[Mesa-dev] [PATCH 1/2] st: Allow accelerated CopyTexImage from RGBA to RGB.

[Brian Paul]

On 03/22/2018 04:18 PM, Eric Anholt wrote:
> There's nothing to worry about here -- the A channel just gets dropped by
> the blit.  This avoids a segfault in the fallback path when copying from a
> RGBA16_SINT renderbuffer to a RGB16_SINT destination represented by an
> RGBA16_SINT texture (the fallback path tries to get/fetch to float
> buffers, but the float pack/unpack functions are NULL for SINT/UINT).
> 
> Fixes KHR-GLES3.packed_pixels.pbo_rectangle.rgba16i on VC5.
> 
> v2: Extract the logic to a helper function and explain what's going on
>      better.
> ---
>   src/mesa/state_tracker/st_cb_texture.c | 32 ++++++++++++++++++++++++++------
>   1 file changed, 26 insertions(+), 6 deletions(-)
> 
> diff --git a/src/mesa/state_tracker/st_cb_texture.c b/src/mesa/state_tracker/st_cb_texture.c
> index 6345ead6396b..5a23c7e8b6cd 100644
> --- a/src/mesa/state_tracker/st_cb_texture.c
> +++ b/src/mesa/state_tracker/st_cb_texture.c
> @@ -2281,6 +2281,31 @@ fallback_copy_texsubimage(struct gl_context *ctx,
>      pipe->transfer_unmap(pipe, src_trans);
>   }
>   
> +static bool
> +st_can_copyteximage_using_blit(struct gl_texture_image *texImage,
> +                               struct gl_renderbuffer *rb)

I think those params could be const-qualified.

Looks great otherwise.  Thanks.

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

> +{
> +   GLenum tex_baseformat = _mesa_get_format_base_format(texImage->TexFormat);
> +
> +   /* We don't blit to a teximage where the GL base format doesn't match the
> +    * texture's chosen format, except in the case of a GL_RGB texture
> +    * represented with GL_RGBA (where the alpha channel is just being
> +    * dropped).
> +    */
> +   if (texImage->_BaseFormat != tex_baseformat &&
> +       ((texImage->_BaseFormat != GL_RGB || tex_baseformat != GL_RGBA))) {
> +      return false;
> +   }
> +
> +   /* We can't blit from a RB where the GL base format doesn't match the RB's
> +    * chosen format (for example, GL RGB or ALPHA with rb->Format of an RGBA
> +    * type, because the other channels will be undefined).
> +    */
> +   if (rb->_BaseFormat != _mesa_get_format_base_format(rb->Format))
> +      return false;
> +
> +   return true;
> +}
>   
>   /**
>    * Do a CopyTex[Sub]Image1/2/3D() using a hardware (blit) path if possible.
> @@ -2324,12 +2349,7 @@ st_CopyTexSubImage(struct gl_context *ctx, GLuint dims,
>         goto fallback;
>      }
>   
> -   /* The base internal format must match the mesa format, so make sure
> -    * e.g. an RGB internal format is really allocated as RGB and not as RGBA.
> -    */
> -   if (texImage->_BaseFormat !=
> -       _mesa_get_format_base_format(texImage->TexFormat) ||
> -       rb->_BaseFormat != _mesa_get_format_base_format(rb->Format)) {
> +   if (!st_can_copyteximage_using_blit(texImage, rb)) {
>         goto fallback;
>      }
>   
>