The XGetImage man page states:
If the drawable is a window, the window must be viewable, and it must be the
case that if there were no inferiors or overlapping windows, the specified
rectangle of the window would be fully visible on the screen and wholly
contained within the outside edges of the window, or a BadMatch error
results. Note that the borders of the window can be included and read with
this request.
However, the server was only checking the requested region against the screen
bounds, allowing XGetImage requests to read pixels outside the bounds of a
window's ancestors. Normally, this would just read other pixels from the
screen, but if one of the ancestor windows is redirected, the window's backing
pixmap may be smaller than the window itself.
This change checks the region against the window's bounding drawable, which is
either the screen pixmap, a redirected window's backing pixmap, or the root
window for servers that don't support GetWindowPixmap.
Signed-off-by: Aaron Plattner <aplattner@nvidia.com>
Reviewed-by: Keith Packard <keithp@keithp.com>
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