Fix flickering during window resize.

Textures still turn white when letting go of the mouse button, though.

Author: Quipyowert2

libgag/include/EventListener.h

@@ -39,6 +39,7 @@ class EventListener {
 	void run();
 	void stop();
 	bool isRunning();
+	bool isResizing();
 	int poll(SDL_Event* e);
 	static EventListener *instance();
 	~EventListener();

libgag/src/EventListener.cpp

@@ -129,8 +129,8 @@ void EventListener::paint()
 //! Handle user resizing the game window on Microsoft Windows.
 // TODO: Handle window resizing on macOS
 //https://stackoverflow.com/a/51597338/8890345
-#ifdef WINDOWS_OR_MINGW
 bool sizeMoveTimerRunning = false;
+#ifdef WINDOWS_OR_MINGW
 int eventWatch(void* self, SDL_Event* event) {
 	if (event->type == SDL_SYSWMEVENT)
 	{
@@ -156,6 +156,10 @@ int eventWatch(void* self, SDL_Event* event) {
 }
 #endif
 
+bool EventListener::isResizing()
+{
+	return sizeMoveTimerRunning;
+}
 /** Listens for events and adds them to a queue.
  *  Call EventListener::poll to get an event from the queue.
  */

libgag/src/GraphicContext.cpp

@@ -1675,7 +1675,7 @@ namespace GAGCore
 		if (_gc->optionFlags & GraphicContext::USEGPU)
 		{
 			// upload
-			if (surface->dirty)
+			if (surface->dirty || EventListener::instance()->isResizing())
 				surface->uploadToTexture();
 
 			// state change