Re: [clutter] gnome-shell / mutter / ARB_texture_rectangle

[Owen Taylor <otaylor redhat com>]

On Thu, 2008-11-06 at 10:04 +0000, Matthew Allum wrote:
> Hi;
> 
> On Wed, 2008-11-05 at 13:03 -0500, Owen Taylor wrote:
> > > 
> > > I think making it usage explicit and contained like this is really the
> > > only way to go in we do bring back in support for ARB_texture_rectangle
> > > without a lot of complexity and other pain elsewhere. 
> > > 
> > > Re devel branch - I dont see why this could not end up in the stable
> > > branch of which we are already having to track pretty much with mutter.
> > 
> > My initial expectation was that there would be significant code churn
> > and API changes, but looking at it, the "remove texture_rectangle
> > support" patch is a lot smaller than I expected and doesn't look to hard
> > or intrusive to reintroduce. 
> 
> Right, it should hopefully be pretty strait forward - all Id request is
> that we then something like a
> cogl_enable_legacy_texture_rectangle(boolean) which enables this old
> logic in texture creation and is well documented as to potential
> downsides it introduces into apps enabling it.

Hmmm:
 
 - It doesn't really seem like an application level thing to me.
   It would be nice to avoid "If you want to use
   ClutterGLXTexturePixmap, then on some hardware
   you need to cogl_enable_legacy_texture_rectangle(TRUE) first"

 - There needs to be some way to force the usage on, because on some
   drivers *with* NPOT textures still have problems with the
   texture_for_pixmap + NPOT texture combination. [*]

 - Environment variables to a) enable texture_rectangle 
   b) disable texture_non_power_of_two globally for the process would
   be the minimum impact change. But I don't particularly like forcing
   the use of texture_rectangle for *all* textures when the only ones
   that need to be texture_rectangle are the texture_for_pixmap.

I'm certainly not tied to the current patch. It was the best approach I
could come up with to come pretty close to GLXTexturePixmap working "out
of the box".

- Owen

[*] I need to investigate whether the NVIDIA drivers are setting
    GLX_TEXTURE_2D_BIT_EXT in GLX_BIND_TO_TEXTURE_TARGETS_EXT
    if they are only setting GLX_TEXTURE_RECTANGLE_BIT_EXT then its
    not a driver bug ... that would be a way of reporting that
    using texture_rectangle is mandatory.