There is wrong usage of memcpy(3) in fb/fbblt.c, I will attach proposed patch.
Due this issue there are framebuffer corruptions when dragging windows to left. You can see example of FB corruptions on https://bugzilla.redhat.com/show_bug.cgi?id=652590.
When I change memcpy to memmove, everything works fine.
Created attachment 45528 [details] [review]
Please submit patches to xorg-devel for review & application, as described in
(It's not necessary to file bug reports for every patch. X.Org generally
uses bug reports to track issues needing investigation still.)
Created attachment 50248 [details] [review]
This uses memcpy, but avoids overlap as required
Adam Jackson discovered that memmove was about twice as slow as memcpy, and so finding cases which can use memcpy remains important for performance. This patch avoids all overlapping copies while retaining the use of memcpy for non-overlapping cases, preserving most of the performance benefit.
I'd like to verify that it resolves the problem you're having, please give it a try.
Sorry for late response.
I just tried to build Xvnc against Fedora's Xorg 1.10.4-1.fc15 (which should have the patch included if I read source correctly) and everything seems fine for me, I see no FB corruptions.
So you can close this bug as fixed.
Thanks for verifying the fix.