QWMatrix wm;
wm.scale( 2, 2 ); // Zooms in by 2 times
wm.rotate( 90 ); // Rotates 90 degrees counter clockwise
// around the origin.
wm.translate( 0, -canvas->height() );
// moves the canvas down so what was visible
// before is still visible.
myCanvasView->setWorldMatrix( wm );