[cairo] New guards for cairo_xlib_surface_create_with_xrender_format()

[Chris Wilson]

On Wed, 2008-04-02 at 07:54 -0700, Carl Worth wrote:
> On Wed, 02 Apr 2008 11:34:07 +0100, Chris Wilson wrote:
> > Is it preferable to prevent such surfaces being created in the first
> > place?
> 
> No, I don't think that's what we want to do at all.
> 
> If there's a XRender format then we've got masks.

No, the crash Frederic Crozat originally reported was triggered by a
similar surface to an 8-bit colour surface. XRender happily wrapped the
pseudocolor Visual into its own XRenderPictFormat with
(gdb) p *xrender_format
$1 = {id = 56, type = PictTypeIndexed, depth = 8, direct = {red = 0,
redMask = 0, green = 0, greenMask = 0, blue = 0, blueMask = 0, 
alpha = 0, alphaMask = 0}, colormap = 32}
-- 
Chris Wilson