Make translucent windows work, and support WA_TranslucentBackground

QWS will make a window translucent if the background brush is not
opaque. Now we also support the cross-platform way of doing it.
This also includes fixes for bugs caused by behavioural changes in
the internal windowsurface/backingstore implementation.

Task-number: QTBUG-5739
Reviewed-by: Tom

1 files changed, 10 insertions, 1 deletions

diff --git a/src/gui/painting/qbackingstore.cpp b/src/gui/painting/qbackingstore.cpp
index c73d9f4c44..8de9eaa5c8 100644
--- a/src/gui/painting/qbackingstore.cpp
+++ b/src/gui/painting/qbackingstore.cpp
@@ -352,6 +352,10 @@ void QWidgetBackingStore::beginPaint(QRegion &toClean, QWidget *widget, QWindowS
     // Always flush repainted areas.
     dirtyOnScreen += toClean;
 
+#ifdef Q_WS_QWS
+    toClean.translate(tlwOffset);
+#endif
+
 #ifdef QT_NO_PAINT_DEBUG
     windowSurface->beginPaint(toClean);
 #else
@@ -766,7 +770,12 @@ void QWidgetBackingStore::paintWindowDecoration()
     if (decorationRegion.isEmpty())
         return;
 
-    windowSurface->beginPaint(decorationRegion);
+    //### The QWS decorations do not always paint the pixels they promise to paint.
+    // This causes painting problems with QWSMemorySurface. Since none of the other
+    // window surfaces actually use the region, passing an empty region is a safe
+    // workaround.
+
+    windowSurface->beginPaint(QRegion());
 
     QPaintEngine *engine = windowSurface->paintDevice()->paintEngine();
     Q_ASSERT(engine);