Add glDrawBuffer(s) to GrGLInterface

[bsalomon, 2011-08-02 17:51:31]

Needed to re-land r2026. Have to set draw buffer to none on the fbo used to
clear stencil buffers.

[TomH, 2011-08-02 17:56:40]

LGTM

[junov, 2011-08-03 14:20:27]

Why are we exposing this? It is a well known slow path in the drivers.
 We should not touch it with a ten foot pole.  Draw textured quads
instead.

On Tue, Aug 2, 2011 at 1:56 PM,  <tomhudson@google.com> wrote:
> LGTM
>
> http://codereview.appspot.com/4841046/
>
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[bsalomon, 2011-08-03 14:41:52]

On 2011/08/03 14:20:27, junov wrote:
> Why are we exposing this? It is a well known slow path in the drivers.
>  We should not touch it with a ten foot pole.  Draw textured quads
> instead.
>

I don't follow. This fn doesn't draw anything; it just maps the gl_FragData[] to
an FBO's color buffers.

I need to set the draw buffer to none on a FBO with no color attachment to make
it FBO complete (in order to clear a stencil buffer).

[junov, 2011-08-03 14:43:24]

Oh, I mistook it for glDrawPixels.  Carry on.

On Wed, Aug 3, 2011 at 10:41 AM,  <bsalomon@google.com> wrote:
> On 2011/08/03 14:20:27, junov wrote:
>>
>> Why are we exposing this? It is a well known slow path in the drivers.
>>  We should not touch it with a ten foot pole.  Draw textured quads
>> instead.
>
>
> I don't follow. This fn doesn't draw anything; it just maps the
> gl_FragData[] to an FBO's color buffers.
>
> I need to set the draw buffer to none on a FBO with no color attachment
> to make it FBO complete (in order to clear a stencil buffer).
>
> http://codereview.appspot.com/4841046/
>