[Mesa-dev] [PATCH 4/5] mesa: Add driver method to determine the possible sample counts

[Jordan Justen]

On Fri, Jan 4, 2013 at 5:43 PM, Ian Romanick <idr at freedesktop.org> wrote:
> From: Ian Romanick <ian.d.romanick at intel.com>
>
> Use this method in _mesa_GetInternalformativ for both GL_SAMPLES and
> GL_NUM_SAMPLE_COUNTS.
>
> v2: internalFormat may not be color renderable by the driver, so zero
> can be returned as a sample count.  Require that drivers supporting the
> extension provide a QuerySamplesForFormat function.  The later was
> suggested by Eric Anholt.
>
> Signed-off-by: Ian Romanick <ian.d.romanick at intel.com>
> Cc: Eric Anholt <eric at anholt.net>
> ---
>  src/mesa/drivers/common/driverfuncs.c |  1 +
>  src/mesa/main/dd.h                    | 16 ++++++++++++++++
>  src/mesa/main/formatquery.c           | 31 +++++++++++++++++++++++++++----
>  3 files changed, 44 insertions(+), 4 deletions(-)
>
> diff --git a/src/mesa/drivers/common/driverfuncs.c b/src/mesa/drivers/common/driverfuncs.c
> index 93fa3c7..3de5199 100644
> --- a/src/mesa/drivers/common/driverfuncs.c
> +++ b/src/mesa/drivers/common/driverfuncs.c
> @@ -91,6 +91,7 @@ _mesa_init_driver_functions(struct dd_function_table *driver)
>
>     /* Texture functions */
>     driver->ChooseTextureFormat = _mesa_choose_tex_format;
> +   driver->QuerySamplesForFormat = NULL;
>     driver->TexImage = _mesa_store_teximage;
>     driver->TexSubImage = _mesa_store_texsubimage;
>     driver->GetTexImage = _mesa_meta_GetTexImage;
> diff --git a/src/mesa/main/dd.h b/src/mesa/main/dd.h
> index 70c5324..07787d4 100644
> --- a/src/mesa/main/dd.h
> +++ b/src/mesa/main/dd.h
> @@ -201,6 +201,22 @@ struct dd_function_table {
>                                       GLenum srcFormat, GLenum srcType );
>
>     /**
> +    * Determine sample counts support for a particular format
> +    *
> +    * \param ctx            GL context
> +    * \param internalFormat GL format enum
> +    * \param samples        Buffer to hold the returned sample counts.
> +    *                       Drivers \b must \b not return more than 16 counts.
> +    *
> +    * \returns
> +    * The number of sample counts actually written to \c samples.  If
> +    * \c internaFormat is not renderable, zero is returned.
> +    */
> +   size_t (*QuerySamplesForFormat)(struct gl_context *ctx,
> +                                   GLenum internalFormat,
> +                                   int samples[16]);
> +
> +   /**
>      * Called by glTexImage[123]D() and glCopyTexImage[12]D()
>      * Allocate texture memory and copy the user's image to the buffer.
>      * The gl_texture_image fields, etc. will be fully initialized.
> diff --git a/src/mesa/main/formatquery.c b/src/mesa/main/formatquery.c
> index 64f10cd..f08ab66 100644
> --- a/src/mesa/main/formatquery.c
> +++ b/src/mesa/main/formatquery.c
> @@ -42,6 +42,8 @@ _mesa_GetInternalformativ(GLenum target, GLenum internalformat, GLenum pname,
>        return;
>     }
>
> +   assert(ctx->Driver.QuerySamplesForFormat != NULL);
> +
>     /* The ARB_internalformat_query spec says:
>      *
>      *     "If the <target> parameter to GetInternalformativ is not one of
> @@ -91,13 +93,34 @@ _mesa_GetInternalformativ(GLenum target, GLenum internalformat, GLenum pname,
>
>     switch (pname) {
>     case GL_SAMPLES:
> -      buffer[0] = ctx->Const.MaxSamples;
> -      count = 1;
> +      count = ctx->Driver.QuerySamplesForFormat(ctx, internalformat, buffer);
>        break;
> -   case GL_NUM_SAMPLE_COUNTS:
> -      buffer[0] = 1;
> +   case GL_NUM_SAMPLE_COUNTS: {
> +      /* The driver can return 0, and we should pass that along to the
> +       * application.  The ARB decided that ARB_internalformat_query should
> +       * behave as ARB_internalformat_query2 in this situation.
> +       *
> +       * The ARB_internalformat_query2 spec says:
> +       *
> +       *     "- NUM_SAMPLE_COUNTS: The number of sample counts that would be
> +       *        returned by querying SAMPLES is returned in <params>.
> +       *        * If <internalformat> is not color-renderable,
> +       *          depth-renderable, or stencil-renderable (as defined in
> +       *          section 4.4.4), or if <target> does not support multiple
> +       *          samples (ie other than TEXTURE_2D_MULTISAMPLE,
> +       *          TEXTURE_2D_MULTISAMPLE_ARRAY, or RENDERBUFFER), 0 is
> +       *          returned."
> +       */
> +      const size_t num_samples =
> +         ctx->Driver.QuerySamplesForFormat(ctx, internalformat, buffer);
> +
> +      /* QuerySamplesForFormat writes some stuff to buffer, so we have to
> +       * separately over-write it with the requested value.
> +       */
> +      buffer[0] = (GLint) num_samples;

What about removing the assert?
if (ctx->Driver.QuerySamplesForFormat) {
   num_samples =
      ctx->Driver.QuerySamplesForFormat(ctx, internalformat, buffer);
} else {
   num_samples = 1;
}

-Jordan