[Mesa-dev] [PATCH 1/3] mesa: Introduce a _mesa_format_has_color_component() helper.

[Brian Paul]

On 03/24/2014 02:52 AM, Kenneth Graunke wrote:
> When considering color write masks, we often want to know whether an
> RGBA component actually contains any meaningful data.  This function
> provides an easy way to answer that question, and handles luminance,
> intensity, and alpha formats correctly.
>
> Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>
> ---
>   src/mesa/main/formats.c | 29 +++++++++++++++++++++++++++++
>   src/mesa/main/formats.h |  4 ++++
>   2 files changed, 33 insertions(+)
>
> diff --git a/src/mesa/main/formats.c b/src/mesa/main/formats.c
> index c3e8049..4fb1f11 100644
> --- a/src/mesa/main/formats.c
> +++ b/src/mesa/main/formats.c
> @@ -2207,6 +2207,35 @@ _mesa_format_num_components(mesa_format format)
>
>
>   /**
> + * Returns true if a color format has data stored in the R/G/B/A channels,
> + * given an index from 0 to 3.
> + */
> +bool
> +_mesa_format_has_color_component(mesa_format format, int component)
> +{
> +   const struct gl_format_info *info = _mesa_get_format_info(format);
> +
> +   assert(info->BaseFormat != GL_DEPTH_COMPONENT &&
> +          info->BaseFormat != GL_DEPTH_STENCIL &&
> +          info->BaseFormat != GL_STENCIL_INDEX);
> +
> +   switch (component) {
> +   case 0:
> +      return (info->RedBits + info->IntensityBits + info->LuminanceBits) > 0;
> +   case 1:
> +      return (info->GreenBits + info->IntensityBits + info->LuminanceBits) > 0;
> +   case 2:
> +      return (info->BlueBits + info->IntensityBits + info->LuminanceBits) > 0;
> +   case 3:
> +      return (info->AlphaBits + info->IntensityBits) > 0;
> +   default:
> +      assert(!"Invalid color component: must be 0..3");
> +      return false;
> +   }
> +}
> +
> +
> +/**
>    * Return number of bytes needed to store an image of the given size
>    * in the given format.
>    */
> diff --git a/src/mesa/main/formats.h b/src/mesa/main/formats.h
> index 3079f03..89bd021 100644
> --- a/src/mesa/main/formats.h
> +++ b/src/mesa/main/formats.h
> @@ -34,6 +34,7 @@
>
>
>   #include <GL/gl.h>
> +#include <stdbool.h>
>
>
>   #ifdef __cplusplus
> @@ -474,6 +475,9 @@ _mesa_get_uncompressed_format(mesa_format format);
>   extern GLuint
>   _mesa_format_num_components(mesa_format format);
>
> +extern bool
> +_mesa_format_has_color_component(mesa_format format, int component);
> +
>   GLboolean
>   _mesa_format_matches_format_and_type(mesa_format mesa_format,
>   				     GLenum format, GLenum type,
>

Reviewed-by: Brian Paul <brianp at vmware.com>