Experimental better alt+-tab handling on Windows

Unconfirmed if/how well this works.

src/ui/KonvergoWindow.cpp

@@ -255,6 +255,17 @@ void KonvergoWindow::onVisibilityChanged(QWindow::Visibility visibility)
     PowerComponent::Get().setFullscreenState(false);
 }
 
+/////////////////////////////////////////////////////////////////////////////////////////
+void KonvergoWindow::focusOutEvent(QFocusEvent * ev)
+{
+#ifdef Q_OS_WIN32
+  // Do this to workaround DWM compositor bugs with fullscreened OpenGL applications.
+  // The compositor will not properly redraw anything when focusing other windows.
+  if (visibility() == QWindow::FullScreen)
+    showMinimized();
+#endif
+}
+
 /////////////////////////////////////////////////////////////////////////////////////////
 void KonvergoWindow::playerPlaybackStarting()
 {

src/ui/KonvergoWindow.h

@@ -49,6 +49,9 @@ Q_SIGNALS:
   void debugInfoChanged();
   void reloadWebClient();
 
+protected:
+  virtual void focusOutEvent(QFocusEvent * ev);
+
 private slots:
   void closingWindow();
   void enableVideoWindow();