Fix crash in when resizing directfb windows

Since QRasterPaintEngine::baseClip was initialized when the
QDirectFBPaintEngine was created and the paintengine persists for the
window surface we run the risk that the baseClip is of the wrong size.
This could lead to crashes and erroneous clipping.

Reviewed-by: Donald <qt-info@nokia.com>

2 files changed, 11 insertions, 5 deletions

diff --git a/src/plugins/gfxdrivers/directfb/qdirectfbwindowsurface.cpp b/src/plugins/gfxdrivers/directfb/qdirectfbwindowsurface.cpp
index a1009ac..15a46d7 100644
--- a/src/plugins/gfxdrivers/directfb/qdirectfbwindowsurface.cpp
+++ b/src/plugins/gfxdrivers/directfb/qdirectfbwindowsurface.cpp
@@ -56,6 +56,7 @@ QDirectFBWindowSurface::QDirectFBWindowSurface(DFBSurfaceFlipFlags flip, QDirect
     , dfbWindow(0)
 #endif
     , engine(0)
+    , engineHeight(-1)
     , flipFlags(flip)
     , boundingRectFlip(scr->directFBFlags() & QDirectFBScreen::BoundingRectFlip)
 {
@@ -77,6 +78,7 @@ QDirectFBWindowSurface::QDirectFBWindowSurface(DFBSurfaceFlipFlags flip, QDirect
     , dfbWindow(0)
 #endif
     , engine(0)
+    , engineHeight(-1)
     , flipFlags(flip)
     , boundingRectFlip(scr->directFBFlags() & QDirectFBScreen::BoundingRectFlip)
 {
@@ -295,11 +297,8 @@ bool QDirectFBWindowSurface::move(const QPoint &moveBy)
 
 QPaintEngine *QDirectFBWindowSurface::paintEngine() const
 {
-    if (!engine) {
-        QDirectFBWindowSurface *that = const_cast<QDirectFBWindowSurface*>(this);
-        that->engine = new QDirectFBPaintEngine(that);
-        return that->engine;
-    }
+    Q_ASSERT(engine);
+    Q_ASSERT(height() <= engineHeight);
     return engine;
 }
 
@@ -427,6 +426,12 @@ void QDirectFBWindowSurface::flush(QWidget *, const QRegion &region,
 
 void QDirectFBWindowSurface::beginPaint(const QRegion &)
 {
+    const int h = height();
+    if (h > engineHeight) {
+        engineHeight = h;
+        delete engine;
+        engine = new QDirectFBPaintEngine(this);
+    }
 }
 
 void QDirectFBWindowSurface::endPaint(const QRegion &)
diff --git a/src/plugins/gfxdrivers/directfb/qdirectfbwindowsurface.h b/src/plugins/gfxdrivers/directfb/qdirectfbwindowsurface.h
index c46d93b..cd88aca 100644
--- a/src/plugins/gfxdrivers/directfb/qdirectfbwindowsurface.h
+++ b/src/plugins/gfxdrivers/directfb/qdirectfbwindowsurface.h
@@ -93,6 +93,7 @@ private:
     IDirectFBWindow *dfbWindow;
 #endif
     QDirectFBPaintEngine *engine;
+    int engineHeight;
 
     enum Mode {
         Primary,