Regression: Horizontal line seen using qDrawBorderPixmap with X11 graphicssystem

To isolate a bug I saw in other projects, I created a QGraphicsObject that paints using qDrawBorderPixmap, the result is that two horizontal lines are seen where the center tiles meet the top or bottom ones.

Some findings I have:

• Bug only appears when running with graphicssystem X11. Painting is fine with "raster" or "opengl"
• Bug is NOT seen in Qt 4.6.3
• Bug is NOT seen if QPainter::smoothPixmapTransform render hint is unset

To reproduce, compile and run the attached example. Click the button to change it from light to dark color. Bug is visible in both images but more noticeable in the dark image. Make sure to run the example with "x11" backend

1. qmake
2. make
3. ./borderpixmapbug - graphicssystem x11