a software cursor problem in XServer

[popeye]

I wrote a video driver in Xorg 1.3 in Fedora 7. I implement hardware acceleration of 2D operation. I use software cursor in my driver. There is a problem with the cursor. When I click a window title and drag the window, the trace of the cursor movement can be seen on the screen. You can see what the problem is like in the attach image files. When I disable the ScreenToScreenCopy acceleration interface, the problem will disapear. Can anyone give me some comments?