[PATCH xserver 2/2 v3] glamor: Avoid overflow between box32 and box16 box

[Olivier Fourdan]

Hi all,

Before I forget, would it be possible to consider these two patches for glamor:

  https://patchwork.freedesktop.org/series/27940/

This patch was successfully tested by Fabrice here (the reproducer is in bug #101894):

  https://lists.x.org/archives/xorg-devel/2017-July/054174.html

And Keith gave his R-b on the same patch here: 

  https://lists.x.org/archives/xorg-devel/2017-August/054416.html

(although that was on a previous -but identical- iteration of this patch)

The two patches are necessary because we need to handle empty source regions (and not just because of possible overflow).

Cheers,
Olivier