Re: [Mesa3d-dev] [PATCH] st/mesa: do not advertise S3TC if the external lib is not available

[José F. <jfo...@vm...>]

On Sat, 2010-02-27 at 09:15 -0800, Marek Olšák wrote:
> Hi,
> 
> S3TC shouldn't be advertised without the external lib and the attached
> patch fixes that. Please review.

Hi Marek,

Actually it is a bit more subtle.

S3TC can and should be advertised if the pipe driver supports ST3C
decompression and *compression*.

No real hardware has circuitry for S3TC compression, granted. But the
vwmare svga gallium driver does it, by deferring everything to the host.

It was the best solution we found to supporting S3TC without having to
rely on closed source or questionable bits in the guest.

So the right fix should be:

screen->is_format_supported(screen, PIPE_FORMAT_DXT5_RGBA,
                                    PIPE_TEXTURE_2D, 
                                    PIPE_TEXTURE_USAGE_SAMPLER, 0) &&
(ctx->Mesa_DXTn || screen->is_format_supported(screen,
PIPE_FORMAT_DXT5_RGBA, PIPE_TEXTURE_2D, PIPE_TEXTURE_USAGE_RENDERTARGET,
0)

Jose