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,