Fix a bug in QDirectFBWindowSurface::scroll

It seems that one cannot do multiple blits within a double-buffered
surface in overlapping one another without doing a Flip in between. I
find this a little odd and will check that it's the correct behavior but
this fixes bugs in scroll(). To see a case that used to produce drawing
errors check out the collidingmouse example and drag the viewport
around.

Reviewed-by: Jervey Kong <jervey.kong@nokia.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/src/plugins/gfxdrivers/directfb/qdirectfbwindowsurface.cpp b/src/plugins/gfxdrivers/directfb/qdirectfbwindowsurface.cpp
index 4cebc96..19103cb 100644
--- a/src/plugins/gfxdrivers/directfb/qdirectfbwindowsurface.cpp
+++ b/src/plugins/gfxdrivers/directfb/qdirectfbwindowsurface.cpp
@@ -274,6 +274,8 @@ static inline void scrollSurface(IDirectFBSurface *surface, const QRect &r, int
 {
     const DFBRectangle rect = { r.x(), r.y(), r.width(), r.height() };
     surface->Blit(surface, surface, &rect, r.x() + dx, r.y() + dy);
+    const DFBRegion region = { rect.x + dx, rect.y + dy, r.right() + dx, r.bottom() + dy };
+    surface->Flip(surface, &region, DSFLIP_BLIT);
 }
 
 bool QDirectFBWindowSurface::scroll(const QRegion &region, int dx, int dy)