Flush window events in MMAL and DRM renderers

app/streaming/video/ffmpeg-renderers/mmal.cpp

@@ -230,6 +230,23 @@ void MmalRenderer::setupBackground(PDECODER_PARAMETERS params)
             return;
         }
 
+        // SDL_CreateRenderer() can end up having to recreate our window (SDL_RecreateWindow())
+        // to ensure it's compatible with the renderer's OpenGL context. If that happens, we
+        // can get spurious SDL_WINDOWEVENT events that will cause us to (again) recreate our
+        // renderer. This can lead to an infinite to renderer recreation, so discard all
+        // SDL_WINDOWEVENT events after SDL_CreateRenderer().
+        Session* session = Session::get();
+        if (session != nullptr) {
+            // If we get here during a session, we need to synchronize with the event loop
+            // to ensure we don't drop any important events.
+            session->flushWindowEvents();
+        }
+        else {
+            // If we get here prior to the start of a session, just pump and flush ourselves.
+            SDL_PumpEvents();
+            SDL_FlushEvent(SDL_WINDOWEVENT);
+        }
+
         SDL_SetRenderDrawColor(m_BackgroundRenderer, 0, 0, 0, SDL_ALPHA_OPAQUE);
         SDL_RenderClear(m_BackgroundRenderer);
         SDL_RenderPresent(m_BackgroundRenderer);