[cairo] [PATCH] gl: Fix bug in cairo_surface_create_similar().

Chris Wilson chris at chris-wilson.co.uk
Wed Dec 7 05:16:40 PST 2011

On Wed, 7 Dec 2011 20:20:33 +0800, 王明 <strgnm at gmail.com> wrote:
> Well, only using glBlendFuncSeperate is not enough to assure alpha value of
> destination surface to be 1.0. For example, if both alpha value of source
> and
> destination surface is 0, then the result alpha is 0.

Except that the blend equation for a CONTENT_COLOR destination is to always
set the output alpha to 1.0.

> But after this commit
> 6b472e12ae11f7b68289cdfd616e765be9a25a98<http://cgit.freedesktop.org/cairo/commit/?id=6b472e12ae11f7b68289cdfd616e765be9a25a98>,

I reiterate that cairo_surface_create_similar(CONTENT_COLOR) was already
being explicitly cleared to (0, 0, 0, 1) prior to the restoration of
that particular fast path. Whatever bug you are seeing is still present,
just now papered over.

Chris Wilson, Intel Open Source Technology Centre

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