The SVGAlib example:
http://doc.trolltech.com/4.6/qws-svgalib.html
Referenced by:
http://doc.trolltech.com/4.6/qt-embedded-accel.html
Does not provide an accurate example of creating your own QScreen driver in 4.5 and 4.6. If will look at the README file in this examples source directory you will see:
This is the SVGA screen driver plugin example from Qt 4.4. The code does
not compile with Qt 4.5, because the internal graphics engine has changed.

This is unsupported code, provided for convenience in case there is
interest in porting it to Qt 4.5.

The documentation needs to change to reflect this fact, or the example's code needs to be updated to reflect the changes made to the paint engine since 4.4. This is a problem since this is the only documented example of implementing a QScreen driver.