Windows: Avoid restarting completely on GPU change.

This retains the logger, avoids an annoying window open/close, and most
importantly for me: keeps the debugger attached.

Core/System.cpp

@@ -97,6 +97,10 @@ static volatile CPUThreadState cpuThreadState = CPU_THREAD_NOT_RUNNING;
 
 static GPUBackend gpuBackend;
 
+void ResetUIState() {
+	globalUIState = UISTATE_MENU;
+}
+
 void UpdateUIState(GlobalUIState newState) {
 	// Never leave the EXIT state.
 	if (globalUIState != newState && globalUIState != UISTATE_EXIT) {

Core/System.h

@@ -54,6 +54,7 @@ enum PSPDirectories {
 class GraphicsContext;
 enum class GPUBackend;
 
+void ResetUIState();
 void UpdateUIState(GlobalUIState newState);
 GlobalUIState GetUIState();
 

UI/GameSettingsScreen.cpp

@@ -1057,8 +1057,7 @@ void GameSettingsScreen::CallbackRenderingBackend(bool yes) {
 	// If the user ends up deciding not to restart, set the config back to the current backend
 	// so it doesn't get switched by accident.
 	if (yes) {
-		g_Config.bRestartRequired = true;
-		PostMessage(MainWindow::GetHWND(), WM_CLOSE, 0, 0);
+		System_SendMessage("graphics_restart", "");
 	} else {
 		g_Config.iGPUBackend = (int)GetGPUBackend();
 	}

Windows/EmuThread.cpp

@@ -112,6 +112,7 @@ unsigned int WINAPI TheThread(void *)
 		args.push_back(string.c_str());
 	}
 
+	bool performingRestart = NativeIsRestarting();
 	NativeInit(static_cast<int>(args.size()), &args[0], "1234", "1234", nullptr);
 
 	Host *nativeHost = host;
@@ -123,6 +124,14 @@ unsigned int WINAPI TheThread(void *)
 
 	std::string error_string;
 	if (!host->InitGraphics(&error_string, &graphicsContext)) {
+		// Before anything: are we restarting right now?
+		if (performingRestart) {
+			// Okay, switching graphics didn't work out.  Probably a driver bug - fallback to restart.
+			// This happens on NVIDIA when switching OpenGL -> Vulkan.
+			g_Config.Save();
+			W32Util::ExitAndRestart();
+		}
+
 		I18NCategory *err = GetI18NCategory("Error");
 		Reporting::ReportMessage("Graphics init error: %s", error_string.c_str());
 

Windows/MainWindow.cpp

@@ -882,6 +882,14 @@ namespace MainWindow
 			BrowseBackgroundDone();
 			break;
 
+		case WM_USER_RESTART_EMUTHREAD:
+			NativeSetRestarting();
+			EmuThread_Stop();
+			coreState = CORE_POWERUP;
+			ResetUIState();
+			EmuThread_Start();
+			break;
+
 		case WM_MENUSELECT:
 			// Called when a menu is opened. Also when an item is selected, but meh.
 			UpdateMenus(true);

Windows/MainWindow.h

@@ -20,6 +20,7 @@ namespace MainWindow
 		WM_USER_WINDOW_TITLE_CHANGED = WM_USER + 103,
 		WM_USER_BROWSE_BOOT_DONE = WM_USER + 104,
 		WM_USER_TOGGLE_FULLSCREEN = WM_USER + 105,
+		WM_USER_RESTART_EMUTHREAD = WM_USER + 106,
 	};
 
 	enum {

Windows/MainWindowMenu.cpp

@@ -770,26 +770,22 @@ namespace MainWindow {
 
 		case ID_OPTIONS_DIRECT3D9:
 			g_Config.iGPUBackend = GPU_BACKEND_DIRECT3D9;
-			g_Config.bRestartRequired = true;
-			PostMessage(MainWindow::GetHWND(), WM_CLOSE, 0, 0);
+			PostMessage(MainWindow::GetHWND(), WM_USER_RESTART_EMUTHREAD, 0, 0);
 			break;
 
 		case ID_OPTIONS_DIRECT3D11:
 			g_Config.iGPUBackend = GPU_BACKEND_DIRECT3D11;
-			g_Config.bRestartRequired = true;
-			PostMessage(MainWindow::GetHWND(), WM_CLOSE, 0, 0);
+			PostMessage(MainWindow::GetHWND(), WM_USER_RESTART_EMUTHREAD, 0, 0);
 			break;
 
 		case ID_OPTIONS_OPENGL:
 			g_Config.iGPUBackend = GPU_BACKEND_OPENGL;
-			g_Config.bRestartRequired = true;
-			PostMessage(MainWindow::GetHWND(), WM_CLOSE, 0, 0);
+			PostMessage(MainWindow::GetHWND(), WM_USER_RESTART_EMUTHREAD, 0, 0);
 			break;
 
 		case ID_OPTIONS_VULKAN:
 			g_Config.iGPUBackend = GPU_BACKEND_VULKAN;
-			g_Config.bRestartRequired = true;
-			PostMessage(MainWindow::GetHWND(), WM_CLOSE, 0, 0);
+			PostMessage(MainWindow::GetHWND(), WM_USER_RESTART_EMUTHREAD, 0, 0);
 			break;
 
 		case ID_OPTIONS_NONBUFFEREDRENDERING:   setRenderingMode(FB_NON_BUFFERED_MODE); break;

Windows/WindowsHost.cpp

@@ -146,7 +146,6 @@ void WindowsHost::ShutdownGraphics() {
 	gfx_->Shutdown();
 	delete gfx_;
 	gfx_ = nullptr;
-	PostMessage(mainWindow_, WM_CLOSE, 0, 0);
 }
 
 void WindowsHost::SetWindowTitle(const char *message) {

Windows/main.cpp

@@ -231,7 +231,11 @@ int System_GetPropertyInt(SystemProperty prop) {
 
 void System_SendMessage(const char *command, const char *parameter) {
 	if (!strcmp(command, "finish")) {
-		PostMessage(MainWindow::GetHWND(), WM_CLOSE, 0, 0);
+		if (!NativeIsRestarting()) {
+			PostMessage(MainWindow::GetHWND(), WM_CLOSE, 0, 0);
+		}
+	} else if (!strcmp(command, "graphics_restart")) {
+		PostMessage(MainWindow::GetHWND(), MainWindow::WM_USER_RESTART_EMUTHREAD, 0, 0);
 	} else if (!strcmp(command, "setclipboardtext")) {
 		if (OpenClipboard(MainWindow::GetDisplayHWND())) {
 			std::wstring data = ConvertUTF8ToWString(parameter);