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

[Brian Paul]

On 03/21/2018 02:54 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.
> ---
>   src/mesa/state_tracker/st_cb_texture.c | 6 ++++--
>   1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/src/mesa/state_tracker/st_cb_texture.c b/src/mesa/state_tracker/st_cb_texture.c
> index 6345ead6396b..469a82a75390 100644
> --- a/src/mesa/state_tracker/st_cb_texture.c
> +++ b/src/mesa/state_tracker/st_cb_texture.c
> @@ -2327,8 +2327,10 @@ st_CopyTexSubImage(struct gl_context *ctx, GLuint dims,
>      /* 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) ||
> +   if ((texImage->_BaseFormat !=
> +        _mesa_get_format_base_format(texImage->TexFormat) &&
> +        (texImage->_BaseFormat != GL_RGB ||
> +         _mesa_get_format_base_format(texImage->TexFormat) != GL_RGBA)) ||
>          rb->_BaseFormat != _mesa_get_format_base_format(rb->Format)) {
>         goto fallback;
>      }

When a conditional starts to get complicated like this, I consider 
putting it into helper/predicate function.  In this case, maybe 
st_texture_renderbuffer_formats_compatible().

In any case, the comment should probably be updated to say "But copying 
from RGBA to RGB is allowed" so there's no confusion between the comment 
and the conditional.

-Brian