Only process events for the window being created at creation time

Fixes https://github.com/libsdl-org/SDL/issues/14524

src/video/windows/SDL_windowsevents.c

@@ -2556,6 +2556,26 @@ void WIN_SendWakeupEvent(SDL_VideoDevice *_this, SDL_Window *window)
     PostMessage(data->hwnd, data->videodata->_SDL_WAKEUP, 0, 0);
 }
 
+// Simplified event pump for using when creating and destroying windows
+void WIN_PumpEventsForHWND(SDL_VideoDevice *_this, HWND hwnd)
+{
+    MSG msg;
+
+    if (g_WindowsEnableMessageLoop) {
+        SDL_processing_messages = true;
+
+        while (PeekMessage(&msg, hwnd, 0, 0, PM_REMOVE)) {
+            WIN_SetMessageTick(msg.time);
+
+            // Always translate the message in case it's a non-SDL window (e.g. with Qt integration)
+            TranslateMessage(&msg);
+            DispatchMessage(&msg);
+        }
+
+        SDL_processing_messages = false;
+    }
+}
+
 void WIN_PumpEvents(SDL_VideoDevice *_this)
 {
     MSG msg;

src/video/windows/SDL_windowsevents.h

@@ -33,6 +33,7 @@ extern LRESULT CALLBACK WIN_DefWindowProc(HWND hwnd, UINT msg, WPARAM wParam, LP
 extern void WIN_PollRawInput(SDL_VideoDevice *_this, Uint64 poll_start);
 extern void WIN_CheckKeyboardAndMouseHotplug(SDL_VideoDevice *_this, bool initial_check);
 extern void WIN_PumpEvents(SDL_VideoDevice *_this);
+extern void WIN_PumpEventsForHWND(SDL_VideoDevice *_this, HWND hwnd);
 extern void WIN_SendWakeupEvent(SDL_VideoDevice *_this, SDL_Window *window);
 extern int WIN_WaitEventTimeout(SDL_VideoDevice *_this, Sint64 timeoutNS);
 

src/video/windows/SDL_windowsopengl.c

@@ -429,7 +429,7 @@ void WIN_GL_InitExtensions(SDL_VideoDevice *_this)
     if (!hwnd) {
         return;
     }
-    WIN_PumpEvents(_this);
+    WIN_PumpEventsForHWND(_this, hwnd);
 
     hdc = GetDC(hwnd);
 
@@ -527,7 +527,7 @@ void WIN_GL_InitExtensions(SDL_VideoDevice *_this)
     _this->gl_data->wglDeleteContext(hglrc);
     ReleaseDC(hwnd, hdc);
     DestroyWindow(hwnd);
-    WIN_PumpEvents(_this);
+    WIN_PumpEventsForHWND(_this, hwnd);
 }
 
 static int WIN_GL_ChoosePixelFormatARB(SDL_VideoDevice *_this, int *iAttribs, float *fAttribs)
@@ -542,7 +542,7 @@ static int WIN_GL_ChoosePixelFormatARB(SDL_VideoDevice *_this, int *iAttribs, fl
     hwnd =
         CreateWindow(SDL_Appname, SDL_Appname, (WS_POPUP | WS_DISABLED), 0, 0,
                      10, 10, NULL, NULL, SDL_Instance, NULL);
-    WIN_PumpEvents(_this);
+    WIN_PumpEventsForHWND(_this, hwnd);
 
     hdc = GetDC(hwnd);
 
@@ -573,7 +573,7 @@ static int WIN_GL_ChoosePixelFormatARB(SDL_VideoDevice *_this, int *iAttribs, fl
     }
     ReleaseDC(hwnd, hdc);
     DestroyWindow(hwnd);
-    WIN_PumpEvents(_this);
+    WIN_PumpEventsForHWND(_this, hwnd);
 
     return pixel_format;
 }

src/video/windows/SDL_windowswindow.c

@@ -722,7 +722,7 @@ bool WIN_CreateWindow(SDL_VideoDevice *_this, SDL_Window *window, SDL_Properties
 
         WIN_UpdateDarkModeForHWND(hwnd);
 
-        WIN_PumpEvents(_this);
+        WIN_PumpEventsForHWND(_this, hwnd);
 
         if (!SetupWindowData(_this, window, hwnd, parent)) {
             DestroyWindow(hwnd);