[Mesa-dev] [PATCH] intel: Set ctx's drawbuffer according to drawables visual

[Brian Paul]

On 08/04/2011 06:31 AM, Benjamin Franzke wrote:
> Fixes https://bugs.freedesktop.org/show_bug.cgi?id=39588
>
> egl_dri2 creates contexts with a doubleBufferConfig when PIXMAP and
> WINDOW bit is request, so _mesa_init_color sets DrawBuffer[0] to
> GL_BACK.
> If a pixmap surface is created egl_dri2 will use a single buffer config,
> so MakeCurrent has to adjust DrawBuffer[0] to the current drawable.
> ---
>   src/mesa/drivers/dri/intel/intel_context.c |    6 ++++++
>   1 files changed, 6 insertions(+), 0 deletions(-)
>
> diff --git a/src/mesa/drivers/dri/intel/intel_context.c b/src/mesa/drivers/dri/intel/intel_context.c
> index fe8be08..0eeffc0 100644
> --- a/src/mesa/drivers/dri/intel/intel_context.c
> +++ b/src/mesa/drivers/dri/intel/intel_context.c
> @@ -970,6 +970,12 @@ intelMakeCurrent(__DRIcontext * driContextPriv,
>   	 readFb = driReadPriv->driverPrivate;
>   	 driContextPriv->dri2.draw_stamp = driDrawPriv->dri2.stamp - 1;
>   	 driContextPriv->dri2.read_stamp = driReadPriv->dri2.stamp - 1;
> +
> +         if (fb->Visual.doubleBufferMode) {
> +            intel->ctx.Color.DrawBuffer[0] = GL_BACK;
> +         } else {
> +            intel->ctx.Color.DrawBuffer[0] = GL_FRONT;
> +         }
>         }
>
>         intel_prepare_render(intel);

This doesn't seem right to me.  We shouldn't be changing context state 
like that during a make-current() call.

During context initialization we call _mesa_init_color() where we set 
ctx->Color.DrawBuffer[0] to either GL_BACK or GL_FRONT depending on 
the visual's double-buffer flag.  You might investigate why that's not 
doing the job.

-Brian