Revert "Windows QPA: Call QWSI::flushWindowSystemEvents() from WM_PAINT for full update only"

This reverts commit a81dfb32d6f9e7a407567511c20b59e537f6a063.

Paint immediately on WM_PAINT in all cases in order to
avoid flicker on resize.

The cases mentioned in commit a81dfb should no longer
apply:
  - QTBUG-38327: QGLWidget is not supported in Qt 6.
  - QTBUG-39842: Fixed by using ExcludeUserInputEvents.

Fixes: QTBUG-89688
Change-Id: If82cf7703d6663982769048e86a7060223730ce7
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>
Reviewed-by: Oliver Wolff <oliver.wolff@qt.io>
(cherry picked from commit 9f894788dda8407c6221aaa1491cd54a5a2b4cb7)

1 files changed, 2 insertions, 3 deletions

diff --git a/src/plugins/platforms/windows/qwindowswindow.cpp b/src/plugins/platforms/windows/qwindowswindow.cpp
index 5987324ac1..f08375d45f 100644
--- a/src/plugins/platforms/windows/qwindowswindow.cpp
+++ b/src/plugins/platforms/windows/qwindowswindow.cpp
@@ -2125,8 +2125,7 @@ bool QWindowsWindow::handleWmPaint(HWND hwnd, UINT message,
     if (!window()->isVisible() && (GetWindowLong(hwnd, GWL_EXSTYLE) & WS_EX_LAYERED) != 0)
         return false;
     // Ignore invalid update bounding rectangles
-    RECT updateRect;
-    if (!GetUpdateRect(m_data.hwnd, &updateRect, FALSE))
+    if (!GetUpdateRect(m_data.hwnd, 0, FALSE))
         return false;
     PAINTSTRUCT ps;
 
@@ -2148,7 +2147,7 @@ bool QWindowsWindow::handleWmPaint(HWND hwnd, UINT message,
     // we still need to send isExposed=true, for compatibility.
     // Our tests depend on it.
     fireExpose(QRegion(qrectFromRECT(ps.rcPaint)), true);
-    if (qSizeOfRect(updateRect) == m_data.geometry.size() && !QWindowsContext::instance()->asyncExpose())
+    if (!QWindowsContext::instance()->asyncExpose())
         QWindowSystemInterface::flushWindowSystemEvents(QEventLoop::ExcludeUserInputEvents);
 
     EndPaint(hwnd, &ps);