Add mechanism to run any closure on the main thread

Common/System/System.h

@@ -100,6 +100,9 @@ enum class SystemRequestType {
 	RUN_CALLBACK_IN_WNDPROC,
 };
 
+// Run a closure on the main thread. Used to safely implement UI that runs on another thread.
+void System_RunOnMainThread(std::function<void()> func);
+
 // Implementations are supposed to process the request, and post the response to the g_RequestManager (see Message.h).
 // This is not to be used directly by applications, instead use the g_RequestManager to make the requests.
 // This can return false if it's known that the platform doesn't support the request, the app is supposed to handle

UI/NativeApp.cpp

@@ -177,7 +177,7 @@ struct PendingMessage {
 	std::string value;
 };
 
-static std::mutex pendingMutex;
+static std::mutex g_pendingMutex;
 static std::vector<PendingMessage> pendingMessages;
 static Draw::DrawContext *g_draw;
 static Draw::Pipeline *colorPipeline;
@@ -185,6 +185,7 @@ static Draw::Pipeline *texColorPipeline;
 static UIContext *uiContext;
 static int g_restartGraphics;
 static bool g_windowHidden = false;
+std::vector<std::function<void()>> g_pendingClosures;
 
 #ifdef _WIN32
 WindowsAudioBackend *winAudioBackend;
@@ -345,6 +346,7 @@ void NativeInit(int argc, const char *argv[], const char *savegame_dir, const ch
 	setlocale( LC_ALL, "C" );
 	std::string user_data_path = savegame_dir;
 	pendingMessages.clear();
+	g_pendingClosures.clear();
 	g_requestManager.Clear();
 
 	// external_dir has all kinds of meanings depending on platform.
@@ -1047,19 +1049,28 @@ void NativeFrame(GraphicsContext *graphicsContext) {
 	g_screenManager->update();
 
 	// Do this after g_screenManager.update() so we can receive setting changes before rendering.
-	std::vector<PendingMessage> toProcess;
 	{
-		std::lock_guard<std::mutex> lock(pendingMutex);
-		toProcess = std::move(pendingMessages);
-		pendingMessages.clear();
-	}
-
-	for (const auto &item : toProcess) {
-		if (HandleGlobalMessage(item.message, item.value)) {
-			// TODO: Add a to-string thingy.
-			INFO_LOG(Log::System, "Handled global message: %d / %s", (int)item.message, item.value.c_str());
+		std::vector<PendingMessage> toProcess;
+		std::vector<std::function<void()>> toRun;
+		{
+			std::lock_guard<std::mutex> lock(g_pendingMutex);
+			toProcess = std::move(pendingMessages);
+			toRun = std::move(g_pendingClosures);
+			pendingMessages.clear();
+			g_pendingClosures.clear();
+		}
+
+		for (auto &item : toRun) {
+			item();
+		}
+
+		for (const auto &item : toProcess) {
+			if (HandleGlobalMessage(item.message, item.value)) {
+				// TODO: Add a to-string thingy.
+				INFO_LOG(Log::System, "Handled global message: %d / %s", (int)item.message, item.value.c_str());
+			}
+			g_screenManager->sendMessage(item.message, item.value.c_str());
 		}
-		g_screenManager->sendMessage(item.message, item.value.c_str());
 	}
 
 	g_requestManager.ProcessRequests();
@@ -1404,13 +1415,18 @@ void NativeAccelerometer(float tiltX, float tiltY, float tiltZ) {
 }
 
 void System_PostUIMessage(UIMessage message, const std::string &value) {
-	std::lock_guard<std::mutex> lock(pendingMutex);
+	std::lock_guard<std::mutex> lock(g_pendingMutex);
 	PendingMessage pendingMessage;
 	pendingMessage.message = message;
 	pendingMessage.value = value;
 	pendingMessages.push_back(pendingMessage);
 }
 
+void System_RunOnMainThread(std::function<void()> func) {
+	std::lock_guard<std::mutex> lock(g_pendingMutex);
+	g_pendingClosures.push_back(std::move(func));
+}
+
 void NativeResized() {
 	// NativeResized can come from any thread so we just set a flag, then process it later.
 	VERBOSE_LOG(Log::G3D, "NativeResized - setting flag");

Windows/MainWindowMenu.cpp

@@ -497,9 +497,7 @@ namespace MainWindow {
 			break;
 
 		case ID_EMULATION_PAUSE:
-			if (!NetworkWarnUserIfOnlineAndCantSpeed()) {
-				System_PostUIMessage(UIMessage::REQUEST_GAME_PAUSE);
-			}
+			System_PostUIMessage(UIMessage::REQUEST_GAME_PAUSE);
 			break;
 
 		case ID_EMULATION_STOP:

headless/Headless.cpp

@@ -93,6 +93,7 @@ bool System_GetPropertyBool(SystemProperty prop) {
 }
 void System_Notify(SystemNotification notification) {}
 void System_PostUIMessage(UIMessage message, const std::string &param) {}
+void System_RunOnMainThread(std::function<void()>) {}
 bool System_MakeRequest(SystemRequestType type, int requestId, const std::string &param1, const std::string &param2, int64_t param3, int64_t param4) {
 	switch (type) {
 	case SystemRequestType::SEND_DEBUG_OUTPUT:

libretro/libretro.cpp

@@ -1913,6 +1913,7 @@ void System_Notify(SystemNotification notification) {
 }
 bool System_MakeRequest(SystemRequestType type, int requestId, const std::string &param1, const std::string &param2, int64_t param3, int64_t param4) { return false; }
 void System_PostUIMessage(UIMessage message, const std::string &param) {}
+void System_RunOnMainThread(std::function<void()>) {}
 void NativeFrame(GraphicsContext *graphicsContext) {}
 void NativeResized() {}
 

unittest/UnitTest.cpp

@@ -112,6 +112,7 @@ bool System_GetPropertyBool(SystemProperty prop) {
 }
 void System_Notify(SystemNotification notification) {}
 void System_PostUIMessage(UIMessage message, const std::string &param) {}
+void System_RunOnMainThread(std::function<void()>) {}
 void System_AudioGetDebugStats(char *buf, size_t bufSize) { if (buf) buf[0] = '\0'; }
 void System_AudioClear() {}
 void System_AudioPushSamples(const s32 *audio, int numSamples, float volume) {}
@@ -119,9 +120,7 @@ void System_AudioPushSamples(const s32 *audio, int numSamples, float volume) {}
 // TODO: To avoid having to define these here, these should probably be turned into system "requests".
 // To clear the secret entirely, just save an empty string.
 bool NativeSaveSecret(std::string_view nameOfSecret, std::string_view data) { return false; }
-std::string NativeLoadSecret(std::string_view nameOfSecret) {
-	return "";
-}
+std::string NativeLoadSecret(std::string_view nameOfSecret) { return ""; }
 
 #if PPSSPP_PLATFORM(ANDROID)
 JNIEnv *getEnv() {