a question about software cursor in Xorg

[truename]

Hi,
  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. You can 
see how to reproduce the problem as following.
  1. open a window, for example a terminal
  2. click the window title bar with the left button of the mouse(do not release the button) 
and continuously drag the window to other places in the screen randomly
  3. release the left button of the mouse
  Now you can see the window of the terminal is corrupted. Among the window rectangular 
region, there are several cursor images which cover the window image. You can see the screen 
shot in the attach files.
  Normally if I move the cursor from one place to another(not dragging a window), everything 
is OK.
  Then I do some further test. In my driver I implement ScreenToScreenCopy acceleration. 
If I disable ScreenToScreenCopy acceleration, the problem disappears.
  Can you give me some comments about my problem? If you need some more information, please 
let me know.
  Harry
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