feat: add ImGui frontend support with game selection and debug panels

include/panda_sdl/frontend_sdl.hpp

@@ -3,6 +3,8 @@
 #include <SDL.h>
 
 #include <filesystem>
+#include <memory>
+#include <optional>
 
 #include "emulator.hpp"
 #include "input_mappings.hpp"
@@ -13,11 +15,26 @@ class FrontendSDL {
 #ifdef PANDA3DS_ENABLE_OPENGL
 	SDL_GLContext glContext;
 #endif
+#ifdef IMGUI_FRONTEND
+	std::unique_ptr<class ImGuiLayer> imgui;
+#endif
 
   public:
 	FrontendSDL();
+	#ifdef IMGUI_FRONTEND
+	FrontendSDL(SDL_Window* existingWindow, SDL_GLContext existingContext);
+	#endif
+	~FrontendSDL();
+	#ifdef IMGUI_FRONTEND
+	struct ImGuiWindowContext {
+		SDL_Window* window = nullptr;
+		SDL_GLContext context = nullptr;
+	};
+	static ImGuiWindowContext createImGuiWindowContext(const EmulatorConfig& bootConfig, const char* windowTitle);
+	#endif
 	bool loadROM(const std::filesystem::path& path);
 	void run();
+	std::optional<std::filesystem::path> selectGame();
 	u32 getMapping(InputMappings::Scancode scancode) { return keyboardMappings.getMapping(scancode); }
 
 	SDL_Window* window = nullptr;
@@ -42,8 +59,12 @@ class FrontendSDL {
 	// And so the user can still use the keyboard to control the analog
 	bool keyboardAnalogX = false;
 	bool keyboardAnalogY = false;
+	bool emuPaused = false;
 
   private:
 	void setupControllerSensors(SDL_GameController* controller);
 	void handleLeftClick(int mouseX, int mouseY);
+	void setPaused(bool paused);
+	void togglePaused();
+	void initialize(SDL_Window* existingWindow, SDL_GLContext existingContext, bool useExternalContext);
 };

include/panda_sdl/imgui_layer.hpp

@@ -0,0 +1,50 @@
+#pragma once
+
+#ifdef IMGUI_FRONTEND
+
+#include <SDL.h>
+
+#include <functional>
+#include <optional>
+
+#include "emulator.hpp"
+
+class ImGuiLayer {
+  public:
+	ImGuiLayer(SDL_Window* window, SDL_GLContext context, Emulator& emu);
+	void init();
+	void shutdown();
+	void processEvent(const SDL_Event& event);
+	void beginFrame();
+	void render();
+	void handleHotkey(const SDL_Event& event);
+	std::optional<std::filesystem::path> runGameSelector();
+
+	bool wantsCaptureKeyboard() const { return captureKeyboard; }
+	bool wantsCaptureMouse() const { return captureMouse; }
+
+	void setPaused(bool paused) { isPaused = paused; }
+	void setPauseCallback(std::function<void(bool)> callback) { onPauseChange = std::move(callback); }
+	void setVsyncCallback(std::function<void(bool)> callback) { onVsyncChange = std::move(callback); }
+
+  private:
+	void drawDebugPanel();
+	void drawPausePanel();
+	void drawSettingsPanel();
+
+	SDL_Window* window = nullptr;
+	SDL_GLContext glContext = nullptr;
+	Emulator& emu;
+
+	bool showDebug = true;
+	bool showPauseMenu = false;
+	bool showSettings = false;
+	bool isPaused = false;
+	bool captureKeyboard = false;
+	bool captureMouse = false;
+
+	std::function<void(bool)> onPauseChange;
+	std::function<void(bool)> onVsyncChange;
+};
+
+#endif