[PATCH] xfixes: Forbid manipulating clip for source-only pictures (#28968)

[Adam Jackson]

On Tue, 2014-04-22 at 07:52 -0700, Keith Packard wrote:

> Duh. Ok, so all three paths fail, two with segfaults and one with
> BadDrawable.

In fairness you're probably right about the CT_PIXMAP paths being
effectively unhittable, my commit message was really talking about the
conceptual problem not the particular paths.

I'm debating whether it's worth forcing clips to be regions in the DIX
code in the next merge window.  Probably?  There are some pathological
regions where expanding them to a8 masks could be less data and/or less
iteration, but I'm not sure it'd be worth the extra complexity in the
renderer to accelerate them.

- ajax