Windows QPA: Improve workaround for non-Areo theme GL rendering.

Reportedly, clearing the clip region is sufficient to fix the issue.
InvalidateRect() should be avoided when handling WM_PAINT as it
may cause events.

Task-number: QTBUG-7865
Change-Id: Id9a7c280fcc2c8242bb34c34e73e53c3146e7a6e
Reviewed-by: Andy Shaw <andy.shaw@qt.io>
Reviewed-by: Oliver Wolff <oliver.wolff@qt.io>
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>

1 files changed, 4 insertions, 3 deletions

diff --git a/src/plugins/platforms/windows/qwindowswindow.cpp b/src/plugins/platforms/windows/qwindowswindow.cpp
index cf13de427e..9c6cb53365 100644
--- a/src/plugins/platforms/windows/qwindowswindow.cpp
+++ b/src/plugins/platforms/windows/qwindowswindow.cpp
@@ -1568,11 +1568,12 @@ bool QWindowsWindow::handleWmPaint(HWND hwnd, UINT message,
         return false;
     PAINTSTRUCT ps;
 
+    BeginPaint(hwnd, &ps);
+
     // Observed painting problems with Aero style disabled (QTBUG-7865).
+    // 5.8: Consider making it dependent on !DwmIsCompositionEnabled().
     if (testFlag(OpenGLSurface) && testFlag(OpenGLDoubleBuffered))
-        InvalidateRect(hwnd, 0, false);
-
-    BeginPaint(hwnd, &ps);
+        SelectClipRgn(ps.hdc, NULL);
 
     // If the a window is obscured by another window (such as a child window)
     // we still need to send isExposed=true, for compatibility.