[Cogl] [PATCH 5/6] framebuffer: Support the GL_RED texture workaround when querying bits

[Robert Bragg]

This looks good to land to me:

Reviewed-by: Robert Bragg <robert at linux.intel.com>

thanks,
- Robert

On Fri, Dec 14, 2012 at 11:43 AM, Neil Roberts <neil at linux.intel.com> wrote:
> When a component-alpha texture is made using a GL3 context a GL_RED
> texture is actually used and a swizzle is set up to hide it. However
> if a framebuffer is then bound to that texture then when the bits are
> queried this workaround will leak out of the API. To fix this it now
> detects the situation and reports the number of red bits as the number
> of alpha bits.
> ---
>  cogl/driver/gl/cogl-framebuffer-gl.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
>
> diff --git a/cogl/driver/gl/cogl-framebuffer-gl.c b/cogl/driver/gl/cogl-framebuffer-gl.c
> index 7e4aaca..41c6b1a 100644
> --- a/cogl/driver/gl/cogl-framebuffer-gl.c
> +++ b/cogl/driver/gl/cogl-framebuffer-gl.c
> @@ -947,6 +947,16 @@ _cogl_framebuffer_init_bits (CoglFramebuffer *framebuffer)
>        GE( ctx, glGetIntegerv (GL_STENCIL_BITS, &framebuffer->bits.stencil) );
>      }
>
> +  /* If we don't have alpha textures then the alpha bits are actually
> +   * stored in the red component */
> +  if ((ctx->private_feature_flags &
> +       COGL_PRIVATE_FEATURE_ALPHA_TEXTURES) == 0 &&
> +      framebuffer->type == COGL_FRAMEBUFFER_TYPE_OFFSCREEN &&
> +      framebuffer->format == COGL_PIXEL_FORMAT_A_8)
> +    {
> +      framebuffer->bits.alpha = framebuffer->bits.red;
> +      framebuffer->bits.red = 0;
> +    }
>
>    COGL_NOTE (OFFSCREEN,
>               "RGBA/D/S Bits for framebuffer[%p, %s]: %d, %d, %d, %d, %d, %d",
> --
> 1.7.11.3.g3c3efa5
>
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