As I understand it, the window id for a redirected window should always refer to the offscreen window contents. However, after resizing a (mapped) redirected window, it looks to me like the window id either refers to the onscreen contents (including any covering windows), or like the old offscreen window pixmap is not copied to the new resized offscreen pixmap. The problem can be seen by grabbing a partially covered (or transparent) redirected window by id immediately before and after resizing it. This is with nvidia driver version 6111 and RenderAccel enabled. This issue may be related to bug 1655 and bug 1656.
Is this still an issue using a more current version of xorg?
No. I think this was fixed in 6.8.2.
Closing.
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