[cairo] [PATCH 2/3] gl/msaa: Ignore the antialiasing property of the clip.

Chris Wilson chris at chris-wilson.co.uk
Thu Dec 15 11:47:22 PST 2011

On Thu, 15 Dec 2011 10:49:27 -0800, Martin Robinson <mrobinson at igalia.com> wrote:
> If the clip suggests anti-aliasing and we don't support it,
> draw the clip anyway. Currently disabling anti-aliasing does
> not disable anti-aliasing on certain clips.

I added a couple of sentences to explain why this is justified, or
rather why I think we can get away with this:

/* We ignore the antialias mode of the clip here, since the user requested
 * unantialiased rendering of their path and we expect that this stencil
 * based rendering of the clip to be a reasonable approximation to
 * the intersection between that clip and the path.
 * In other words, what the user expects when they try to perform
 * a geometric intersection between an unantialiased polygon and an
 * antialiased polygon is open to interpretation. And we choose the
 * fast option.

Can anyone poke a hole in that argument? Or come up with a strict
definition of that the intersection should be?

In the mean time I've pushed both of the patches along with a switch
back to spans by default. Use CAIRO_GL_COMPOSITOR=msaa to continue
testing and improving the msaa compositor. (The reason is simply I don't
have enough memory to keep the driver happy whilst running


Chris Wilson, Intel Open Source Technology Centre

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