Fix multi-window architecture and swap file cleanup

Multi-window:
- Per-window ImGui contexts (fixes input, scroll, and rendering isolation)
- Per-instance scroll and mouse state in ImGuiRenderer (no more statics)
- Proper GL context activation during window destruction
- ValidateBufferIndex guards against stale curbuf_ across shared buffers
- Editor methods (CurrentBuffer, SwitchTo, CloseBuffer, etc.) use Buffers()
  accessor to respect shared buffer lists
- New windows open with an untitled buffer
- Scratch buffer reuse works in secondary windows
- CMD-w on macOS closes only the focused window
- Deferred new-window creation to avoid mid-frame ImGui context corruption

Swap file cleanup:
- SaveAs prompt handler now calls ResetJournal
- cmd_save_and_quit now calls ResetJournal
- Editor::Reset detaches all buffers before clearing
- Tests for save-and-quit and editor-reset swap cleanup

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

CMakeLists.txt

@@ -4,7 +4,7 @@ project(kte)
 include(GNUInstallDirs)
 
 set(CMAKE_CXX_STANDARD 20)
-set(KTE_VERSION "1.8.3")
+set(KTE_VERSION "1.9.0")
 
 # Default to terminal-only build to avoid SDL/OpenGL dependency by default.
 # Enable with -DBUILD_GUI=ON when SDL2/OpenGL/Freetype are available.
@@ -327,6 +327,7 @@ if (BUILD_TESTS)
             tests/test_swap_edge_cases.cc
             tests/test_swap_recovery_prompt.cc
             tests/test_swap_cleanup.cc
+            tests/test_swap_cleanup2.cc
             tests/test_swap_git_editor.cc
             tests/test_piece_table.cc
             tests/test_search.cc

Command.cc

@@ -752,6 +752,8 @@ cmd_save_and_quit(CommandContext &ctx)
 		if (buf->IsFileBacked()) {
 			if (buf->Save(err)) {
 				buf->SetDirty(false);
+				if (auto *sm = ctx.editor.Swap())
+					sm->ResetJournal(*buf);
 			} else {
 				ctx.editor.SetStatus(err);
 				return false;
@@ -759,6 +761,8 @@ cmd_save_and_quit(CommandContext &ctx)
 		} else if (!buf->Filename().empty()) {
 			if (buf->SaveAs(buf->Filename(), err)) {
 				buf->SetDirty(false);
+				if (auto *sm = ctx.editor.Swap())
+					sm->ResetJournal(*buf);
 			} else {
 				ctx.editor.SetStatus(err);
 				return false;
@@ -2568,6 +2572,10 @@ cmd_newline(CommandContext &ctx)
 							ctx.editor.SetStatus(err);
 						} else {
 							buf->SetDirty(false);
+							if (auto *sm = ctx.editor.Swap()) {
+								sm->NotifyFilenameChanged(*buf);
+								sm->ResetJournal(*buf);
+							}
 							ctx.editor.SetStatus("Saved as " + value);
 							if (auto *u = buf->Undo())
 								u->mark_saved();

Editor.cc

@@ -69,20 +69,22 @@ Editor::SetStatus(const std::string &message)
 Buffer *
 Editor::CurrentBuffer()
 {
-	if (buffers_.empty() || curbuf_ >= buffers_.size()) {
+	auto &bufs = Buffers();
+	if (bufs.empty() || curbuf_ >= bufs.size()) {
 		return nullptr;
 	}
-	return &buffers_[curbuf_];
+	return &bufs[curbuf_];
 }
 
 
 const Buffer *
 Editor::CurrentBuffer() const
 {
-	if (buffers_.empty() || curbuf_ >= buffers_.size()) {
+	const auto &bufs = Buffers();
+	if (bufs.empty() || curbuf_ >= bufs.size()) {
 		return nullptr;
 	}
-	return &buffers_[curbuf_];
+	return &bufs[curbuf_];
 }
 
 
@@ -117,8 +119,9 @@ Editor::DisplayNameFor(const Buffer &buf) const
 
 	// Prepare list of other buffer paths
 	std::vector<std::vector<std::filesystem::path> > others;
-	others.reserve(buffers_.size());
-	for (const auto &b: buffers_) {
+	const auto &bufs = Buffers();
+	others.reserve(bufs.size());
+	for (const auto &b: bufs) {
 		if (&b == &buf)
 			continue;
 		if (b.Filename().empty())
@@ -161,41 +164,44 @@ Editor::DisplayNameFor(const Buffer &buf) const
 std::size_t
 Editor::AddBuffer(const Buffer &buf)
 {
-	buffers_.push_back(buf);
+	auto &bufs = Buffers();
+	bufs.push_back(buf);
 	// Attach swap recorder
 	if (swap_) {
-		swap_->Attach(&buffers_.back());
-		buffers_.back().SetSwapRecorder(swap_->RecorderFor(&buffers_.back()));
+		swap_->Attach(&bufs.back());
+		bufs.back().SetSwapRecorder(swap_->RecorderFor(&bufs.back()));
 	}
-	if (buffers_.size() == 1) {
+	if (bufs.size() == 1) {
 		curbuf_ = 0;
 	}
-	return buffers_.size() - 1;
+	return bufs.size() - 1;
 }
 
 
 std::size_t
 Editor::AddBuffer(Buffer &&buf)
 {
-	buffers_.push_back(std::move(buf));
+	auto &bufs = Buffers();
+	bufs.push_back(std::move(buf));
 	if (swap_) {
-		swap_->Attach(&buffers_.back());
-		buffers_.back().SetSwapRecorder(swap_->RecorderFor(&buffers_.back()));
+		swap_->Attach(&bufs.back());
+		bufs.back().SetSwapRecorder(swap_->RecorderFor(&bufs.back()));
 	}
-	if (buffers_.size() == 1) {
+	if (bufs.size() == 1) {
 		curbuf_ = 0;
 	}
-	return buffers_.size() - 1;
+	return bufs.size() - 1;
 }
 
 
 bool
 Editor::OpenFile(const std::string &path, std::string &err)
 {
-	// If there is exactly one unnamed, empty, clean buffer, reuse it instead
-	// of creating a new one.
-	if (buffers_.size() == 1) {
-		Buffer &cur                  = buffers_[curbuf_];
+	// If the current buffer is an unnamed, empty, clean scratch buffer, reuse
+	// it instead of creating a new one.
+	auto &bufs_ref = Buffers();
+	if (!bufs_ref.empty() && curbuf_ < bufs_ref.size()) {
+		Buffer &cur                  = bufs_ref[curbuf_];
 		const bool unnamed           = cur.Filename().empty() && !cur.IsFileBacked();
 		const bool clean             = !cur.Dirty();
 		const std::size_t nrows      = cur.Nrows();
@@ -268,7 +274,7 @@ 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));
 	if (swap_) {
-		swap_->NotifyFilenameChanged(buffers_[idx]);
+		swap_->NotifyFilenameChanged(Buffers()[idx]);
 	}
 	SwitchTo(idx);
 	// Defensive: ensure any active prompt is closed after a successful open
@@ -446,12 +452,13 @@ Editor::ProcessPendingOpens()
 bool
 Editor::SwitchTo(std::size_t index)
 {
-	if (index >= buffers_.size()) {
+	auto &bufs = Buffers();
+	if (index >= bufs.size()) {
 		return false;
 	}
 	curbuf_ = index;
 	// Robustness: ensure a valid highlighter is installed when switching buffers
-	Buffer &b = buffers_[curbuf_];
+	Buffer &b = bufs[curbuf_];
 	if (b.SyntaxEnabled()) {
 		b.EnsureHighlighter();
 		if (auto *eng = b.Highlighter()) {
@@ -478,21 +485,22 @@ Editor::SwitchTo(std::size_t index)
 bool
 Editor::CloseBuffer(std::size_t index)
 {
-	if (index >= buffers_.size()) {
+	auto &bufs = Buffers();
+	if (index >= bufs.size()) {
 		return false;
 	}
 	if (swap_) {
 		// Always remove swap file when closing a buffer on normal exit.
 		// Swap files are for crash recovery; on clean close, we don't need them.
 		// This prevents stale swap files from accumulating (e.g., when used as git editor).
-		swap_->Detach(&buffers_[index], true);
-		buffers_[index].SetSwapRecorder(nullptr);
+		swap_->Detach(&bufs[index], true);
+		bufs[index].SetSwapRecorder(nullptr);
 	}
-	buffers_.erase(buffers_.begin() + static_cast<std::ptrdiff_t>(index));
-	if (buffers_.empty()) {
+	bufs.erase(bufs.begin() + static_cast<std::ptrdiff_t>(index));
+	if (bufs.empty()) {
 		curbuf_ = 0;
-	} else if (curbuf_ >= buffers_.size()) {
-		curbuf_ = buffers_.size() - 1;
+	} else if (curbuf_ >= bufs.size()) {
+		curbuf_ = bufs.size() - 1;
 	}
 	return true;
 }
@@ -516,7 +524,12 @@ Editor::Reset()
 	// Reset close-confirm/save state
 	close_confirm_pending_ = false;
 	close_after_save_      = false;
-	buffers_.clear();
+	auto &bufs = Buffers();
+	if (swap_) {
+		for (auto &buf : bufs)
+			swap_->Detach(&buf, true);
+	}
+	bufs.clear();
 	curbuf_ = 0;
 }
 

Editor.h

@@ -521,7 +521,7 @@ public:
 	// Buffers
 	[[nodiscard]] std::size_t BufferCount() const
 	{
-		return buffers_.size();
+		return Buffers().size();
 	}
 
 
@@ -531,6 +531,19 @@ public:
 	}
 
 
+	// Clamp curbuf_ to valid range. Call when the shared buffer list may
+	// have been modified by another editor (e.g., buffer closed in another window).
+	void ValidateBufferIndex()
+	{
+		const auto &bufs = Buffers();
+		if (bufs.empty()) {
+			curbuf_ = 0;
+		} else if (curbuf_ >= bufs.size()) {
+			curbuf_ = bufs.size() - 1;
+		}
+	}
+
+
 	Buffer *CurrentBuffer();
 
 	const Buffer *CurrentBuffer() const;

ImGuiFrontend.cc

@@ -30,7 +30,7 @@
 static auto kGlslVersion = "#version 150"; // GL 3.2 core (macOS compatible)
 
 // ---------------------------------------------------------------------------
-// Helpers shared between Init and OpenNewWindow_
+// Helpers
 // ---------------------------------------------------------------------------
 
 static void
@@ -96,6 +96,63 @@ update_editor_dimensions(Editor &ed, float disp_w, float disp_h)
 }
 
 
+// ---------------------------------------------------------------------------
+// SetupImGuiStyle_ — apply theme, fonts, and flags to the current ImGui context
+// ---------------------------------------------------------------------------
+void
+GUIFrontend::SetupImGuiStyle_()
+{
+	ImGuiIO &io = ImGui::GetIO();
+
+	// Disable imgui.ini for secondary windows (primary sets its own path in Init)
+	io.IniFilename = nullptr;
+
+	io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;
+	io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad;
+	ImGui::StyleColorsDark();
+
+	if (config_.background == "light")
+		kte::SetBackgroundMode(kte::BackgroundMode::Light);
+	else
+		kte::SetBackgroundMode(kte::BackgroundMode::Dark);
+	kte::ApplyThemeByName(config_.theme);
+
+	// Load fonts into this context's font atlas.
+	// Font registry is global and already populated by Init; just load into this atlas.
+	if (!kte::Fonts::FontRegistry::Instance().LoadFont(config_.font, (float) config_.font_size)) {
+		LoadGuiFont_(nullptr, (float) config_.font_size);
+	}
+}
+
+
+// ---------------------------------------------------------------------------
+// Destroy a single window's ImGui context + SDL/GL resources
+// ---------------------------------------------------------------------------
+void
+GUIFrontend::DestroyWindowResources_(WindowState &ws)
+{
+	if (ws.imgui_ctx) {
+		// Must activate this window's GL context before shutting down the
+		// OpenGL3 backend, otherwise it deletes another context's resources.
+		if (ws.window && ws.gl_ctx)
+			SDL_GL_MakeCurrent(ws.window, ws.gl_ctx);
+		ImGui::SetCurrentContext(ws.imgui_ctx);
+		ImGui_ImplOpenGL3_Shutdown();
+		ImGui_ImplSDL2_Shutdown();
+		ImGui::DestroyContext(ws.imgui_ctx);
+		ws.imgui_ctx = nullptr;
+	}
+	if (ws.gl_ctx) {
+		SDL_GL_DeleteContext(ws.gl_ctx);
+		ws.gl_ctx = nullptr;
+	}
+	if (ws.window) {
+		SDL_DestroyWindow(ws.window);
+		ws.window = nullptr;
+	}
+}
+
+
 bool
 GUIFrontend::Init(int &argc, char **argv, Editor &ed)
 {
@@ -172,9 +229,10 @@ GUIFrontend::Init(int &argc, char **argv, Editor &ed)
 	SDL_GL_MakeCurrent(win, gl_ctx);
 	SDL_GL_SetSwapInterval(1); // vsync
 
+	// Create primary ImGui context
 	IMGUI_CHECKVERSION();
-	ImGui::CreateContext();
-	ImGuiIO &io = ImGui::GetIO();
+	ImGuiContext *imgui_ctx = ImGui::CreateContext();
+	ImGuiIO &io             = ImGui::GetIO();
 
 	// Set custom ini filename path to ~/.config/kte/imgui.ini
 	if (const char *home = std::getenv("HOME")) {
@@ -236,11 +294,12 @@ GUIFrontend::Init(int &argc, char **argv, Editor &ed)
 	}
 
 	// Build primary WindowState
-	auto ws    = std::make_unique<WindowState>();
-	ws->window = win;
-	ws->gl_ctx = gl_ctx;
-	ws->width  = init_w;
-	ws->height = init_h;
+	auto ws       = std::make_unique<WindowState>();
+	ws->window    = win;
+	ws->gl_ctx    = gl_ctx;
+	ws->imgui_ctx = imgui_ctx;
+	ws->width     = init_w;
+	ws->height    = init_h;
 	// The primary window's editor IS the editor passed in from main; we don't
 	// use ws->editor for the primary — instead we keep a pointer to &ed.
 	// We store a sentinel: window index 0 uses the external editor reference.
@@ -255,8 +314,6 @@ GUIFrontend::Init(int &argc, char **argv, Editor &ed)
 bool
 GUIFrontend::OpenNewWindow_(Editor &primary)
 {
-	SDL_GL_MakeCurrent(windows_[0]->window, windows_[0]->gl_ctx);
-
 	Uint32 win_flags = SDL_WINDOW_OPENGL | SDL_WINDOW_RESIZABLE | SDL_WINDOW_ALLOW_HIGHDPI;
 	int w            = windows_[0]->width;
 	int h            = windows_[0]->height;
@@ -277,25 +334,48 @@ GUIFrontend::OpenNewWindow_(Editor &primary)
 	SDL_GL_MakeCurrent(win, gl_ctx);
 	SDL_GL_SetSwapInterval(1);
 
-	// Secondary windows share the ImGui context already created in Init.
-	// We need to init the SDL2/OpenGL backends for this new window.
-	// ImGui_ImplSDL2 supports multiple windows via SDL_GetWindowID checks.
-	ImGui_ImplOpenGL3_Init(kGlslVersion);
+	// Each window gets its own ImGui context — ImGui requires exactly one
+	// NewFrame/Render cycle per context per frame.
+	ImGuiContext *imgui_ctx = ImGui::CreateContext();
+	ImGui::SetCurrentContext(imgui_ctx);
 
-	auto ws    = std::make_unique<WindowState>();
-	ws->window = win;
-	ws->gl_ctx = gl_ctx;
-	ws->width  = w;
-	ws->height = h;
+	SetupImGuiStyle_();
+
+	if (!ImGui_ImplSDL2_InitForOpenGL(win, gl_ctx)) {
+		ImGui::DestroyContext(imgui_ctx);
+		SDL_GL_DeleteContext(gl_ctx);
+		SDL_DestroyWindow(win);
+		return false;
+	}
+	if (!ImGui_ImplOpenGL3_Init(kGlslVersion)) {
+		ImGui_ImplSDL2_Shutdown();
+		ImGui::DestroyContext(imgui_ctx);
+		SDL_GL_DeleteContext(gl_ctx);
+		SDL_DestroyWindow(win);
+		return false;
+	}
+
+	auto ws       = std::make_unique<WindowState>();
+	ws->window    = win;
+	ws->gl_ctx    = gl_ctx;
+	ws->imgui_ctx = imgui_ctx;
+	ws->width     = w;
+	ws->height    = h;
 
 	// Secondary editor shares the primary's buffer list
 	ws->editor.SetSharedBuffers(&primary.Buffers());
 	ws->editor.SetDimensions(primary.Rows(), primary.Cols());
+
+	// Open a new untitled buffer and switch to it in the new window.
+	ws->editor.AddBuffer(Buffer());
+	ws->editor.SwitchTo(ws->editor.BufferCount() - 1);
+
 	ws->input.Attach(&ws->editor);
 
 	windows_.push_back(std::move(ws));
 
-	// Restore primary GL context as current
+	// Restore primary context
+	ImGui::SetCurrentContext(windows_[0]->imgui_ctx);
 	SDL_GL_MakeCurrent(windows_[0]->window, windows_[0]->gl_ctx);
 	return true;
 }
@@ -305,10 +385,10 @@ void
 GUIFrontend::Step(Editor &ed, bool &running)
 {
 	// --- Event processing ---
+	// SDL events carry a window ID. Route each event to the correct window's
+	// ImGui context (for ImGui_ImplSDL2_ProcessEvent) and input handler.
 	SDL_Event e;
 	while (SDL_PollEvent(&e)) {
-		ImGui_ImplSDL2_ProcessEvent(&e);
-
 		// Determine which window this event belongs to
 		Uint32 event_win_id = 0;
 		switch (e.type) {
@@ -329,6 +409,9 @@ GUIFrontend::Step(Editor &ed, bool &running)
 		case SDL_MOUSEWHEEL:
 			event_win_id = e.wheel.windowID;
 			break;
+		case SDL_MOUSEMOTION:
+			event_win_id = e.motion.windowID;
+			break;
 		default:
 			break;
 		}
@@ -338,59 +421,67 @@ GUIFrontend::Step(Editor &ed, bool &running)
 			break;
 		}
 
+		// Find the target window and route the event to its ImGui context
+		WindowState *target = nullptr;
+		std::size_t target_idx = 0;
+		if (event_win_id != 0) {
+			for (std::size_t i = 0; i < windows_.size(); ++i) {
+				if (SDL_GetWindowID(windows_[i]->window) == event_win_id) {
+					target     = windows_[i].get();
+					target_idx = i;
+					break;
+				}
+			}
+		}
+
+		if (target && target->imgui_ctx) {
+			// Set this window's ImGui context so ImGui_ImplSDL2_ProcessEvent
+			// updates the correct IO state.
+			ImGui::SetCurrentContext(target->imgui_ctx);
+			ImGui_ImplSDL2_ProcessEvent(&e);
+		}
+
 		if (e.type == SDL_WINDOWEVENT) {
 			if (e.window.event == SDL_WINDOWEVENT_CLOSE) {
-				// Mark the window as dead; primary window close = quit
-				for (std::size_t i = 0; i < windows_.size(); ++i) {
-					if (SDL_GetWindowID(windows_[i]->window) == e.window.windowID) {
-						if (i == 0) {
-							running = false;
-						} else {
-							windows_[i]->alive = false;
-						}
-						break;
+				if (target) {
+					if (target_idx == 0) {
+						running = false;
+					} else {
+						target->alive = false;
 					}
 				}
 			} else if (e.window.event == SDL_WINDOWEVENT_SIZE_CHANGED) {
-				for (auto &ws: windows_) {
-					if (SDL_GetWindowID(ws->window) == e.window.windowID) {
-						ws->width  = e.window.data1;
-						ws->height = e.window.data2;
-						break;
-					}
+				if (target) {
+					target->width  = e.window.data1;
+					target->height = e.window.data2;
 				}
 			}
 		}
 
 		// Route input events to the correct window's input handler
-		if (event_win_id != 0) {
-			// Primary window (index 0) uses the external editor &ed
-			if (windows_.size() > 0 &&
-			    SDL_GetWindowID(windows_[0]->window) == event_win_id) {
-				windows_[0]->input.ProcessSDLEvent(e);
-			} else {
-				for (std::size_t i = 1; i < windows_.size(); ++i) {
-					if (SDL_GetWindowID(windows_[i]->window) == event_win_id) {
-						windows_[i]->input.ProcessSDLEvent(e);
-						break;
-					}
-				}
-			}
+		if (target) {
+			target->input.ProcessSDLEvent(e);
 		}
 	}
 
 	if (!running)
 		return;
 
-	// --- Apply pending font change ---
+	// --- Apply pending font change (to all contexts) ---
 	{
 		std::string fname;
 		float fsize = 0.0f;
 		if (kte::Fonts::FontRegistry::Instance().ConsumePendingFontRequest(fname, fsize)) {
 			if (!fname.empty() && fsize > 0.0f) {
-				kte::Fonts::FontRegistry::Instance().LoadFont(fname, fsize);
-				ImGui_ImplOpenGL3_DestroyFontsTexture();
-				ImGui_ImplOpenGL3_CreateFontsTexture();
+				for (auto &ws : windows_) {
+					if (!ws->alive || !ws->imgui_ctx)
+						continue;
+					ImGui::SetCurrentContext(ws->imgui_ctx);
+					SDL_GL_MakeCurrent(ws->window, ws->gl_ctx);
+					kte::Fonts::FontRegistry::Instance().LoadFont(fname, fsize);
+					ImGui_ImplOpenGL3_DestroyFontsTexture();
+					ImGui_ImplOpenGL3_CreateFontsTexture();
+				}
 			}
 		}
 	}
@@ -404,7 +495,12 @@ GUIFrontend::Step(Editor &ed, bool &running)
 
 		Editor &wed = (wi == 0) ? ed : ws.editor;
 
+		// Shared buffer list may have been modified by another window.
+		wed.ValidateBufferIndex();
+
+		// Activate this window's GL and ImGui contexts
 		SDL_GL_MakeCurrent(ws.window, ws.gl_ctx);
+		ImGui::SetCurrentContext(ws.imgui_ctx);
 
 		// Start a new ImGui frame
 		ImGui_ImplOpenGL3_NewFrame();
@@ -442,12 +538,6 @@ GUIFrontend::Step(Editor &ed, bool &running)
 			}
 		}
 
-		// Handle new-window request
-		if (wed.NewWindowRequested()) {
-			wed.SetNewWindowRequested(false);
-			OpenNewWindow_(ed); // always share primary editor's buffers
-		}
-
 		if (wi == 0 && wed.QuitRequested()) {
 			running = false;
 		}
@@ -466,52 +556,40 @@ GUIFrontend::Step(Editor &ed, bool &running)
 		SDL_GL_SwapWindow(ws.window);
 	}
 
+	// Handle deferred new-window requests (must happen outside the render loop
+	// to avoid corrupting an in-progress ImGui frame).
+	for (std::size_t wi = 0; wi < windows_.size(); ++wi) {
+		Editor &wed = (wi == 0) ? ed : windows_[wi]->editor;
+		if (wed.NewWindowRequested()) {
+			wed.SetNewWindowRequested(false);
+			OpenNewWindow_(ed);
+		}
+	}
+
 	// Remove dead secondary windows
 	for (auto it = windows_.begin() + 1; it != windows_.end();) {
 		if (!(*it)->alive) {
-			SDL_GL_MakeCurrent((*it)->window, (*it)->gl_ctx);
-			ImGui_ImplOpenGL3_Shutdown();
-			SDL_GL_DeleteContext((*it)->gl_ctx);
-			SDL_DestroyWindow((*it)->window);
+			DestroyWindowResources_(**it);
 			it = windows_.erase(it);
-			// Restore primary context
-			SDL_GL_MakeCurrent(windows_[0]->window, windows_[0]->gl_ctx);
 		} else {
 			++it;
 		}
 	}
+
+	// Restore primary context
+	if (!windows_.empty()) {
+		ImGui::SetCurrentContext(windows_[0]->imgui_ctx);
+		SDL_GL_MakeCurrent(windows_[0]->window, windows_[0]->gl_ctx);
+	}
 }
 
 
 void
 GUIFrontend::Shutdown()
 {
-	// Destroy secondary windows first
-	for (std::size_t i = 1; i < windows_.size(); ++i) {
-		SDL_GL_MakeCurrent(windows_[i]->window, windows_[i]->gl_ctx);
-		ImGui_ImplOpenGL3_Shutdown();
-		SDL_GL_DeleteContext(windows_[i]->gl_ctx);
-		SDL_DestroyWindow(windows_[i]->window);
-	}
-	windows_.resize(std::min(windows_.size(), std::size_t(1)));
-
-	// Destroy primary window
-	if (!windows_.empty()) {
-		SDL_GL_MakeCurrent(windows_[0]->window, windows_[0]->gl_ctx);
-	}
-	ImGui_ImplOpenGL3_Shutdown();
-	ImGui_ImplSDL2_Shutdown();
-	ImGui::DestroyContext();
-
-	if (!windows_.empty()) {
-		if (windows_[0]->gl_ctx) {
-			SDL_GL_DeleteContext(windows_[0]->gl_ctx);
-			windows_[0]->gl_ctx = nullptr;
-		}
-		if (windows_[0]->window) {
-			SDL_DestroyWindow(windows_[0]->window);
-			windows_[0]->window = nullptr;
-		}
+	// Destroy all windows (secondary first, then primary)
+	for (auto it = windows_.rbegin(); it != windows_.rend(); ++it) {
+		DestroyWindowResources_(**it);
 	}
 	windows_.clear();
 	SDL_Quit();

ImGuiFrontend.h

@@ -13,6 +13,7 @@
 
 
 struct SDL_Window;
+struct ImGuiContext;
 typedef void *SDL_GLContext;
 
 class GUIFrontend final : public Frontend {
@@ -28,10 +29,13 @@ public:
 	void Shutdown() override;
 
 private:
-	// Per-window state
+	// Per-window state — each window owns its own ImGui context so that
+	// NewFrame/Render cycles are fully independent (ImGui requires exactly
+	// one NewFrame per Render per context).
 	struct WindowState {
-		SDL_Window *window   = nullptr;
-		SDL_GLContext gl_ctx = nullptr;
+		SDL_Window *window       = nullptr;
+		SDL_GLContext gl_ctx     = nullptr;
+		ImGuiContext *imgui_ctx  = nullptr;
 		ImGuiInputHandler input{};
 		ImGuiRenderer renderer{};
 		Editor editor{};
@@ -44,6 +48,9 @@ private:
 	// Returns false if window creation fails.
 	bool OpenNewWindow_(Editor &primary);
 
+	// Initialize fonts and theme for a given ImGui context (must be current).
+	void SetupImGuiStyle_();
+	static void DestroyWindowResources_(WindowState &ws);
 	static bool LoadGuiFont_(const char *path, float size_px);
 
 	GUIConfig config_{};

ImGuiRenderer.cc

@@ -76,19 +76,16 @@ ImGuiRenderer::Draw(Editor &ed)
 		// Two-way sync between Buffer::Rowoffs and ImGui scroll position:
 		// - If command layer changed Buffer::Rowoffs since last frame, drive ImGui scroll from it.
 		// - Otherwise, propagate ImGui scroll to Buffer::Rowoffs so command layer has an up-to-date view.
-		static long prev_buf_rowoffs = -1; // previous frame's Buffer::Rowoffs
-		static long prev_buf_coloffs = -1; // previous frame's Buffer::Coloffs
-
 		const long buf_rowoffs = static_cast<long>(buf->Rowoffs());
 		const long buf_coloffs = static_cast<long>(buf->Coloffs());
 
 		// Detect programmatic change (e.g., page_down command changed rowoffs)
 		// Use SetNextWindowScroll BEFORE BeginChild to set initial scroll position
-		if (prev_buf_rowoffs >= 0 && buf_rowoffs != prev_buf_rowoffs) {
+		if (prev_buf_rowoffs_ >= 0 && buf_rowoffs != prev_buf_rowoffs_) {
 			float target_y = static_cast<float>(buf_rowoffs) * row_h;
 			ImGui::SetNextWindowScroll(ImVec2(-1.0f, target_y));
 		}
-		if (prev_buf_coloffs >= 0 && buf_coloffs != prev_buf_coloffs) {
+		if (prev_buf_coloffs_ >= 0 && buf_coloffs != prev_buf_coloffs_) {
 			float target_x = static_cast<float>(buf_coloffs) * space_w;
 			float target_y = static_cast<float>(buf_rowoffs) * row_h;
 			ImGui::SetNextWindowScroll(ImVec2(target_x, target_y));
@@ -116,25 +113,22 @@ ImGuiRenderer::Draw(Editor &ed)
 		// Synchronize buffer offsets from ImGui scroll if user scrolled manually
 		bool forced_scroll = false;
 		{
-			static float prev_scroll_y = -1.0f; // previous frame's ImGui scroll Y in pixels
-			static float prev_scroll_x = -1.0f; // previous frame's ImGui scroll X in pixels
-
 			const long scroll_top  = static_cast<long>(scroll_y / row_h);
 			const long scroll_left = static_cast<long>(scroll_x / space_w);
 
 			// Check if rowoffs was programmatically changed this frame
-			if (prev_buf_rowoffs >= 0 && buf_rowoffs != prev_buf_rowoffs) {
+			if (prev_buf_rowoffs_ >= 0 && buf_rowoffs != prev_buf_rowoffs_) {
 				forced_scroll = true;
 			}
 
 			// If user scrolled (not programmatic), update buffer offsets accordingly
-			if (prev_scroll_y >= 0.0f && scroll_y != prev_scroll_y && !forced_scroll) {
+			if (prev_scroll_y_ >= 0.0f && scroll_y != prev_scroll_y_ && !forced_scroll) {
 				if (Buffer *mbuf = const_cast<Buffer *>(buf)) {
 					mbuf->SetOffsets(static_cast<std::size_t>(std::max(0L, scroll_top)),
 					                 mbuf->Coloffs());
 				}
 			}
-			if (prev_scroll_x >= 0.0f && scroll_x != prev_scroll_x && !forced_scroll) {
+			if (prev_scroll_x_ >= 0.0f && scroll_x != prev_scroll_x_ && !forced_scroll) {
 				if (Buffer *mbuf = const_cast<Buffer *>(buf)) {
 					mbuf->SetOffsets(mbuf->Rowoffs(),
 					                 static_cast<std::size_t>(std::max(0L, scroll_left)));
@@ -142,11 +136,11 @@ ImGuiRenderer::Draw(Editor &ed)
 			}
 
 			// Update trackers for next frame
-			prev_scroll_y = scroll_y;
-			prev_scroll_x = scroll_x;
+			prev_scroll_y_ = scroll_y;
+			prev_scroll_x_ = scroll_x;
 		}
-		prev_buf_rowoffs = buf_rowoffs;
-		prev_buf_coloffs = buf_coloffs;
+		prev_buf_rowoffs_ = buf_rowoffs;
+		prev_buf_coloffs_ = buf_coloffs;
 		// Cache current horizontal offset in rendered columns for click handling
 		const std::size_t coloffs_now = buf->Coloffs();
 
@@ -169,7 +163,7 @@ ImGuiRenderer::Draw(Editor &ed)
 		const std::size_t vsel_sy = vsel_active ? buf->VisualLineStartY() : 0;
 		const std::size_t vsel_ey = vsel_active ? buf->VisualLineEndY() : 0;
 
-		static bool mouse_selecting = false;
+		// (mouse_selecting__ is a member variable)
 		auto mouse_pos_to_buf       = [&]() -> std::pair<std::size_t, std::size_t> {
 			ImVec2 mp = ImGui::GetIO().MousePos;
 			// Convert mouse pos to buffer row
@@ -211,7 +205,7 @@ ImGuiRenderer::Draw(Editor &ed)
 
 		// Mouse-driven selection: set mark on double-click or drag, update cursor on any press/drag
 		if (ImGui::IsWindowHovered() && ImGui::IsMouseClicked(ImGuiMouseButton_Left)) {
-			mouse_selecting = true;
+			mouse_selecting_ = true;
 			auto [by, bx]   = mouse_pos_to_buf();
 			char tmp[64];
 			std::snprintf(tmp, sizeof(tmp), "%zu:%zu", by, bx);
@@ -225,7 +219,7 @@ ImGuiRenderer::Draw(Editor &ed)
 				}
 			}
 		}
-		if (mouse_selecting && ImGui::IsWindowHovered() && ImGui::IsMouseDown(ImGuiMouseButton_Left)) {
+		if (mouse_selecting_ && ImGui::IsWindowHovered() && ImGui::IsMouseDown(ImGuiMouseButton_Left)) {
 			auto [by, bx] = mouse_pos_to_buf();
 			// If we are dragging (mouse moved while down), ensure mark is set to start selection
 			if (ImGui::IsMouseDragging(ImGuiMouseButton_Left, 1.0f)) {
@@ -242,8 +236,8 @@ ImGuiRenderer::Draw(Editor &ed)
 			std::snprintf(tmp, sizeof(tmp), "%zu:%zu", by, bx);
 			Execute(ed, CommandId::MoveCursorTo, std::string(tmp));
 		}
-		if (mouse_selecting && ImGui::IsMouseReleased(ImGuiMouseButton_Left)) {
-			mouse_selecting = false;
+		if (mouse_selecting_ && ImGui::IsMouseReleased(ImGuiMouseButton_Left)) {
+			mouse_selecting_ = false;
 		}
 		for (std::size_t i = rowoffs; i < lines.size(); ++i) {
 			// Capture the screen position before drawing the line

ImGuiRenderer.h

@@ -11,4 +11,13 @@ public:
 	~ImGuiRenderer() override = default;
 
 	void Draw(Editor &ed) override;
+
+private:
+	// Per-window scroll tracking for two-way sync between Buffer offsets and ImGui scroll.
+	// These must be per-instance (not static) so each window maintains independent state.
+	long prev_buf_rowoffs_ = -1;
+	long prev_buf_coloffs_ = -1;
+	float prev_scroll_y_   = -1.0f;
+	float prev_scroll_x_   = -1.0f;
+	bool mouse_selecting_  = false;
 };

tests/test_swap_cleanup2.cc

@@ -0,0 +1,125 @@
+#include "Test.h"
+
+#include "Command.h"
+#include "Editor.h"
+
+#include "tests/TestHarness.h"
+
+#include <cstdio>
+#include <cstdlib>
+#include <filesystem>
+#include <fstream>
+#include <string>
+#include <unistd.h>
+
+namespace fs = std::filesystem;
+
+
+static void
+write_file_bytes(const std::string &path, const std::string &bytes)
+{
+	std::ofstream out(path, std::ios::binary | std::ios::trunc);
+	out.write(bytes.data(), (std::streamsize) bytes.size());
+}
+
+
+// RAII helper to set XDG_STATE_HOME for the duration of a test and clean up.
+struct XdgStateGuard {
+	fs::path root;
+	std::string old_xdg;
+	bool had_old;
+
+	explicit XdgStateGuard(const std::string &suffix)
+	{
+		root = fs::temp_directory_path() /
+		       (std::string("kte_ut_xdg_") + suffix + "_" + std::to_string((int) ::getpid()));
+		fs::remove_all(root);
+		fs::create_directories(root);
+
+		const char *p = std::getenv("XDG_STATE_HOME");
+		had_old       = (p != nullptr);
+		if (p)
+			old_xdg = p;
+		setenv("XDG_STATE_HOME", root.string().c_str(), 1);
+	}
+
+	~XdgStateGuard()
+	{
+		if (had_old)
+			setenv("XDG_STATE_HOME", old_xdg.c_str(), 1);
+		else
+			unsetenv("XDG_STATE_HOME");
+		fs::remove_all(root);
+	}
+};
+
+
+TEST(SwapCleanup_SaveAndQuit)
+{
+	ktet::InstallDefaultCommandsOnce();
+	XdgStateGuard xdg("save_quit");
+
+	const std::string path = (xdg.root / "work" / "file.txt").string();
+	fs::create_directories(xdg.root / "work");
+	write_file_bytes(path, "hello\n");
+
+	Editor ed;
+	ed.SetDimensions(24, 80);
+	ed.AddBuffer(Buffer());
+	std::string err;
+	ASSERT_TRUE(ed.OpenFile(path, err));
+	Buffer *b = ed.CurrentBuffer();
+	ASSERT_TRUE(b != nullptr);
+
+	// Edit to create swap file
+	ASSERT_TRUE(Execute(ed, CommandId::MoveFileStart));
+	ASSERT_TRUE(Execute(ed, CommandId::InsertText, "Z"));
+	ASSERT_TRUE(b->Dirty());
+
+	ed.Swap()->Flush(b);
+	const std::string swp = kte::SwapManager::ComputeSwapPathForTests(*b);
+	ASSERT_TRUE(fs::exists(swp));
+
+	// Save-and-quit should clean up the swap file
+	ASSERT_TRUE(Execute(ed, CommandId::SaveAndQuit));
+	ed.Swap()->Flush(b);
+	ASSERT_TRUE(!fs::exists(swp));
+
+	// Cleanup
+	std::remove(path.c_str());
+}
+
+
+TEST(SwapCleanup_EditorReset)
+{
+	ktet::InstallDefaultCommandsOnce();
+	XdgStateGuard xdg("editor_reset");
+
+	const std::string path = (xdg.root / "work" / "file.txt").string();
+	fs::create_directories(xdg.root / "work");
+	write_file_bytes(path, "hello\n");
+
+	Editor ed;
+	ed.SetDimensions(24, 80);
+	ed.AddBuffer(Buffer());
+	std::string err;
+	ASSERT_TRUE(ed.OpenFile(path, err));
+	Buffer *b = ed.CurrentBuffer();
+	ASSERT_TRUE(b != nullptr);
+
+	// Edit to create swap file
+	ASSERT_TRUE(Execute(ed, CommandId::MoveFileStart));
+	ASSERT_TRUE(Execute(ed, CommandId::InsertText, "W"));
+	ASSERT_TRUE(b->Dirty());
+
+	ed.Swap()->Flush(b);
+	const std::string swp = kte::SwapManager::ComputeSwapPathForTests(*b);
+	ASSERT_TRUE(fs::exists(swp));
+
+	// Reset (simulates clean editor exit) should remove swap files
+	ed.Reset();
+	ASSERT_TRUE(!fs::exists(swp));
+
+	// Cleanup
+	std::remove(path.c_str());
+}