[cairo] Road to 1.10

Alexander Larsson alexl at redhat.com
Mon Feb 16 02:19:11 PST 2009

On Mon, 2009-02-16 at 09:42 +0000, Chris Wilson wrote:
> On Mon, 2009-02-16 at 10:11 +0100, Alexander Larsson wrote:
> > This is more of a feature request, since I've no time to implement this
> > myself as things stand. But, after Gtk+ 2.16 is released (should be
> > shortly now) we will try to merge the client side windows branch. The
> > client side windows branch of gtk virtualizes all drawing to GdkWindows
> > such that we can emulate the effects of subwindow clipping on the client
> > side.
> I agree that a form of device clipping is necessary to safely expose a
> sub-surface to a direct rendering client, in particular I've been
> thinking about this with regards to wayland.
> So at the moment my thought is basically to add a clip extents to a
> surface which may be smaller than its true extents. The biggest
> difficultly lies in applying source clipping. Not too difficult for
> cairo-drm where we can set up a sampler to a subset of a surface, but
> for xlib support, I fear we may need to make a copy of the sub-surface
> for the source.

Yes, source clipping is problematic too. I don't even know what
semantics cairo has here. X fills the target with the window background
and optionally sends GraphicExposures when you copy from a source that
is covered by some other window and thus is clipped out. It also lets
you select if you want to include inferiour windows or not in the
source, but it doesn't strike me as very useful to not include them
(especially if we're not generating GraphicsExposures).

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