Windows QPA: remove SWP_NOCOPYBITS for plain moves

The SWP_NOCOPYBITS flag helps suppress some jittering during resizes. At the moment this is called even for plain moves with no window resizing. Make sure that the window geometry has changed before applying the SWP_NOCOPYBITS flag Fixes: QTBUG-115992 Pick-to: 6.6 6.5 Change-Id: Ic0cb32d9eb3b557bf2b2ef5b6ba80d34e27c5c19 Reviewed-by: Oliver Wolff <[email protected]> Reviewed-by: Pavel Dubsky <[email protected]> Cherry-picked into adsk-contrib-maya-v6.5.3 by Keith Kyzivat <[email protected]> on 20231219 to fix MAYA-131850 (cherry picked from commit 9a64449)
autodesk-forks · Dec 19, 2023 · c4af263 · c4af263
1 parent a9b7395
commit c4af263
Showing 1 changed file with 8 additions and 4 deletions.
diff --git a/src/plugins/platforms/windows/qwindowswindow.cpp b/src/plugins/platforms/windows/qwindowswindow.cpp
@@ -2709,10 +2709,17 @@ void QWindowsWindow::propagateSizeHints()
 bool QWindowsWindow::handleGeometryChangingMessage(MSG *message, const QWindow *qWindow, const QMargins &margins)
 {
     auto *windowPos = reinterpret_cast<WINDOWPOS *>(message->lParam);
+    const QRect suggestedFrameGeometry(windowPos->x, windowPos->y,
+                                       windowPos->cx, windowPos->cy);
+    const QRect suggestedGeometry = suggestedFrameGeometry - margins;
 
     // Tell Windows to discard the entire contents of the client area, as re-using
     // parts of the client area would lead to jitter during resize.
-    windowPos->flags |= SWP_NOCOPYBITS;
+    // Check the suggestedGeometry against the current one to only discard during
+    // resize, and not a plain move. We also look for SWP_NOSIZE since that, too,
+    // implies an identical size, and comparing QRects wouldn't work with null cx/cy
+    if (!(windowPos->flags & SWP_NOSIZE) && suggestedGeometry.size() != qWindow->geometry().size())
+        windowPos->flags |= SWP_NOCOPYBITS;
 
     if ((windowPos->flags & SWP_NOZORDER) == 0) {
         if (QWindowsWindow *platformWindow = QWindowsWindow::windowsWindowOf(qWindow)) {
@@ -2728,9 +2735,6 @@ bool QWindowsWindow::handleGeometryChangingMessage(MSG *message, const QWindow *
         return false;
     if (windowPos->flags & SWP_NOSIZE)
         return false;
-    const QRect suggestedFrameGeometry(windowPos->x, windowPos->y,
-                                       windowPos->cx, windowPos->cy);
-    const QRect suggestedGeometry = suggestedFrameGeometry - margins;
     const QRectF correctedGeometryF = QPlatformWindow::closestAcceptableGeometry(qWindow, suggestedGeometry);
     if (!correctedGeometryF.isValid())
         return false;