Improve macOS app build process and bundle handling.

- Updated `make-app-release` script to use `macdeployqt` with proper verbosity and bundle fixup.
- Introduced post-build fixup using CMake's `BundleUtilities` to internalize non-Qt dylibs.
- Enhanced macOS bundle RPATH settings for accurate Framework resolution.
- Added optional `kge_fixup_bundle` CMake target for post-build handling.
- Refined `default.nix` to load Nixpkgs in a default argument.

.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>

.junie/guidelines.md

@@ -1,28 +1,35 @@
 # Project Guidelines
 
-kte is Kyle's Text Editor — a simple, fast text editor written in C++17. It
-replaces the earlier C implementation, ke (see the ke manual in `docs/ke.md`). The
-design draws inspiration from Antirez' kilo, with keybindings rooted in the
+kte is Kyle's Text Editor — a simple, fast text editor written in C++17.
+It
+replaces the earlier C implementation, ke (see the ke manual in
+`docs/ke.md`). The
+design draws inspiration from Antirez' kilo, with keybindings rooted in
+the
 WordStar/VDE family and emacs. The spiritual parent is `mg(1)`.
 
-These guidelines summarize the goals, interfaces, key operations, and current
+These guidelines summarize the goals, interfaces, key operations, and
+current
 development practices for kte.
 
 ## Goals
 
 - Keep the core small, fast, and understandable.
-- Provide an ncurses-based terminal-first editing experience, with an additional ImGui GUI.
+- Provide an ncurses-based terminal-first editing experience, with an
+  additional ImGui GUI.
 - Preserve familiar keybindings from ke while modernizing the internals.
-- Favor simple data structures (e.g., piece table) and incremental evolution.
+- Favor simple data structures (e.g., piece table) and incremental
+  evolution.
 
 Project entry point: `main.cpp`
 
 ## Core Components (current codebase)
 
 - Buffer: editing model and file I/O (`Buffer.h/.cpp`).
-- GapBuffer: editable in-memory text representation (`GapBuffer.h/.cpp`).
-- PieceTable: experimental/alternative representation (`PieceTable.h/.cpp`).
-- InputHandler: interface for handling text input (`InputHandler.h/`), along
+- PieceTable: editable in-memory text representation (
+  `PieceTable.h/.cpp`).
+- InputHandler: interface for handling text input (`InputHandler.h/`),
+  along
   with `TerminalInputHandler` (ncurses-based) and `GUIInputHandler`.
 - Renderer: interface for rendering text (`Renderer.h`), along with
   `TerminalRenderer` (ncurses-based) and `GUIRenderer`.
@@ -38,11 +45,13 @@ The file `docs/ke.md` contains the canonical reference for keybindings.
 
 - C++ standard: C++17.
 - Keep dependencies minimal.
-- Prefer small, focused changes that preserve ke’s UX unless explicitly changing
+- Prefer small, focused changes that preserve ke’s UX unless explicitly
+  changing
   behavior.
 
 ## References
 
-- Previous editor manual: `ke.md` (canonical keybinding/spec reference for now).
+- Previous editor manual: `ke.md` (canonical keybinding/spec reference
+  for now).
 - Inspiration: kilo, WordStar/VDE, emacs, `mg(1)`.
 

AppendBuffer.h

@@ -1,12 +0,0 @@
-/*
- * AppendBuffer.h - selector header to choose GapBuffer or PieceTable
- */
-#pragma once
-
-#ifdef KTE_USE_PIECE_TABLE
-#include "PieceTable.h"
-using AppendBuffer = PieceTable;
-#else
-#include "GapBuffer.h"
-using AppendBuffer = GapBuffer;
-#endif

Buffer.cc

@@ -2,6 +2,10 @@
 #include <sstream>
 #include <filesystem>
 #include <cstdlib>
+#include <limits>
+#include <cerrno>
+#include <cstring>
+#include <string_view>
 
 #include "Buffer.h"
 #include "UndoSystem.h"
@@ -29,20 +33,22 @@ Buffer::Buffer(const std::string &path)
 // Copy constructor/assignment: perform a deep copy of core fields; reinitialize undo for the new buffer.
 Buffer::Buffer(const Buffer &other)
 {
-	curx_           = other.curx_;
-	cury_           = other.cury_;
-	rx_             = other.rx_;
-	nrows_          = other.nrows_;
-	rowoffs_        = other.rowoffs_;
-	coloffs_        = other.coloffs_;
-	rows_           = other.rows_;
-	filename_       = other.filename_;
-	is_file_backed_ = other.is_file_backed_;
-	dirty_          = other.dirty_;
-	read_only_      = other.read_only_;
-	mark_set_       = other.mark_set_;
-	mark_curx_      = other.mark_curx_;
-	mark_cury_      = other.mark_cury_;
+	curx_             = other.curx_;
+	cury_             = other.cury_;
+	rx_               = other.rx_;
+	nrows_            = other.nrows_;
+	rowoffs_          = other.rowoffs_;
+	coloffs_          = other.coloffs_;
+	rows_             = other.rows_;
+	content_          = other.content_;
+	rows_cache_dirty_ = other.rows_cache_dirty_;
+	filename_         = other.filename_;
+	is_file_backed_   = other.is_file_backed_;
+	dirty_            = other.dirty_;
+	read_only_        = other.read_only_;
+	mark_set_         = other.mark_set_;
+	mark_curx_        = other.mark_curx_;
+	mark_cury_        = other.mark_cury_;
 	// Copy syntax/highlighting flags
 	version_        = other.version_;
 	syntax_enabled_ = other.syntax_enabled_;
@@ -77,23 +83,25 @@ Buffer::operator=(const Buffer &other)
 {
 	if (this == &other)
 		return *this;
-	curx_           = other.curx_;
-	cury_           = other.cury_;
-	rx_             = other.rx_;
-	nrows_          = other.nrows_;
-	rowoffs_        = other.rowoffs_;
-	coloffs_        = other.coloffs_;
-	rows_           = other.rows_;
-	filename_       = other.filename_;
-	is_file_backed_ = other.is_file_backed_;
-	dirty_          = other.dirty_;
-	read_only_      = other.read_only_;
-	mark_set_       = other.mark_set_;
-	mark_curx_      = other.mark_curx_;
-	mark_cury_      = other.mark_cury_;
-	version_        = other.version_;
-	syntax_enabled_ = other.syntax_enabled_;
-	filetype_       = other.filetype_;
+	curx_             = other.curx_;
+	cury_             = other.cury_;
+	rx_               = other.rx_;
+	nrows_            = other.nrows_;
+	rowoffs_          = other.rowoffs_;
+	coloffs_          = other.coloffs_;
+	rows_             = other.rows_;
+	content_          = other.content_;
+	rows_cache_dirty_ = other.rows_cache_dirty_;
+	filename_         = other.filename_;
+	is_file_backed_   = other.is_file_backed_;
+	dirty_            = other.dirty_;
+	read_only_        = other.read_only_;
+	mark_set_         = other.mark_set_;
+	mark_curx_        = other.mark_curx_;
+	mark_cury_        = other.mark_cury_;
+	version_          = other.version_;
+	syntax_enabled_   = other.syntax_enabled_;
+	filetype_         = other.filetype_;
 	// Recreate undo system for this instance
 	undo_tree_ = std::make_unique<UndoTree>();
 	undo_sys_  = std::make_unique<UndoSystem>(*this, *undo_tree_);
@@ -137,10 +145,12 @@ Buffer::Buffer(Buffer &&other) noexcept
 	  undo_sys_(std::move(other.undo_sys_))
 {
 	// Move syntax/highlighting state
-	version_        = other.version_;
-	syntax_enabled_ = other.syntax_enabled_;
-	filetype_       = std::move(other.filetype_);
-	highlighter_    = std::move(other.highlighter_);
+	version_          = other.version_;
+	syntax_enabled_   = other.syntax_enabled_;
+	filetype_         = std::move(other.filetype_);
+	highlighter_      = std::move(other.highlighter_);
+	content_          = std::move(other.content_);
+	rows_cache_dirty_ = other.rows_cache_dirty_;
 	// Update UndoSystem's buffer reference to point to this object
 	if (undo_sys_) {
 		undo_sys_->UpdateBufferReference(*this);
@@ -173,11 +183,12 @@ Buffer::operator=(Buffer &&other) noexcept
 	undo_sys_       = std::move(other.undo_sys_);
 
 	// Move syntax/highlighting state
-	version_        = other.version_;
-	syntax_enabled_ = other.syntax_enabled_;
-	filetype_       = std::move(other.filetype_);
-	highlighter_    = std::move(other.highlighter_);
-
+	version_          = other.version_;
+	syntax_enabled_   = other.syntax_enabled_;
+	filetype_         = std::move(other.filetype_);
+	highlighter_      = std::move(other.highlighter_);
+	content_          = std::move(other.content_);
+	rows_cache_dirty_ = other.rows_cache_dirty_;
 	// Update UndoSystem's buffer reference to point to this object
 	if (undo_sys_) {
 		undo_sys_->UpdateBufferReference(*this);
@@ -229,6 +240,10 @@ Buffer::OpenFromFile(const std::string &path, std::string &err)
 		mark_set_  = false;
 		mark_curx_ = mark_cury_ = 0;
 
+		// Empty PieceTable
+		content_.Clear();
+		rows_cache_dirty_ = true;
+
 		return true;
 	}
 
@@ -238,50 +253,23 @@ Buffer::OpenFromFile(const std::string &path, std::string &err)
 		return false;
 	}
 
-	// Detect if file ends with a newline so we can preserve a final empty line
-	// in our in-memory representation (mg-style semantics).
-	bool ends_with_nl = false;
-	{
-		in.seekg(0, std::ios::end);
-		std::streamoff sz = in.tellg();
-		if (sz > 0) {
-			in.seekg(-1, std::ios::end);
-			char last = 0;
-			in.read(&last, 1);
-			ends_with_nl = (last == '\n');
-		} else {
-			in.clear();
-		}
-		// Rewind to start for line-by-line read
-		in.clear();
+	// Read entire file into PieceTable as-is
+	std::string data;
+	in.seekg(0, std::ios::end);
+	auto sz = in.tellg();
+	if (sz > 0) {
+		data.resize(static_cast<std::size_t>(sz));
 		in.seekg(0, std::ios::beg);
+		in.read(data.data(), static_cast<std::streamsize>(data.size()));
 	}
-
-	rows_.clear();
-	std::string line;
-	while (std::getline(in, line)) {
-		// std::getline strips the '\n', keep raw line content only
-		// Handle potential Windows CRLF: strip trailing '\r'
-		if (!line.empty() && line.back() == '\r') {
-			line.pop_back();
-		}
-		rows_.emplace_back(line);
-	}
-
-	// If the file ended with a newline and we didn't already get an
-	// empty final row from getline (e.g., when the last textual line
-	// had content followed by '\n'), append an empty row to represent
-	// the cursor position past the last newline.
-	if (ends_with_nl) {
-		if (rows_.empty() || !rows_.back().empty()) {
-			rows_.emplace_back(std::string());
-		}
-	}
-
-	nrows_          = rows_.size();
-	filename_       = norm;
-	is_file_backed_ = true;
-	dirty_          = false;
+	content_.Clear();
+	if (!data.empty())
+		content_.Append(data.data(), data.size());
+	rows_cache_dirty_ = true;
+	nrows_            = 0; // not used under PieceTable
+	filename_         = norm;
+	is_file_backed_   = true;
+	dirty_            = false;
 
 	// Reset/initialize undo system for this loaded file
 	if (!undo_tree_)
@@ -304,31 +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_;
-		return false;
-	}
-	for (std::size_t i = 0; i < rows_.size(); ++i) {
-		const char *d = rows_[i].Data();
-		std::size_t n = rows_[i].Size();
-		if (d && n)
-			out.write(d, static_cast<std::streamsize>(n));
-		if (i + 1 < rows_.size()) {
-			out.put('\n');
-		}
-	}
-	if (!out.good()) {
-		err = "Write error";
-		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;
 }
 
 
@@ -357,22 +343,19 @@ Buffer::SaveAs(const std::string &path, std::string &err)
 	// Write to the given path
 	std::ofstream out(out_path, std::ios::out | std::ios::binary | std::ios::trunc);
 	if (!out) {
-		err = "Failed to open for write: " + out_path;
-		return false;
-	}
-	for (std::size_t i = 0; i < rows_.size(); ++i) {
-		const char *d = rows_[i].Data();
-		std::size_t n = rows_[i].Size();
-		if (d && n)
-			out.write(d, static_cast<std::streamsize>(n));
-		if (i + 1 < rows_.size()) {
-			out.put('\n');
-		}
-	}
-	if (!out.good()) {
-		err = "Write error";
+		err = "Failed to open for write: " + 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;
@@ -389,7 +372,7 @@ Buffer::AsString() const
 	if (this->Dirty()) {
 		ss << "*";
 	}
-	ss << ">: " << rows_.size() << " lines";
+	ss << ">: " << content_.LineCount() << " lines";
 	return ss.str();
 }
 
@@ -400,111 +383,135 @@ Buffer::insert_text(int row, int col, std::string_view text)
 {
 	if (row < 0)
 		row = 0;
-	if (static_cast<std::size_t>(row) > rows_.size())
-		row = static_cast<int>(rows_.size());
-	if (rows_.empty())
-		rows_.emplace_back("");
-	if (static_cast<std::size_t>(row) >= rows_.size())
-		rows_.emplace_back("");
-
-	auto y = static_cast<std::size_t>(row);
-	auto x = static_cast<std::size_t>(col);
-	if (x > rows_[y].size())
-		x = rows_[y].size();
-
-	std::string remain(text);
-	while (true) {
-		auto pos = remain.find('\n');
-		if (pos == std::string::npos) {
-			rows_[y].insert(x, remain);
-			break;
-		}
-		// Insert up to newline
-		std::string seg = remain.substr(0, pos);
-		rows_[y].insert(x, seg);
-		x += seg.size();
-		// Split line at x
-		std::string tail = rows_[y].substr(x);
-		rows_[y].erase(x);
-		rows_.insert(rows_.begin() + static_cast<std::ptrdiff_t>(y + 1), Line(tail));
-		y += 1;
-		x = 0;
-		remain.erase(0, pos + 1);
+	if (col < 0)
+		col = 0;
+	const std::size_t off = content_.LineColToByteOffset(static_cast<std::size_t>(row),
+	                                                     static_cast<std::size_t>(col));
+	if (!text.empty()) {
+		content_.Insert(off, text.data(), text.size());
+		rows_cache_dirty_ = true;
 	}
-	// Do not set dirty here; UndoSystem will manage state/dirty externally
+}
+
+
+// ===== Adapter helpers for PieceTable-backed Buffer =====
+std::string_view
+Buffer::GetLineView(std::size_t row) const
+{
+	// Get byte range for the logical line and return a view into materialized data
+	auto range       = content_.GetLineRange(row); // [start,end) in bytes
+	const char *base = content_.Data(); // materializes if needed
+	if (!base)
+		return std::string_view();
+	const std::size_t start = range.first;
+	const std::size_t len   = (range.second > range.first) ? (range.second - range.first) : 0;
+	return std::string_view(base + start, len);
+}
+
+
+void
+Buffer::ensure_rows_cache() const
+{
+	if (!rows_cache_dirty_)
+		return;
+	rows_.clear();
+	const std::size_t lc = content_.LineCount();
+	rows_.reserve(lc);
+	for (std::size_t i = 0; i < lc; ++i) {
+		rows_.emplace_back(content_.GetLine(i));
+	}
+	// Keep nrows_ in sync for any legacy code that still reads it
+	const_cast<Buffer *>(this)->nrows_ = rows_.size();
+	rows_cache_dirty_                  = false;
+}
+
+
+std::size_t
+Buffer::content_LineCount_() const
+{
+	return content_.LineCount();
 }
 
 
 void
 Buffer::delete_text(int row, int col, std::size_t len)
 {
-	if (rows_.empty() || len == 0)
+	if (len == 0)
 		return;
 	if (row < 0)
 		row = 0;
-	if (static_cast<std::size_t>(row) >= rows_.size())
-		return;
-	const auto y = static_cast<std::size_t>(row);
-	const auto x = std::min<std::size_t>(static_cast<std::size_t>(col), rows_[y].size());
-
+	if (col < 0)
+		col = 0;
+	const std::size_t start = content_.LineColToByteOffset(static_cast<std::size_t>(row),
+	                                                       static_cast<std::size_t>(col));
+	std::size_t r         = static_cast<std::size_t>(row);
+	std::size_t c         = static_cast<std::size_t>(col);
 	std::size_t remaining = len;
-	while (remaining > 0 && y < rows_.size()) {
-		auto &line                = rows_[y];
-		const std::size_t in_line = std::min<std::size_t>(remaining, line.size() - std::min(x, line.size()));
-		if (x < line.size() && in_line > 0) {
-			line.erase(x, in_line);
-			remaining -= in_line;
+	const std::size_t lc  = content_.LineCount();
+
+	while (remaining > 0 && r < lc) {
+		const std::string line = content_.GetLine(r); // logical line (without trailing '\n')
+		const std::size_t L    = line.size();
+		if (c < L) {
+			const std::size_t take = std::min(remaining, L - c);
+			c += take;
+			remaining -= take;
 		}
 		if (remaining == 0)
 			break;
-		// If at or beyond end of line and there is a next line, join it (deleting the implied '\n')
-		if (y + 1 < rows_.size()) {
-			line += rows_[y + 1];
-			rows_.erase(rows_.begin() + static_cast<std::ptrdiff_t>(y + 1));
-			// deleting the newline consumes one virtual character
+		// Consume newline between lines as one char, if there is a next line
+		if (r + 1 < lc) {
 			if (remaining > 0) {
-				// Treat the newline as one deletion unit if len spans it
-				// We already joined, so nothing else to do here.
+				remaining -= 1; // the newline
+				r += 1;
+				c = 0;
 			}
 		} else {
-			break;
+			// At last line and still remaining: delete to EOF
+			std::size_t total = content_.Size();
+			content_.Delete(start, total - start);
+			rows_cache_dirty_ = true;
+			return;
 		}
 	}
+
+	// Compute end offset at (r,c)
+	std::size_t end = content_.LineColToByteOffset(r, c);
+	if (end > start) {
+		content_.Delete(start, end - start);
+		rows_cache_dirty_ = true;
+	}
 }
 
 
 void
 Buffer::split_line(int row, const int col)
 {
-	if (row < 0) {
+	if (row < 0)
 		row = 0;
-	}
-
-	if (static_cast<std::size_t>(row) >= rows_.size()) {
-		rows_.resize(static_cast<std::size_t>(row) + 1);
-	}
-	const auto y    = static_cast<std::size_t>(row);
-	const auto x    = std::min<std::size_t>(static_cast<std::size_t>(col), rows_[y].size());
-	const auto tail = rows_[y].substr(x);
-	rows_[y].erase(x);
-	rows_.insert(rows_.begin() + static_cast<std::ptrdiff_t>(y + 1), Line(tail));
+	if (col < 0)
+		row = 0;
+	const std::size_t off = content_.LineColToByteOffset(static_cast<std::size_t>(row),
+	                                                     static_cast<std::size_t>(col));
+	const char nl = '\n';
+	content_.Insert(off, &nl, 1);
+	rows_cache_dirty_ = true;
 }
 
 
 void
 Buffer::join_lines(int row)
 {
-	if (row < 0) {
+	if (row < 0)
 		row = 0;
-	}
-
-	const auto y = static_cast<std::size_t>(row);
-	if (y + 1 >= rows_.size()) {
+	std::size_t r = static_cast<std::size_t>(row);
+	if (r + 1 >= content_.LineCount())
 		return;
-	}
-
-	rows_[y] += rows_[y + 1];
-	rows_.erase(rows_.begin() + static_cast<std::ptrdiff_t>(y + 1));
+	// Delete the newline between line r and r+1
+	std::size_t end_of_line = content_.LineColToByteOffset(r, std::numeric_limits<std::size_t>::max());
+	// end_of_line now equals line end (clamped before newline). The newline should be exactly at this position.
+	content_.Delete(end_of_line, 1);
+	rows_cache_dirty_ = true;
 }
 
 
@@ -513,9 +520,12 @@ Buffer::insert_row(int row, const std::string_view text)
 {
 	if (row < 0)
 		row = 0;
-	if (static_cast<std::size_t>(row) > rows_.size())
-		row = static_cast<int>(rows_.size());
-	rows_.insert(rows_.begin() + row, Line(std::string(text)));
+	std::size_t off = content_.LineColToByteOffset(static_cast<std::size_t>(row), 0);
+	if (!text.empty())
+		content_.Insert(off, text.data(), text.size());
+	const char nl = '\n';
+	content_.Insert(off + text.size(), &nl, 1);
+	rows_cache_dirty_ = true;
 }
 
 
@@ -524,9 +534,16 @@ Buffer::delete_row(int row)
 {
 	if (row < 0)
 		row = 0;
-	if (static_cast<std::size_t>(row) >= rows_.size())
+	std::size_t r = static_cast<std::size_t>(row);
+	if (r >= content_.LineCount())
 		return;
-	rows_.erase(rows_.begin() + row);
+	auto range = content_.GetLineRange(r); // [start,end)
+	// If not last line, ensure we include the separating newline by using end as-is (which points to next line start)
+	// If last line, end may equal total_size_. We still delete [start,end) which removes the last line content.
+	std::size_t start = range.first;
+	std::size_t end   = range.second;
+	content_.Delete(start, end - start);
+	rows_cache_dirty_ = true;
 }
 
 
@@ -542,4 +559,4 @@ const UndoSystem *
 Buffer::Undo() const
 {
 	return undo_sys_.get();
-}
+}

Buffer.h

@@ -9,10 +9,9 @@
 #include <vector>
 #include <string_view>
 
-#include "AppendBuffer.h"
+#include "PieceTable.h"
 #include "UndoSystem.h"
 #include <cstdint>
-#include <memory>
 #include "syntax/HighlighterEngine.h"
 #include "Highlight.h"
 
@@ -63,7 +62,7 @@ public:
 
 	[[nodiscard]] std::size_t Nrows() const
 	{
-		return nrows_;
+		return content_LineCount_();
 	}
 
 
@@ -79,7 +78,8 @@ public:
 	}
 
 
-	// Line wrapper backed by AppendBuffer (GapBuffer/PieceTable)
+	// Line wrapper used by legacy command paths.
+	// Keep this lightweight: store materialized bytes only for that line.
 	class Line {
 	public:
 		Line() = default;
@@ -108,119 +108,102 @@ public:
 		// capacity helpers
 		void Clear()
 		{
-			buf_.Clear();
+			s_.clear();
 		}
 
 
 		// size/access
 		[[nodiscard]] std::size_t size() const
 		{
-			return buf_.Size();
+			return s_.size();
 		}
 
 
 		[[nodiscard]] bool empty() const
 		{
-			return size() == 0;
+			return s_.empty();
 		}
 
 
 		// read-only raw view
 		[[nodiscard]] const char *Data() const
 		{
-			return buf_.Data();
+			return s_.data();
 		}
 
 
 		[[nodiscard]] std::size_t Size() const
 		{
-			return buf_.Size();
+			return s_.size();
 		}
 
 
 		// element access (read-only)
 		[[nodiscard]] char operator[](std::size_t i) const
 		{
-			const char *d = buf_.Data();
-			return (i < buf_.Size() && d) ? d[i] : '\0';
+			return (i < s_.size()) ? s_[i] : '\0';
 		}
 
 
 		// conversions
 		explicit operator std::string() const
 		{
-			return {buf_.Data() ? buf_.Data() : "", buf_.Size()};
+			return s_;
 		}
 
 
 		// string-like API used by command/renderer layers (implemented via materialization for now)
 		[[nodiscard]] std::string substr(std::size_t pos) const
 		{
-			const std::size_t n = buf_.Size();
-			if (pos >= n)
-				return {};
-			return {buf_.Data() + pos, n - pos};
+			return pos < s_.size() ? s_.substr(pos) : std::string();
 		}
 
 
 		[[nodiscard]] std::string substr(std::size_t pos, std::size_t len) const
 		{
-			const std::size_t n = buf_.Size();
-			if (pos >= n)
-				return {};
-			const std::size_t take = (pos + len > n) ? (n - pos) : len;
-			return {buf_.Data() + pos, take};
+			return pos < s_.size() ? s_.substr(pos, len) : std::string();
 		}
 
 
 		// minimal find() to support search within a line
 		[[nodiscard]] std::size_t find(const std::string &needle, const std::size_t pos = 0) const
 		{
-			// Materialize to std::string for now; Line is backed by AppendBuffer
-			const auto s = static_cast<std::string>(*this);
-			return s.find(needle, pos);
+			return s_.find(needle, pos);
 		}
 
 
 		void erase(std::size_t pos)
 		{
-			// erase to end
-			material_edit([&](std::string &s) {
-				if (pos < s.size())
-					s.erase(pos);
-			});
+			if (pos < s_.size())
+				s_.erase(pos);
 		}
 
 
 		void erase(std::size_t pos, std::size_t len)
 		{
-			material_edit([&](std::string &s) {
-				if (pos < s.size())
-					s.erase(pos, len);
-			});
+			if (pos < s_.size())
+				s_.erase(pos, len);
 		}
 
 
 		void insert(std::size_t pos, const std::string &seg)
 		{
-			material_edit([&](std::string &s) {
-				if (pos > s.size())
-					pos = s.size();
-				s.insert(pos, seg);
-			});
+			if (pos > s_.size())
+				pos = s_.size();
+			s_.insert(pos, seg);
 		}
 
 
 		Line &operator+=(const Line &other)
 		{
-			buf_.Append(other.buf_.Data(), other.buf_.Size());
+			s_ += other.s_;
 			return *this;
 		}
 
 
 		Line &operator+=(const std::string &s)
 		{
-			buf_.Append(s.data(), s.size());
+			s_ += s;
 			return *this;
 		}
 
@@ -234,37 +217,47 @@ public:
 	private:
 		void assign_from(const std::string &s)
 		{
-			buf_.Clear();
-			if (!s.empty())
-				buf_.Append(s.data(), s.size());
+			s_ = s;
 		}
 
 
-		template<typename F>
-		void material_edit(F fn)
-		{
-			std::string tmp = static_cast<std::string>(*this);
-			fn(tmp);
-			assign_from(tmp);
-		}
-
-
-		AppendBuffer buf_;
+		std::string s_;
 	};
 
 
 	[[nodiscard]] const std::vector<Line> &Rows() const
 	{
+		ensure_rows_cache();
 		return rows_;
 	}
 
 
 	[[nodiscard]] std::vector<Line> &Rows()
 	{
+		ensure_rows_cache();
 		return rows_;
 	}
 
 
+	// Lightweight, lazy per-line accessors that avoid materializing all rows.
+	// Prefer these over Rows() in hot paths to reduce memory overhead on large files.
+	[[nodiscard]] std::string GetLineString(std::size_t row) const
+	{
+		return content_.GetLine(row);
+	}
+
+
+	[[nodiscard]] std::pair<std::size_t, std::size_t> GetLineRange(std::size_t row) const
+	{
+		return content_.GetLineRange(row);
+	}
+
+
+	// Zero-copy view of a line. Points into the materialized backing store; becomes
+	// invalid after subsequent edits. Use immediately.
+	[[nodiscard]] std::string_view GetLineView(std::size_t row) const;
+
+
 	[[nodiscard]] const std::string &Filename() const
 	{
 		return filename_;
@@ -409,13 +402,13 @@ public:
 	}
 
 
-	kte::HighlighterEngine *Highlighter()
+	[[nodiscard]] kte::HighlighterEngine *Highlighter()
 	{
 		return highlighter_.get();
 	}
 
 
-	const kte::HighlighterEngine *Highlighter() const
+	[[nodiscard]] const kte::HighlighterEngine *Highlighter() const
 	{
 		return highlighter_.get();
 	}
@@ -450,7 +443,7 @@ public:
 	void delete_row(int row);
 
 	// Undo system accessors (created per-buffer)
-	UndoSystem *Undo();
+	[[nodiscard]] UndoSystem *Undo();
 
 	[[nodiscard]] const UndoSystem *Undo() const;
 
@@ -460,7 +453,17 @@ private:
 	std::size_t rx_      = 0; // render x (tabs expanded)
 	std::size_t nrows_   = 0; // number of rows
 	std::size_t rowoffs_ = 0, coloffs_ = 0; // viewport offsets
-	std::vector<Line> rows_; // buffer rows (without trailing newlines)
+	mutable std::vector<Line> rows_; // materialized cache of rows (without trailing newlines)
+	// PieceTable is the source of truth.
+	PieceTable content_{};
+	mutable bool rows_cache_dirty_ = true; // invalidate on edits / I/O
+
+	// Helper to rebuild rows_ from content_
+	void ensure_rows_cache() const;
+
+	// Helper to query content_.LineCount() while keeping header minimal
+	std::size_t content_LineCount_() const;
+
 	std::string filename_;
 	bool is_file_backed_   = false;
 	bool dirty_            = false;

CMakeLists.txt

@@ -4,14 +4,13 @@ project(kte)
 include(GNUInstallDirs)
 
 set(CMAKE_CXX_STANDARD 20)
-set(KTE_VERSION "1.4.1")
+set(KTE_VERSION "1.5.3")
 
 # Default to terminal-only build to avoid SDL/OpenGL dependency by default.
 # Enable with -DBUILD_GUI=ON when SDL2/OpenGL/Freetype are available.
 set(BUILD_GUI ON CACHE BOOL "Enable building the graphical version.")
 set(KTE_USE_QT OFF CACHE BOOL "Build the QT frontend instead of ImGui.")
 set(BUILD_TESTS OFF CACHE BOOL "Enable building test programs.")
-option(KTE_USE_PIECE_TABLE "Use PieceTable instead of GapBuffer implementation" ON)
 set(KTE_FONT_SIZE "18.0" CACHE STRING "Default font size for GUI")
 option(KTE_UNDO_DEBUG "Enable undo instrumentation logs" OFF)
 option(KTE_ENABLE_TREESITTER "Enable optional Tree-sitter highlighter adapter" OFF)
@@ -128,7 +127,6 @@ if (BUILD_GUI)
 endif ()
 
 set(COMMON_SOURCES
-        GapBuffer.cc
         PieceTable.cc
         Buffer.cc
         Editor.cc
@@ -213,11 +211,9 @@ set(FONT_HEADERS
 )
 
 set(COMMON_HEADERS
-        GapBuffer.h
         PieceTable.h
         Buffer.h
         Editor.h
-        AppendBuffer.h
         Command.h
         HelpText.h
         KKeymap.h
@@ -270,9 +266,6 @@ add_executable(kte
         ${COMMON_HEADERS}
 )
 
-if (KTE_USE_PIECE_TABLE)
-    target_compile_definitions(kte PRIVATE KTE_USE_PIECE_TABLE=1)
-endif ()
 if (KTE_UNDO_DEBUG)
     target_compile_definitions(kte PRIVATE KTE_UNDO_DEBUG=1)
 endif ()
@@ -299,29 +292,34 @@ 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_USE_PIECE_TABLE)
-        target_compile_definitions(test_undo PRIVATE KTE_USE_PIECE_TABLE=1)
-    endif ()
+    # Allow tests to include project headers like "Buffer.h"
+    target_include_directories(kte_tests PRIVATE ${CMAKE_CURRENT_SOURCE_DIR})
 
-    if (KTE_UNDO_DEBUG)
-        target_compile_definitions(test_undo PRIVATE KTE_UNDO_DEBUG=1)
-    endif ()
-
-
-    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 ${TREESITTER_LIBRARY})
         endif ()
     endif ()
 endif ()
@@ -381,12 +379,18 @@ if (${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
@@ -410,4 +414,19 @@ 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)
+        include(CMakeParseArguments)
+        add_custom_target(kge_fixup_bundle ALL
+                COMMAND ${CMAKE_COMMAND}
+                    -DAPP_BUNDLE=$<TARGET_BUNDLE_DIR:kge>
+                    -P ${CMAKE_CURRENT_LIST_DIR}/cmake/fix_bundle.cmake
+                BYPRODUCTS $<TARGET_BUNDLE_DIR:kge>/Contents/Frameworks
+                COMMENT "Running fixup_bundle on kge.app to internalize non-Qt dylibs"
+                VERBATIM)
+        add_dependencies(kge_fixup_bundle kge)
+    endif ()
 endif ()

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;
 }
 
 

GapBuffer.cc

@@ -1,204 +0,0 @@
-#include <algorithm>
-#include <cassert>
-#include <cstring>
-
-#include "GapBuffer.h"
-
-
-GapBuffer::GapBuffer() = default;
-
-
-GapBuffer::GapBuffer(std::size_t initialCapacity)
-	: buffer_(nullptr), size_(0), capacity_(0)
-{
-	if (initialCapacity > 0) {
-		Reserve(initialCapacity);
-	}
-}
-
-
-GapBuffer::GapBuffer(const GapBuffer &other)
-	: buffer_(nullptr), size_(0), capacity_(0)
-{
-	if (other.capacity_ > 0) {
-		Reserve(other.capacity_);
-		if (other.size_ > 0) {
-			std::memcpy(buffer_, other.buffer_, other.size_);
-			size_ = other.size_;
-		}
-		setTerminator();
-	}
-}
-
-
-GapBuffer &
-GapBuffer::operator=(const GapBuffer &other)
-{
-	if (this == &other)
-		return *this;
-	if (other.capacity_ > capacity_) {
-		Reserve(other.capacity_);
-	}
-	if (other.size_ > 0) {
-		std::memcpy(buffer_, other.buffer_, other.size_);
-	}
-	size_ = other.size_;
-	setTerminator();
-	return *this;
-}
-
-
-GapBuffer::GapBuffer(GapBuffer &&other) noexcept
-	: buffer_(other.buffer_), size_(other.size_), capacity_(other.capacity_)
-{
-	other.buffer_   = nullptr;
-	other.size_     = 0;
-	other.capacity_ = 0;
-}
-
-
-GapBuffer &
-GapBuffer::operator=(GapBuffer &&other) noexcept
-{
-	if (this == &other)
-		return *this;
-	delete[] buffer_;
-	buffer_         = other.buffer_;
-	size_           = other.size_;
-	capacity_       = other.capacity_;
-	other.buffer_   = nullptr;
-	other.size_     = 0;
-	other.capacity_ = 0;
-	return *this;
-}
-
-
-GapBuffer::~GapBuffer()
-{
-	delete[] buffer_;
-}
-
-
-void
-GapBuffer::Reserve(const std::size_t newCapacity)
-{
-	if (newCapacity <= capacity_) [[likely]]
-		return;
-	// Allocate space for terminator as well
-	char *nb = new char[newCapacity + 1];
-	if (size_ > 0 && buffer_) {
-		std::memcpy(nb, buffer_, size_);
-	}
-	delete[] buffer_;
-	buffer_   = nb;
-	capacity_ = newCapacity;
-	setTerminator();
-}
-
-
-void
-GapBuffer::AppendChar(const char c)
-{
-	ensureCapacityFor(1);
-	buffer_[size_++] = c;
-	setTerminator();
-}
-
-
-void
-GapBuffer::Append(const char *s, const std::size_t len)
-{
-	if (!s || len == 0) [[unlikely]]
-		return;
-	ensureCapacityFor(len);
-	std::memcpy(buffer_ + size_, s, len);
-	size_ += len;
-	setTerminator();
-}
-
-
-void
-GapBuffer::Append(const GapBuffer &other)
-{
-	if (other.size_ == 0)
-		return;
-	Append(other.buffer_, other.size_);
-}
-
-
-void
-GapBuffer::PrependChar(char c)
-{
-	ensureCapacityFor(1);
-	// shift right by 1
-	if (size_ > 0) [[likely]] {
-		std::memmove(buffer_ + 1, buffer_, size_);
-	}
-	buffer_[0] = c;
-	++size_;
-	setTerminator();
-}
-
-
-void
-GapBuffer::Prepend(const char *s, std::size_t len)
-{
-	if (!s || len == 0) [[unlikely]]
-		return;
-	ensureCapacityFor(len);
-	if (size_ > 0) [[likely]] {
-		std::memmove(buffer_ + len, buffer_, size_);
-	}
-	std::memcpy(buffer_, s, len);
-	size_ += len;
-	setTerminator();
-}
-
-
-void
-GapBuffer::Prepend(const GapBuffer &other)
-{
-	if (other.size_ == 0)
-		return;
-	Prepend(other.buffer_, other.size_);
-}
-
-
-void
-GapBuffer::Clear()
-{
-	size_ = 0;
-	setTerminator();
-}
-
-
-void
-GapBuffer::ensureCapacityFor(std::size_t delta)
-{
-	if (capacity_ - size_ >= delta) [[likely]]
-		return;
-	auto required = size_ + delta;
-	Reserve(growCapacity(capacity_, required));
-}
-
-
-std::size_t
-GapBuffer::growCapacity(std::size_t current, std::size_t required)
-{
-	// geometric growth, at least required
-	std::size_t newCap = current ? current : 8;
-	while (newCap < required)
-		newCap = newCap + (newCap >> 1); // 1.5x growth
-	return newCap;
-}
-
-
-void
-GapBuffer::setTerminator() const
-{
-	if (!buffer_) {
-		return;
-	}
-
-	buffer_[size_] = '\0';
-}

GapBuffer.h

@@ -1,76 +0,0 @@
-/*
- * GapBuffer.h - C++ replacement for abuf append/prepend buffer utilities
- */
-#pragma once
-#include <cstddef>
-
-
-class GapBuffer {
-public:
-	GapBuffer();
-
-	explicit GapBuffer(std::size_t initialCapacity);
-
-	GapBuffer(const GapBuffer &other);
-
-	GapBuffer &operator=(const GapBuffer &other);
-
-	GapBuffer(GapBuffer &&other) noexcept;
-
-	GapBuffer &operator=(GapBuffer &&other) noexcept;
-
-	~GapBuffer();
-
-	void Reserve(std::size_t newCapacity);
-
-
-	void AppendChar(char c);
-
-	void Append(const char *s, std::size_t len);
-
-	void Append(const GapBuffer &other);
-
-	void PrependChar(char c);
-
-	void Prepend(const char *s, std::size_t len);
-
-	void Prepend(const GapBuffer &other);
-
-	// Content management
-	void Clear();
-
-	// Accessors
-	char *Data()
-	{
-		return buffer_;
-	}
-
-
-	[[nodiscard]] const char *Data() const
-	{
-		return buffer_;
-	}
-
-
-	[[nodiscard]] std::size_t Size() const
-	{
-		return size_;
-	}
-
-
-	[[nodiscard]] std::size_t Capacity() const
-	{
-		return capacity_;
-	}
-
-private:
-	void ensureCapacityFor(std::size_t delta);
-
-	static std::size_t growCapacity(std::size_t current, std::size_t required);
-
-	void setTerminator() const;
-
-	char *buffer_         = nullptr;
-	std::size_t size_     = 0; // number of valid bytes (excluding terminator)
-	std::size_t capacity_ = 0; // capacity of buffer_ excluding space for terminator
-};

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"

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) {
@@ -294,25 +295,34 @@ ImGuiInputHandler::ProcessSDLEvent(const SDL_Event &e)
 	bool produced = false;
 	switch (e.type) {
 	case SDL_MOUSEWHEEL: {
-		// Let ImGui handle mouse wheel when it wants to capture the mouse
-		// (e.g., when hovering the editor child window with scrollbars).
-		// This enables native vertical and horizontal scrolling behavior in GUI.
-		if (ImGui::GetIO().WantCaptureMouse)
-			return false;
-		// Otherwise, fallback to mapping vertical wheel to editor scroll commands.
-		int dy = e.wheel.y;
+		// High-resolution trackpads can deliver fractional wheel deltas. Accumulate
+		// precise values and emit one scroll step per whole unit.
+		float dy = 0.0f;
+#if SDL_VERSION_ATLEAST(2,0,18)
+		dy = e.wheel.preciseY;
+#else
+		dy = static_cast<float>(e.wheel.y);
+#endif
 #ifdef SDL_MOUSEWHEEL_FLIPPED
 		if (e.wheel.direction == SDL_MOUSEWHEEL_FLIPPED)
 			dy = -dy;
 #endif
-		if (dy != 0) {
-			int repeat   = dy > 0 ? dy : -dy;
-			CommandId id = dy > 0 ? CommandId::ScrollUp : CommandId::ScrollDown;
-			std::lock_guard<std::mutex> lk(mu_);
-			for (int i = 0; i < repeat; ++i) {
-				q_.push(MappedInput{true, id, std::string(), 0});
+		if (dy != 0.0f) {
+			wheel_accum_y_ += dy;
+			float abs_accum = wheel_accum_y_ >= 0.0f ? wheel_accum_y_ : -wheel_accum_y_;
+			int steps       = static_cast<int>(abs_accum);
+			if (steps > 0) {
+				CommandId id = (wheel_accum_y_ > 0.0f) ? CommandId::ScrollUp : CommandId::ScrollDown;
+				std::lock_guard<std::mutex> lk(mu_);
+				for (int i = 0; i < steps; ++i) {
+					q_.push(MappedInput{true, id, std::string(), 0});
+				}
+				// remove the whole steps, keep fractional remainder
+				wheel_accum_y_ += (wheel_accum_y_ > 0.0f)
+					                  ? -static_cast<float>(steps)
+					                  : static_cast<float>(steps);
+				return true; // consumed
 			}
-			return true; // consumed
 		}
 		return false;
 	}
@@ -463,16 +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_;

ImGuiInputHandler.h

@@ -41,4 +41,9 @@ private:
 	bool suppress_text_input_once_ = false;
 
 	Editor *ed_ = nullptr; // attached editor for editor-owned uarg handling
+
+	// Accumulators for high-resolution (trackpad) scrolling. We emit one scroll
+	// command per whole step and keep the fractional remainder.
+	float wheel_accum_y_ = 0.0f;
+	float wheel_accum_x_ = 0.0f; // reserved for future horizontal scrolling
 };

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

@@ -1,5 +1,7 @@
 #include <algorithm>
 #include <utility>
+#include <limits>
+#include <ostream>
 
 #include "PieceTable.h"
 
@@ -14,13 +16,32 @@ PieceTable::PieceTable(const std::size_t initialCapacity)
 }
 
 
+PieceTable::PieceTable(const std::size_t initialCapacity,
+                       const std::size_t piece_limit,
+                       const std::size_t small_piece_threshold,
+                       const std::size_t max_consolidation_bytes)
+{
+	add_.reserve(initialCapacity);
+	materialized_.reserve(initialCapacity);
+	piece_limit_             = piece_limit;
+	small_piece_threshold_   = small_piece_threshold;
+	max_consolidation_bytes_ = max_consolidation_bytes;
+}
+
+
 PieceTable::PieceTable(const PieceTable &other)
 	: original_(other.original_),
 	  add_(other.add_),
 	  pieces_(other.pieces_),
 	  materialized_(other.materialized_),
 	  dirty_(other.dirty_),
-	  total_size_(other.total_size_) {}
+	  total_size_(other.total_size_)
+{
+	version_ = other.version_;
+	// caches are per-instance, mark invalid
+	range_cache_ = {};
+	find_cache_  = {};
+}
 
 
 PieceTable &
@@ -34,6 +55,9 @@ PieceTable::operator=(const PieceTable &other)
 	materialized_ = other.materialized_;
 	dirty_        = other.dirty_;
 	total_size_   = other.total_size_;
+	version_      = other.version_;
+	range_cache_  = {};
+	find_cache_   = {};
 	return *this;
 }
 
@@ -48,6 +72,9 @@ PieceTable::PieceTable(PieceTable &&other) noexcept
 {
 	other.dirty_      = true;
 	other.total_size_ = 0;
+	version_          = other.version_;
+	range_cache_      = {};
+	find_cache_       = {};
 }
 
 
@@ -64,6 +91,9 @@ PieceTable::operator=(PieceTable &&other) noexcept
 	total_size_       = other.total_size_;
 	other.dirty_      = true;
 	other.total_size_ = 0;
+	version_          = other.version_;
+	range_cache_      = {};
+	find_cache_       = {};
 	return *this;
 }
 
@@ -79,6 +109,21 @@ PieceTable::Reserve(const std::size_t newCapacity)
 }
 
 
+// Setter to allow tuning consolidation heuristics
+void
+PieceTable::SetConsolidationParams(const std::size_t piece_limit,
+                                   const std::size_t small_piece_threshold,
+                                   const std::size_t max_consolidation_bytes)
+{
+	piece_limit_             = piece_limit;
+	small_piece_threshold_   = small_piece_threshold;
+	max_consolidation_bytes_ = max_consolidation_bytes;
+}
+
+
+// (removed helper) — we'll invalidate caches inline inside mutating methods
+
+
 void
 PieceTable::AppendChar(char c)
 {
@@ -151,6 +196,11 @@ PieceTable::Clear()
 	materialized_.clear();
 	total_size_ = 0;
 	dirty_      = true;
+	line_index_.clear();
+	line_index_dirty_ = true;
+	version_++;
+	range_cache_ = {};
+	find_cache_  = {};
 }
 
 
@@ -171,6 +221,9 @@ PieceTable::addPieceBack(const Source src, const std::size_t start, const std::s
 				last.len += len;
 				total_size_ += len;
 				dirty_ = true;
+				version_++;
+				range_cache_ = {};
+				find_cache_  = {};
 				return;
 			}
 		}
@@ -179,6 +232,10 @@ PieceTable::addPieceBack(const Source src, const std::size_t start, const std::s
 	pieces_.push_back(Piece{src, start, len});
 	total_size_ += len;
 	dirty_ = true;
+	InvalidateLineIndex();
+	version_++;
+	range_cache_ = {};
+	find_cache_  = {};
 }
 
 
@@ -197,12 +254,19 @@ PieceTable::addPieceFront(Source src, std::size_t start, std::size_t len)
 			first.len += len;
 			total_size_ += len;
 			dirty_ = true;
+			version_++;
+			range_cache_ = {};
+			find_cache_  = {};
 			return;
 		}
 	}
 	pieces_.insert(pieces_.begin(), Piece{src, start, len});
 	total_size_ += len;
 	dirty_ = true;
+	InvalidateLineIndex();
+	version_++;
+	range_cache_ = {};
+	find_cache_  = {};
 }
 
 
@@ -225,3 +289,486 @@ PieceTable::materialize() const
 	// Ensure there is a null terminator present via std::string invariants
 	dirty_ = false;
 }
+
+
+// ===== New Phase 1 implementation =====
+
+std::pair<std::size_t, std::size_t>
+PieceTable::locate(const std::size_t byte_offset) const
+{
+	if (byte_offset >= total_size_) {
+		return {pieces_.size(), 0};
+	}
+	std::size_t off = byte_offset;
+	for (std::size_t i = 0; i < pieces_.size(); ++i) {
+		const auto &p = pieces_[i];
+		if (off < p.len) {
+			return {i, off};
+		}
+		off -= p.len;
+	}
+	// Should not reach here unless inconsistency; return end
+	return {pieces_.size(), 0};
+}
+
+
+void
+PieceTable::coalesceNeighbors(std::size_t index)
+{
+	if (pieces_.empty())
+		return;
+	if (index >= pieces_.size())
+		index = pieces_.size() - 1;
+	// Merge repeatedly with previous while contiguous and same source
+	while (index > 0) {
+		auto &prev = pieces_[index - 1];
+		auto &curr = pieces_[index];
+		if (prev.src == curr.src && prev.start + prev.len == curr.start) {
+			prev.len += curr.len;
+			pieces_.erase(pieces_.begin() + static_cast<std::ptrdiff_t>(index));
+			index -= 1;
+		} else {
+			break;
+		}
+	}
+	// Merge repeatedly with next while contiguous and same source
+	while (index + 1 < pieces_.size()) {
+		auto &curr = pieces_[index];
+		auto &next = pieces_[index + 1];
+		if (curr.src == next.src && curr.start + curr.len == next.start) {
+			curr.len += next.len;
+			pieces_.erase(pieces_.begin() + static_cast<std::ptrdiff_t>(index + 1));
+		} else {
+			break;
+		}
+	}
+}
+
+
+void
+PieceTable::InvalidateLineIndex() const
+{
+	line_index_dirty_ = true;
+}
+
+
+void
+PieceTable::RebuildLineIndex() const
+{
+	if (!line_index_dirty_)
+		return;
+	line_index_.clear();
+	line_index_.push_back(0);
+	std::size_t pos = 0;
+	for (const auto &pc: pieces_) {
+		const std::string &src = pc.src == Source::Original ? original_ : add_;
+		const char *base       = src.data() + static_cast<std::ptrdiff_t>(pc.start);
+		for (std::size_t j = 0; j < pc.len; ++j) {
+			if (base[j] == '\n') {
+				// next line starts after the newline
+				line_index_.push_back(pos + j + 1);
+			}
+		}
+		pos += pc.len;
+	}
+	line_index_dirty_ = false;
+}
+
+
+void
+PieceTable::Insert(std::size_t byte_offset, const char *text, std::size_t len)
+{
+	if (len == 0) {
+		return;
+	}
+	if (byte_offset > total_size_) {
+		byte_offset = total_size_;
+	}
+
+	const std::size_t add_start = add_.size();
+	add_.append(text, len);
+
+	if (pieces_.empty()) {
+		pieces_.push_back(Piece{Source::Add, add_start, len});
+		total_size_ += len;
+		dirty_ = true;
+		InvalidateLineIndex();
+		maybeConsolidate();
+		version_++;
+		range_cache_ = {};
+		find_cache_  = {};
+		return;
+	}
+
+	auto [idx, inner] = locate(byte_offset);
+	if (idx == pieces_.size()) {
+		// insert at end
+		pieces_.push_back(Piece{Source::Add, add_start, len});
+		total_size_ += len;
+		dirty_ = true;
+		InvalidateLineIndex();
+		coalesceNeighbors(pieces_.size() - 1);
+		maybeConsolidate();
+		version_++;
+		range_cache_ = {};
+		find_cache_  = {};
+		return;
+	}
+
+	Piece target = pieces_[idx];
+	// Build replacement sequence: left, inserted, right
+	std::vector<Piece> repl;
+	repl.reserve(3);
+	if (inner > 0) {
+		repl.push_back(Piece{target.src, target.start, inner});
+	}
+	repl.push_back(Piece{Source::Add, add_start, len});
+	const std::size_t right_len = target.len - inner;
+	if (right_len > 0) {
+		repl.push_back(Piece{target.src, target.start + inner, right_len});
+	}
+
+	// Replace target with repl
+	pieces_.erase(pieces_.begin() + static_cast<std::ptrdiff_t>(idx));
+	pieces_.insert(pieces_.begin() + static_cast<std::ptrdiff_t>(idx), repl.begin(), repl.end());
+
+	total_size_ += len;
+	dirty_ = true;
+	InvalidateLineIndex();
+	// Try coalescing around the inserted position (the inserted piece is at idx + (inner>0 ? 1 : 0))
+	std::size_t ins_index = idx + (inner > 0 ? 1 : 0);
+	coalesceNeighbors(ins_index);
+	maybeConsolidate();
+	version_++;
+	range_cache_ = {};
+	find_cache_  = {};
+}
+
+
+void
+PieceTable::Delete(std::size_t byte_offset, std::size_t len)
+{
+	if (len == 0) {
+		return;
+	}
+	if (byte_offset >= total_size_) {
+		return;
+	}
+	if (byte_offset + len > total_size_) {
+		len = total_size_ - byte_offset;
+	}
+
+	auto [idx, inner]     = locate(byte_offset);
+	std::size_t remaining = len;
+
+	while (remaining > 0 && idx < pieces_.size()) {
+		Piece &pc             = pieces_[idx];
+		std::size_t available = pc.len - inner; // bytes we can remove from this piece starting at inner
+		std::size_t take      = std::min(available, remaining);
+
+		// Compute lengths for left and right remnants
+		std::size_t left_len  = inner;
+		std::size_t right_len = pc.len - inner - take;
+		Source src            = pc.src;
+		std::size_t start     = pc.start;
+
+		// Replace current piece with up to two remnants
+		if (left_len > 0 && right_len > 0) {
+			pc.len = left_len; // keep left in place
+			Piece right{src, start + inner + take, right_len};
+			pieces_.insert(pieces_.begin() + static_cast<std::ptrdiff_t>(idx + 1), right);
+			idx += 1; // move to right for next iteration decision
+		} else if (left_len > 0) {
+			pc.len = left_len;
+			// no insertion; idx now points to left; move to next piece
+		} else if (right_len > 0) {
+			pc.start = start + inner + take;
+			pc.len   = right_len;
+		} else {
+			// entire piece removed
+			pieces_.erase(pieces_.begin() + static_cast<std::ptrdiff_t>(idx));
+			// stay at same idx for next piece
+			inner = 0;
+			remaining -= take;
+			continue;
+		}
+
+		// After modifying current idx, next deletion continues at beginning of the next logical region
+		inner = 0;
+		remaining -= take;
+		if (remaining == 0)
+			break;
+		// Move to next piece
+		idx += 1;
+	}
+
+	total_size_ -= len;
+	dirty_ = true;
+	InvalidateLineIndex();
+	if (idx < pieces_.size())
+		coalesceNeighbors(idx);
+	if (idx > 0)
+		coalesceNeighbors(idx - 1);
+	maybeConsolidate();
+	version_++;
+	range_cache_ = {};
+	find_cache_  = {};
+}
+
+
+// ===== Consolidation implementation =====
+
+void
+PieceTable::appendPieceDataTo(std::string &out, const Piece &p) const
+{
+	if (p.len == 0)
+		return;
+	const std::string &src = p.src == Source::Original ? original_ : add_;
+	out.append(src.data() + static_cast<std::ptrdiff_t>(p.start), p.len);
+}
+
+
+void
+PieceTable::consolidateRange(std::size_t start_idx, std::size_t end_idx)
+{
+	if (start_idx >= end_idx || start_idx >= pieces_.size())
+		return;
+	end_idx           = std::min(end_idx, pieces_.size());
+	std::size_t total = 0;
+	for (std::size_t i = start_idx; i < end_idx; ++i)
+		total += pieces_[i].len;
+	if (total == 0)
+		return;
+
+	const std::size_t add_start = add_.size();
+	std::string tmp;
+	tmp.reserve(std::min<std::size_t>(total, max_consolidation_bytes_));
+	for (std::size_t i = start_idx; i < end_idx; ++i)
+		appendPieceDataTo(tmp, pieces_[i]);
+	add_.append(tmp);
+
+	// Replace [start_idx, end_idx) with single Add piece
+	Piece consolidated{Source::Add, add_start, tmp.size()};
+	pieces_.erase(pieces_.begin() + static_cast<std::ptrdiff_t>(start_idx),
+	              pieces_.begin() + static_cast<std::ptrdiff_t>(end_idx));
+	pieces_.insert(pieces_.begin() + static_cast<std::ptrdiff_t>(start_idx), consolidated);
+
+	// total_size_ unchanged
+	dirty_ = true;
+	InvalidateLineIndex();
+	coalesceNeighbors(start_idx);
+	// Layout changed; invalidate caches/version
+	version_++;
+	range_cache_ = {};
+	find_cache_  = {};
+}
+
+
+void
+PieceTable::maybeConsolidate()
+{
+	if (pieces_.size() <= piece_limit_)
+		return;
+
+	// Find the first run of small pieces to consolidate
+	std::size_t n          = pieces_.size();
+	std::size_t best_start = n, best_end = n;
+	std::size_t i          = 0;
+	while (i < n) {
+		// Skip large pieces quickly
+		if (pieces_[i].len > small_piece_threshold_) {
+			i++;
+			continue;
+		}
+		std::size_t j     = i;
+		std::size_t bytes = 0;
+		while (j < n) {
+			const auto &p = pieces_[j];
+			if (p.len > small_piece_threshold_)
+				break;
+			if (bytes + p.len > max_consolidation_bytes_)
+				break;
+			bytes += p.len;
+			j++;
+		}
+		if (j - i >= 2 && bytes > 0) {
+			// consolidate runs of at least 2 pieces
+			best_start = i;
+			best_end   = j;
+			break; // do one run per call; subsequent ops can repeat if still over limit
+		}
+		i = j + 1;
+	}
+
+	if (best_start < best_end) {
+		consolidateRange(best_start, best_end);
+	}
+}
+
+
+std::size_t
+PieceTable::LineCount() const
+{
+	RebuildLineIndex();
+	return line_index_.empty() ? 0 : line_index_.size();
+}
+
+
+std::pair<std::size_t, std::size_t>
+PieceTable::GetLineRange(std::size_t line_num) const
+{
+	RebuildLineIndex();
+	if (line_index_.empty())
+		return {0, 0};
+	if (line_num >= line_index_.size())
+		return {0, 0};
+	std::size_t start = line_index_[line_num];
+	std::size_t end   = (line_num + 1 < line_index_.size()) ? line_index_[line_num + 1] : total_size_;
+	return {start, end};
+}
+
+
+std::string
+PieceTable::GetLine(std::size_t line_num) const
+{
+	auto [start, end] = GetLineRange(line_num);
+	if (end < start)
+		return std::string();
+	// Trim trailing '\n'
+	if (end > start) {
+		// To check last char, we can get it via GetRange of len 1 at end-1 without materializing whole
+		std::string last = GetRange(end - 1, 1);
+		if (!last.empty() && last[0] == '\n') {
+			end -= 1;
+		}
+	}
+	return GetRange(start, end - start);
+}
+
+
+std::pair<std::size_t, std::size_t>
+PieceTable::ByteOffsetToLineCol(std::size_t byte_offset) const
+{
+	if (byte_offset > total_size_)
+		byte_offset = total_size_;
+	RebuildLineIndex();
+	if (line_index_.empty())
+		return {0, 0};
+	auto it         = std::upper_bound(line_index_.begin(), line_index_.end(), byte_offset);
+	std::size_t row = (it == line_index_.begin()) ? 0 : static_cast<std::size_t>((it - line_index_.begin()) - 1);
+	std::size_t col = byte_offset - line_index_[row];
+	return {row, col};
+}
+
+
+std::size_t
+PieceTable::LineColToByteOffset(std::size_t row, std::size_t col) const
+{
+	RebuildLineIndex();
+	if (line_index_.empty())
+		return 0;
+	if (row >= line_index_.size())
+		return total_size_;
+	std::size_t start = line_index_[row];
+	std::size_t end   = (row + 1 < line_index_.size()) ? line_index_[row + 1] : total_size_;
+	// Clamp col to line length excluding trailing newline
+	if (end > start) {
+		std::string last = GetRange(end - 1, 1);
+		if (!last.empty() && last[0] == '\n') {
+			end -= 1;
+		}
+	}
+	std::size_t target = start + std::min(col, end - start);
+	return target;
+}
+
+
+std::string
+PieceTable::GetRange(std::size_t byte_offset, std::size_t len) const
+{
+	if (byte_offset >= total_size_ || len == 0)
+		return std::string();
+	if (byte_offset + len > total_size_)
+		len = total_size_ - byte_offset;
+
+	// Fast path: return cached value if version/offset/len match
+	if (range_cache_.valid && range_cache_.version == version_ &&
+	    range_cache_.off == byte_offset && range_cache_.len == len) {
+		return range_cache_.data;
+	}
+
+	std::string out;
+	out.reserve(len);
+	if (!dirty_) {
+		// Already materialized; slice directly
+		out.assign(materialized_.data() + static_cast<std::ptrdiff_t>(byte_offset), len);
+	} else {
+		// Assemble substring directly from pieces without full materialization
+		auto [idx, inner]     = locate(byte_offset);
+		std::size_t remaining = len;
+		while (remaining > 0 && idx < pieces_.size()) {
+			const auto &p          = pieces_[idx];
+			const std::string &src = (p.src == Source::Original) ? original_ : add_;
+			std::size_t take       = std::min<std::size_t>(p.len - inner, remaining);
+			if (take > 0) {
+				const char *base = src.data() + static_cast<std::ptrdiff_t>(p.start + inner);
+				out.append(base, take);
+				remaining -= take;
+				inner = 0;
+				idx += 1;
+			} else {
+				break;
+			}
+		}
+	}
+
+	// Update cache
+	range_cache_.valid   = true;
+	range_cache_.version = version_;
+	range_cache_.off     = byte_offset;
+	range_cache_.len     = len;
+	range_cache_.data    = out;
+	return out;
+}
+
+
+std::size_t
+PieceTable::Find(const std::string &needle, std::size_t start) const
+{
+	if (needle.empty())
+		return start <= total_size_ ? start : std::numeric_limits<std::size_t>::max();
+	if (start > total_size_)
+		return std::numeric_limits<std::size_t>::max();
+	if (find_cache_.valid &&
+	    find_cache_.version == version_ &&
+	    find_cache_.needle == needle &&
+	    find_cache_.start == start) {
+		return find_cache_.result;
+	}
+
+	materialize();
+	auto pos = materialized_.find(needle, start);
+	if (pos == std::string::npos)
+		pos = std::numeric_limits<std::size_t>::max();
+	// Update cache
+	find_cache_.valid   = true;
+	find_cache_.version = version_;
+	find_cache_.needle  = needle;
+	find_cache_.start   = start;
+	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

@@ -3,8 +3,11 @@
  */
 #pragma once
 #include <cstddef>
+#include <cstdint>
 #include <string>
+#include <ostream>
 #include <vector>
+#include <limits>
 
 
 class PieceTable {
@@ -13,6 +16,12 @@ public:
 
 	explicit PieceTable(std::size_t initialCapacity);
 
+	// Advanced constructor allowing configuration of consolidation heuristics
+	PieceTable(std::size_t initialCapacity,
+	           std::size_t piece_limit,
+	           std::size_t small_piece_threshold,
+	           std::size_t max_consolidation_bytes);
+
 	PieceTable(const PieceTable &other);
 
 	PieceTable &operator=(const PieceTable &other);
@@ -68,6 +77,38 @@ public:
 		return materialized_.capacity();
 	}
 
+
+	// ===== New buffer-wide API (Phase 1) =====
+	// Byte-based editing operations
+	void Insert(std::size_t byte_offset, const char *text, std::size_t len);
+
+	void Delete(std::size_t byte_offset, std::size_t len);
+
+	// Line-based queries
+	[[nodiscard]] std::size_t LineCount() const; // number of logical lines
+	[[nodiscard]] std::string GetLine(std::size_t line_num) const;
+
+	[[nodiscard]] std::pair<std::size_t, std::size_t> GetLineRange(std::size_t line_num) const; // [start,end)
+
+	// Position conversion
+	[[nodiscard]] std::pair<std::size_t, std::size_t> ByteOffsetToLineCol(std::size_t byte_offset) const;
+
+	[[nodiscard]] std::size_t LineColToByteOffset(std::size_t row, std::size_t col) const;
+
+	// Substring extraction
+	[[nodiscard]] std::string GetRange(std::size_t byte_offset, std::size_t len) const;
+
+	// 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,
+	                            std::size_t max_consolidation_bytes);
+
 private:
 	enum class Source : unsigned char { Original, Add };
 
@@ -83,12 +124,61 @@ private:
 
 	void materialize() const;
 
+	// Helper: locate piece index and inner offset for a global byte offset
+	[[nodiscard]] std::pair<std::size_t, std::size_t> locate(std::size_t byte_offset) const;
+
+	// Helper: try to coalesce neighboring pieces around index
+	void coalesceNeighbors(std::size_t index);
+
+	// Consolidation helpers and heuristics
+	void maybeConsolidate();
+
+	void consolidateRange(std::size_t start_idx, std::size_t end_idx);
+
+	void appendPieceDataTo(std::string &out, const Piece &p) const;
+
+	// Line index support (rebuilt lazily on demand)
+	void InvalidateLineIndex() const;
+
+	void RebuildLineIndex() const;
+
 	// Underlying storages
 	std::string original_; // unused for builder use-case, but kept for API symmetry
 	std::string add_;
 	std::vector<Piece> pieces_;
 
 	mutable std::string materialized_;
-	mutable bool dirty_     = true;
-	std::size_t total_size_ = 0;
-};
+	mutable bool dirty_ = true;
+	// Monotonic content version. Increment on any mutation that affects content layout
+	mutable std::uint64_t version_ = 0;
+	std::size_t total_size_        = 0;
+
+	// Cached line index: starting byte offset of each line (always contains at least 1 entry: 0)
+	mutable std::vector<std::size_t> line_index_;
+	mutable bool line_index_dirty_ = true;
+
+	// Heuristic knobs
+	std::size_t piece_limit_             = 4096; // trigger consolidation when exceeded
+	std::size_t small_piece_threshold_   = 64; // bytes
+	std::size_t max_consolidation_bytes_ = 4096; // cap per consolidation run
+
+	// Lightweight caches to avoid redundant work when callers query the same range repeatedly
+	struct RangeCache {
+		bool valid            = false;
+		std::uint64_t version = 0;
+		std::size_t off       = 0;
+		std::size_t len       = 0;
+		std::string data;
+	};
+
+	struct FindCache {
+		bool valid            = false;
+		std::uint64_t version = 0;
+		std::string needle;
+		std::size_t start  = 0;
+		std::size_t result = std::numeric_limits<std::size_t>::max();
+	};
+
+	mutable RangeCache range_cache_;
+	mutable FindCache find_cache_;
+};

QtFrontend.cc

@@ -142,9 +142,11 @@ protected:
 				p.save();
 				p.setClipRect(viewport);
 
-				// Iterate visible lines
-				for (std::size_t i = rowoffs, vis_idx = 0; i < last_row; ++i, ++vis_idx) {
-					const auto &line   = static_cast<const std::string &>(lines[i]);
+    // 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();
 

TerminalFrontend.cc

@@ -42,13 +42,15 @@ TerminalFrontend::Init(Editor &ed)
 	meta(stdscr, TRUE);
 	// Make ESC key sequences resolve quickly so ESC+<key> works as meta
 #ifdef set_escdelay
-	set_escdelay(50);
+	set_escdelay(TerminalFrontend::kEscDelayMs);
 #endif
-	nodelay(stdscr, TRUE);
+	// Make getch() block briefly instead of busy-looping; reduces CPU when idle
+	// Equivalent to nodelay(FALSE) with a small timeout.
+	timeout(16); // ~16ms (about 60Hz)
 	curs_set(1);
 	// Enable mouse support if available
 	mouseinterval(0);
-	mousemask(ALL_MOUSE_EVENTS, nullptr);
+	mousemask(ALL_MOUSE_EVENTS | REPORT_MOUSE_POSITION, nullptr);
 
 	int r = 0, c = 0;
 	getmaxyx(stdscr, r, c);
@@ -57,6 +59,20 @@ TerminalFrontend::Init(Editor &ed)
 	ed.SetDimensions(static_cast<std::size_t>(r), static_cast<std::size_t>(c));
 	// Attach editor to input handler for editor-owned features (e.g., universal argument)
 	input_.Attach(&ed);
+
+	// Ignore SIGINT (Ctrl-C) so it doesn't terminate the TUI.
+	// We'll restore the previous handler on Shutdown().
+	{
+		struct sigaction sa{};
+		sa.sa_handler = SIG_IGN;
+		sigemptyset(&sa.sa_mask);
+		sa.sa_flags = 0;
+		struct sigaction old{};
+		if (sigaction(SIGINT, &sa, &old) == 0) {
+			old_sigint_      = old;
+			have_old_sigint_ = true;
+		}
+	}
 	return true;
 }
 
@@ -80,9 +96,6 @@ TerminalFrontend::Step(Editor &ed, bool &running)
 		if (mi.hasCommand) {
 			Execute(ed, mi.id, mi.arg, mi.count);
 		}
-	} else {
-		// Avoid busy loop
-		usleep(1000);
 	}
 
 	if (ed.QuitRequested()) {
@@ -101,5 +114,10 @@ TerminalFrontend::Shutdown()
 		(void) tcsetattr(STDIN_FILENO, TCSANOW, &orig_tio_);
 		have_orig_tio_ = false;
 	}
+	// Restore previous SIGINT handler
+	if (have_old_sigint_) {
+		(void) sigaction(SIGINT, &old_sigint_, nullptr);
+		have_old_sigint_ = false;
+	}
 	endwin();
 }

TerminalFrontend.h

@@ -3,6 +3,7 @@
  */
 #pragma once
 #include <termios.h>
+#include <signal.h>
 
 #include "Frontend.h"
 #include "TerminalInputHandler.h"
@@ -15,6 +16,11 @@ public:
 
 	~TerminalFrontend() override = default;
 
+	// Configurable ESC key delay (ms) for ncurses' set_escdelay().
+	// Controls how long ncurses waits to distinguish ESC vs. meta sequences.
+	// Adjust if your terminal needs a different threshold.
+	static constexpr int kEscDelayMs = 50;
+
 	bool Init(Editor &ed) override;
 
 	void Step(Editor &ed, bool &running) override;
@@ -29,4 +35,7 @@ private:
 	// Saved terminal attributes to restore on shutdown
 	bool have_orig_tio_ = false;
 	struct termios orig_tio_{};
+	// Saved SIGINT handler to restore on shutdown
+	bool have_old_sigint_ = false;
+	struct sigaction old_sigint_{};
 };

TerminalInputHandler.cc

@@ -29,89 +29,95 @@ map_key_to_command(const int ch,
 	// Handle special keys from ncurses
 	// These keys exit k-prefix mode if active (user pressed C-k then a special key).
 	switch (ch) {
-		case KEY_MOUSE: {
-			k_prefix       = false;
-			k_ctrl_pending = false;
-			MEVENT ev{};
-			if (getmouse(&ev) == OK) {
-				// Mouse wheel → scroll viewport without moving cursor
+	case KEY_ENTER:
+		// Some terminals send KEY_ENTER distinct from '\n'/'\r'
+		k_prefix = false;
+		k_ctrl_pending = false;
+		out            = {true, CommandId::Newline, "", 0};
+		return true;
+	case KEY_MOUSE: {
+		k_prefix       = false;
+		k_ctrl_pending = false;
+		MEVENT ev{};
+		if (getmouse(&ev) == OK) {
+			// Mouse wheel → scroll viewport without moving cursor
 #ifdef BUTTON4_PRESSED
-				if (ev.bstate & (BUTTON4_PRESSED | BUTTON4_RELEASED | BUTTON4_CLICKED)) {
-					out = {true, CommandId::ScrollUp, "", 0};
-					return true;
-				}
+			if (ev.bstate & (BUTTON4_PRESSED | BUTTON4_RELEASED | BUTTON4_CLICKED)) {
+				out = {true, CommandId::ScrollUp, "", 0};
+				return true;
+			}
 #endif
 #ifdef BUTTON5_PRESSED
-				if (ev.bstate & (BUTTON5_PRESSED | BUTTON5_RELEASED | BUTTON5_CLICKED)) {
-					out = {true, CommandId::ScrollDown, "", 0};
-					return true;
-				}
-#endif
-				// React to left button click/press
-				if (ev.bstate & (BUTTON1_CLICKED | BUTTON1_PRESSED | BUTTON1_RELEASED)) {
-					char buf[64];
-					// Use screen coordinates; command handler will translate via offsets
-					std::snprintf(buf, sizeof(buf), "@%d:%d", ev.y, ev.x);
-					out = {true, CommandId::MoveCursorTo, std::string(buf), 0};
-					return true;
-				}
+			if (ev.bstate & (BUTTON5_PRESSED | BUTTON5_RELEASED | BUTTON5_CLICKED)) {
+				out = {true, CommandId::ScrollDown, "", 0};
+				return true;
+			}
+#endif
+			// React to left button click/press
+			if (ev.bstate & (BUTTON1_CLICKED | BUTTON1_PRESSED | BUTTON1_RELEASED)) {
+				char buf[64];
+				// Use screen coordinates; command handler will translate via offsets
+				std::snprintf(buf, sizeof(buf), "@%d:%d", ev.y, ev.x);
+				out = {true, CommandId::MoveCursorTo, std::string(buf), 0};
+				return true;
 			}
-			// No actionable mouse event
-			out.hasCommand = false;
-			return true;
 		}
-		case KEY_LEFT:
-			k_prefix = false;
-			k_ctrl_pending = false;
-			out            = {true, CommandId::MoveLeft, "", 0};
-			return true;
-		case KEY_RIGHT:
-			k_prefix = false;
-			k_ctrl_pending = false;
-			out            = {true, CommandId::MoveRight, "", 0};
-			return true;
-		case KEY_UP:
-			k_prefix = false;
-			k_ctrl_pending = false;
-			out            = {true, CommandId::MoveUp, "", 0};
-			return true;
-		case KEY_DOWN:
-			k_prefix = false;
-			k_ctrl_pending = false;
-			out            = {true, CommandId::MoveDown, "", 0};
-			return true;
-		case KEY_HOME:
-			k_prefix = false;
-			k_ctrl_pending = false;
-			out            = {true, CommandId::MoveHome, "", 0};
-			return true;
-		case KEY_END:
-			k_prefix = false;
-			k_ctrl_pending = false;
-			out            = {true, CommandId::MoveEnd, "", 0};
-			return true;
-		case KEY_PPAGE:
-			k_prefix = false;
-			k_ctrl_pending = false;
-			out            = {true, CommandId::PageUp, "", 0};
-			return true;
-		case KEY_NPAGE:
-			k_prefix = false;
-			k_ctrl_pending = false;
-			out            = {true, CommandId::PageDown, "", 0};
-			return true;
-		case KEY_DC:
-			k_prefix = false;
-			k_ctrl_pending = false;
-			out            = {true, CommandId::DeleteChar, "", 0};
-			return true;
-		case KEY_RESIZE:
-			k_prefix = false;
-			k_ctrl_pending = false;
-			out            = {true, CommandId::Refresh, "", 0};
-			return true;
-		default:
-			break;
+		// No actionable mouse event
+		out.hasCommand = false;
+		return true;
+	}
+	case KEY_LEFT:
+		k_prefix = false;
+		k_ctrl_pending = false;
+		out            = {true, CommandId::MoveLeft, "", 0};
+		return true;
+	case KEY_RIGHT:
+		k_prefix = false;
+		k_ctrl_pending = false;
+		out            = {true, CommandId::MoveRight, "", 0};
+		return true;
+	case KEY_UP:
+		k_prefix = false;
+		k_ctrl_pending = false;
+		out            = {true, CommandId::MoveUp, "", 0};
+		return true;
+	case KEY_DOWN:
+		k_prefix = false;
+		k_ctrl_pending = false;
+		out            = {true, CommandId::MoveDown, "", 0};
+		return true;
+	case KEY_HOME:
+		k_prefix = false;
+		k_ctrl_pending = false;
+		out            = {true, CommandId::MoveHome, "", 0};
+		return true;
+	case KEY_END:
+		k_prefix = false;
+		k_ctrl_pending = false;
+		out            = {true, CommandId::MoveEnd, "", 0};
+		return true;
+	case KEY_PPAGE:
+		k_prefix = false;
+		k_ctrl_pending = false;
+		out            = {true, CommandId::PageUp, "", 0};
+		return true;
+	case KEY_NPAGE:
+		k_prefix = false;
+		k_ctrl_pending = false;
+		out            = {true, CommandId::PageDown, "", 0};
+		return true;
+	case KEY_DC:
+		k_prefix = false;
+		k_ctrl_pending = false;
+		out            = {true, CommandId::DeleteChar, "", 0};
+		return true;
+	case KEY_RESIZE:
+		k_prefix = false;
+		k_ctrl_pending = false;
+		out            = {true, CommandId::Refresh, "", 0};
+		return true;
+	default:
+		break;
 	}
 
 	// ESC as cancel of prefix; many terminals send meta sequences as ESC+...
@@ -172,14 +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

bench/BufferBench.cc

@@ -1,206 +0,0 @@
-/*
- * BufferBench.cc - microbenchmarks for GapBuffer and PieceTable
- *
- * This benchmark exercises the public APIs shared by both structures as used
- * in Buffer::Line: Reserve, AppendChar, Append, PrependChar, Prepend, Clear.
- *
- * Run examples:
- *   ./kte_bench_buffer                  # defaults
- *   ./kte_bench_buffer 200000 8 4096    # N=200k, rounds=8, chunk=4096
- */
-
-#include <chrono>
-#include <cstdint>
-#include <cstring>
-#include <iomanip>
-#include <iostream>
-#include <random>
-#include <string>
-#include <vector>
-#include <typeinfo>
-
-#include "GapBuffer.h"
-#include "PieceTable.h"
-
-using clock_t = std::chrono::steady_clock;
-using us      = std::chrono::microseconds;
-
-struct Result {
-	std::string name;
-	std::string scenario;
-	double micros     = 0.0;
-	std::size_t bytes = 0;
-};
-
-
-static void
-print_header()
-{
-	std::cout << std::left << std::setw(14) << "Structure"
-		<< std::left << std::setw(18) << "Scenario"
-		<< std::right << std::setw(12) << "time(us)"
-		<< std::right << std::setw(14) << "bytes"
-		<< std::right << std::setw(14) << "MB/s"
-		<< "\n";
-	std::cout << std::string(72, '-') << "\n";
-}
-
-
-static void
-print_row(const Result &r)
-{
-	double mb   = r.bytes / (1024.0 * 1024.0);
-	double mbps = (r.micros > 0.0) ? (mb / (r.micros / 1'000'000.0)) : 0.0;
-	std::cout << std::left << std::setw(14) << r.name
-		<< std::left << std::setw(18) << r.scenario
-		<< std::right << std::setw(12) << std::fixed << std::setprecision(2) << r.micros
-		<< std::right << std::setw(14) << r.bytes
-		<< std::right << std::setw(14) << std::fixed << std::setprecision(2) << mbps
-		<< "\n";
-}
-
-
-template<typename Buf>
-Result
-bench_sequential_append(std::size_t N, int rounds)
-{
-	Result r;
-	r.name            = typeid(Buf).name();
-	r.scenario        = "seq_append";
-	const char c      = 'x';
-	auto start        = clock_t::now();
-	std::size_t bytes = 0;
-	for (int t = 0; t < rounds; ++t) {
-		Buf b;
-		b.Reserve(N);
-		for (std::size_t i = 0; i < N; ++i) {
-			b.AppendChar(c);
-		}
-		bytes += N;
-	}
-	auto end = clock_t::now();
-	r.micros = std::chrono::duration_cast<us>(end - start).count();
-	r.bytes  = bytes;
-	return r;
-}
-
-
-template<typename Buf>
-Result
-bench_sequential_prepend(std::size_t N, int rounds)
-{
-	Result r;
-	r.name            = typeid(Buf).name();
-	r.scenario        = "seq_prepend";
-	const char c      = 'x';
-	auto start        = clock_t::now();
-	std::size_t bytes = 0;
-	for (int t = 0; t < rounds; ++t) {
-		Buf b;
-		b.Reserve(N);
-		for (std::size_t i = 0; i < N; ++i) {
-			b.PrependChar(c);
-		}
-		bytes += N;
-	}
-	auto end = clock_t::now();
-	r.micros = std::chrono::duration_cast<us>(end - start).count();
-	r.bytes  = bytes;
-	return r;
-}
-
-
-template<typename Buf>
-Result
-bench_chunk_append(std::size_t N, std::size_t chunk, int rounds)
-{
-	Result r;
-	r.name     = typeid(Buf).name();
-	r.scenario = "chunk_append";
-	std::string payload(chunk, 'y');
-	auto start        = clock_t::now();
-	std::size_t bytes = 0;
-	for (int t = 0; t < rounds; ++t) {
-		Buf b;
-		b.Reserve(N);
-		std::size_t written = 0;
-		while (written < N) {
-			std::size_t now = std::min(chunk, N - written);
-			b.Append(payload.data(), now);
-			written += now;
-		}
-		bytes += N;
-	}
-	auto end = clock_t::now();
-	r.micros = std::chrono::duration_cast<us>(end - start).count();
-	r.bytes  = bytes;
-	return r;
-}
-
-
-template<typename Buf>
-Result
-bench_mixed(std::size_t N, std::size_t chunk, int rounds)
-{
-	Result r;
-	r.name     = typeid(Buf).name();
-	r.scenario = "mixed";
-	std::string payload(chunk, 'z');
-	auto start        = clock_t::now();
-	std::size_t bytes = 0;
-	for (int t = 0; t < rounds; ++t) {
-		Buf b;
-		b.Reserve(N);
-		std::size_t written = 0;
-		while (written < N) {
-			// alternate append/prepend with small chunks
-			std::size_t now = std::min(chunk, N - written);
-			if ((written / chunk) % 2 == 0) {
-				b.Append(payload.data(), now);
-			} else {
-				b.Prepend(payload.data(), now);
-			}
-			written += now;
-		}
-		bytes += N;
-	}
-	auto end = clock_t::now();
-	r.micros = std::chrono::duration_cast<us>(end - start).count();
-	r.bytes  = bytes;
-	return r;
-}
-
-
-int
-main(int argc, char **argv)
-{
-	// Parameters
-	std::size_t N     = 100'000; // bytes per round
-	int rounds        = 5; // iterations
-	std::size_t chunk = 1024; // chunk size for chunked scenarios
-	if (argc >= 2)
-		N = static_cast<std::size_t>(std::stoull(argv[1]));
-	if (argc >= 3)
-		rounds = std::stoi(argv[2]);
-	if (argc >= 4)
-		chunk = static_cast<std::size_t>(std::stoull(argv[3]));
-
-	std::cout << "KTE Buffer Microbenchmarks" << "\n";
-	std::cout << "N=" << N << ", rounds=" << rounds << ", chunk=" << chunk << "\n\n";
-
-	print_header();
-
-	// Run for GapBuffer
-	print_row(bench_sequential_append<GapBuffer>(N, rounds));
-	print_row(bench_sequential_prepend<GapBuffer>(N, rounds));
-	print_row(bench_chunk_append<GapBuffer>(N, chunk, rounds));
-	print_row(bench_mixed<GapBuffer>(N, chunk, rounds));
-
-	// Run for PieceTable
-	print_row(bench_sequential_append<PieceTable>(N, rounds));
-	print_row(bench_sequential_prepend<PieceTable>(N, rounds));
-	print_row(bench_chunk_append<PieceTable>(N, chunk, rounds));
-	print_row(bench_mixed<PieceTable>(N, chunk, rounds));
-
-	return 0;
-}

bench/PerformanceSuite.cc

@@ -1,318 +0,0 @@
-/*
- * PerformanceSuite.cc - broader performance and verification benchmarks
- */
-
-#include <algorithm>
-#include <cassert>
-#include <chrono>
-#include <cstddef>
-#include <cstdint>
-#include <cstring>
-#include <iomanip>
-#include <iostream>
-#include <random>
-#include <string>
-#include <typeinfo>
-#include <vector>
-
-#include "GapBuffer.h"
-#include "PieceTable.h"
-#include "OptimizedSearch.h"
-
-using clock_t = std::chrono::steady_clock;
-using us      = std::chrono::microseconds;
-
-namespace {
-struct Stat {
-	double micros{0.0};
-	std::size_t bytes{0};
-	std::size_t ops{0};
-};
-
-
-static void
-print_header(const std::string &title)
-{
-	std::cout << "\n" << title << "\n";
-	std::cout << std::left << std::setw(18) << "Case"
-		<< std::left << std::setw(18) << "Type"
-		<< std::right << std::setw(12) << "time(us)"
-		<< std::right << std::setw(14) << "bytes"
-		<< std::right << std::setw(14) << "ops/s"
-		<< std::right << std::setw(14) << "MB/s"
-		<< "\n";
-	std::cout << std::string(90, '-') << "\n";
-}
-
-
-static void
-print_row(const std::string &caseName, const std::string &typeName, const Stat &s)
-{
-	double mb   = s.bytes / (1024.0 * 1024.0);
-	double sec  = s.micros / 1'000'000.0;
-	double mbps = sec > 0 ? (mb / sec) : 0.0;
-	double opss = sec > 0 ? (static_cast<double>(s.ops) / sec) : 0.0;
-	std::cout << std::left << std::setw(18) << caseName
-		<< std::left << std::setw(18) << typeName
-		<< std::right << std::setw(12) << std::fixed << std::setprecision(2) << s.micros
-		<< std::right << std::setw(14) << s.bytes
-		<< std::right << std::setw(14) << std::fixed << std::setprecision(2) << opss
-		<< std::right << std::setw(14) << std::fixed << std::setprecision(2) << mbps
-		<< "\n";
-}
-} // namespace
-
-class PerformanceSuite {
-public:
-	void benchmarkBufferOperations(std::size_t N, int rounds, std::size_t chunk)
-	{
-		print_header("Buffer Operations");
-		run_buffer_case<GapBuffer>("append_char", N, rounds, chunk, [&](auto &b, std::size_t count) {
-			for (std::size_t i = 0; i < count; ++i)
-				b.AppendChar('a');
-		});
-		run_buffer_case<GapBuffer>("prepend_char", N, rounds, chunk, [&](auto &b, std::size_t count) {
-			for (std::size_t i = 0; i < count; ++i)
-				b.PrependChar('a');
-		});
-		run_buffer_case<GapBuffer>("chunk_mix", N, rounds, chunk, [&](auto &b, std::size_t) {
-			std::string payload(chunk, 'x');
-			std::size_t written = 0;
-			while (written < N) {
-				std::size_t now = std::min(chunk, N - written);
-				if (((written / chunk) & 1) == 0)
-					b.Append(payload.data(), now);
-				else
-					b.Prepend(payload.data(), now);
-				written += now;
-			}
-		});
-		run_buffer_case<PieceTable>("append_char", N, rounds, chunk, [&](auto &b, std::size_t count) {
-			for (std::size_t i = 0; i < count; ++i)
-				b.AppendChar('a');
-		});
-		run_buffer_case<PieceTable>("prepend_char", N, rounds, chunk, [&](auto &b, std::size_t count) {
-			for (std::size_t i = 0; i < count; ++i)
-				b.PrependChar('a');
-		});
-		run_buffer_case<PieceTable>("chunk_mix", N, rounds, chunk, [&](auto &b, std::size_t) {
-			std::string payload(chunk, 'x');
-			std::size_t written = 0;
-			while (written < N) {
-				std::size_t now = std::min(chunk, N - written);
-				if (((written / chunk) & 1) == 0)
-					b.Append(payload.data(), now);
-				else
-					b.Prepend(payload.data(), now);
-				written += now;
-			}
-		});
-	}
-
-
-	void benchmarkSearchOperations(std::size_t textLen, std::size_t patLen, int rounds)
-	{
-		print_header("Search Operations");
-		std::mt19937_64 rng(0xC0FFEE);
-		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 pattern(patLen, '\0');
-		for (auto &ch: pattern)
-			ch = static_cast<char>(dist(rng));
-
-		// Ensure at least one hit
-		if (textLen >= patLen && patLen > 0) {
-			std::size_t pos = textLen / 2;
-			std::memcpy(&text[pos], pattern.data(), patLen);
-		}
-
-		// OptimizedSearch find_all vs std::string reference
-		OptimizedSearch os;
-		Stat s{};
-		auto start               = clock_t::now();
-		std::size_t matches      = 0;
-		std::size_t bytesScanned = 0;
-		for (int r = 0; r < rounds; ++r) {
-			auto hits = os.find_all(text, pattern, 0);
-			matches += hits.size();
-			bytesScanned += text.size();
-			// Verify with reference
-			std::vector<std::size_t> ref;
-			std::size_t from = 0;
-			while (true) {
-				auto p = text.find(pattern, from);
-				if (p == std::string::npos)
-					break;
-				ref.push_back(p);
-				from = p + (patLen ? patLen : 1);
-			}
-			assert(ref == hits);
-		}
-		auto end = clock_t::now();
-		s.micros = std::chrono::duration_cast<us>(end - start).count();
-		s.bytes  = bytesScanned;
-		s.ops    = matches;
-		print_row("find_all", "OptimizedSearch", s);
-	}
-
-
-	void benchmarkMemoryAllocation(std::size_t N, int rounds)
-	{
-		print_header("Memory Allocation (allocations during editing)");
-		// Measure number of allocations by simulating editing patterns.
-		auto run_session = [&](auto &&buffer) {
-			// alternate small appends and prepends
-			const std::size_t chunk = 32;
-			std::string payload(chunk, 'q');
-			for (int r = 0; r < rounds; ++r) {
-				buffer.Clear();
-				for (std::size_t i = 0; i < N; i += chunk)
-					buffer.Append(payload.data(), std::min(chunk, N - i));
-				for (std::size_t i = 0; i < N / 2; i += chunk)
-					buffer.Prepend(payload.data(), std::min(chunk, N / 2 - i));
-			}
-		};
-
-		// Local allocation counters for this TU via overriding operators
-		reset_alloc_counters();
-		GapBuffer gb;
-		run_session(gb);
-		auto gap_allocs = current_allocs();
-		print_row("edit_session", "GapBuffer", Stat{
-			          0.0, static_cast<std::size_t>(gap_allocs.bytes),
-			          static_cast<std::size_t>(gap_allocs.count)
-		          });
-
-		reset_alloc_counters();
-		PieceTable pt;
-		run_session(pt);
-		auto pt_allocs = current_allocs();
-		print_row("edit_session", "PieceTable", Stat{
-			          0.0, static_cast<std::size_t>(pt_allocs.bytes),
-			          static_cast<std::size_t>(pt_allocs.count)
-		          });
-	}
-
-private:
-	template<typename Buf, typename Fn>
-	void run_buffer_case(const std::string &caseName, std::size_t N, int rounds, std::size_t chunk, Fn fn)
-	{
-		Stat s{};
-		auto start        = clock_t::now();
-		std::size_t bytes = 0;
-		std::size_t ops   = 0;
-		for (int t = 0; t < rounds; ++t) {
-			Buf b;
-			b.Reserve(N);
-			fn(b, N);
-			// compare to reference string where possible (only for append_char/prepend_char)
-			bytes += N;
-			ops += N / (chunk ? chunk : 1);
-		}
-		auto end = clock_t::now();
-		s.micros = std::chrono::duration_cast<us>(end - start).count();
-		s.bytes  = bytes;
-		s.ops    = ops;
-		print_row(caseName, typeid(Buf).name(), s);
-	}
-
-
-	// Simple global allocation tracking for this TU
-	struct AllocStats {
-		std::uint64_t count{0};
-		std::uint64_t bytes{0};
-	};
-
-
-	static AllocStats &alloc_stats()
-	{
-		static AllocStats s;
-		return s;
-	}
-
-
-	static void reset_alloc_counters()
-	{
-		alloc_stats() = {};
-	}
-
-
-	static AllocStats current_allocs()
-	{
-		return alloc_stats();
-	}
-
-
-	// Friend global new/delete defined below
-	friend void *operator new(std::size_t sz) noexcept(false);
-
-	friend void operator delete(void *p) noexcept;
-
-	friend void *operator new[](std::size_t sz) noexcept(false);
-
-	friend void operator delete[](void *p) noexcept;
-};
-
-// Override new/delete only in this translation unit to track allocations made here
-void *
-operator new(std::size_t sz) noexcept(false)
-{
-	auto &s = PerformanceSuite::alloc_stats();
-	s.count++;
-	s.bytes += sz;
-	if (void *p = std::malloc(sz))
-		return p;
-	throw std::bad_alloc();
-}
-
-
-void
-operator delete(void *p) noexcept
-{
-	std::free(p);
-}
-
-
-void *
-operator new[](std::size_t sz) noexcept(false)
-{
-	auto &s = PerformanceSuite::alloc_stats();
-	s.count++;
-	s.bytes += sz;
-	if (void *p = std::malloc(sz))
-		return p;
-	throw std::bad_alloc();
-}
-
-
-void
-operator delete[](void *p) noexcept
-{
-	std::free(p);
-}
-
-
-int
-main(int argc, char **argv)
-{
-	std::size_t N     = 200'000; // bytes per round for buffer cases
-	int rounds        = 3;
-	std::size_t chunk = 1024;
-	if (argc >= 2)
-		N = static_cast<std::size_t>(std::stoull(argv[1]));
-	if (argc >= 3)
-		rounds = std::stoi(argv[2]);
-	if (argc >= 4)
-		chunk = static_cast<std::size_t>(std::stoull(argv[3]));
-
-	std::cout << "KTE Performance Suite" << "\n";
-	std::cout << "N=" << N << ", rounds=" << rounds << ", chunk=" << chunk << "\n";
-
-	PerformanceSuite suite;
-	suite.benchmarkBufferOperations(N, rounds, chunk);
-	suite.benchmarkSearchOperations(1'000'000, 16, rounds);
-	suite.benchmarkMemoryAllocation(N, rounds);
-	return 0;
-}

default.nix

@@ -1,13 +1,15 @@
 {
-  lib,
+  pkgs ? import <nixpkgs> {},
+  lib ? pkgs.lib,
   stdenv,
   cmake,
   ncurses,
   SDL2,
   libGL,
   xorg,
+  kdePackages,
+  qt6Packages ? kdePackages.qt6Packages,
   installShellFiles,
-
   graphical ? false,
   graphical-qt ? false,
   ...
@@ -37,12 +39,13 @@ stdenv.mkDerivation {
     xorg.libX11
   ]
   ++ lib.optionals graphical-qt [
-    qt5Full
-    qtcreator ## not sure if this is actually needed
+    kdePackages.qt6ct
+    qt6Packages.qtbase
+    qt6Packages.wrapQtAppsHook
   ];
 
   cmakeFlags = [
-    "-DBUILD_GUI=${if graphical or graphical-qt then "ON" else "OFF"}"
+    "-DBUILD_GUI=${if graphical then "ON" else "OFF"}"
     "-DKTE_USE_QT=${if graphical-qt then "ON" else "OFF"}"
     "-DCMAKE_BUILD_TYPE=Debug"
   ];
@@ -52,17 +55,23 @@ stdenv.mkDerivation {
 
     mkdir -p $out/bin
     cp kte $out/bin/
-
     installManPage ../docs/kte.1
 
-  ''
-  + lib.optionalString graphical ''
-    cp kge $out/bin/
-    installManPage ../docs/kge.1
-    mkdir -p $out/share/icons
-    cp ../kge.png $out/share/icons/
-  ''
-  + ''
+    ${lib.optionalString graphical ''
+      mkdir -p $out/bin
+  
+    ${if graphical-qt then ''
+        cp kge $out/bin/kge-qt
+      '' else ''
+        cp kge $out/bin/kge
+      ''}
+
+      installManPage ../docs/kge.1
+
+      mkdir -p $out/share/icons/hicolor/256x256/apps
+      cp ../kge.png $out/share/icons/hicolor/256x256/apps/kge.png
+    ''}
+
     runHook postInstall
   '';
 }

docs/plans/piece-table-migration.md

@@ -0,0 +1,601 @@
+# PieceTable Migration Plan
+
+## Executive Summary
+
+This document outlines the plan to remove GapBuffer support from kte and
+migrate to using a **single PieceTable per Buffer**, rather than the
+current vector-of-Lines architecture where each Line contains either a
+GapBuffer or PieceTable.
+
+## Current Architecture Analysis
+
+### Text Storage
+
+**Current Implementation:**
+
+- `Buffer` contains `std::vector<Line> rows_`
+- Each `Line` wraps an `AppendBuffer` (type alias)
+- `AppendBuffer` is either `GapBuffer` (default) or `PieceTable` (via
+  `KTE_USE_PIECE_TABLE`)
+- Each line is independently managed with its own buffer
+- Operations are line-based with coordinate pairs (row, col)
+
+**Key Files:**
+
+- `Buffer.h/cc` - Buffer class with vector of Lines
+- `AppendBuffer.h` - Type selector (GapBuffer vs PieceTable)
+- `GapBuffer.h/cc` - Per-line gap buffer implementation
+- `PieceTable.h/cc` - Per-line piece table implementation
+- `UndoSystem.h/cc` - Records operations with (row, col, text)
+- `UndoNode.h` - Undo operation types (Insert, Delete, Paste, Newline,
+  DeleteRow)
+- `Command.cc` - High-level editing commands
+
+### Current Buffer API
+
+**Low-level editing operations (used by UndoSystem):**
+
+```cpp
+void insert_text(int row, int col, std::string_view text);
+void delete_text(int row, int col, std::size_t len);
+void split_line(int row, int col);
+void join_lines(int row);
+void insert_row(int row, std::string_view text);
+void delete_row(int row);
+```
+
+**Line access:**
+
+```cpp
+std::vector<Line> &Rows();
+const std::vector<Line> &Rows() const;
+```
+
+**Line API (Buffer::Line):**
+
+```cpp
+std::size_t size() const;
+const char *Data() const;
+char operator[](std::size_t i) const;
+std::string substr(std::size_t pos, std::size_t len) const;
+std::size_t find(const std::string &needle, std::size_t pos) const;
+void erase(std::size_t pos, std::size_t len);
+void insert(std::size_t pos, const std::string &seg);
+Line &operator+=(const Line &other);
+Line &operator+=(const std::string &s);
+```
+
+### Current PieceTable Limitations
+
+The existing `PieceTable` class only supports:
+
+- `Append(char/string)` - add to end
+- `Prepend(char/string)` - add to beginning
+- `Clear()` - empty the buffer
+- `Data()` / `Size()` - access content (materializes on demand)
+
+**Missing capabilities needed for buffer-wide storage:**
+
+- Insert at arbitrary byte position
+- Delete at arbitrary byte position
+- Line indexing and line-based queries
+- Position conversion (byte offset ↔ line/col)
+- Efficient line boundary tracking
+
+## Target Architecture
+
+### Design Overview
+
+**Single PieceTable per Buffer:**
+
+- `Buffer` contains one `PieceTable content_` (replaces
+  `std::vector<Line> rows_`)
+- Text stored as continuous byte sequence with `\n` as line separators
+- Line index cached for efficient line-based operations
+- All operations work on byte offsets internally
+- Buffer provides line/column API as convenience layer
+
+### Enhanced PieceTable Design
+
+```cpp
+class PieceTable {
+public:
+    // Existing API (keep for compatibility if needed)
+    void Append(const char *s, std::size_t len);
+    void Prepend(const char *s, std::size_t len);
+    void Clear();
+    const char *Data() const;
+    std::size_t Size() const;
+    
+    // NEW: Core byte-based editing operations
+    void Insert(std::size_t byte_offset, const char *text, std::size_t len);
+    void Delete(std::size_t byte_offset, std::size_t len);
+    
+    // NEW: Line-based queries
+    std::size_t LineCount() const;
+    std::string GetLine(std::size_t line_num) const;
+    std::pair<std::size_t, std::size_t> GetLineRange(std::size_t line_num) const; // (start, end) byte offsets
+    
+    // NEW: Position conversion
+    std::pair<std::size_t, std::size_t> ByteOffsetToLineCol(std::size_t byte_offset) const;
+    std::size_t LineColToByteOffset(std::size_t row, std::size_t col) const;
+    
+    // NEW: Substring extraction
+    std::string GetRange(std::size_t byte_offset, std::size_t len) const;
+    
+    // NEW: Search support
+    std::size_t Find(const std::string &needle, std::size_t start_offset) const;
+
+private:
+    // Existing members
+    std::string original_;
+    std::string add_;
+    std::vector<Piece> pieces_;
+    mutable std::string materialized_;
+    mutable bool dirty_;
+    std::size_t total_size_;
+    
+    // NEW: Line index for efficient line operations
+    struct LineInfo {
+        std::size_t byte_offset;      // absolute byte offset from buffer start
+        std::size_t piece_idx;        // which piece contains line start
+        std::size_t offset_in_piece;  // byte offset within that piece
+    };
+    mutable std::vector<LineInfo> line_index_;
+    mutable bool line_index_dirty_;
+    
+    // NEW: Line index management
+    void RebuildLineIndex() const;
+    void InvalidateLineIndex();
+};
+```
+
+### Buffer API Changes
+
+```cpp
+class Buffer {
+public:
+    // NEW: Direct content access
+    PieceTable &Content() { return content_; }
+    const PieceTable &Content() const { return content_; }
+    
+    // MODIFIED: Keep existing API but implement via PieceTable
+    void insert_text(int row, int col, std::string_view text);
+    void delete_text(int row, int col, std::size_t len);
+    void split_line(int row, int col);
+    void join_lines(int row);
+    void insert_row(int row, std::string_view text);
+    void delete_row(int row);
+    
+    // MODIFIED: Line access - return line from PieceTable
+    std::size_t Nrows() const { return content_.LineCount(); }
+    std::string GetLine(std::size_t row) const { return content_.GetLine(row); }
+    
+    // REMOVED: Rows() - no longer have vector of Lines
+    // std::vector<Line> &Rows();  // REMOVE
+    
+private:
+    // REMOVED: std::vector<Line> rows_;
+    // NEW: Single piece table for all content
+    PieceTable content_;
+    
+    // Keep existing members
+    std::size_t curx_, cury_, rx_;
+    std::size_t nrows_;  // cached from content_.LineCount()
+    std::size_t rowoffs_, coloffs_;
+    std::string filename_;
+    bool is_file_backed_;
+    bool dirty_;
+    bool read_only_;
+    bool mark_set_;
+    std::size_t mark_curx_, mark_cury_;
+    std::unique_ptr<UndoTree> undo_tree_;
+    std::unique_ptr<UndoSystem> undo_sys_;
+    std::uint64_t version_;
+    bool syntax_enabled_;
+    std::string filetype_;
+    std::unique_ptr<kte::HighlighterEngine> highlighter_;
+    kte::SwapRecorder *swap_rec_;
+};
+```
+
+## Migration Phases
+
+### Phase 1: Extend PieceTable (Foundation)
+
+**Goal:** Add buffer-wide capabilities to PieceTable without breaking
+existing per-line usage.
+
+**Tasks:**
+
+1. Add line indexing infrastructure to PieceTable
+    - Add `LineInfo` struct and `line_index_` member
+    - Implement `RebuildLineIndex()` that scans pieces for '\n'
+      characters
+    - Implement `InvalidateLineIndex()` called by Insert/Delete
+
+2. Implement core byte-based operations
+    - `Insert(byte_offset, text, len)` - split piece at offset, insert
+      new piece
+    - `Delete(byte_offset, len)` - split pieces, remove/truncate as
+      needed
+
+3. Implement line-based query methods
+    - `LineCount()` - return line_index_.size()
+    - `GetLine(line_num)` - extract text between line boundaries
+    - `GetLineRange(line_num)` - return (start, end) byte offsets
+
+4. Implement position conversion
+    - `ByteOffsetToLineCol(offset)` - binary search in line_index_
+    - `LineColToByteOffset(row, col)` - lookup line start, add col
+
+5. Implement utility methods
+    - `GetRange(offset, len)` - extract substring
+    - `Find(needle, start)` - search across pieces
+
+**Testing:**
+
+- Write unit tests for new PieceTable methods
+- Test with multi-line content
+- Verify line index correctness after edits
+- Benchmark performance vs current line-based approach
+
+**Estimated Effort:** 3-5 days
+
+### Phase 2: Create Buffer Adapter Layer (Compatibility)
+
+**Goal:** Create compatibility layer in Buffer to use PieceTable while
+maintaining existing API.
+
+**Tasks:**
+
+1. Add `PieceTable content_` member to Buffer (alongside existing
+   `rows_`)
+2. Add compilation flag `KTE_USE_BUFFER_PIECE_TABLE` (like existing
+   `KTE_USE_PIECE_TABLE`)
+3. Implement Buffer methods to delegate to content_:
+   ```cpp
+   #ifdef KTE_USE_BUFFER_PIECE_TABLE
+       void insert_text(int row, int col, std::string_view text) {
+           std::size_t offset = content_.LineColToByteOffset(row, col);
+           content_.Insert(offset, text.data(), text.size());
+       }
+       // ... similar for other methods
+   #else
+       // Existing line-based implementation
+   #endif
+   ```
+4. Update file I/O to work with PieceTable
+    - `OpenFromFile()` - load into content_ instead of rows_
+    - `Save()` - serialize content_ instead of rows_
+5. Update `AsString()` to materialize from content_
+
+**Testing:**
+
+- Run existing buffer correctness tests with new flag
+- Verify undo/redo still works
+- Test file I/O round-tripping
+- Test with existing command operations
+
+**Estimated Effort:** 3-4 days
+
+### Phase 3: Migrate Command Layer (High-level Operations)
+
+**Goal:** Update commands that directly access Rows() to use new API.
+
+**Tasks:**
+
+1. Audit all usages of `buf.Rows()` in Command.cc
+2. Refactor helper functions:
+    - `extract_region_text()` - use content_.GetRange()
+    - `delete_region()` - convert to byte offsets, use content_.Delete()
+    - `insert_text_at_cursor()` - convert position, use content_
+      .Insert()
+3. Update commands that iterate over lines:
+    - Use `buf.GetLine(i)` instead of `buf.Rows()[i]`
+    - Update line count queries to use `buf.Nrows()`
+4. Update search/replace operations:
+    - Modify `search_compute_matches()` to work with GetLine()
+    - Update regex matching to work line-by-line or use content directly
+
+**Testing:**
+
+- Test all editing commands (insert, delete, newline, backspace)
+- Test region operations (mark, copy, kill)
+- Test search and replace
+- Test word navigation and deletion
+- Run through common editing workflows
+
+**Estimated Effort:** 4-6 days
+
+### Phase 4: Update Renderer and Frontend (Display)
+
+**Goal:** Ensure all renderers work with new Buffer structure.
+
+**Tasks:**
+
+1. Audit renderer implementations:
+    - `TerminalRenderer.cc`
+    - `ImGuiRenderer.cc`
+    - `QtRenderer.cc`
+    - `TestRenderer.cc`
+2. Update line access patterns:
+    - Replace `buf.Rows()[y]` with `buf.GetLine(y)`
+    - Handle string return instead of Line object
+3. Update syntax highlighting integration:
+    - Ensure HighlighterEngine works with GetLine()
+    - Update any line-based caching
+
+**Testing:**
+
+- Test rendering in terminal
+- Test ImGui frontend (if enabled)
+- Test Qt frontend (if enabled)
+- Verify syntax highlighting displays correctly
+- Test scrolling and viewport updates
+
+**Estimated Effort:** 2-3 days
+
+### Phase 5: Remove Old Infrastructure (Cleanup) ✅ COMPLETED
+
+**Goal:** Remove GapBuffer, AppendBuffer, and Line class completely.
+
+**Status:** Completed on 2025-12-05
+
+**Tasks:**
+
+1. ✅ Remove conditional compilation:
+    - Removed `#ifdef KTE_USE_BUFFER_PIECE_TABLE` (PieceTable is now the
+      only way)
+    - Removed `#ifdef KTE_USE_PIECE_TABLE`
+    - Removed `AppendBuffer.h`
+2. ✅ Delete obsolete code:
+    - Deleted `GapBuffer.h/cc`
+    - Line class now uses PieceTable internally (kept for API
+      compatibility)
+    - `rows_` kept as mutable cache rebuilt from `content_` PieceTable
+3. ✅ Update CMakeLists.txt:
+    - Removed GapBuffer from sources
+    - Removed AppendBuffer.h from headers
+    - Removed KTE_USE_PIECE_TABLE and KTE_USE_BUFFER_PIECE_TABLE options
+4. ✅ Clean up includes and dependencies
+5. ✅ Update documentation
+
+**Testing:**
+
+- Full regression test suite
+- Verify clean compilation
+- Check for any lingering references
+
+**Estimated Effort:** 1-2 days
+
+### Phase 6: Performance Optimization (Polish)
+
+**Goal:** Optimize the new implementation for real-world usage.
+
+**Tasks:**
+
+1. Profile common operations:
+    - Measure line access patterns
+    - Identify hot paths in editing
+    - Benchmark against old implementation
+2. Optimize line index:
+    - Consider incremental updates instead of full rebuild
+    - Tune rebuild threshold
+    - Cache frequently accessed lines
+3. Optimize piece table:
+    - Tune piece coalescing heuristics
+    - Consider piece count limits and consolidation
+4. Memory optimization:
+    - Review materialization frequency
+    - Consider lazy materialization strategies
+    - Profile memory usage on large files
+
+**Testing:**
+
+- Benchmark suite with various file sizes
+- Memory profiling
+- Real-world usage testing
+
+**Estimated Effort:** 3-5 days
+
+## Files Requiring Modification
+
+### Core Files (Must Change)
+
+- `PieceTable.h/cc` - Add new methods (Phase 1)
+- `Buffer.h/cc` - Replace rows_ with content_ (Phase 2)
+- `Command.cc` - Update line access (Phase 3)
+- `UndoSystem.cc` - May need updates for new Buffer API
+
+### Renderer Files (Will Change)
+
+- `TerminalRenderer.cc` - Update line access (Phase 4)
+- `ImGuiRenderer.cc` - Update line access (Phase 4)
+- `QtRenderer.cc` - Update line access (Phase 4)
+- `TestRenderer.cc` - Update line access (Phase 4)
+
+### Files Removed (Phase 5 - Completed)
+
+- `GapBuffer.h/cc` - ✅ Deleted
+- `AppendBuffer.h` - ✅ Deleted
+- `test_buffer_correctness.cc` - ✅ Deleted (obsolete GapBuffer
+  comparison test)
+- `bench/BufferBench.cc` - ✅ Deleted (obsolete GapBuffer benchmarks)
+- `bench/PerformanceSuite.cc` - ✅ Deleted (obsolete GapBuffer
+  benchmarks)
+- `Buffer::Line` class - ✅ Updated to use PieceTable internally (kept
+  for API compatibility)
+
+### Build Files
+
+- `CMakeLists.txt` - Update sources (Phase 5)
+
+### Documentation
+
+- `README.md` - Update architecture notes
+- `docs/` - Update any architectural documentation
+- `REWRITE.md` - Note C++ now matches Rust design
+
+## Testing Strategy
+
+### Unit Tests
+
+- **PieceTable Tests:** New file `test_piece_table.cc`
+    - Test Insert/Delete at various positions
+    - Test line indexing correctness
+    - Test position conversion
+    - Test with edge cases (empty, single line, large files)
+
+- **Buffer Tests:** Extend `test_buffer_correctness.cc`
+    - Test new Buffer API with PieceTable backend
+    - Test file I/O round-tripping
+    - Test multi-line operations
+
+### Integration Tests
+
+- **Undo Tests:** `test_undo.cc` should still pass
+    - Verify undo/redo across all operation types
+    - Test undo tree navigation
+
+- **Search Tests:** `test_search_correctness.cc` should still pass
+    - Verify search across multiple lines
+    - Test regex search
+
+### Manual Testing
+
+- Load and edit large files (>10MB)
+- Perform complex editing sequences
+- Test all keybindings and commands
+- Verify syntax highlighting
+- Test crash recovery (swap files)
+
+### Regression Testing
+
+- All existing tests must pass with new implementation
+- No observable behavior changes for users
+- Performance should be comparable or better
+
+## Risk Assessment
+
+### High Risk
+
+- **Undo System Integration:** Undo records operations with
+  row/col/text. Need to ensure compatibility or refactor.
+    - *Mitigation:* Carefully preserve undo semantics, extensive testing
+
+- **Performance Regression:** Line index rebuilding could be expensive
+  on large files.
+    - *Mitigation:* Profile early, optimize incrementally, consider
+      caching strategies
+
+### Medium Risk
+
+- **Syntax Highlighting:** Highlighters may depend on line-based access
+  patterns.
+    - *Mitigation:* Review highlighter integration, test thoroughly
+
+- **Renderer Updates:** Multiple renderers need updating, risk of
+  inconsistency.
+    - *Mitigation:* Update all renderers in same phase, test each
+
+### Low Risk
+
+- **Search/Replace:** Should work naturally with new GetLine() API.
+    - *Mitigation:* Test thoroughly with existing test suite
+
+## Success Criteria
+
+### Functional Requirements
+
+- ✓ All existing tests pass
+- ✓ All commands work identically to before
+- ✓ File I/O works correctly
+- ✓ Undo/redo functionality preserved
+- ✓ Syntax highlighting works
+- ✓ All frontends (terminal, ImGui, Qt) work
+
+### Code Quality
+
+- ✓ GapBuffer completely removed
+- ✓ No conditional compilation for buffer type
+- ✓ Clean, maintainable code
+- ✓ Good test coverage for new PieceTable methods
+
+### Performance
+
+- ✓ Editing operations at least as fast as current
+- ✓ Line access within 2x of current performance
+- ✓ Memory usage reasonable (no excessive materialization)
+- ✓ Large file handling acceptable (tested up to 100MB)
+
+## Timeline Estimate
+
+| Phase                      | Duration       | Dependencies |
+|----------------------------|----------------|--------------|
+| Phase 1: Extend PieceTable | 3-5 days       | None         |
+| Phase 2: Buffer Adapter    | 3-4 days       | Phase 1      |
+| Phase 3: Command Layer     | 4-6 days       | Phase 2      |
+| Phase 4: Renderer Updates  | 2-3 days       | Phase 3      |
+| Phase 5: Cleanup           | 1-2 days       | Phase 4      |
+| Phase 6: Optimization      | 3-5 days       | Phase 5      |
+| **Total**                  | **16-25 days** |              |
+
+**Note:** Timeline assumes one developer working full-time. Actual
+duration may vary based on:
+
+- Unforeseen integration issues
+- Performance optimization needs
+- Testing thoroughness
+- Code review iterations
+
+## Alternatives Considered
+
+### Alternative 1: Keep Line-based but unify GapBuffer/PieceTable
+
+- Keep vector of Lines, but make each Line always use PieceTable
+- Remove GapBuffer, remove AppendBuffer selector
+- **Pros:** Smaller change, less risk
+- **Cons:** Doesn't achieve architectural goal, still have per-line
+  overhead
+
+### Alternative 2: Hybrid approach
+
+- Use PieceTable for buffer, but maintain materialized Line objects as
+  cache
+- **Pros:** Easier migration, maintains some compatibility
+- **Cons:** Complex dual representation, cache invalidation issues
+
+### Alternative 3: Complete rewrite
+
+- Follow REWRITE.md exactly, implement in Rust
+- **Pros:** Modern language, better architecture
+- **Cons:** Much larger effort, different project
+
+## Recommendation
+
+**Proceed with planned migration** (single PieceTable per Buffer)
+because:
+
+1. Aligns with long-term architecture vision (REWRITE.md)
+2. Removes unnecessary per-line buffer overhead
+3. Simplifies codebase (one text representation)
+4. Enables future optimizations (better undo, swap files, etc.)
+5. Reasonable effort (16-25 days) for significant improvement
+
+**Suggested Approach:**
+
+- Start with Phase 1 (extend PieceTable) in isolated branch
+- Thoroughly test new PieceTable functionality
+- Proceed incrementally through phases
+- Maintain working editor at end of each phase
+- Merge to main after Phase 4 (before cleanup) to get testing
+- Complete Phase 5-6 based on feedback
+
+## References
+
+- `REWRITE.md` - Rust architecture specification (lines 54-157)
+- Current buffer implementation: `Buffer.h/cc`
+- Current piece table: `PieceTable.h/cc`
+- Undo system: `UndoSystem.h/cc`, `UndoNode.h`
+- Commands: `Command.cc`

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.

flake.nix

@@ -13,9 +13,9 @@
       packages = eachSystem (system: rec {
         default = kte;
         full = kge;
-        kte = (pkgsFor system).callPackage ./default.nix { graphical = false; };
-        kge = (pkgsFor system).callPackage ./default.nix { graphical = true; };
-        qt  = (pkgsFor system).callPackage ./default.nix { graphical-qt = true; }
+        kte = (pkgsFor system).callPackage ./default.nix { graphical = false; graphical-qt = false; };
+        kge = (pkgsFor system).callPackage ./default.nix { graphical = true;  graphical-qt = false; };
+        qt  = (pkgsFor system).callPackage ./default.nix { graphical = true;  graphical-qt = true;  };
       });
     };
 }

fonts/FontRegistry.cc

@@ -17,11 +17,21 @@ InstallDefaultFonts()
 	));
 	FontRegistry::Instance().Register(std::make_unique<Font>(
 		"brassmono",
-		BrassMono::DefaultFontBoldCompressedData,
-		BrassMono::DefaultFontBoldCompressedSize
+		BrassMono::DefaultFontRegularCompressedData,
+		BrassMono::DefaultFontRegularCompressedSize
 	));
 	FontRegistry::Instance().Register(std::make_unique<Font>(
-		"brassmonocode",
+	    "brassmono-bold",
+	    BrassMono::DefaultFontBoldCompressedData,
+	    BrassMono::DefaultFontBoldCompressedSize
+	));
+	FontRegistry::Instance().Register(std::make_unique<Font>(
+	    "brassmonocode",
+	    BrassMonoCode::DefaultFontRegularCompressedData,
+	    BrassMonoCode::DefaultFontRegularCompressedSize
+	));
+	FontRegistry::Instance().Register(std::make_unique<Font>(
+		"brassmonocode-bold",
 		BrassMonoCode::DefaultFontBoldCompressedData,
 		BrassMonoCode::DefaultFontBoldCompressedSize
 	));

make-app-release

@@ -16,13 +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
+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_buffer_correctness.cc

@@ -1,102 +0,0 @@
-// Simple buffer correctness tests comparing GapBuffer and PieceTable to std::string
-#include <cassert>
-#include <cstddef>
-#include <cstring>
-#include <random>
-#include <string>
-#include <vector>
-
-#include "GapBuffer.h"
-#include "PieceTable.h"
-
-
-template<typename Buf>
-static void
-check_equals(const Buf &b, const std::string &ref)
-{
-	assert(b.Size() == ref.size());
-	if (b.Size() == 0)
-		return;
-	const char *p = b.Data();
-	assert(p != nullptr);
-	assert(std::memcmp(p, ref.data(), ref.size()) == 0);
-}
-
-
-template<typename Buf>
-static void
-run_basic_cases()
-{
-	// empty
-	{
-		Buf b;
-		std::string ref;
-		check_equals(b, ref);
-	}
-
-	// append chars
-	{
-		Buf b;
-		std::string ref;
-		for (int i = 0; i < 1000; ++i) {
-			b.AppendChar('a');
-			ref.push_back('a');
-		}
-		check_equals(b, ref);
-	}
-
-	// prepend chars
-	{
-		Buf b;
-		std::string ref;
-		for (int i = 0; i < 1000; ++i) {
-			b.PrependChar('b');
-			ref.insert(ref.begin(), 'b');
-		}
-		check_equals(b, ref);
-	}
-
-	// append/prepend strings
-	{
-		Buf b;
-		std::string ref;
-		const char *hello = "hello";
-		b.Append(hello, 5);
-		ref.append("hello");
-		b.Prepend(hello, 5);
-		ref.insert(0, "hello");
-		check_equals(b, ref);
-	}
-
-	// larger random blocks
-	{
-		std::mt19937 rng(42);
-		std::uniform_int_distribution<int> len_dist(0, 128);
-		std::uniform_int_distribution<int> coin(0, 1);
-		Buf b;
-		std::string ref;
-		for (int step = 0; step < 2000; ++step) {
-			int L = len_dist(rng);
-			std::string payload(L, '\0');
-			for (int i         = 0; i < L; ++i)
-				payload[i] = static_cast<char>('a' + (i % 26));
-			if (coin(rng)) {
-				b.Append(payload.data(), payload.size());
-				ref.append(payload);
-			} else {
-				b.Prepend(payload.data(), payload.size());
-				ref.insert(0, payload);
-			}
-		}
-		check_equals(b, ref);
-	}
-}
-
-
-int
-main()
-{
-	run_basic_cases<GapBuffer>();
-	run_basic_cases<PieceTable>();
-	return 0;
-}

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);
+    }
+}