[PATCH 0/2] Attempt to fix FIXES for Xinerama

[Adam Jackson]

On Mon, 2013-11-04 at 17:49 -0500, Adam Jackson wrote:
> Regular readers will be noticing a theme, by this point.  Basically the
> Xinerama enablement in the Composite stack works if and only if all your
> backend screens are overlapped at +0+0.  This was sufficient for Nomad, since
> effectively all the backends are intentionally mirrored views, but people
> running hardware servers typically want Big Desktop not Mirror All The Things.
> 
> The first patch in this series is sufficient to fix 'xcompmgr -n', which is the
> trivial Render-based mode.  But I think it's wrong conceptually.  One there's
> nothing comparable in RenderSetPictureClipRectangles, and two it isn't
> symmetric with how GC clips work (where the translation happens in ValidateGC).
> So I think Xinerama wants to wrap ValidatePicture, and that the existing
> R[ender]SPCR[ects] is merely exactly as broken as F[ixes]SPCR[egion].
> Hopefully Keith will tell me if I'm on the right track, and/or someone else
> will join me in the Xineramarchaeology.
> 
> The second patch I merely believe to be correct since it's the same pattern in
> the code.

On reflection, these are clearly wrong for non-root windows, they should
be translating relative to drawable origin not the screen origin; they
happen to be the same for root windows but not for children.

New versions to follow.

- ajax