#7612 BLOC 8.2.0 (: XRender cursor rendering broken with XShmPutImage

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#7612: XRender cursor rendering broken with XShmPutImage
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   Reporter:  bert             |       Owner:  bernie                             
       Type:  defect           |      Status:  new                                
   Priority:  blocker          |   Milestone:  8.2.0 (was Update.2)               
  Component:  x window system  |     Version:  Development build as of this date  
 Resolution:                   |    Keywords:  8.2.0:? joyride-2208:- blocks:8.2.0
Next_action:  diagnose         |    Verified:  0                                  
  Blockedby:                   |    Blocking:                                     
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Comment(by ohshima):

 I started from your cursortest.c and trying to put the essence of the
 problem.  It is harder than I thought, though.  One thing I found out that
 it only happens that XShm is used.  And of course the problem occurs only
 when some animation is going.  I modified your cursortest.c to reproduce
 the problem, but haven't made the timing and stuff right yet...

 I think understand the importance of unit test but still don't see what is
 the real difference between your cursortest.c and squeak BTW; yours
 doesn't really automatically test the appearance on the screen.  And the
 problem only occurs in the case when something is animating, so number of
 operations to be examined is not going to be 1.  And, the cursor doesn't
 have to be changed.  It only happens once at the start up (that is why I
 suggested to use the debugger there), and subsequent partial screen
 updates, that I think is not related to compositing, is causing the
 problem.

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Ticket URL: <http://dev.laptop.org/ticket/7612#comment:15>
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