuiCol_PlotLines]             = blue;
+	c[ImGuiCol_PlotLinesHovered]      = blueH;
+	c[ImGuiCol_PlotHistogram]         = blue;
+	c[ImGuiCol_PlotHistogramHovered]  = blueH;
+}

themes/Solarized.h

@@ -0,0 +1,184 @@
+// themes/Solarized.h — Solarized Dark/Light ImGui themes (header-only)
+#pragma once
+#include "ThemeHelpers.h"
+
+
+// Expects to be included from GUITheme.h after <imgui.h> and RGBA() helper
+
+static void
+ApplySolarizedDarkTheme()
+{
+	// Base colors from Ethan Schoonover Solarized
+	const ImVec4 base03 = RGBA(0x002b36);
+	const ImVec4 base02 = RGBA(0x073642);
+	const ImVec4 base01 = RGBA(0x586e75);
+	const ImVec4 base00 = RGBA(0x657b83);
+	const ImVec4 base0  = RGBA(0x839496);
+	const ImVec4 base1  = RGBA(0x93a1a1);
+	const ImVec4 base2  = RGBA(0xeee8d5);
+	const ImVec4 yellow = RGBA(0xb58900);
+	const ImVec4 orange = RGBA(0xcb4b16);
+	const ImVec4 blue   = RGBA(0x268bd2);
+	const ImVec4 cyan   = RGBA(0x2aa198);
+
+	ImGuiStyle &style      = ImGui::GetStyle();
+	style.WindowPadding    = ImVec2(8.0f, 8.0f);
+	style.FramePadding     = ImVec2(6.0f, 4.0f);
+	style.CellPadding      = ImVec2(6.0f, 4.0f);
+	style.ItemSpacing      = ImVec2(6.0f, 6.0f);
+	style.ItemInnerSpacing = ImVec2(6.0f, 4.0f);
+	style.ScrollbarSize    = 14.0f;
+	style.GrabMinSize      = 10.0f;
+	style.WindowRounding   = 3.0f;
+	style.FrameRounding    = 3.0f;
+	style.PopupRounding    = 3.0f;
+	style.GrabRounding     = 3.0f;
+	style.TabRounding      = 3.0f;
+	style.WindowBorderSize = 1.0f;
+	style.FrameBorderSize  = 1.0f;
+
+	ImVec4 *c                         = style.Colors;
+	c[ImGuiCol_Text]                  = base0;
+	c[ImGuiCol_TextDisabled]          = ImVec4(base01.x, base01.y, base01.z, 1.0f);
+	c[ImGuiCol_WindowBg]              = base03;
+	c[ImGuiCol_ChildBg]               = base03;
+	c[ImGuiCol_PopupBg]               = ImVec4(base02.x, base02.y, base02.z, 0.98f);
+	c[ImGuiCol_Border]                = base02;
+	c[ImGuiCol_BorderShadow]          = RGBA(0x000000, 0.0f);
+	c[ImGuiCol_FrameBg]               = base02;
+	c[ImGuiCol_FrameBgHovered]        = base01;
+	c[ImGuiCol_FrameBgActive]         = base00;
+	c[ImGuiCol_TitleBg]               = base02;
+	c[ImGuiCol_TitleBgActive]         = base01;
+	c[ImGuiCol_TitleBgCollapsed]      = base02;
+	c[ImGuiCol_MenuBarBg]             = base02;
+	c[ImGuiCol_ScrollbarBg]           = base02;
+	c[ImGuiCol_ScrollbarGrab]         = base01;
+	c[ImGuiCol_ScrollbarGrabHovered]  = base00;
+	c[ImGuiCol_ScrollbarGrabActive]   = blue;
+	c[ImGuiCol_CheckMark]             = cyan;
+	c[ImGuiCol_SliderGrab]            = cyan;
+	c[ImGuiCol_SliderGrabActive]      = blue;
+	c[ImGuiCol_Button]                = base01;
+	c[ImGuiCol_ButtonHovered]         = base00;
+	c[ImGuiCol_ButtonActive]          = blue;
+	c[ImGuiCol_Header]                = base01;
+	c[ImGuiCol_HeaderHovered]         = base00;
+	c[ImGuiCol_HeaderActive]          = base00;
+	c[ImGuiCol_Separator]             = base01;
+	c[ImGuiCol_SeparatorHovered]      = base00;
+	c[ImGuiCol_SeparatorActive]       = blue;
+	c[ImGuiCol_ResizeGrip]            = ImVec4(base1.x, base1.y, base1.z, 0.12f);
+	c[ImGuiCol_ResizeGripHovered]     = ImVec4(cyan.x, cyan.y, cyan.z, 0.67f);
+	c[ImGuiCol_ResizeGripActive]      = blue;
+	c[ImGuiCol_Tab]                   = base01;
+	c[ImGuiCol_TabHovered]            = base00;
+	c[ImGuiCol_TabActive]             = base02;
+	c[ImGuiCol_TabUnfocused]          = base01;
+	c[ImGuiCol_TabUnfocusedActive]    = base02;
+	c[ImGuiCol_TableHeaderBg]         = base01;
+	c[ImGuiCol_TableBorderStrong]     = base00;
+	c[ImGuiCol_TableBorderLight]      = ImVec4(base00.x, base00.y, base00.z, 0.6f);
+	c[ImGuiCol_TableRowBg]            = ImVec4(base02.x, base02.y, base02.z, 0.2f);
+	c[ImGuiCol_TableRowBgAlt]         = ImVec4(base02.x, base02.y, base02.z, 0.35f);
+	c[ImGuiCol_TextSelectedBg]        = ImVec4(cyan.x, cyan.y, cyan.z, 0.30f);
+	c[ImGuiCol_DragDropTarget]        = yellow;
+	c[ImGuiCol_NavHighlight]          = blue;
+	c[ImGuiCol_NavWindowingHighlight] = ImVec4(base2.x, base2.y, base2.z, 0.70f);
+	c[ImGuiCol_NavWindowingDimBg]     = ImVec4(base03.x, base03.y, base03.z, 0.60f);
+	c[ImGuiCol_ModalWindowDimBg]      = ImVec4(base03.x, base03.y, base03.z, 0.60f);
+	c[ImGuiCol_PlotLines]             = cyan;
+	c[ImGuiCol_PlotLinesHovered]      = blue;
+	c[ImGuiCol_PlotHistogram]         = yellow;
+	c[ImGuiCol_PlotHistogramHovered]  = orange;
+}
+
+
+static inline void
+ApplySolarizedLightTheme()
+{
+	// Base colors from Ethan Schoonover Solarized (light variant)
+	const ImVec4 base3  = RGBA(0xfdf6e3);
+	const ImVec4 base2  = RGBA(0xeee8d5);
+	const ImVec4 base1  = RGBA(0x93a1a1);
+	const ImVec4 base0  = RGBA(0x839496);
+	const ImVec4 base00 = RGBA(0x657b83);
+	const ImVec4 base01 = RGBA(0x586e75);
+	const ImVec4 base02 = RGBA(0x073642);
+	const ImVec4 base03 = RGBA(0x002b36);
+	const ImVec4 yellow = RGBA(0xb58900);
+	const ImVec4 orange = RGBA(0xcb4b16);
+	const ImVec4 blue   = RGBA(0x268bd2);
+	const ImVec4 cyan   = RGBA(0x2aa198);
+
+	ImGuiStyle &style      = ImGui::GetStyle();
+	style.WindowPadding    = ImVec2(8.0f, 8.0f);
+	style.FramePadding     = ImVec2(6.0f, 4.0f);
+	style.CellPadding      = ImVec2(6.0f, 4.0f);
+	style.ItemSpacing      = ImVec2(6.0f, 6.0f);
+	style.ItemInnerSpacing = ImVec2(6.0f, 4.0f);
+	style.ScrollbarSize    = 14.0f;
+	style.GrabMinSize      = 10.0f;
+	style.WindowRounding   = 3.0f;
+	style.FrameRounding    = 3.0f;
+	style.PopupRounding    = 3.0f;
+	style.GrabRounding     = 3.0f;
+	style.TabRounding      = 3.0f;
+	style.WindowBorderSize = 1.0f;
+	style.FrameBorderSize  = 1.0f;
+
+	ImVec4 *c                         = style.Colors;
+	c[ImGuiCol_Text]                  = base00;
+	c[ImGuiCol_TextDisabled]          = ImVec4(base01.x, base01.y, base01.z, 1.0f);
+	c[ImGuiCol_WindowBg]              = base3;
+	c[ImGuiCol_ChildBg]               = base3;
+	c[ImGuiCol_PopupBg]               = ImVec4(base2.x, base2.y, base2.z, 0.98f);
+	c[ImGuiCol_Border]                = base1;
+	c[ImGuiCol_BorderShadow]          = RGBA(0x000000, 0.0f);
+	c[ImGuiCol_FrameBg]               = base2;
+	c[ImGuiCol_FrameBgHovered]        = base1;
+	c[ImGuiCol_FrameBgActive]         = base0;
+	c[ImGuiCol_TitleBg]               = base2;
+	c[ImGuiCol_TitleBgActive]         = base1;
+	c[ImGuiCol_TitleBgCollapsed]      = base2;
+	c[ImGuiCol_MenuBarBg]             = base2;
+	c[ImGuiCol_ScrollbarBg]           = base2;
+	c[ImGuiCol_ScrollbarGrab]         = base1;
+	c[ImGuiCol_ScrollbarGrabHovered]  = base0;
+	c[ImGuiCol_ScrollbarGrabActive]   = blue;
+	c[ImGuiCol_CheckMark]             = cyan;
+	c[ImGuiCol_SliderGrab]            = cyan;
+	c[ImGuiCol_SliderGrabActive]      = blue;
+	c[ImGuiCol_Button]                = base1;
+	c[ImGuiCol_ButtonHovered]         = base0;
+	c[ImGuiCol_ButtonActive]          = blue;
+	c[ImGuiCol_Header]                = base1;
+	c[ImGuiCol_HeaderHovered]         = base0;
+	c[ImGuiCol_HeaderActive]          = base0;
+	c[ImGuiCol_Separator]             = base1;
+	c[ImGuiCol_SeparatorHovered]      = base0;
+	c[ImGuiCol_SeparatorActive]       = blue;
+	c[ImGuiCol_ResizeGrip]            = ImVec4(base1.x, base1.y, base1.z, 0.12f);
+	c[ImGuiCol_ResizeGripHovered]     = ImVec4(cyan.x, cyan.y, cyan.z, 0.67f);
+	c[ImGuiCol_ResizeGripActive]      = blue;
+	c[ImGuiCol_Tab]                   = base1;
+	c[ImGuiCol_TabHovered]            = base0;
+	c[ImGuiCol_TabActive]             = base2;
+	c[ImGuiCol_TabUnfocused]          = base1;
+	c[ImGuiCol_TabUnfocusedActive]    = base2;
+	c[ImGuiCol_TableHeaderBg]         = base1;
+	c[ImGuiCol_TableBorderStrong]     = base0;
+	c[ImGuiCol_TableBorderLight]      = ImVec4(base0.x, base0.y, base0.z, 0.6f);
+	c[ImGuiCol_TableRowBg]            = ImVec4(base02.x, base02.y, base02.z, 0.2f);
+	c[ImGuiCol_TableRowBgAlt]         = ImVec4(base02.x, base02.y, base02.z, 0.35f);
+	c[ImGuiCol_TextSelectedBg]        = ImVec4(cyan.x, cyan.y, cyan.z, 0.30f);
+	c[ImGuiCol_DragDropTarget]        = yellow;
+	c[ImGuiCol_NavHighlight]          = blue;
+	c[ImGuiCol_NavWindowingHighlight] = ImVec4(base2.x, base2.y, base2.z, 0.70f);
+	c[ImGuiCol_NavWindowingDimBg]     = ImVec4(base03.x, base03.y, base03.z, 0.60f);
+	c[ImGuiCol_ModalWindowDimBg]      = ImVec4(base03.x, base03.y, base03.z, 0.60f);
+	c[ImGuiCol_PlotLines]             = cyan;
+	c[ImGuiCol_PlotLinesHovered]      = blue;
+	c[ImGuiCol_PlotHistogram]         = yellow;
+	c[ImGuiCol_PlotHistogramHovered]  = orange;
+}

themes/ThemeHelpers.h

@@ -0,0 +1,17 @@
+#ifndef KTE_THEMEHELPERS_H
+#define KTE_THEMEHELPERS_H
+
+#include "imgui.h"
+
+// Small helper to convert packed RGB (0xRRGGBB) + optional alpha to ImVec4
+static ImVec4
+RGBA(const unsigned int rgb, float a = 1.0f)
+{
+	const float r = static_cast<float>(rgb >> 16 & 0xFF) / 255.0f;
+	const float g = static_cast<float>(rgb >> 8 & 0xFF) / 255.0f;
+	const float b = static_cast<float>(rgb & 0xFF) / 255.0f;
+	return {r, g, b, a};
+}
+
+
+#endif //KTE_THEMEHELPERS_H