Refactor ImGui editor layout and scrolling logic for improved precision and consistency.

- Added full UTF-8 support for terminal rendering, including multi-width character handling.
- Improved font handling in ImGui with expanded glyph support (Greek, Mathematical Operators).
- Updated locale initialization to enable proper character rendering.
- Bumped version to 1.5.8.

.idea/codeStyles/codeStyleConfig.xml

@@ -1,5 +1,6 @@
 <component name="ProjectCodeStyleConfiguration">
   <state>
+    <option name="USE_PER_PROJECT_SETTINGS" value="true" />
     <option name="PREFERRED_PROJECT_CODE_STYLE" value="sccl" />
   </state>
 </component>

.idea/editor.xml

@@ -19,7 +19,7 @@
     <option name="/Default/CodeInspection/Highlighting/InspectionSeverities/=CppBoostFormatTooManyArgs/@EntryIndexedValue" value="WARNING" type="string" />
     <option name="/Default/CodeInspection/Highlighting/InspectionSeverities/=CppCStyleCast/@EntryIndexedValue" value="SUGGESTION" type="string" />
     <option name="/Default/CodeInspection/Highlighting/InspectionSeverities/=CppCVQualifierCanNotBeAppliedToReference/@EntryIndexedValue" value="WARNING" type="string" />
-    <option name="/Default/CodeInspection/Highlighting/InspectionSeverities/=CppClassCanBeFinal/@EntryIndexedValue" value="HINT" type="string" />
+    <option name="/Default/CodeInspection/Highlighting/InspectionSeverities/=CppClassCanBeFinal/@EntryIndexedValue" value="DO_NOT_SHOW" type="string" />
     <option name="/Default/CodeInspection/Highlighting/InspectionSeverities/=CppClassIsIncomplete/@EntryIndexedValue" value="WARNING" type="string" />
     <option name="/Default/CodeInspection/Highlighting/InspectionSeverities/=CppClassNeedsConstructorBecauseOfUninitializedMember/@EntryIndexedValue" value="WARNING" type="string" />
     <option name="/Default/CodeInspection/Highlighting/InspectionSeverities/=CppClassNeverUsed/@EntryIndexedValue" value="WARNING" type="string" />
@@ -58,6 +58,7 @@
     <option name="/Default/CodeInspection/Highlighting/InspectionSeverities/=CppDefaultInitializationWithNoUserConstructor/@EntryIndexedValue" value="WARNING" type="string" />
     <option name="/Default/CodeInspection/Highlighting/InspectionSeverities/=CppDefaultIsUsedAsIdentifier/@EntryIndexedValue" value="WARNING" type="string" />
     <option name="/Default/CodeInspection/Highlighting/InspectionSeverities/=CppDefaultedSpecialMemberFunctionIsImplicitlyDeleted/@EntryIndexedValue" value="WARNING" type="string" />
+    <option name="/Default/CodeInspection/Highlighting/InspectionSeverities/=CppDefinitionsOrder/@EntryIndexedValue" value="HINT" type="string" />
     <option name="/Default/CodeInspection/Highlighting/InspectionSeverities/=CppDeletingVoidPointer/@EntryIndexedValue" value="WARNING" type="string" />
     <option name="/Default/CodeInspection/Highlighting/InspectionSeverities/=CppDependentTemplateWithoutTemplateKeyword/@EntryIndexedValue" value="WARNING" type="string" />
     <option name="/Default/CodeInspection/Highlighting/InspectionSeverities/=CppDependentTypeWithoutTypenameKeyword/@EntryIndexedValue" value="WARNING" type="string" />

.idea/kte.iml

@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<module classpath="CMake" type="CPP_MODULE" version="4">
+<module classpath="CIDR" type="CPP_MODULE" version="4">
   <component name="FacetManager">
     <facet type="Python" name="Python facet">
       <configuration sdkName="" />

Buffer.cc

@@ -292,28 +292,29 @@ Buffer::OpenFromFile(const std::string &path, std::string &err)
 bool
 Buffer::Save(std::string &err) const
 {
-	if (!is_file_backed_ || filename_.empty()) {
-		err = "Buffer is not file-backed; use SaveAs()";
-		return false;
-	}
-	std::ofstream out(filename_, std::ios::out | std::ios::binary | std::ios::trunc);
-	if (!out) {
-		err = "Failed to open for write: " + filename_ + ". Error: " + std::string(std::strerror(errno));
-		return false;
-	}
-	// Write the entire buffer in a single block to minimize I/O calls.
-	const char *data = content_.Data();
-	const auto size  = static_cast<std::streamsize>(content_.Size());
-	if (data != nullptr && size > 0) {
-		out.write(data, size);
-	}
-	if (!out.good()) {
-		err = "Write error: " + filename_ + ". Error: " + std::string(std::strerror(errno));
-		return false;
-	}
-	// Note: const method cannot change dirty_. Intentionally const to allow UI code
-	// to decide when to flip dirty flag after successful save.
-	return true;
+    if (!is_file_backed_ || filename_.empty()) {
+        err = "Buffer is not file-backed; use SaveAs()";
+        return false;
+    }
+    std::ofstream out(filename_, std::ios::out | std::ios::binary | std::ios::trunc);
+    if (!out) {
+        err = "Failed to open for write: " + filename_ + ". Error: " + std::string(std::strerror(errno));
+        return false;
+    }
+    // Stream the content directly from the piece table to avoid relying on
+    // full materialization, which may yield an empty pointer when size > 0.
+    if (content_.Size() > 0) {
+        content_.WriteToStream(out);
+    }
+    // Ensure data hits the OS buffers
+    out.flush();
+    if (!out.good()) {
+        err = "Write error: " + filename_ + ". Error: " + std::string(std::strerror(errno));
+        return false;
+    }
+    // Note: const method cannot change dirty_. Intentionally const to allow UI code
+    // to decide when to flip dirty flag after successful save.
+    return true;
 }
 
 
@@ -345,16 +346,16 @@ Buffer::SaveAs(const std::string &path, std::string &err)
 		err = "Failed to open for write: " + out_path + ". Error: " + std::string(std::strerror(errno));
 		return false;
 	}
-	// Write whole content in a single I/O operation
-	const char *data = content_.Data();
-	const auto size  = static_cast<std::streamsize>(content_.Size());
-	if (data != nullptr && size > 0) {
-		out.write(data, size);
-	}
-	if (!out.good()) {
-		err = "Write error: " + out_path + ". Error: " + std::string(std::strerror(errno));
-		return false;
-	}
+ // Stream content without forcing full materialization
+ if (content_.Size() > 0) {
+     content_.WriteToStream(out);
+ }
+ // Ensure data hits the OS buffers
+    out.flush();
+    if (!out.good()) {
+        err = "Write error: " + out_path + ". Error: " + std::string(std::strerror(errno));
+        return false;
+    }
 
 	filename_       = out_path;
 	is_file_backed_ = true;

CMakeLists.txt

@@ -4,7 +4,7 @@ project(kte)
 include(GNUInstallDirs)
 
 set(CMAKE_CXX_STANDARD 20)
-set(KTE_VERSION "1.5.1")
+set(KTE_VERSION "1.5.8")
 
 # Default to terminal-only build to avoid SDL/OpenGL dependency by default.
 # Enable with -DBUILD_GUI=ON when SDL2/OpenGL/Freetype are available.
@@ -63,7 +63,7 @@ endif ()
 
 message(STATUS "Build system: ${CMAKE_HOST_SYSTEM_NAME}")
 
-if (${BUILD_GUI})
+if (BUILD_GUI)
     include(cmake/imgui.cmake)
 endif ()
 
@@ -208,6 +208,7 @@ set(FONT_HEADERS
         fonts/Syne.h
         fonts/Triplicate.h
         fonts/Unispace.h
+        fonts/BerkeleyMono.h
 )
 
 set(COMMON_HEADERS
@@ -255,6 +256,7 @@ if (BUILD_GUI)
                 ImGuiFrontend.h
                 ImGuiInputHandler.h
                 ImGuiRenderer.h
+                fonts/BerkeleyMono.h
         )
     endif ()
 endif ()
@@ -292,30 +294,39 @@ install(TARGETS kte
 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}
+    # Unified unit test runner
+    add_executable(kte_tests
+            tests/TestRunner.cc
+            tests/Test.h
+            tests/test_buffer_io.cc
+            tests/test_piece_table.cc
+            tests/test_search.cc
+
+            # minimal engine sources required by Buffer
+            PieceTable.cc
+            Buffer.cc
+            OptimizedSearch.cc
+            UndoNode.cc
+            UndoTree.cc
+            UndoSystem.cc
+            ${SYNTAX_SOURCES}
     )
 
-    if (KTE_UNDO_DEBUG)
-        target_compile_definitions(test_undo PRIVATE KTE_UNDO_DEBUG=1)
-    endif ()
+    # Allow tests to include project headers like "Buffer.h"
+    target_include_directories(kte_tests PRIVATE ${CMAKE_CURRENT_SOURCE_DIR})
 
-
-    target_link_libraries(test_undo ${CURSES_LIBRARIES})
+    # Keep tests free of ncurses/GUI deps
     if (KTE_ENABLE_TREESITTER)
         if (TREESITTER_INCLUDE_DIR)
-            target_include_directories(test_undo PRIVATE ${TREESITTER_INCLUDE_DIR})
+            target_include_directories(kte_tests PRIVATE ${TREESITTER_INCLUDE_DIR})
         endif ()
         if (TREESITTER_LIBRARY)
-            target_link_libraries(test_undo ${TREESITTER_LIBRARY})
+            target_link_libraries(kte_tests ${TREESITTER_LIBRARY})
         endif ()
     endif ()
 endif ()
 
-if (${BUILD_GUI})
+if (BUILD_GUI)
     # ImGui::CreateContext();
     # ImGuiIO& io = ImGui::GetIO();
 
@@ -370,12 +381,18 @@ if (${BUILD_GUI})
                 ${CMAKE_CURRENT_BINARY_DIR}/kge-Info.plist
                 @ONLY)
 
+        # Ensure proper macOS bundle properties and RPATH so our bundled
+        # frameworks are preferred over system/Homebrew ones.
         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")
+                MACOSX_BUNDLE_INFO_PLIST "${CMAKE_CURRENT_BINARY_DIR}/kge-Info.plist"
+                # Prefer the app's bundled frameworks at runtime
+                INSTALL_RPATH "@executable_path/../Frameworks"
+                BUILD_WITH_INSTALL_RPATH TRUE
+        )
 
         add_dependencies(kge kte)
         add_custom_command(TARGET kge POST_BUILD
@@ -399,4 +416,20 @@ if (${BUILD_GUI})
     # 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)
+
+    # Optional post-build bundle fixup (can also be run from scripts).
+    # This provides a CMake target to run BundleUtilities' fixup_bundle on the
+    # built app, useful after macdeployqt to ensure non-Qt dylibs are internalized.
+    if (APPLE AND TARGET kge)
+        get_target_property(IS_BUNDLE kge MACOSX_BUNDLE)
+        if (IS_BUNDLE)
+            add_custom_target(kge_fixup_bundle ALL
+                    COMMAND ${CMAKE_COMMAND}
+                    -DAPP_BUNDLE=${CMAKE_CURRENT_BINARY_DIR}/$<TARGET_PROPERTY:kge,MACOSX_BUNDLE_BUNDLE_NAME>.app
+                    -P ${CMAKE_CURRENT_LIST_DIR}/cmake/fix_bundle.cmake
+                    COMMENT "Running fixup_bundle on kge.app to internalize non-Qt dylibs"
+                    VERBATIM)
+            add_dependencies(kge_fixup_bundle kge)
+        endif ()
+    endif ()
 endif ()

Command.cc

@@ -237,8 +237,8 @@ extract_region_text(const Buffer &buf, std::size_t sx, std::size_t sy, std::size
 	{
 		const auto &line = rows[sy];
 		std::size_t xs   = std::min(sx, line.size());
-		out += line.substr(xs);
-		out += '\n';
+		out              += line.substr(xs);
+		out              += '\n';
 	}
 	// middle lines full
 	for (std::size_t y = sy + 1; y < ey; ++y) {
@@ -249,7 +249,7 @@ extract_region_text(const Buffer &buf, std::size_t sx, std::size_t sy, std::size
 	{
 		const auto &line = rows[ey];
 		std::size_t xe   = std::min(ex, line.size());
-		out += line.substr(0, xe);
+		out              += line.substr(0, xe);
 	}
 	return out;
 }
@@ -277,7 +277,7 @@ delete_region(Buffer &buf, std::size_t sx, std::size_t sy, std::size_t ex, std::
 		buf.delete_text(static_cast<int>(sy), static_cast<int>(xs), xe - xs);
 	} else {
 		// Multi-line: delete from (sx,sy) to (ex,ey)
-		// Strategy: 
+		// Strategy:
 		// 1. Save suffix of last line (from ex to end)
 		// 2. Delete tail of first line (from sx to end)
 		// 3. Delete all lines from sy+1 to ey (inclusive)
@@ -1585,6 +1585,19 @@ cmd_buffer_close(const CommandContext &ctx)
 }
 
 
+// Create a new empty, unnamed buffer and switch to it
+static bool
+cmd_buffer_new(const CommandContext &ctx)
+{
+	// Create an empty buffer and add it to the editor
+	Buffer empty;
+	std::size_t idx = ctx.editor.AddBuffer(std::move(empty));
+	ctx.editor.SwitchTo(idx);
+	ctx.editor.SetStatus("New buffer");
+	return true;
+}
+
+
 // --- Editing ---
 static bool
 cmd_insert_text(CommandContext &ctx)
@@ -1909,7 +1922,7 @@ cmd_insert_text(CommandContext &ctx)
 	// If in search mode, treat printable input as query update
 	if (ctx.editor.SearchActive()) {
 		std::string q = ctx.editor.SearchQuery();
-		q += ctx.arg; // arg already printable text
+		q             += ctx.arg; // arg already printable text
 		ctx.editor.SetSearchQuery(q);
 
 		// Recompute matches and move cursor to current index
@@ -1955,24 +1968,29 @@ cmd_insert_text(CommandContext &ctx)
 		return false;
 	}
 	ensure_at_least_one_line(*buf);
-	auto &rows    = buf->Rows();
-	std::size_t y = buf->Cury();
-	std::size_t x = buf->Curx();
-	if (y >= rows.size()) {
-		rows.resize(y + 1);
-	}
-	int repeat = ctx.count > 0 ? ctx.count : 1;
+	std::size_t y     = buf->Cury();
+	std::size_t x     = buf->Curx();
+	std::size_t ins_y = y;
+	std::size_t ins_x = x; // remember insertion start for undo positioning
+	int repeat        = ctx.count > 0 ? ctx.count : 1;
+
+	// Apply edits to the underlying PieceTable through Buffer::insert_text,
+	// not directly to the legacy rows_ cache. This ensures Save() persists text.
 	for (int i = 0; i < repeat; ++i) {
-		rows[y].insert(x, ctx.arg);
+		buf->insert_text(static_cast<int>(y), static_cast<int>(x), std::string_view(ctx.arg));
 		x += ctx.arg.size();
 	}
 	buf->SetDirty(true);
-	// Record undo after buffer modification but before cursor update
+	// Record undo for this contiguous insert at the original insertion point
 	if (auto *u = buf->Undo()) {
+		// Position cursor at insertion start for the undo record
+		buf->SetCursor(ins_x, ins_y);
 		u->Begin(UndoType::Insert);
 		for (int i = 0; i < repeat; ++i) {
 			u->Append(std::string_view(ctx.arg));
 		}
+		// Finalize this contiguous insert as a single undoable action
+		u->commit();
 	}
 	buf->SetCursor(x, y);
 	ensure_cursor_visible(ctx.editor, *buf);
@@ -2307,48 +2325,53 @@ cmd_newline(CommandContext &ctx)
 			// Save original cursor to restore after operations
 			std::size_t orig_x = buf->Curx();
 			std::size_t orig_y = buf->Cury();
-			auto &rows         = buf->Rows();
 			std::size_t total  = 0;
 			UndoSystem *u      = buf->Undo();
 			if (u)
 				u->commit(); // end any pending batch
-			for (std::size_t y = 0; y < rows.size(); ++y) {
+			for (std::size_t y = 0; y < buf->Rows().size(); ++y) {
 				std::size_t pos = 0;
-				while (!find.empty()) {
-					pos = rows[y].find(find, pos);
-					if (pos == std::string::npos)
+				while (true) {
+					const auto &rows_view = buf->Rows();
+					if (y >= rows_view.size())
 						break;
-					// Perform delete of matched segment
-					rows[y].erase(pos, find.size());
+					std::string line = static_cast<std::string>(rows_view[y]);
+					if (find.empty())
+						break;
+					std::size_t p = line.find(find, pos);
+					if (p == std::string::npos)
+						break;
+					// Delete matched segment from the piece table
+					buf->delete_text(static_cast<int>(y), static_cast<int>(p), find.size());
 					if (u) {
-						buf->SetCursor(pos, y);
+						buf->SetCursor(p, y);
 						u->Begin(UndoType::Delete);
 						u->Append(std::string_view(find));
 					}
-					// Insert replacement
+					// Insert replacement if provided
 					if (!with.empty()) {
-						rows[y].insert(pos, with);
+						buf->insert_text(static_cast<int>(y), static_cast<int>(p),
+						                 std::string_view(with));
 						if (u) {
-							buf->SetCursor(pos, y);
+							buf->SetCursor(p, y);
 							u->Begin(UndoType::Insert);
 							u->Append(std::string_view(with));
 						}
-						pos += with.size();
-					}
-					++total;
-					if (with.empty()) {
-						// Avoid infinite loop when replacing with empty
-						// pos remains the same; move forward by 1 to continue search
-						if (pos < rows[y].size())
+						pos = p + with.size();
+					} else {
+						// When replacing with empty, continue after the deletion point to avoid re-matching
+						pos = p;
+						if (pos < static_cast<std::size_t>(buf->Rows()[y].size()))
 							++pos;
 						else
 							break;
 					}
+					++total;
 				}
 			}
 			buf->SetDirty(true);
 			// Restore original cursor
-			if (orig_y < rows.size())
+			if (orig_y < buf->Rows().size())
 				buf->SetCursor(orig_x, orig_y);
 			ensure_cursor_visible(ctx.editor, *buf);
 			char msg[128];
@@ -2383,6 +2406,10 @@ cmd_newline(CommandContext &ctx)
 				ctx.editor.SetStatus(err.empty() ? std::string("Failed to open ") + value : err);
 			} else {
 				ctx.editor.SetStatus(std::string("Opened ") + value);
+				// Center the view on the cursor (e.g. if the buffer restored a cursor position)
+				cmd_center_on_cursor(ctx);
+				// Close the prompt so subsequent typing edits the buffer, not the prompt
+				ctx.editor.CancelPrompt();
 			}
 		} else if (kind == Editor::PromptKind::BufferSwitch) {
 			// Resolve to a buffer index by exact match against path or basename;
@@ -2452,6 +2479,8 @@ cmd_newline(CommandContext &ctx)
 							ctx.editor.SetStatus("Saved as " + value);
 							if (auto *u = buf->Undo())
 								u->mark_saved();
+							// Close the prompt on successful save-as
+							ctx.editor.CancelPrompt();
 							// If a close-after-save was requested (from closing a dirty, unnamed buffer),
 							// close the buffer now.
 							if (ctx.editor.CloseAfterSave()) {
@@ -2516,9 +2545,13 @@ cmd_newline(CommandContext &ctx)
 									"  Now: ")
 								+ (cur ? buffer_display_name(*cur) : std::string("")));
 						}
+						// Close the prompt after successful confirmation
+						ctx.editor.CancelPrompt();
 					}
 				} else {
 					ctx.editor.SetStatus("Save canceled");
+					// Close the prompt after negative confirmation
+					ctx.editor.CancelPrompt();
 				}
 				ctx.editor.ClearPendingOverwritePath();
 				// Regardless of answer, end any close-after-save pending state for safety.
@@ -2705,13 +2738,15 @@ cmd_newline(CommandContext &ctx)
 				ctx.editor.SetSearchIndex(-1);
 				return true;
 			}
-			auto &rows          = buf->Rows();
 			std::size_t changed = 0;
-			for (auto &line: rows) {
-				std::string before = static_cast<std::string>(line);
+			// Iterate by index to allow modifications via PieceTable helpers
+			for (std::size_t y = 0; y < buf->Rows().size(); ++y) {
+				std::string before = static_cast<std::string>(buf->Rows()[y]);
 				std::string after  = std::regex_replace(before, rx, repl);
 				if (after != before) {
-					line = after;
+					// Replace entire line y with 'after' using PieceTable ops
+					buf->delete_row(static_cast<int>(y));
+					buf->insert_row(static_cast<int>(y), std::string_view(after));
 					++changed;
 				}
 			}
@@ -2746,26 +2781,17 @@ cmd_newline(CommandContext &ctx)
 		return false;
 	}
 	ensure_at_least_one_line(*buf);
-	auto &rows    = buf->Rows();
 	std::size_t y = buf->Cury();
 	std::size_t x = buf->Curx();
 	int repeat    = ctx.count > 0 ? ctx.count : 1;
 	for (int i = 0; i < repeat; ++i) {
-		if (y >= rows.size())
-			rows.resize(y + 1);
-		auto &line = rows[y];
-		std::string tail;
-		if (x < line.size()) {
-			tail = line.substr(x);
-			line.erase(x);
-		}
-		rows.insert(rows.begin() + static_cast<std::ptrdiff_t>(y + 1), Buffer::Line(tail));
+		buf->split_line(static_cast<int>(y), static_cast<int>(x));
+		// Move to start of next line
 		y += 1;
 		x = 0;
 	}
 	buf->SetCursor(x, y);
 	buf->SetDirty(true);
-	// Record newline after buffer modification; commit immediately for single-step undo
 	if (auto *u = buf->Undo()) {
 		u->Begin(UndoType::Newline);
 		u->commit();
@@ -2828,44 +2854,42 @@ cmd_backspace(CommandContext &ctx)
 		return false;
 	}
 	ensure_at_least_one_line(*buf);
-	auto &rows    = buf->Rows();
 	std::size_t y = buf->Cury();
 	std::size_t x = buf->Curx();
 	UndoSystem *u = buf->Undo();
 	int repeat    = ctx.count > 0 ? ctx.count : 1;
 	for (int i = 0; i < repeat; ++i) {
+		// Refresh a read-only view of lines for char capture/lengths
+		const auto &rows_view = buf->Rows();
 		if (x > 0) {
-			// Delete character before cursor
-			char deleted = rows[y][x - 1];
-			rows[y].erase(x - 1, 1);
-			--x;
-			// Update buffer cursor BEFORE Begin so batching sees correct cursor for backspace
+			char deleted = '\0';
+			if (y < rows_view.size() && x - 1 < rows_view[y].size())
+				deleted = rows_view[y][x - 1];
+			buf->delete_text(static_cast<int>(y), static_cast<int>(x - 1), 1);
+			x -= 1;
 			buf->SetCursor(x, y);
-			// Record undo after deletion and cursor update
 			if (u) {
 				u->Begin(UndoType::Delete);
-				u->Append(deleted);
+				if (deleted != '\0')
+					u->Append(deleted);
 			}
 		} else if (y > 0) {
-			// join with previous line
-			std::size_t prev_len = rows[y - 1].size();
-			rows[y - 1] += rows[y];
-			rows.erase(rows.begin() + static_cast<std::ptrdiff_t>(y));
+			// Compute previous line length before join
+			std::size_t prev_len = 0;
+			if (y - 1 < rows_view.size())
+				prev_len = rows_view[y - 1].size();
+			buf->join_lines(static_cast<int>(y - 1));
 			y = y - 1;
 			x = prev_len;
-			// Update cursor to the join point BEFORE Begin to keep invariants consistent
 			buf->SetCursor(x, y);
-			// Record a newline deletion that joined lines; commit immediately
 			if (u) {
 				u->Begin(UndoType::Newline);
 				u->commit();
 			}
 		} else {
-			// at very start; nothing to do
 			break;
 		}
 	}
-	// Ensure buffer cursor reflects final x,y
 	buf->SetCursor(x, y);
 	buf->SetDirty(true);
 	ensure_cursor_visible(ctx.editor, *buf);
@@ -2882,28 +2906,23 @@ cmd_delete_char(CommandContext &ctx)
 		return false;
 	}
 	ensure_at_least_one_line(*buf);
-	auto &rows    = buf->Rows();
 	std::size_t y = buf->Cury();
 	std::size_t x = buf->Curx();
 	UndoSystem *u = buf->Undo();
 	int repeat    = ctx.count > 0 ? ctx.count : 1;
 	for (int i = 0; i < repeat; ++i) {
-		if (y >= rows.size())
+		const auto &rows_view = buf->Rows();
+		if (y >= rows_view.size())
 			break;
-		if (x < rows[y].size()) {
-			// Forward delete at cursor
-			char deleted = rows[y][x];
-			rows[y].erase(x, 1);
-			// Record undo after deletion (cursor stays at same position)
+		if (x < rows_view[y].size()) {
+			char deleted = rows_view[y][x];
+			buf->delete_text(static_cast<int>(y), static_cast<int>(x), 1);
 			if (u) {
 				u->Begin(UndoType::Delete);
 				u->Append(deleted);
 			}
-		} else if (y + 1 < rows.size()) {
-			// join next line
-			rows[y] += rows[y + 1];
-			rows.erase(rows.begin() + static_cast<std::ptrdiff_t>(y + 1));
-			// Record newline deletion at end of this line; commit immediately
+		} else if (y + 1 < rows_view.size()) {
+			buf->join_lines(static_cast<int>(y));
 			if (u) {
 				u->Begin(UndoType::Newline);
 				u->commit();
@@ -2965,23 +2984,23 @@ cmd_kill_to_eol(CommandContext &ctx)
 		return false;
 	}
 	ensure_at_least_one_line(*buf);
-	auto &rows    = buf->Rows();
 	std::size_t y = buf->Cury();
 	std::size_t x = buf->Curx();
 	int repeat    = ctx.count > 0 ? ctx.count : 1;
 	std::string killed_total;
 	for (int i = 0; i < repeat; ++i) {
-		if (y >= rows.size())
+		const auto &rows_view = buf->Rows();
+		if (y >= rows_view.size())
 			break;
-		if (x < rows[y].size()) {
+		if (x < rows_view[y].size()) {
 			// delete from cursor to end of line
-			killed_total += rows[y].substr(x);
-			rows[y].erase(x);
-		} else if (y + 1 < rows.size()) {
+			killed_total    += rows_view[y].substr(x);
+			std::size_t len = rows_view[y].size() - x;
+			buf->delete_text(static_cast<int>(y), static_cast<int>(x), len);
+		} else if (y + 1 < rows_view.size()) {
 			// at EOL: delete the newline (join with next line)
 			killed_total += "\n";
-			rows[y] += rows[y + 1];
-			rows.erase(rows.begin() + static_cast<std::ptrdiff_t>(y + 1));
+			buf->join_lines(static_cast<int>(y));
 		} else {
 			// nothing to delete
 			break;
@@ -3009,32 +3028,35 @@ cmd_kill_line(CommandContext &ctx)
 		return false;
 	}
 	ensure_at_least_one_line(*buf);
-	auto &rows    = buf->Rows();
 	std::size_t y = buf->Cury();
 	std::size_t x = buf->Curx();
 	(void) x; // cursor x will be reset to 0
 	int repeat = ctx.count > 0 ? ctx.count : 1;
 	std::string killed_total;
 	for (int i = 0; i < repeat; ++i) {
-		if (rows.empty())
+		const auto &rows_view = buf->Rows();
+		if (rows_view.empty())
 			break;
-		if (rows.size() == 1) {
+		if (rows_view.size() == 1) {
 			// last remaining line: clear its contents
-			killed_total += static_cast<std::string>(rows[0]);
-			rows[0].Clear();
+			killed_total += static_cast<std::string>(rows_view[0]);
+			if (!rows_view[0].empty())
+				buf->delete_text(0, 0, rows_view[0].size());
 			y = 0;
-		} else if (y < rows.size()) {
+		} else if (y < rows_view.size()) {
 			// erase current line; keep y pointing at the next line
-			killed_total += static_cast<std::string>(rows[y]);
+			killed_total += static_cast<std::string>(rows_view[y]);
 			killed_total += "\n";
-			rows.erase(rows.begin() + static_cast<std::ptrdiff_t>(y));
-			if (y >= rows.size()) {
+			buf->delete_row(static_cast<int>(y));
+			const auto &rows_after = buf->Rows();
+			if (y >= rows_after.size()) {
 				// deleted last line; move to previous
-				y = rows.size() - 1;
+				y = rows_after.empty() ? 0 : rows_after.size() - 1;
 			}
 		} else {
 			// out of range
-			y = rows.empty() ? 0 : rows.size() - 1;
+			const auto &rows2 = buf->Rows();
+			y                 = rows2.empty() ? 0 : rows2.size() - 1;
 		}
 	}
 	buf->SetCursor(0, y);
@@ -3097,9 +3119,9 @@ cmd_move_file_end(CommandContext &ctx)
 	if (!buf)
 		return false;
 	ensure_at_least_one_line(*buf);
-	auto &rows    = buf->Rows();
-	std::size_t y = rows.empty() ? 0 : rows.size() - 1;
-	std::size_t x = rows.empty() ? 0 : rows[y].size();
+	const auto &rows = buf->Rows();
+	std::size_t y    = rows.empty() ? 0 : rows.size() - 1;
+	std::size_t x    = rows.empty() ? 0 : rows[y].size();
 	buf->SetCursor(x, y);
 	ensure_cursor_visible(ctx.editor, *buf);
 	return true;
@@ -3796,34 +3818,9 @@ cmd_delete_word_prev(CommandContext &ctx)
 				break;
 			--x;
 		}
-		// Now delete from (x, y) to (start_x, start_y)
-		std::string deleted;
-		if (y == start_y) {
-			// same line
-			if (x < start_x) {
-				deleted = rows[y].substr(x, start_x - x);
-				rows[y].erase(x, start_x - x);
-			}
-		} else {
-			// spans multiple lines
-			// First, collect text from (x, y) to end of line y
-			deleted = rows[y].substr(x);
-			rows[y].erase(x);
-			// Then collect complete lines between y and start_y
-			for (std::size_t ly = y + 1; ly < start_y; ++ly) {
-				deleted += "\n";
-				deleted += static_cast<std::string>(rows[ly]);
-			}
-			// Finally, collect from beginning of start_y to start_x
-			if (start_y < rows.size()) {
-				deleted += "\n";
-				deleted += rows[start_y].substr(0, start_x);
-				rows[y] += rows[start_y].substr(start_x);
-				// Remove lines from y+1 to start_y inclusive
-				rows.erase(rows.begin() + static_cast<std::ptrdiff_t>(y + 1),
-				           rows.begin() + static_cast<std::ptrdiff_t>(start_y + 1));
-			}
-		}
+		// Now delete from (x, y) to (start_x, start_y) using PieceTable
+		std::string deleted = extract_region_text(*buf, x, y, start_x, start_y);
+		delete_region(*buf, x, y, start_x, start_y);
 		// Prepend to killed_total (since we're deleting backwards)
 		killed_total = deleted + killed_total;
 	}
@@ -3850,10 +3847,10 @@ cmd_delete_word_next(CommandContext &ctx)
 	if (auto *u = buf->Undo())
 		u->commit();
 	ensure_at_least_one_line(*buf);
-	auto &rows    = buf->Rows();
-	std::size_t y = buf->Cury();
-	std::size_t x = buf->Curx();
-	int repeat    = ctx.count > 0 ? ctx.count : 1;
+	const auto &rows = buf->Rows();
+	std::size_t y    = buf->Cury();
+	std::size_t x    = buf->Curx();
+	int repeat       = ctx.count > 0 ? ctx.count : 1;
 	std::string killed_total;
 	for (int i = 0; i < repeat; ++i) {
 		if (y >= rows.size())
@@ -3892,37 +3889,11 @@ cmd_delete_word_next(CommandContext &ctx)
 				continue;
 			}
 		}
-		// Now delete from (start_x, start_y) to (x, y)
-		std::string deleted;
-		if (start_y == y) {
-			// same line
-			if (start_x < x) {
-				deleted = rows[y].substr(start_x, x - start_x);
-				rows[y].erase(start_x, x - start_x);
-				x = start_x;
-			}
-		} else {
-			// spans multiple lines
-			// First, collect text from start_x to end of line start_y
-			deleted = rows[start_y].substr(start_x);
-			rows[start_y].erase(start_x);
-			// Then collect complete lines between start_y and y
-			for (std::size_t ly = start_y + 1; ly < y; ++ly) {
-				deleted += "\n";
-				deleted += static_cast<std::string>(rows[ly]);
-			}
-			// Finally, collect from beginning of y to x
-			if (y < rows.size()) {
-				deleted += "\n";
-				deleted += rows[y].substr(0, x);
-				rows[start_y] += rows[y].substr(x);
-				// Remove lines from start_y+1 to y inclusive
-				rows.erase(rows.begin() + static_cast<std::ptrdiff_t>(start_y + 1),
-				           rows.begin() + static_cast<std::ptrdiff_t>(y + 1));
-			}
-			y = start_y;
-			x = start_x;
-		}
+		// Now delete from (start_x, start_y) to (x, y) using PieceTable
+		std::string deleted = extract_region_text(*buf, start_x, start_y, x, y);
+		delete_region(*buf, start_x, start_y, x, y);
+		y            = start_y;
+		x            = start_x;
 		killed_total += deleted;
 	}
 	buf->SetCursor(x, y);
@@ -3954,9 +3925,8 @@ cmd_indent_region(CommandContext &ctx)
 		ctx.editor.SetStatus("No region to indent");
 		return false;
 	}
-	auto &rows = buf->Rows();
-	for (std::size_t y = sy; y <= ey && y < rows.size(); ++y) {
-		rows[y].insert(0, "\t");
+	for (std::size_t y = sy; y <= ey && y < buf->Rows().size(); ++y) {
+		buf->insert_text(static_cast<int>(y), 0, std::string_view("\t"));
 	}
 	buf->SetDirty(true);
 	buf->ClearMark();
@@ -3980,19 +3950,21 @@ cmd_unindent_region(CommandContext &ctx)
 		ctx.editor.SetStatus("No region to unindent");
 		return false;
 	}
-	auto &rows = buf->Rows();
-	for (std::size_t y = sy; y <= ey && y < rows.size(); ++y) {
-		auto &line = rows[y];
+	for (std::size_t y = sy; y <= ey && y < buf->Rows().size(); ++y) {
+		const auto &rows_view = buf->Rows();
+		if (y >= rows_view.size())
+			break;
+		const std::string line = static_cast<std::string>(rows_view[y]);
 		if (!line.empty()) {
 			if (line[0] == '\t') {
-				line.erase(0, 1);
+				buf->delete_text(static_cast<int>(y), 0, 1);
 			} else if (line[0] == ' ') {
 				std::size_t spaces = 0;
 				while (spaces < line.size() && spaces < 8 && line[spaces] == ' ') {
 					++spaces;
 				}
 				if (spaces > 0)
-					line.erase(0, spaces);
+					buf->delete_text(static_cast<int>(y), 0, spaces);
 			}
 		}
 	}
@@ -4125,8 +4097,8 @@ cmd_reflow_paragraph(CommandContext &ctx)
 				line.push_back(' ');
 				++cur_len;
 			}
-			line += wrd;
-			cur_len += wrd.size();
+			line               += wrd;
+			cur_len            += wrd.size();
 			first_word_on_line = false;
 		}
 		if (!line.empty())
@@ -4230,10 +4202,18 @@ cmd_reflow_paragraph(CommandContext &ctx)
 	if (new_lines.empty())
 		new_lines.push_back("");
 
-	rows.erase(rows.begin() + static_cast<std::ptrdiff_t>(para_start),
-	           rows.begin() + static_cast<std::ptrdiff_t>(para_end + 1));
-	rows.insert(rows.begin() + static_cast<std::ptrdiff_t>(para_start),
-	            new_lines.begin(), new_lines.end());
+	// Replace paragraph lines via PieceTable-backed operations
+	for (std::size_t i = para_end; i + 1 > para_start; --i) {
+		buf->delete_row(static_cast<int>(i));
+		if (i == 0)
+			break; // prevent wrap on size_t
+	}
+	// Insert new lines starting at para_start
+	std::size_t insert_y = para_start;
+	for (const auto &ln: new_lines) {
+		buf->insert_row(static_cast<int>(insert_y), std::string_view(ln));
+		insert_y += 1;
+	}
 
 	// Place cursor at the end of the paragraph
 	std::size_t new_last_y = para_start + (new_lines.empty() ? 0 : new_lines.size() - 1);
@@ -4251,6 +4231,9 @@ cmd_reload_buffer(CommandContext &ctx)
 	Buffer *buf = ctx.editor.CurrentBuffer();
 	if (!buf)
 		return false;
+	// Remember the current cursor position so we can attempt to restore it
+	const std::size_t old_x     = buf->Curx();
+	const std::size_t old_y     = buf->Cury();
 	const std::string &filename = buf->Filename();
 	if (filename.empty()) {
 		ctx.editor.SetStatus("Cannot reload unnamed buffer");
@@ -4261,6 +4244,19 @@ cmd_reload_buffer(CommandContext &ctx)
 		ctx.editor.SetStatus(std::string("Reload failed: ") + err);
 		return false;
 	}
+	// Try to restore the cursor to its previous position if still valid; otherwise clamp
+	{
+		auto &rows              = buf->Rows();
+		const std::size_t nrows = rows.size();
+		if (nrows == 0) {
+			buf->SetCursor(0, 0);
+		} else {
+			const std::size_t new_y    = old_y < nrows ? old_y : (nrows - 1);
+			const std::size_t line_len = rows[new_y].size();
+			const std::size_t new_x    = old_x < line_len ? old_x : line_len;
+			buf->SetCursor(new_x, new_y);
+		}
+	}
 	ctx.editor.SetStatus(std::string("Reloaded ") + filename);
 	ensure_cursor_visible(ctx.editor, *buf);
 	return true;
@@ -4378,6 +4374,7 @@ InstallDefaultCommands()
 		CommandId::BufferSwitchStart, "buffer-switch-start", "Begin buffer switch prompt",
 		cmd_buffer_switch_start, false, false
 	});
+	CommandRegistry::Register({CommandId::BufferNew, "buffer-new", "Open new empty buffer", cmd_buffer_new});
 	CommandRegistry::Register({CommandId::BufferNext, "buffer-next", "Switch to next buffer", cmd_buffer_next});
 	CommandRegistry::Register({CommandId::BufferPrev, "buffer-prev", "Switch to previous buffer", cmd_buffer_prev});
 	CommandRegistry::Register({
@@ -4569,4 +4566,4 @@ Execute(Editor &ed, const std::string &name, const std::string &arg, int count)
 		return false;
 	CommandContext ctx{ed, arg, count};
 	return cmd->handler ? cmd->handler(ctx) : false;
-}
+}

Command.h

@@ -31,6 +31,7 @@ enum class CommandId {
 	VisualFontPickerToggle,
 	// Buffers
 	BufferSwitchStart, // begin buffer switch prompt
+	BufferNew, // create a new empty, unnamed buffer (C-k i)
 	BufferClose,
 	BufferNext,
 	BufferPrev,

Editor.cc

@@ -197,9 +197,11 @@ Editor::OpenFile(const std::string &path, std::string &err)
 					eng->InvalidateFrom(0);
 				}
 			}
-			return true;
-		}
-	}
+            // Defensive: ensure any active prompt is closed after a successful open
+            CancelPrompt();
+            return true;
+        }
+    }
 
 	Buffer b;
 	if (!b.OpenFromFile(path, err)) {
@@ -237,8 +239,10 @@ Editor::OpenFile(const std::string &path, std::string &err)
 	}
 	// Add as a new buffer and switch to it
 	std::size_t idx = AddBuffer(std::move(b));
-	SwitchTo(idx);
-	return true;
+    SwitchTo(idx);
+    // Defensive: ensure any active prompt is closed after a successful open
+    CancelPrompt();
+    return true;
 }
 
 

HelpText.cc

@@ -31,6 +31,7 @@ HelpText::Text()
 		"  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 i        New empty buffer\n"
 		"  C-k f        Flush kill ring\n"
 		"  C-k g        Jump to line\n"
 		"  C-k h        Show this help\n"

ImGuiFrontend.cc

@@ -18,6 +18,7 @@
 #include "GUITheme.h"
 #include "fonts/Font.h" // embedded default font (DefaultFont)
 #include "fonts/FontRegistry.h"
+#include "fonts/IosevkaExtended.h"
 #include "syntax/HighlighterRegistry.h"
 #include "syntax/NullHighlighter.h"
 
@@ -261,11 +262,11 @@ GUIFrontend::Step(Editor &ed, bool &running)
 
 	// Update editor logical rows/cols using current ImGui metrics and display size
 	{
-		ImGuiIO &io  = ImGui::GetIO();
-		float line_h = ImGui::GetTextLineHeightWithSpacing();
-		float ch_w   = ImGui::CalcTextSize("M").x;
-		if (line_h <= 0.0f)
-			line_h = 16.0f;
+		ImGuiIO &io = ImGui::GetIO();
+		float row_h = ImGui::GetTextLineHeightWithSpacing();
+		float ch_w  = ImGui::CalcTextSize("M").x;
+		if (row_h <= 0.0f)
+			row_h = 16.0f;
 		if (ch_w <= 0.0f)
 			ch_w = 8.0f;
 		// Prefer ImGui IO display size; fall back to cached SDL window size
@@ -273,20 +274,20 @@ GUIFrontend::Step(Editor &ed, bool &running)
 		float disp_h = io.DisplaySize.y > 0 ? io.DisplaySize.y : static_cast<float>(height_);
 
 		// Account for the GUI window padding and the status bar height used in ImGuiRenderer.
-		// ImGuiRenderer pushes WindowPadding = (6,6) every frame, so use the same constants here
-		// to avoid mismatches that would cause premature scrolling.
 		const float pad_x = 6.0f;
 		const float pad_y = 6.0f;
-		// Status bar reserves one frame height (with spacing) inside the window
-		float status_h = ImGui::GetFrameHeightWithSpacing();
 
-		float avail_w = std::max(0.0f, disp_w - 2.0f * pad_x);
-		float avail_h = std::max(0.0f, disp_h - 2.0f * pad_y - status_h);
+		// Use the same logic as ImGuiRenderer for available height and status bar reservation.
+		float wanted_bar_h   = ImGui::GetFrameHeight();
+		float total_avail_h  = std::max(0.0f, disp_h - 2.0f * pad_y);
+		float actual_avail_h = std::floor((total_avail_h - wanted_bar_h) / row_h) * row_h;
 
 		// Visible content rows inside the scroll child
-		auto content_rows = static_cast<std::size_t>(std::floor(avail_h / line_h));
+		auto content_rows = static_cast<std::size_t>(std::max(0.0f, std::floor(actual_avail_h / row_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 rows = content_rows + 1;
+
+		float avail_w    = std::max(0.0f, disp_w - 2.0f * pad_x);
 		std::size_t cols = static_cast<std::size_t>(std::max(1.0f, std::floor(avail_w / ch_w)));
 
 		// Only update if changed to avoid churn
@@ -357,14 +358,32 @@ GUIFrontend::LoadGuiFont_(const char * /*path*/, const float size_px)
 {
 	const ImGuiIO &io = ImGui::GetIO();
 	io.Fonts->Clear();
-	const ImFont *font = io.Fonts->AddFontFromMemoryCompressedTTF(
+
+	ImFontConfig config;
+	config.MergeMode = false;
+
+	// Load Basic Latin + Latin Supplement
+	io.Fonts->AddFontFromMemoryCompressedTTF(
 		kte::Fonts::DefaultFontData,
 		kte::Fonts::DefaultFontSize,
-		size_px);
-	if (!font) {
-		font = io.Fonts->AddFontDefault();
-	}
-	(void) font;
+		size_px,
+		&config,
+		io.Fonts->GetGlyphRangesDefault());
+
+	// Merge Greek and Mathematical symbols from IosevkaExtended
+	config.MergeMode                       = true;
+	static const ImWchar extended_ranges[] = {
+		0x0370, 0x03FF, // Greek and Coptic
+		0x2200, 0x22FF, // Mathematical Operators
+		0,
+	};
+	io.Fonts->AddFontFromMemoryCompressedTTF(
+		kte::Fonts::IosevkaExtended::DefaultFontRegularCompressedData,
+		kte::Fonts::IosevkaExtended::DefaultFontRegularCompressedSize,
+		size_px,
+		&config,
+		extended_ranges);
+
 	io.Fonts->Build();
 	return true;
 }

ImGuiInputHandler.cc

@@ -158,16 +158,17 @@ map_key(const SDL_Keycode key,
 			ascii_key = static_cast<int>(key);
 		}
 		bool ctrl2 = (mod & KMOD_CTRL) != 0;
-		// If user typed a literal 'C' (or '^') as a control qualifier, keep k-prefix active
-		if (ascii_key == 'C' || ascii_key == 'c' || ascii_key == '^') {
-			k_ctrl_pending = true;
-			// Keep waiting for the next suffix; show status and suppress ensuing TEXTINPUT
-			if (ed)
-				ed->SetStatus("C-k C _");
-			suppress_textinput_once = true;
-			out.hasCommand          = false;
-			return true;
-		}
+  // If user typed a literal 'C' (uppercase) or '^' as a control qualifier, keep k-prefix active
+  // Do NOT treat lowercase 'c' as a qualifier; 'c' is a valid k-command (BufferClose).
+  if (ascii_key == 'C' || ascii_key == '^') {
+      k_ctrl_pending = true;
+      // Keep waiting for the next suffix; show status and suppress ensuing TEXTINPUT
+      if (ed)
+          ed->SetStatus("C-k C _");
+      suppress_textinput_once = true;
+      out.hasCommand          = false;
+      return true;
+  }
 		// Otherwise, consume the k-prefix now for the actual suffix
 		k_prefix = false;
 		if (ascii_key != 0) {
@@ -472,16 +473,16 @@ ImGuiInputHandler::ProcessSDLEvent(const SDL_Event &e)
 					ascii_key = static_cast<int>(c0);
 				}
 				if (ascii_key != 0) {
-					// Qualifier via TEXTINPUT: 'C' or '^'
-					if (ascii_key == 'C' || ascii_key == 'c' || ascii_key == '^') {
-						k_ctrl_pending_ = true;
-						if (ed_)
-							ed_->SetStatus("C-k C _");
-						// Keep k-prefix active; do not emit a command
-						k_prefix_ = true;
-						produced  = true;
-						break;
-					}
+     // Qualifier via TEXTINPUT: uppercase 'C' or '^' only
+     if (ascii_key == 'C' || ascii_key == '^') {
+         k_ctrl_pending_ = true;
+         if (ed_)
+             ed_->SetStatus("C-k C _");
+         // Keep k-prefix active; do not emit a command
+         k_prefix_ = true;
+         produced  = true;
+         break;
+     }
 					// Map via k-prefix table; do not pass Ctrl for TEXTINPUT case
 					CommandId id;
 					bool pass_ctrl  = k_ctrl_pending_;

ImGuiRenderer.cc

@@ -94,8 +94,17 @@ ImGuiRenderer::Draw(Editor &ed)
 			ImGui::SetNextWindowScroll(ImVec2(target_x, target_y));
 		}
 
-		// Reserve space for status bar at bottom
-		ImGui::BeginChild("scroll", ImVec2(0, -ImGui::GetFrameHeightWithSpacing()), false,
+		// Reserve space for status bar at bottom.
+		// We calculate a height that is an exact multiple of the line height
+		// to avoid partial lines and "scroll past end" jitter.
+		float total_avail_h = ImGui::GetContentRegionAvail().y;
+		float wanted_bar_h  = ImGui::GetFrameHeight();
+		float child_h_plan  = std::max(0.0f, std::floor((total_avail_h - wanted_bar_h) / row_h) * row_h);
+		float real_bar_h    = total_avail_h - child_h_plan;
+
+		ImGui::PushStyleVar(ImGuiStyleVar_WindowPadding, ImVec2(0, 0));
+		ImGui::PushStyleVar(ImGuiStyleVar_ItemSpacing, ImVec2(0, 0));
+		ImGui::BeginChild("scroll", ImVec2(0, child_h_plan), false,
 		                  ImGuiWindowFlags_HorizontalScrollbar | ImGuiWindowFlags_NoScrollWithMouse);
 
 		// Get child window position and scroll for click handling
@@ -138,90 +147,6 @@ ImGuiRenderer::Draw(Editor &ed)
 		}
 		prev_buf_rowoffs = buf_rowoffs;
 		prev_buf_coloffs = buf_coloffs;
-
-		// Synchronize cursor and scrolling.
-		// Ensure the cursor is visible, but avoid aggressive centering so that
-		// the same lines remain visible until the cursor actually goes off-screen.
-		{
-			// Compute visible row range using the child window height
-			float child_h  = ImGui::GetWindowHeight();
-			long first_row = static_cast<long>(scroll_y / row_h);
-			long vis_rows  = static_cast<long>(child_h / row_h);
-			if (vis_rows < 1)
-				vis_rows = 1;
-			long last_row = first_row + vis_rows - 1;
-
-			long cyr = static_cast<long>(cy);
-			if (cyr < first_row) {
-				// Scroll just enough to bring the cursor line to the top
-				float target = static_cast<float>(cyr) * row_h;
-				if (target < 0.f)
-					target = 0.f;
-				float max_y = ImGui::GetScrollMaxY();
-				if (max_y >= 0.f && target > max_y)
-					target = max_y;
-				ImGui::SetScrollY(target);
-				scroll_y  = ImGui::GetScrollY();
-				first_row = static_cast<long>(scroll_y / row_h);
-				last_row  = first_row + vis_rows - 1;
-			} else if (cyr > last_row) {
-				// Scroll just enough to bring the cursor line to the bottom
-				long new_first = cyr - vis_rows + 1;
-				if (new_first < 0)
-					new_first = 0;
-				float target = static_cast<float>(new_first) * row_h;
-				float max_y  = ImGui::GetScrollMaxY();
-				if (target < 0.f)
-					target = 0.f;
-				if (max_y >= 0.f && target > max_y)
-					target = max_y;
-				ImGui::SetScrollY(target);
-				scroll_y  = ImGui::GetScrollY();
-				first_row = static_cast<long>(scroll_y / row_h);
-				last_row  = first_row + vis_rows - 1;
-			}
-
-			// Horizontal scroll: ensure cursor column is visible
-			float child_w = ImGui::GetWindowWidth();
-			long vis_cols = static_cast<long>(child_w / space_w);
-			if (vis_cols < 1)
-				vis_cols = 1;
-			long first_col = static_cast<long>(scroll_x / space_w);
-			long last_col  = first_col + vis_cols - 1;
-
-			// Compute cursor's rendered X position (accounting for tabs)
-			std::size_t cursor_rx = 0;
-			if (cy < lines.size()) {
-				std::string cur_line   = static_cast<std::string>(lines[cy]);
-				const std::size_t tabw = 8;
-				for (std::size_t i = 0; i < cx && i < cur_line.size(); ++i) {
-					if (cur_line[i] == '\t') {
-						cursor_rx += tabw - (cursor_rx % tabw);
-					} else {
-						cursor_rx += 1;
-					}
-				}
-			}
-			long cxr = static_cast<long>(cursor_rx);
-			if (cxr < first_col || cxr > last_col) {
-				float target_x = static_cast<float>(cxr) * space_w;
-				// Center horizontally if possible
-				target_x -= (child_w / 2.0f);
-				if (target_x < 0.f)
-					target_x = 0.f;
-				float max_x = ImGui::GetScrollMaxX();
-				if (max_x >= 0.f && target_x > max_x)
-					target_x = max_x;
-				ImGui::SetScrollX(target_x);
-				scroll_x = ImGui::GetScrollX();
-			}
-			// 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());
-			}
-		}
 		// Cache current horizontal offset in rendered columns for click handling
 		const std::size_t coloffs_now = buf->Coloffs();
 
@@ -489,23 +414,98 @@ ImGuiRenderer::Draw(Editor &ed)
 				ImGui::GetWindowDrawList()->AddRectFilled(p0, p1, col);
 			}
 		}
+		// Synchronize cursor and scrolling after rendering all lines so content size is known.
+		{
+			float child_h_actual = ImGui::GetWindowHeight();
+			float child_w_actual = ImGui::GetWindowWidth();
+			float scroll_y_now   = ImGui::GetScrollY();
+			float scroll_x_now   = ImGui::GetScrollX();
+
+			long first_row = static_cast<long>(scroll_y_now / row_h);
+			long vis_rows  = static_cast<long>(std::round(child_h_actual / row_h));
+			if (vis_rows < 1)
+				vis_rows = 1;
+			long last_row = first_row + vis_rows - 1;
+
+			long cyr = static_cast<long>(cy);
+			if (cyr < first_row) {
+				float target = static_cast<float>(cyr) * row_h;
+				if (target < 0.f)
+					target = 0.f;
+				float max_y = ImGui::GetScrollMaxY();
+				if (max_y >= 0.f && target > max_y)
+					target = max_y;
+				ImGui::SetScrollY(target);
+				first_row = static_cast<long>(target / row_h);
+				last_row  = first_row + vis_rows - 1;
+			} else if (cyr > last_row) {
+				long new_first = cyr - vis_rows + 1;
+				if (new_first < 0)
+					new_first = 0;
+				float target = static_cast<float>(new_first) * row_h;
+				float max_y  = ImGui::GetScrollMaxY();
+				if (target < 0.f)
+					target = 0.f;
+				if (max_y >= 0.f && target > max_y)
+					target = max_y;
+				ImGui::SetScrollY(target);
+				first_row = static_cast<long>(target / row_h);
+				last_row  = first_row + vis_rows - 1;
+			}
+
+			// Horizontal scroll: ensure cursor column is visible
+			long vis_cols = static_cast<long>(std::round(child_w_actual / space_w));
+			if (vis_cols < 1)
+				vis_cols = 1;
+			long first_col = static_cast<long>(scroll_x_now / space_w);
+			long last_col  = first_col + vis_cols - 1;
+
+			std::size_t cursor_rx = 0;
+			if (cy < lines.size()) {
+				std::string cur_line   = static_cast<std::string>(lines[cy]);
+				const std::size_t tabw = 8;
+				for (std::size_t i = 0; i < cx && i < cur_line.size(); ++i) {
+					if (cur_line[i] == '\t') {
+						cursor_rx += tabw - (cursor_rx % tabw);
+					} else {
+						cursor_rx += 1;
+					}
+				}
+			}
+			long cxr = static_cast<long>(cursor_rx);
+			if (cxr < first_col || cxr > last_col) {
+				float target_x = static_cast<float>(cxr) * space_w;
+				target_x       -= (child_w_actual / 2.0f);
+				if (target_x < 0.f)
+					target_x = 0.f;
+				float max_x = ImGui::GetScrollMaxX();
+				if (max_x >= 0.f && target_x > max_x)
+					target_x = max_x;
+				ImGui::SetScrollX(target_x);
+			}
+
+			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());
+			}
+		}
 		ImGui::EndChild();
+		ImGui::PopStyleVar(2); // WindowPadding, ItemSpacing
 
-		// Status bar spanning full width
-		ImGui::Separator();
-
-		// Compute full content width and draw a filled background rectangle
+		// Status bar area starting right after the scroll child
 		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);
+		ImVec2 win_sz  = ImGui::GetWindowSize();
+		float x0       = win_pos.x;
+		float x1       = win_pos.x + win_sz.x;
+		float y0       = ImGui::GetCursorScreenPos().y;
+		float bar_h    = real_bar_h;
+
+		ImVec2 p0(x0, y0);
+		ImVec2 p1(x1, y0 + 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();
@@ -560,7 +560,7 @@ ImGuiRenderer::Draw(Editor &ed)
 								              (size_t) std::max<size_t>(
 									              1, (size_t) (tail.size() / 4)))
 							              : 1;
-						start += skip;
+						start                 += skip;
 						std::string candidate = tail.substr(start);
 						ImVec2 cand_sz        = ImGui::CalcTextSize(candidate.c_str());
 						if (cand_sz.x <= avail_px) {
@@ -591,11 +591,9 @@ ImGuiRenderer::Draw(Editor &ed)
 
 			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::SetCursorScreenPos(ImVec2(left_x, y0 + (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;
@@ -618,11 +616,11 @@ ImGuiRenderer::Draw(Editor &ed)
 				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             += "[";
+					left             += std::to_string(static_cast<unsigned long long>(idx1));
+					left             += "/";
+					left             += std::to_string(static_cast<unsigned long long>(total));
+					left             += "] ";
 				}
 			}
 			left += fname;
@@ -631,9 +629,9 @@ ImGuiRenderer::Draw(Editor &ed)
 			// 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";
+				left                 += " ";
+				left                 += std::to_string(lcount);
+				left                 += "L";
 			}
 
 			// Build right text (cursor/mark)
@@ -671,20 +669,21 @@ ImGuiRenderer::Draw(Editor &ed)
 				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::SetCursorScreenPos(ImVec2(left_x, y0 + (bar_h - left_sz.y) * 0.5f));
+					ImGui::PushClipRect(ImVec2(left_x, y0), ImVec2(right_x - pad, y0 + bar_h),
+					                    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::SetCursorScreenPos(ImVec2(left_x, y0 + (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));
+			                                 y0 + (bar_h - right_sz.y) * 0.5f));
 			ImGui::TextUnformatted(right.c_str());
 
 			// Draw middle message centered in remaining space
@@ -696,14 +695,12 @@ ImGuiRenderer::Draw(Editor &ed)
 					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::PushClipRect(ImVec2(mid_left, y0), ImVec2(mid_right, y0 + bar_h), true);
+					ImGui::SetCursorScreenPos(ImVec2(msg_x, y0 + (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));
 		}
 	}
 

KKeymap.cc

@@ -42,6 +42,9 @@ KLookupKCommand(const int ascii_key, const bool ctrl, CommandId &out) -> bool
 	case 'a':
 		out = CommandId::MarkAllAndJumpEnd;
 		return true;
+	case 'i':
+		out = CommandId::BufferNew; // C-k i new empty buffer
+		return true;
 	case 'k':
 		out = CommandId::CenterOnCursor; // C-k k center current line
 		return true;

PieceTable.cc

@@ -1,6 +1,7 @@
 #include <algorithm>
 #include <utility>
 #include <limits>
+#include <ostream>
 
 #include "PieceTable.h"
 
@@ -757,3 +758,17 @@ PieceTable::Find(const std::string &needle, std::size_t start) const
 	find_cache_.result  = pos;
 	return pos;
 }
+
+
+void
+PieceTable::WriteToStream(std::ostream &out) const
+{
+    // Stream the content piece-by-piece without forcing full materialization
+    for (const auto &p : pieces_) {
+        if (p.len == 0)
+            continue;
+        const std::string &src = (p.src == Source::Original) ? original_ : add_;
+        const char *base       = src.data() + static_cast<std::ptrdiff_t>(p.start);
+        out.write(base, static_cast<std::streamsize>(p.len));
+    }
+}

PieceTable.h

@@ -5,6 +5,7 @@
 #include <cstddef>
 #include <cstdint>
 #include <string>
+#include <ostream>
 #include <vector>
 #include <limits>
 
@@ -100,6 +101,9 @@ public:
 	// Simple search utility; returns byte offset or npos
 	[[nodiscard]] std::size_t Find(const std::string &needle, std::size_t start = 0) const;
 
+	// Stream out content without materializing the entire buffer
+	void WriteToStream(std::ostream &out) const;
+
 	// Heuristic configuration
 	void SetConsolidationParams(std::size_t piece_limit,
 	                            std::size_t small_piece_threshold,

QtFrontend.cc

@@ -142,13 +142,13 @@ protected:
 				p.save();
 				p.setClipRect(viewport);
 
-    // Iterate visible lines
-    for (std::size_t i = rowoffs, vis_idx = 0; i < last_row; ++i, ++vis_idx) {
-        // Materialize the Buffer::Line into a std::string for
-        // regex/iterator usage and general string ops.
-        const std::string line = static_cast<std::string>(lines[i]);
-					const int y        = viewport.y() + static_cast<int>(vis_idx) * line_h;
-					const int baseline = y + fm.ascent();
+				// Iterate visible lines
+				for (std::size_t i = rowoffs, vis_idx = 0; i < last_row; ++i, ++vis_idx) {
+					// Materialize the Buffer::Line into a std::string for
+					// regex/iterator usage and general string ops.
+					const std::string line = static_cast<std::string>(lines[i]);
+					const int y            = viewport.y() + static_cast<int>(vis_idx) * line_h;
+					const int baseline     = y + fm.ascent();
 
 					// Helper: convert src col -> rx with tab expansion
 					auto src_to_rx_line = [&](std::size_t src_col) -> std::size_t {
@@ -453,11 +453,11 @@ protected:
 					std::size_t total = ed_->BufferCount();
 					if (total > 0) {
 						std::size_t idx1 = ed_->CurrentBufferIndex() + 1; // 1-based
-						left += QStringLiteral("  [");
-						left += QString::number(static_cast<qlonglong>(idx1));
-						left += QStringLiteral("/");
-						left += QString::number(static_cast<qlonglong>(total));
-						left += QStringLiteral("] ");
+						left             += QStringLiteral("  [");
+						left             += QString::number(static_cast<qlonglong>(idx1));
+						left             += QStringLiteral("/");
+						left             += QString::number(static_cast<qlonglong>(total));
+						left             += QStringLiteral("] ");
 					} else {
 						left += QStringLiteral("  ");
 					}
@@ -477,9 +477,9 @@ protected:
 
 					// total lines suffix " <n>L"
 					unsigned long lcount = static_cast<unsigned long>(buf->Rows().size());
-					left += QStringLiteral(" ");
-					left += QString::number(static_cast<qlonglong>(lcount));
-					left += QStringLiteral("L");
+					left                 += QStringLiteral(" ");
+					left                 += QString::number(static_cast<qlonglong>(lcount));
+					left                 += QStringLiteral("L");
 				}
 
 				// Build right segment: cursor and mark
@@ -602,12 +602,12 @@ protected:
 		int d_cols = 0;
 		if (std::fabs(v_scroll_accum_) >= 1.0 && (!horiz_mode || std::fabs(v_scroll_accum_) > std::fabs(
 			                                          h_scroll_accum_))) {
-			d_rows = static_cast<int>(v_scroll_accum_);
+			d_rows          = static_cast<int>(v_scroll_accum_);
 			v_scroll_accum_ -= d_rows;
 		}
 		if (std::fabs(h_scroll_accum_) >= 1.0 && (horiz_mode || std::fabs(h_scroll_accum_) >= std::fabs(
 			                                          v_scroll_accum_))) {
-			d_cols = static_cast<int>(h_scroll_accum_);
+			d_cols          = static_cast<int>(h_scroll_accum_);
 			h_scroll_accum_ -= d_cols;
 		}
 

TerminalFrontend.cc

@@ -73,6 +73,7 @@ TerminalFrontend::Init(Editor &ed)
 			have_old_sigint_ = true;
 		}
 	}
+
 	return true;
 }
 
@@ -120,4 +121,4 @@ TerminalFrontend::Shutdown()
 		have_old_sigint_ = false;
 	}
 	endwin();
-}
+}

TerminalInputHandler.cc

@@ -178,14 +178,15 @@ map_key_to_command(const int ch,
 			ctrl      = true;
 			ascii_key = 'a' + (ch - 1);
 		}
-		// If user typed literal 'C'/'c' or '^' as a qualifier, keep k-prefix and set pending
-		if (ascii_key == 'C' || ascii_key == 'c' || ascii_key == '^') {
-			k_ctrl_pending = true;
-			if (ed)
-				ed->SetStatus("C-k C _");
-			out.hasCommand = false;
-			return true;
-		}
+  // If user typed literal 'C' or '^' as a qualifier, keep k-prefix and set pending
+  // Note: Do NOT treat lowercase 'c' as a qualifier, since 'c' is a valid C-k command (BufferClose).
+  if (ascii_key == 'C' || ascii_key == '^') {
+      k_ctrl_pending = true;
+      if (ed)
+          ed->SetStatus("C-k C _");
+      out.hasCommand = false;
+      return true;
+  }
 		// For actual suffix, consume the k-prefix
 		k_prefix = false;
 		// Do NOT lowercase here; KLookupKCommand handles case-sensitive bindings

TerminalRenderer.cc

@@ -1,3 +1,6 @@
+#include <clocale>
+#define _XOPEN_SOURCE_EXTENDED 1
+#include <cwchar>
 #include <algorithm>
 #include <cstdio>
 #include <filesystem>
@@ -157,35 +160,52 @@ TerminalRenderer::Draw(Editor &ed)
 					// 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;
+					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;
+					wchar_t wch   = L' ';
+					int wch_len   = 1;
+					int disp_w    = 1;
+
 					if (src_i < line.size()) {
-						unsigned char c = static_cast<unsigned char>(line[src_i]);
-						if (c == '\t') {
+						// Decode UTF-8
+						std::mbstate_t state = std::mbstate_t();
+						size_t res           = std::mbrtowc(
+							&wch, &line[src_i], line.size() - src_i, &state);
+						if (res == (size_t) -1 || res == (size_t) -2) {
+							// Invalid or incomplete; treat as single byte
+							wch     = static_cast<unsigned char>(line[src_i]);
+							wch_len = 1;
+						} else if (res == 0) {
+							wch     = L'\0';
+							wch_len = 1;
+						} else {
+							wch_len = static_cast<int>(res);
+						}
+
+						if (wch == L'\t') {
 							std::size_t next_tab = tabw - (render_col % tabw);
 							if (render_col + next_tab <= coloffs) {
 								render_col += next_tab;
-								++src_i;
+								src_i      += wch_len;
 								continue;
 							}
 							// Emit spaces for tab
@@ -194,7 +214,7 @@ TerminalRenderer::Draw(Editor &ed)
 								std::size_t to_skip = std::min<std::size_t>(
 									next_tab, coloffs - render_col);
 								render_col += to_skip;
-								next_tab -= to_skip;
+								next_tab   -= to_skip;
 							}
 							// Now render visible spaces
 							while (next_tab > 0 && written < cols) {
@@ -233,23 +253,34 @@ TerminalRenderer::Draw(Editor &ed)
 								++render_col;
 								--next_tab;
 							}
-							++src_i;
+							src_i += wch_len;
 							continue;
 						} else {
 							// normal char
+							disp_w = wcwidth(wch);
+							if (disp_w < 0)
+								disp_w = 1; // non-printable or similar
+
 							if (render_col < coloffs) {
-								++render_col;
-								++src_i;
+								render_col += disp_w;
+								src_i      += wch_len;
 								continue;
 							}
-							ch       = static_cast<char>(c);
 							from_src = true;
 						}
 					} else {
 						// beyond EOL, fill spaces
-						ch       = ' ';
+						wch      = L' ';
+						wch_len  = 1;
+						disp_w   = 1;
 						from_src = false;
 					}
+
+					if (written + disp_w > cols) {
+						// would overflow, just break
+						break;
+					}
+
 					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 <
@@ -273,11 +304,20 @@ TerminalRenderer::Draw(Editor &ed)
 					if (!in_hl && from_src) {
 						apply_token_attr(token_at(src_i));
 					}
-					addch(static_cast<unsigned char>(ch));
-					++written;
-					++render_col;
+
+					if (from_src) {
+						cchar_t cch;
+						wchar_t warr[2] = {wch, L'\0'};
+						setcchar(&cch, warr, A_NORMAL, 0, nullptr);
+						add_wch(&cch);
+					} else {
+						addch(' ');
+					}
+
+					written    += disp_w;
+					render_col += disp_w;
 					if (from_src)
-						++src_i;
+						src_i += wch_len;
 					if (src_i >= line.size() && written >= cols)
 						break;
 				}
@@ -297,23 +337,35 @@ TerminalRenderer::Draw(Editor &ed)
 		// Place terminal cursor at logical position accounting for tabs and coloffs.
 		// Recompute the rendered X using the same logic as the drawing loop to avoid
 		// any drift between the command-layer computation and the terminal renderer.
-		std::size_t cy = buf->Cury();
-		std::size_t cx = buf->Curx();
-		int cur_y = static_cast<int>(cy) - static_cast<int>(buf->Rowoffs());
+		std::size_t cy            = buf->Cury();
+		std::size_t cx            = buf->Curx();
+		int cur_y                 = static_cast<int>(cy) - static_cast<int>(buf->Rowoffs());
 		std::size_t rx_recomputed = 0;
 		if (cy < lines.size()) {
 			const std::string line_for_cursor = static_cast<std::string>(lines[cy]);
-			std::size_t src_i_cur = 0;
-			std::size_t render_col_cur = 0;
+			std::size_t src_i_cur             = 0;
+			std::size_t render_col_cur        = 0;
 			while (src_i_cur < line_for_cursor.size() && src_i_cur < cx) {
-				unsigned char ccur = static_cast<unsigned char>(line_for_cursor[src_i_cur]);
-				if (ccur == '\t') {
-					std::size_t next_tab = tabw - (render_col_cur % tabw);
-					render_col_cur += next_tab;
-					++src_i_cur;
+				std::mbstate_t state = std::mbstate_t();
+				wchar_t wch;
+				size_t res = std::mbrtowc(
+					&wch, &line_for_cursor[src_i_cur], line_for_cursor.size() - src_i_cur,
+					&state);
+
+				if (res == (size_t) -1 || res == (size_t) -2) {
+					render_col_cur += 1;
+					src_i_cur      += 1;
+				} else if (res == 0) {
+					src_i_cur += 1;
 				} else {
-					++render_col_cur;
-					++src_i_cur;
+					if (wch == L'\t') {
+						std::size_t next_tab = tabw - (render_col_cur % tabw);
+						render_col_cur       += next_tab;
+					} else {
+						int dw         = wcwidth(wch);
+						render_col_cur += (dw < 0) ? 1 : dw;
+					}
+					src_i_cur += res;
 				}
 			}
 			rx_recomputed = render_col_cur;
@@ -403,9 +455,9 @@ TerminalRenderer::Draw(Editor &ed)
 	{
 		const char *app = "kte";
 		left.reserve(256);
-		left += app;
-		left += " ";
-		left += KTE_VERSION_STR; // already includes leading 'v'
+		left            += app;
+		left            += " ";
+		left            += KTE_VERSION_STR; // already includes leading 'v'
 		const Buffer *b = buf;
 		std::string fname;
 		if (b) {
@@ -426,11 +478,11 @@ TerminalRenderer::Draw(Editor &ed)
 			std::size_t total = ed.BufferCount();
 			if (total > 0) {
 				std::size_t idx1 = ed.CurrentBufferIndex() + 1; // human-friendly 1-based
-				left += "[";
-				left += std::to_string(static_cast<unsigned long long>(idx1));
-				left += "/";
-				left += std::to_string(static_cast<unsigned long long>(total));
-				left += "] ";
+				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;
@@ -442,9 +494,9 @@ TerminalRenderer::Draw(Editor &ed)
 		// Append total line count as "<n>L"
 		if (b) {
 			unsigned long lcount = static_cast<unsigned long>(b->Rows().size());
-			left += " ";
-			left += std::to_string(lcount);
-			left += "L";
+			left                 += " ";
+			left                 += std::to_string(lcount);
+			left                 += "L";
 		}
 	}
 

cmake/fix_bundle.cmake

@@ -0,0 +1,78 @@
+cmake_minimum_required(VERSION 3.15)
+
+# Fix up a macOS .app bundle by copying non-Qt dylibs into
+# Contents/Frameworks and rewriting install names to use @rpath/@loader_path.
+#
+# Usage:
+#   cmake -DAPP_BUNDLE=/path/to/kge.app -P cmake/fix_bundle.cmake
+
+if (NOT APP_BUNDLE)
+    message(FATAL_ERROR "APP_BUNDLE not set. Invoke with -DAPP_BUNDLE=/path/to/App.app")
+endif ()
+
+get_filename_component(APP_DIR "${APP_BUNDLE}" ABSOLUTE)
+set(EXECUTABLE "${APP_DIR}/Contents/MacOS/kge")
+
+if (NOT EXISTS "${EXECUTABLE}")
+    message(FATAL_ERROR "Executable not found at: ${EXECUTABLE}")
+endif ()
+
+include(BundleUtilities)
+
+# Directories to search when resolving prerequisites. We include Homebrew so that
+# if any deps are currently resolved from there, fixup_bundle will copy them into
+# the bundle and rewrite install names to be self-contained.
+set(DIRS
+        "/usr/local/lib"
+        "/opt/homebrew/lib"
+        "/opt/homebrew/opt"
+)
+
+# Note: We pass empty plugin list so fixup_bundle scans the executable and all
+# libs it references recursively. Qt frameworks already live in the bundle after
+# macdeployqt; this step is primarily for non-Qt dylibs (glib, icu, pcre2, zstd,
+# dbus, etc.).
+# fixup_bundle often fails if copied libraries are read-only.
+# We also try to use the system install_name_tool and otool to avoid issues with Anaconda's version.
+# Note: BundleUtilities uses find_program(gp_otool "otool") internally, so we might need to set it differently.
+set(gp_otool "/usr/bin/otool")
+set(CMAKE_INSTALL_NAME_TOOL "/usr/bin/install_name_tool")
+set(CMAKE_OTOOL "/usr/bin/otool")
+set(ENV{PATH} "/usr/bin:/bin:/usr/sbin:/sbin")
+
+execute_process(COMMAND chmod -R u+w "${APP_DIR}/Contents/Frameworks")
+
+fixup_bundle("${APP_DIR}" "" "${DIRS}")
+
+# On Apple Silicon (and modern macOS in general), modifications by fixup_bundle
+# invalidate code signatures. We must re-sign the bundle (at least ad-hoc)
+# for it to be allowed to run.
+# We sign deep, but sometimes explicit signing of components is more reliable.
+message(STATUS "Re-signing ${APP_DIR} after fixup...")
+
+# 1. Sign dylibs in Frameworks
+file(GLOB_RECURSE DYLIBS "${APP_DIR}/Contents/Frameworks/*.dylib")
+foreach (DYLIB ${DYLIBS})
+    message(STATUS "Signing ${DYLIB}...")
+    execute_process(COMMAND /usr/bin/codesign --force --sign - "${DYLIB}")
+endforeach ()
+
+# 2. Sign nested executables
+message(STATUS "Signing nested kte...")
+execute_process(COMMAND /usr/bin/codesign --force --sign - "${APP_DIR}/Contents/MacOS/kte")
+
+# 3. Sign the main executable explicitly
+message(STATUS "Signing main kge...")
+execute_process(COMMAND /usr/bin/codesign --force --sign - "${APP_DIR}/Contents/MacOS/kge")
+
+# 4. Sign the main bundle
+execute_process(
+        COMMAND /usr/bin/codesign --force --deep --sign - "${APP_DIR}"
+        RESULT_VARIABLE CODESIGN_RESULT
+)
+
+if (NOT CODESIGN_RESULT EQUAL 0)
+    message(FATAL_ERROR "Codesign failed with error: ${CODESIGN_RESULT}")
+endif ()
+
+message(STATUS "fix_bundle.cmake completed for ${APP_DIR}")

default.nix

@@ -1,5 +1,6 @@
 {
-  lib,
+  pkgs ? import <nixpkgs> {},
+  lib ? pkgs.lib,
   stdenv,
   cmake,
   ncurses,

docs/plans/test-plan.md

@@ -0,0 +1,163 @@
+### Unit testing plan (headless, no interactive frontend)
+
+#### Principles
+- Headless-only: exercise core components directly (`PieceTable`, `Buffer`, `UndoSystem`, `OptimizedSearch`, and minimal `Editor` flows) without starting `kte` or `kge`.
+- Deterministic and fast: avoid timers, GUI, environment-specific behavior; prefer in-memory operations and temporary files.
+- Regression-focused: encode prior failures (save/newline mismatch, legacy `rows_` writes) as explicit tests to prevent recurrences.
+
+#### Harness and execution
+- Single binary: use target `kte_tests` (already present) to compile and run all tests under `tests/` with the minimal in-tree framework (`tests/Test.h`, `tests/TestRunner.cc`).
+- No GUI/ncurses deps: link only engine sources (PieceTable/Buffer/Undo/Search/Undo* and syntax minimal set), not frontends.
+- How to build/run:
+  - Debug profile:
+    ```
+    cmake -S /Users/kyle/src/kte -B /Users/kyle/src/kte/cmake-build-debug -DBUILD_TESTS=ON && \
+    cmake --build /Users/kyle/src/kte/cmake-build-debug --target kte_tests && \
+    /Users/kyle/src/kte/cmake-build-debug/kte_tests
+    ```
+  - Release profile:
+    ```
+    cmake -S /Users/kyle/src/kte -B /Users/kyle/src/kte/cmake-build-release -DBUILD_TESTS=ON && \
+    cmake --build /Users/kyle/src/kte/cmake-build-release --target kte_tests && \
+    /Users/kyle/src/kte/cmake-build-release/kte_tests
+    ```
+
+---
+
+### Test catalog (summary table)
+
+The table below catalogs all unit tests defined in this plan. It is headless-only and maps directly to the suites A–H described later. “Implemented” reflects current coverage in `kte_tests`.
+
+| Suite | ID  | Name                                      | Description (1‑line)                                                                 | Headless | Implemented |
+|:-----:|:---:|:------------------------------------------|:-------------------------------------------------------------------------------------|:--------:|:-----------:|
+| A | 1 | SaveAs then Save (append) | New buffer → write two lines → `SaveAs` → append → `Save`; verify exact bytes. | Yes | ✓ |
+| A | 2 | Open existing then Save | Open seeded file, append, `Save`; verify overwrite bytes. | Yes | ✓ |
+| A | 3 | Open non-existent then SaveAs | Start from non-existent path, insert `hello, world\n`, `SaveAs`; verify bytes. | Yes | ✓ |
+| A | 4 | Trailing newline preservation | Verify saving preserves presence/absence of final `\n`. | Yes | Planned |
+| A | 5 | Empty buffer saves | Empty → `SaveAs` → 0 bytes; then insert `\n` → `Save` → 1 byte. | Yes | Planned |
+| A | 6 | Large file streaming | 1–4 MiB with periodic newlines; size and content integrity. | Yes | Planned |
+| A | 7 | Tilde expansion | `SaveAs` with `~/...`; re-open to confirm path/content. | Yes | Planned |
+| A | 8 | Error propagation | Save to unwritable path → expect failure and error message. | Yes | Planned |
+| B | 1 | Insert/Delete LineCount | Basic inserts/deletes and line counting sanity. | Yes | ✓ |
+| B | 2 | Line/Col conversions | `LineColToByteOffset` and reverse around boundaries. | Yes | ✓ |
+| B | 3 | Delete spanning newlines | Delete ranges that cross line breaks; verify bytes/lines. | Yes | Planned |
+| B | 4 | Split/Join equivalence | `split_line` followed by `join_lines` yields original bytes. | Yes | Planned |
+| B | 5 | Stream vs Data equivalence | `WriteToStream` matches `GetRange`/`Data()` after edits. | Yes | Planned |
+| B | 6 | UTF‑8 bytes stability | Multibyte sequences behave correctly (byte-based ops). | Yes | Planned |
+| C | 1 | insert_text/delete_text | Edits at start/middle/end; `Rows()` mirrors PieceTable. | Yes | Planned |
+| C | 2 | split_line/join_lines | Effects and snapshots across multiple positions. | Yes | Planned |
+| C | 3 | insert_row/delete_row | Replace paragraph by row ops; verify bytes/linecount. | Yes | Planned |
+| C | 4 | Cache invalidation | After each mutation, `Rows()` matches `LineCount()`. | Yes | Planned |
+| D | 1 | Grouped insert undo | Contiguous typing undone/redone as a group. | Yes | Planned |
+| D | 2 | Delete/Newline undo/redo | Backspace/Delete and Newline transitions across undo/redo. | Yes | Planned |
+| D | 3 | Mark saved & dirty | Dirty/save markers interact correctly with undo/redo. | Yes | Planned |
+| E | 1 | Search parity basic | `OptimizedSearch::find_all` vs `std::string` reference. | Yes | ✓ |
+| E | 2 | Large text search | ~1 MiB random text/patterns parity. | Yes | Planned |
+| F | 1 | Editor open & reload | Open via `Editor`, modify, reload, verify on-disk bytes. | Yes | Planned |
+| F | 2 | Read-only toggle | Toggle and verify enforcement/behavior of saves. | Yes | Planned |
+| F | 3 | Prompt lifecycle | Start/Accept/Cancel prompt doesn’t corrupt state. | Yes | Planned |
+| G | 1 | Saved only newline regression | Insert text + newline; `Save` includes both bytes. | Yes | Planned |
+| G | 2 | Backspace crash regression | PieceTable-backed delete/join path remains stable. | Yes | Planned |
+| G | 3 | Overwrite-confirm path | Saving over existing path succeeds and is correct. | Yes | Planned |
+| H | 1 | Many small edits | 10k small edits; final bytes correct within time bounds. | Yes | Planned |
+| H | 2 | Consolidation equivalence | After many edits, stream vs data produce identical bytes. | Yes | Planned |
+
+Legend: Implemented = ✓, Planned = to be added per Coverage roadmap.
+
+### Test suites and cases
+
+#### A) Filesystem I/O via Buffer
+1) SaveAs then Save (append)
+   - New buffer → `insert_text` two lines (explicit `\n`) → `SaveAs(tmp)` → insert a third line → `Save()`.
+   - Assert file bytes equal exact expected string.
+2) Open existing then Save
+   - Seed a file on disk; `OpenFromFile(path)` → append line → `Save()`.
+   - Assert file bytes updated exactly.
+3) Open non-existent then SaveAs
+   - `OpenFromFile(nonexistent)` → assert `IsFileBacked()==false` → insert `"hello, world\n"` → `SaveAs(path)`.
+   - Read back exact bytes.
+4) Trailing newline preservation
+   - Case (a) last line without `\n`; (b) last line with `\n` → save and verify bytes unchanged.
+5) Empty buffer saves
+   - `SaveAs(tmp)` on empty buffer → 0-byte file. Then insert `"\n"` and `Save()` → 1-byte file.
+6) Large file streaming
+   - Insert ~1–4 MiB of data with periodic newlines. `SaveAs` then `Save`; verify size matches `content_.Size()` and bytes integrity.
+7) Path normalization and tilde expansion
+   - `SaveAs("~/.../file.txt")` → verify path expands to `$HOME` and file content round-trips with `OpenFromFile`.
+8) Error propagation (guarded)
+   - Attempt save into a non-writable path; expect `Save/SaveAs` returns false with non-empty error. Mark as skipped in environments lacking such path.
+
+#### B) PieceTable semantics
+1) Line counting and deletion across lines
+   - Insert `"abc\n123\nxyz"` → 3 lines; delete middle line range → 2 lines; validate `GetLine` contents.
+2) Position conversions
+   - Validate `LineColToByteOffset` and `ByteOffsetToLineCol` at start/end of lines and EOF, especially around `\n`.
+3) Delete spanning newlines
+   - Remove a range that crosses line boundaries; verify resulting bytes, `LineCount` and line contents.
+4) Split/join equivalence
+   - Split at various columns; then join adjacent lines; verify bytes equal original.
+5) WriteToStream vs materialized `Data()`
+   - After multiple inserts/deletes (without forcing `Data()`), stream to `std::ostringstream`; compare with `GetRange(0, Size())`, then call `Data()` and re-compare.
+6) UTF-8 bytes stability
+   - Insert multibyte sequences (e.g., `"héllo"`, `"中文"`, emoji) as raw bytes; ensure line counting and conversions behave (byte-based API; no crashes/corruption).
+
+#### C) Buffer editing helpers and rows cache correctness
+1) `insert_text`/`delete_text`
+   - Apply at start/middle/end of lines; immediately call `Rows()` and validate contents/lengths mirror PieceTable.
+2) `split_line` and `join_lines`
+   - Verify content effects and `Rows()` snapshots for multiple positions and consecutive operations.
+3) `insert_row`/`delete_row`
+   - Replace a paragraph by deleting N rows then inserting N′ rows; verify bytes and `LineCount`.
+4) Cache invalidation
+   - After each mutation, fetch `Rows()`; assert `Nrows() == content.LineCount()` and no stale data remains.
+
+#### D) UndoSystem semantics
+1) Grouped contiguous insert undo
+   - Emulate typing at a single location via repeated `insert_text`; one `undo()` should remove the whole run; `redo()` restores it.
+2) Delete/newline undo/redo
+   - Simulate backspace/delete (`delete_text` and `join_lines`) and newline (`split_line`); verify content transitions across `undo()`/`redo()`.
+3) Mark saved and dirty flag
+   - After successful save, call `UndoSystem::mark_saved()` (via existing pathways) and ensure dirty state pairing behaves as intended (at least: `SetDirty(false)` plus save does not break undo/redo).
+
+#### E) Search algorithms
+1) Parity with `std::string::find`
+   - Use `OptimizedSearch::find_all` across edge cases (empty needle/text, overlaps like `"aaaaa"` vs `"aa"`, Unicode byte sequences). Compare to reference implementation.
+2) Large text
+   - Random ASCII text ~1 MiB; random patterns; results match reference.
+
+#### F) Editor non-interactive flows (no frontend)
+1) Open and reload
+   - Through `Editor`, open file; modify the underlying `Buffer` directly; invoke reload (`Buffer::OpenFromFile` or `cmd_reload_buffer` if you bring `Command.cc` into the test target). Verify bytes match the on-disk file after reload.
+2) Read-only toggle
+   - Toggle `Buffer::ToggleReadOnly()`; confirm flag value changes and that subsequent saves still execute when not read-only (or, if enforcement exists, that mutations are appropriately restricted).
+3) Prompt lifecycle (headless)
+   - Exercise `StartPrompt` → `AcceptPrompt` → `CancelPrompt`; ensure state resets and does not corrupt buffer/editor state.
+
+#### G) Regression tests for reported bugs
+1) “Saved only newline”
+   - Build buffer content via `insert_text` followed by `split_line` for newline; `Save` then validate bytes include both the text and newline.
+2) Backspace crash path
+   - Mimic backspace behavior using PieceTable-backed helpers (`delete_text`/`join_lines`); ensure no dependency on legacy `rows_` mutation and no memory issues.
+3) Overwrite-confirm path behavior
+   - Start with non-file-backed buffer named to collide with an existing file; perform `SaveAs(existing_path)` and assert success and correctness on disk (unit test bypasses interactive confirm, validating underlying write path).
+
+#### H) Performance/stress sanity
+1) Many small edits
+   - 10k single-char inserts and interleaved deletes; assert final bytes; keep within conservative runtime bounds.
+2) Consolidation heuristics
+   - After many edits, call both `WriteToStream` and `Data()` and verify identical bytes.
+
+---
+
+### Coverage roadmap
+- Phase 1 (already implemented and passing):
+  - Buffer I/O basics (A.1–A.3), PieceTable basics (B.1–B.2), Search parity (E.1).
+- Phase 2 (add next):
+  - Buffer I/O edge cases (A.4–A.7), deeper PieceTable ops (B.3–B.6), Buffer helpers and cache (C.1–C.4), Undo semantics (D.1–D.2), Regression set (G.1–G.3).
+- Phase 3:
+  - Editor flows (F.1–F.3), performance/stress (H.1–H.2), and optional integration of `Command.cc` into the test target to exercise non-interactive command execution paths directly.
+
+### Notes
+- Use per-test temp files under the repo root or a unique temp directory; ensure cleanup after assertions.
+- For HOME-dependent tests (tilde expansion), set `HOME` in the test process if not present or skip with a clear message.
+- On macOS Debug, a benign allocator warning may appear; rely on process exit code for pass/fail.

fonts/Font.cc

@@ -1,4 +1,5 @@
 #include "Font.h"
+#include "IosevkaExtended.h"
 
 #include "imgui.h"
 
@@ -8,16 +9,32 @@ Font::Load(const float size) const
 {
 	const ImGuiIO &io = ImGui::GetIO();
 	io.Fonts->Clear();
-	const ImFont *font = io.Fonts->AddFontFromMemoryCompressedTTF(
+
+	ImFontConfig config;
+	config.MergeMode = false;
+
+	// Load Basic Latin + Latin Supplement
+	io.Fonts->AddFontFromMemoryCompressedTTF(
 		this->data_,
 		this->size_,
-		size);
+		size,
+		&config,
+		io.Fonts->GetGlyphRangesDefault());
 
-	if (!font) {
-		font = io.Fonts->AddFontDefault();
-	}
+	// Merge Greek and Mathematical symbols from IosevkaExtended as fallback
+	config.MergeMode                       = true;
+	static const ImWchar extended_ranges[] = {
+		0x0370, 0x03FF, // Greek and Coptic
+		0x2200, 0x22FF, // Mathematical Operators
+		0,
+	};
+	io.Fonts->AddFontFromMemoryCompressedTTF(
+		kte::Fonts::IosevkaExtended::DefaultFontRegularCompressedData,
+		kte::Fonts::IosevkaExtended::DefaultFontRegularCompressedSize,
+		size,
+		&config,
+		extended_ranges);
 
-	(void) font;
 	io.Fonts->Build();
 }
 } // namespace kte::Fonts

fonts/Font.h

@@ -3,12 +3,12 @@
 #include <string>
 #include <utility>
 
-#include "BrassMonoCode.h"
+#include "BerkeleyMono.h"
 
 namespace kte::Fonts {
 // Provide default embedded font aliases used by GUIFrontend fallback loader
-inline const unsigned int DefaultFontSize  = BrassMonoCode::DefaultFontBoldCompressedSize;
-inline const unsigned int *DefaultFontData = BrassMonoCode::DefaultFontBoldCompressedData;
+inline const unsigned int DefaultFontSize  = BerkeleyMono::DefaultFontRegularCompressedSize;
+inline const unsigned int *DefaultFontData = BerkeleyMono::DefaultFontRegularCompressedData;
 
 class Font {
 public:
@@ -31,4 +31,4 @@ private:
 	const unsigned int *data_{nullptr};
 	unsigned int size_{0};
 };
-}
+}

fonts/FontList.h

@@ -1,5 +1,6 @@
 #pragma once
 #include "B612Mono.h"
+#include "BerkeleyMono.h"
 #include "BrassMono.h"
 #include "BrassMonoCode.h"
 #include "FiraCode.h"
@@ -14,4 +15,4 @@
 #include "SpaceMono.h"
 #include "Syne.h"
 #include "Triplicate.h"
-#include "Unispace.h"
+#include "Unispace.h"

fonts/FontRegistry.cc

@@ -7,28 +7,38 @@ InstallDefaultFonts()
 {
 	FontRegistry::Instance().Register(std::make_unique<Font>(
 		"default",
-		BrassMono::DefaultFontBoldCompressedData,
-		BrassMono::DefaultFontBoldCompressedSize
+		BerkeleyMono::DefaultFontBoldCompressedData,
+		BerkeleyMono::DefaultFontBoldCompressedSize
 	));
 	FontRegistry::Instance().Register(std::make_unique<Font>(
 		"b612",
 		B612Mono::DefaultFontRegularCompressedData,
 		B612Mono::DefaultFontRegularCompressedSize
 	));
+	FontRegistry::Instance().Register(std::make_unique<Font>(
+		"berkeley",
+		BerkeleyMono::DefaultFontRegularCompressedData,
+		BerkeleyMono::DefaultFontRegularCompressedSize
+	));
+	FontRegistry::Instance().Register(std::make_unique<Font>(
+		"berkeley-bold",
+		BerkeleyMono::DefaultFontBoldCompressedData,
+		BerkeleyMono::DefaultFontBoldCompressedSize
+	));
 	FontRegistry::Instance().Register(std::make_unique<Font>(
 		"brassmono",
 		BrassMono::DefaultFontRegularCompressedData,
 		BrassMono::DefaultFontRegularCompressedSize
 	));
 	FontRegistry::Instance().Register(std::make_unique<Font>(
-	    "brassmono-bold",
-	    BrassMono::DefaultFontBoldCompressedData,
-	    BrassMono::DefaultFontBoldCompressedSize
+		"brassmono-bold",
+		BrassMono::DefaultFontBoldCompressedData,
+		BrassMono::DefaultFontBoldCompressedSize
 	));
 	FontRegistry::Instance().Register(std::make_unique<Font>(
-	    "brassmonocode",
-	    BrassMonoCode::DefaultFontRegularCompressedData,
-	    BrassMonoCode::DefaultFontRegularCompressedSize
+		"brassmonocode",
+		BrassMonoCode::DefaultFontRegularCompressedData,
+		BrassMonoCode::DefaultFontRegularCompressedSize
 	));
 	FontRegistry::Instance().Register(std::make_unique<Font>(
 		"brassmonocode-bold",
@@ -101,4 +111,4 @@ InstallDefaultFonts()
 		Unispace::DefaultFontRegularCompressedSize
 	));
 }
-}
+}

main.cc

@@ -1,3 +1,4 @@
+#include <clocale>
 #include <cctype>
 #include <cerrno>
 #include <cstdio>
@@ -113,6 +114,8 @@ RunStressHighlighter(unsigned seconds)
 int
 main(int argc, const char *argv[])
 {
+	std::setlocale(LC_ALL, "");
+
 	Editor editor;
 
 	// CLI parsing using getopt_long
@@ -192,13 +195,11 @@ main(int argc, const char *argv[])
 	} else if (req_term) {
 		use_gui = false;
 	} else {
-
-
-	// Default depends on build target: kge defaults to GUI, kte to terminal
+		// Default depends on build target: kge defaults to GUI, kte to terminal
 #if defined(KTE_DEFAULT_GUI)
-	use_gui = true;
+		use_gui = true;
 #else
-	use_gui = false;
+		use_gui = false;
 #endif
 	}
 #endif
@@ -307,6 +308,8 @@ main(int argc, const char *argv[])
 		return 1;
 	}
 
+	Execute(editor, CommandId::CenterOnCursor);
+
 	bool running = true;
 	while (running) {
 		fe->Step(editor, running);
@@ -315,4 +318,4 @@ main(int argc, const char *argv[])
 	fe->Shutdown();
 
 	return 0;
-}
+}

make-app-release

@@ -16,14 +16,18 @@ open .
 cd ..
 
 mkdir -p cmake-build-release-qt
-cmake -S . -B cmake-build-release -DBUILD_GUI=ON -DCMAKE_BUILD_TYPE=Release -DENABLE_ASAN=OFF
+cmake -S . -B cmake-build-release-qt -DBUILD_GUI=ON -DKTE_USE_QT=ON -DCMAKE_BUILD_TYPE=Release -DENABLE_ASAN=OFF
 
 cd cmake-build-release-qt
 make clean
 rm -fr kge.app* kge-qt.app*
 make
-mv kge.app kge-qt.app
-macdeployqt kge-qt.app -always-overwrite
+mv -f kge.app kge-qt.app
+# Use the same Qt's macdeployqt as used for building; ensure it overwrites in-bundle paths
+macdeployqt kge-qt.app -always-overwrite -verbose=3
+
+# Run CMake BundleUtilities fixup to internalize non-Qt dylibs and rewrite install names
+cmake -DAPP_BUNDLE="$(pwd)/kge-qt.app" -P "${PWD%/*}/cmake/fix_bundle.cmake"
 zip -r kge-qt.app.zip kge-qt.app 
 sha256sum kge-qt.app.zip
 open .

test_search_correctness.cc

@@ -1,74 +0,0 @@
-// Verify OptimizedSearch against std::string reference across patterns and sizes
-#include <cassert>
-#include <cstddef>
-#include <random>
-#include <string>
-#include <vector>
-
-#include "OptimizedSearch.h"
-
-
-static std::vector<std::size_t>
-ref_find_all(const std::string &text, const std::string &pat)
-{
-	std::vector<std::size_t> res;
-	if (pat.empty())
-		return res;
-	std::size_t from = 0;
-	while (true) {
-		auto p = text.find(pat, from);
-		if (p == std::string::npos)
-			break;
-		res.push_back(p);
-		from = p + pat.size(); // non-overlapping
-	}
-	return res;
-}
-
-
-static void
-run_case(std::size_t textLen, std::size_t patLen, unsigned seed)
-{
-	std::mt19937 rng(seed);
-	std::uniform_int_distribution<int> dist('a', 'z');
-	std::string text(textLen, '\0');
-	for (auto &ch: text)
-		ch = static_cast<char>(dist(rng));
-	std::string pat(patLen, '\0');
-	for (auto &ch: pat)
-		ch = static_cast<char>(dist(rng));
-
-	// Guarantee at least one match when possible
-	if (textLen >= patLen && patLen > 0) {
-		std::size_t pos = textLen / 3;
-		if (pos + patLen <= text.size())
-			std::copy(pat.begin(), pat.end(), text.begin() + static_cast<long>(pos));
-	}
-
-	OptimizedSearch os;
-	auto got = os.find_all(text, pat, 0);
-	auto ref = ref_find_all(text, pat);
-	assert(got == ref);
-}
-
-
-int
-main()
-{
-	// Edge cases
-	run_case(0, 0, 1);
-	run_case(0, 1, 2);
-	run_case(1, 0, 3);
-	run_case(1, 1, 4);
-
-	// Various sizes
-	for (std::size_t t = 128; t <= 4096; t *= 2) {
-		for (std::size_t p = 1; p <= 64; p *= 2) {
-			run_case(t, p, static_cast<unsigned>(t + p));
-		}
-	}
-	// Larger random
-	run_case(100000, 16, 12345);
-	run_case(250000, 32, 67890);
-	return 0;
-}

test_undo.cc

@@ -1,338 +0,0 @@
-#include <cassert>
-#include <fstream>
-#include <iostream>
-
-#include "Buffer.h"
-#include "Command.h"
-#include "Editor.h"
-#include "TestFrontend.h"
-
-
-int
-main()
-{
-	// Install default commands
-	InstallDefaultCommands();
-
-	Editor editor;
-	TestFrontend frontend;
-
-	// Initialize frontend
-	if (!frontend.Init(editor)) {
-		std::cerr << "Failed to initialize frontend\n";
-		return 1;
-	}
-
-	// Create a temporary test file
-	std::string err;
-	const char *tmpfile = "/tmp/kte_test_undo.txt";
-	{
-		std::ofstream f(tmpfile);
-		if (!f) {
-			std::cerr << "Failed to create temp file\n";
-			return 1;
-		}
-		f << "\n"; // Write one newline so file isn't empty
-		f.close();
-	}
-
-	if (!editor.OpenFile(tmpfile, err)) {
-		std::cerr << "Failed to open test file: " << err << "\n";
-		return 1;
-	}
-
-	Buffer *buf = editor.CurrentBuffer();
-	assert(buf != nullptr);
-
-	// Initialize cursor to (0,0) explicitly
-	buf->SetCursor(0, 0);
-
-	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");
-
-	while (!frontend.Input().IsEmpty() && running) {
-		frontend.Step(editor, running);
-	}
-
-	assert(buf->Rows().size() >= 1);
-	std::string line_after_insert = std::string(buf->Rows()[0]);
-	assert(line_after_insert == "Hello");
-	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);
-
-	while (!frontend.Input().IsEmpty() && running) {
-		frontend.Step(editor, running);
-	}
-
-	assert(buf->Rows().size() >= 1);
-	std::string line_after_undo = std::string(buf->Rows()[0]);
-	assert(line_after_undo == "");
-	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);
-
-	while (!frontend.Input().IsEmpty() && running) {
-		frontend.Step(editor, running);
-	}
-
-	assert(buf->Rows().size() >= 1);
-	std::string line_after_redo = std::string(buf->Rows()[0]);
-	assert(line_after_redo == "Hello");
-	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]) == "");
-
-	// 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]) == "");
-
-	// 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";
-
-	// 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";
-
-	// 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";
-
-	// 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");
-
-	// 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";
-
-	// 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 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";
-
-	frontend.Shutdown();
-
-	std::cout << "====================================\n";
-	std::cout << "All tests passed!\n";
-
-	return 0;
-}

tests/Test.h

@@ -0,0 +1,63 @@
+// Minimal header-only unit test framework for kte
+#pragma once
+#include <functional>
+#include <iostream>
+#include <string>
+#include <vector>
+#include <chrono>
+#include <sstream>
+
+namespace ktet {
+
+struct TestCase {
+    std::string name;
+    std::function<void()> fn;
+};
+
+inline std::vector<TestCase>& registry() {
+    static std::vector<TestCase> r;
+    return r;
+}
+
+struct Registrar {
+    Registrar(const char* name, std::function<void()> fn) {
+        registry().push_back(TestCase{std::string(name), std::move(fn)});
+    }
+};
+
+// Assertions
+struct AssertionFailure {
+    std::string msg;
+};
+
+inline void expect(bool cond, const char* expr, const char* file, int line) {
+    if (!cond) {
+        std::cerr << file << ":" << line << ": EXPECT failed: " << expr << "\n";
+    }
+}
+
+inline void assert_true(bool cond, const char* expr, const char* file, int line) {
+    if (!cond) {
+        throw AssertionFailure{std::string(file) + ":" + std::to_string(line) + ": ASSERT failed: " + expr};
+    }
+}
+
+template<typename A, typename B>
+inline void assert_eq_impl(const A& a, const B& b, const char* ea, const char* eb, const char* file, int line) {
+    if (!(a == b)) {
+        std::ostringstream oss;
+        oss << file << ":" << line << ": ASSERT_EQ failed: " << ea << " == " << eb;
+        throw AssertionFailure{oss.str()};
+    }
+}
+
+} // namespace ktet
+
+#define TEST(name) \
+    static void name(); \
+    static ::ktet::Registrar _reg_##name(#name, &name); \
+    static void name()
+
+#define EXPECT_TRUE(x) ::ktet::expect((x), #x, __FILE__, __LINE__)
+#define ASSERT_TRUE(x) ::ktet::assert_true((x), #x, __FILE__, __LINE__)
+#define ASSERT_EQ(a,b) ::ktet::assert_eq_impl((a),(b), #a, #b, __FILE__, __LINE__)

tests/TestRunner.cc

@@ -0,0 +1,33 @@
+#include "Test.h"
+#include <iostream>
+#include <chrono>
+
+int main() {
+    using namespace std::chrono;
+    auto &reg = ktet::registry();
+    std::cout << "kte unit tests: " << reg.size() << " test(s)\n";
+    int failed = 0;
+    auto t0 = steady_clock::now();
+    for (const auto &tc : reg) {
+        auto ts = steady_clock::now();
+        try {
+            tc.fn();
+            auto te = steady_clock::now();
+            auto ms = duration_cast<milliseconds>(te - ts).count();
+            std::cout << "[ OK ] " << tc.name << " (" << ms << " ms)\n";
+        } catch (const ktet::AssertionFailure &e) {
+            ++failed;
+            std::cerr << "[FAIL] " << tc.name << " -> " << e.msg << "\n";
+        } catch (const std::exception &e) {
+            ++failed;
+            std::cerr << "[EXCP] " << tc.name << " -> " << e.what() << "\n";
+        } catch (...) {
+            ++failed;
+            std::cerr << "[EXCP] " << tc.name << " -> unknown exception\n";
+        }
+    }
+    auto t1 = steady_clock::now();
+    auto total_ms = duration_cast<milliseconds>(t1 - t0).count();
+    std::cout << "Done in " << total_ms << " ms. Failures: " << failed << "\n";
+    return failed == 0 ? 0 : 1;
+}

tests/test_buffer_io.cc

@@ -0,0 +1,79 @@
+#include "Test.h"
+#include <fstream>
+#include <cstdio>
+#include <string>
+#include "Buffer.h"
+
+static std::string read_all(const std::string &path) {
+    std::ifstream in(path, std::ios::binary);
+    return std::string((std::istreambuf_iterator<char>(in)), std::istreambuf_iterator<char>());
+}
+
+TEST(Buffer_SaveAs_and_Save_new_file) {
+    const std::string path = "./.kte_ut_buffer_io_1.tmp";
+    std::remove(path.c_str());
+
+    Buffer b;
+    // insert two lines
+    b.insert_text(0, 0, std::string("Hello, world!\n"));
+    b.insert_text(1, 0, std::string("Second line\n"));
+
+    std::string err;
+    ASSERT_TRUE(b.SaveAs(path, err));
+    ASSERT_EQ(err.empty(), true);
+
+    // append another line then Save()
+    b.insert_text(2, 0, std::string("Third\n"));
+    b.SetDirty(true);
+    ASSERT_TRUE(b.Save(err));
+    ASSERT_EQ(err.empty(), true);
+
+    std::string got = read_all(path);
+    ASSERT_EQ(got, std::string("Hello, world!\nSecond line\nThird\n"));
+
+    std::remove(path.c_str());
+}
+
+TEST(Buffer_Save_after_Open_existing) {
+    const std::string path = "./.kte_ut_buffer_io_2.tmp";
+    std::remove(path.c_str());
+    {
+        std::ofstream out(path, std::ios::binary);
+        out << "abc\n123\n";
+    }
+
+    Buffer b;
+    std::string err;
+    ASSERT_TRUE(b.OpenFromFile(path, err));
+    ASSERT_EQ(err.empty(), true);
+
+    b.insert_text(2, 0, std::string("tail\n"));
+    b.SetDirty(true);
+    ASSERT_TRUE(b.Save(err));
+    ASSERT_EQ(err.empty(), true);
+
+    std::string got = read_all(path);
+    ASSERT_EQ(got, std::string("abc\n123\ntail\n"));
+    std::remove(path.c_str());
+}
+
+TEST(Buffer_Open_nonexistent_then_SaveAs) {
+    const std::string path = "./.kte_ut_buffer_io_3.tmp";
+    std::remove(path.c_str());
+
+    Buffer b;
+    std::string err;
+    ASSERT_TRUE(b.OpenFromFile(path, err));
+    ASSERT_EQ(err.empty(), true);
+    ASSERT_EQ(b.IsFileBacked(), false);
+
+    b.insert_text(0, 0, std::string("hello, world"));
+    b.insert_text(0, 12, std::string("\n"));
+    b.SetDirty(true);
+    ASSERT_TRUE(b.SaveAs(path, err));
+    ASSERT_EQ(err.empty(), true);
+
+    std::string got = read_all(path);
+    ASSERT_EQ(got, std::string("hello, world\n"));
+    std::remove(path.c_str());
+}

tests/test_piece_table.cc

@@ -0,0 +1,49 @@
+#include "Test.h"
+#include "PieceTable.h"
+#include <string>
+
+TEST(PieceTable_Insert_Delete_LineCount) {
+    PieceTable pt;
+    // start empty
+    ASSERT_EQ(pt.Size(), (std::size_t)0);
+    ASSERT_EQ(pt.LineCount(), (std::size_t)1); // empty buffer has 1 logical line
+
+    // Insert some text with newlines
+    const char *t = "abc\n123\nxyz"; // last line without trailing NL
+    pt.Insert(0, t, 11);
+    ASSERT_EQ(pt.Size(), (std::size_t)11);
+    ASSERT_EQ(pt.LineCount(), (std::size_t)3);
+
+    // Check get line
+    ASSERT_EQ(pt.GetLine(0), std::string("abc"));
+    ASSERT_EQ(pt.GetLine(1), std::string("123"));
+    ASSERT_EQ(pt.GetLine(2), std::string("xyz"));
+
+    // Delete middle line entirely including its trailing NL
+    auto r = pt.GetLineRange(1); // [start,end) points to start of line 1 to start of line 2
+    pt.Delete(r.first, r.second - r.first);
+    ASSERT_EQ(pt.LineCount(), (std::size_t)2);
+    ASSERT_EQ(pt.GetLine(0), std::string("abc"));
+    ASSERT_EQ(pt.GetLine(1), std::string("xyz"));
+}
+
+TEST(PieceTable_LineCol_Conversions) {
+    PieceTable pt;
+    std::string s = "hello\nworld\n"; // two lines with trailing NL
+    pt.Insert(0, s.data(), s.size());
+
+    // Byte offsets of starts
+    auto off0 = pt.LineColToByteOffset(0, 0);
+    auto off1 = pt.LineColToByteOffset(1, 0);
+    auto off2 = pt.LineColToByteOffset(2, 0); // EOF
+    ASSERT_EQ(off0, (std::size_t)0);
+    ASSERT_EQ(off1, (std::size_t)6); // "hello\n"
+    ASSERT_EQ(off2, pt.Size());
+
+    auto lc0 = pt.ByteOffsetToLineCol(0);
+    auto lc1 = pt.ByteOffsetToLineCol(6);
+    ASSERT_EQ(lc0.first, (std::size_t)0);
+    ASSERT_EQ(lc0.second, (std::size_t)0);
+    ASSERT_EQ(lc1.first, (std::size_t)1);
+    ASSERT_EQ(lc1.second, (std::size_t)0);
+}

tests/test_search.cc

@@ -0,0 +1,36 @@
+#include "Test.h"
+#include "OptimizedSearch.h"
+#include <string>
+#include <vector>
+
+static std::vector<std::size_t> ref_find_all(const std::string &text, const std::string &pat) {
+    std::vector<std::size_t> res;
+    if (pat.empty()) return res;
+    std::size_t from = 0;
+    while (true) {
+        auto p = text.find(pat, from);
+        if (p == std::string::npos) break;
+        res.push_back(p);
+        from = p + pat.size();
+    }
+    return res;
+}
+
+TEST(OptimizedSearch_basic_cases) {
+    OptimizedSearch os;
+    struct Case { std::string text; std::string pat; } cases[] = {
+        {"", ""},
+        {"", "a"},
+        {"a", ""},
+        {"a", "a"},
+        {"aaaaa", "aa"},
+        {"hello world", "world"},
+        {"abcabcabc", "abc"},
+        {"the quick brown fox", "fox"},
+    };
+    for (auto &c : cases) {
+        auto got = os.find_all(c.text, c.pat, 0);
+        auto ref = ref_find_all(c.text, c.pat);
+        ASSERT_EQ(got, ref);
+    }
+}