Re: [Mesa3d-dev] Proposed new DD texture interface

[Brian P. <br...@va...>]

Gareth Hughes wrote:
> 
> Keith Whitwell wrote:
> >
> > I'll chime in without having read the whole thread.
> >
> > Allowing DD functions to fail is always a bad idea.  It blurs the distinction
> > between the actuall work required in core mesa to implement a function, and
> > the fallback case.  These two pieces of code are at very different levels of
> > abstraction -- they are actually seperated by a whole level.  You can get the
> > same effect by bundling up the fallback case and giving it a well-known name.
> > If the driver can't handle a case, it explicitly calls the fallback code.
> >
> > This is what 'swrast' is all about.  A good example is ctx->DD.Clear, which
> > used to be allowed to fail or perform a partial execution.  As a result the
> > core coded needed to either implement software fallbacks, or know about the
> > existence of 'swrast' and call into it itself -- this is pretty clunky.  Now,
> > the same behaviour is simply achieved by requiring the driver to call into
> > swrast if it is unable to fulfill the request from core mesa.  To my eye this
> > is cleaner, and the requirement on the driver is pretty trivial.
> 
> Thank you, Keith.  This is exactly what I'm going for.
> 
> What I'd like to see is the Tex[Sub]Image* DD calls hand the raw image
> data to the driver, and what gets hung off the gl_texture_image
> structure is an image in whatever format the driver wants it in.  It is
> up to the driver to choose the format and to do the conversion, if
> required.

Right.


> This is why I'd like the conversion utility functions to
> accept any input, have conversion fastpaths for common cases in a
> pluggable way (to allow MMX assembly), but have the generic case
> handling as well.
> 
> I think this fits the spirit of 3.5 more than the current approach.

Yes, this is all fine.

I think we're in complete agreement with the goals, but still not
clear on the implementation.  More in another follow-up.

-Brian