Moving a child widget right after show() does not work as expected.

The problem was that we did an accelerated move, i.e. scrolled the
widget's contents in the backing store and repainted the old area. We
cannot do this trick when the widget has been invalidated (show(),
resize()). In this case the widget had never been painted, so we
basically scrolled the content of its parent and the widget itself
appeared as invisible.

Auto-test included.

Task-number: 255117
Reviewed-by: Paul

1 files changed, 4 insertions, 1 deletions

diff --git a/src/gui/painting/qbackingstore.cpp b/src/gui/painting/qbackingstore.cpp
index 0f7933cca9..3bbdf7ff86 100644
--- a/src/gui/painting/qbackingstore.cpp
+++ b/src/gui/painting/qbackingstore.cpp
@@ -258,7 +258,10 @@ void QWidgetBackingStore::unflushPaint(QWidget *widget, const QRegion &rgn)
 bool QWidgetBackingStore::bltRect(const QRect &rect, int dx, int dy, QWidget *widget)
 {
     const QPoint pos(tlwOffset + widget->mapTo(tlw, rect.topLeft()));
-    return windowSurface->scroll(QRect(pos, rect.size()), dx, dy);
+    const QRect tlwRect(QRect(pos, rect.size()));
+    if (dirty.intersects(tlwRect))
+        return false; // We don't want to scroll junk.
+    return windowSurface->scroll(tlwRect, dx, dy);
 }
 
 void QWidgetBackingStore::releaseBuffer()