[cairo] API to disable subpixel antialiasing per-surface

[Robert O'Callahan]

On Wed, Jan 12, 2011 at 10:42 AM, Behdad Esfahbod <behdad at behdad.org> wrote:

> On 01/10/11 17:47, Robert O'Callahan wrote:
> >
> >     How about we enable per-channel masks, so you can represent the
> operation
> >     truthfully?  Sure, you need to keep an RGB mask and an ARGB source,
> but at
> >     least it's not impossible.
> >
> >
> > I guess so, but won't it be slow?
>
> Don't know.  That's what's happening whe you render subpixel text.
>

I mean we'd have to carry around an RGB mask for lots of surfaces; we'd have
to alter that mask when we draw *anything*, not just text, into those
surfaces; and the cost of compositing those surfaces would increase.

We're actually already doing something like this for our GPU-accelerated
layers backends (which don't use cairo for compositing), but there it's not
so bad because at least the composition is relatively cheap. I'm rather
scared of doing it when we can only use the CPU.

Rob
-- 
"Now the Bereans were of more noble character than the Thessalonians, for
they received the message with great eagerness and examined the Scriptures
every day to see if what Paul said was true." [Acts 17:11]
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