Bug 1237617 - Call nsWindow::ForcePresent during going active r=bas.schouten

widget/windows/nsWindow.cpp

@@ -55,6 +55,7 @@
  **************************************************************/
 
 #include "gfx2DGlue.h"
+#include "gfxEnv.h"
 #include "gfxPlatform.h"
 #include "gfxPrefs.h"
 #include "mozilla/MathAlgorithms.h"
@@ -4985,6 +4986,15 @@ nsWindow::ProcessMessage(UINT msg, WPARAM& wParam, LPARAM& lParam,
       if (!mCustomNonClient)
         break;
 
+      // There is a case that rendered result is not kept. Bug 1237617
+      if (wParam == TRUE &&
+          !gfxEnv::DisableForcePresent() &&
+          gfxWindowsPlatform::GetPlatform()->DwmCompositionEnabled()) {
+        nsCOMPtr<nsIRunnable> event =
+          NS_NewRunnableMethod(this, &nsWindow::ForcePresent);
+        NS_DispatchToMainThread(event);
+      }
+
       // let the dwm handle nc painting on glass
       // Never allow native painting if we are on fullscreen
       if(mSizeMode != nsSizeMode_Fullscreen &&