Hi; On Wed, 2008-11-05 at 10:22 -0500, Owen Taylor wrote: > So, I've been working on getting the beginnings of gnome-shell going > based on mutter (metacity-clutter.) And a large part of that has been > debugging mutter on various hardware. > > The biggest problem so far is that ClutterGLXPixmapTexture has no > support for the ARB_texture_rectangle extension. So, it either uses > ARB_texture_non_power_of_two, or it falls back to tiling. > > Talking to Neil, he said that support for ARB_texture_rectangle used to > exist in clutter, but was removed because there was an assumption that > if EXT_texture_for_pixmap extension was present, then > ARB_texture_non_power_of_two would be present as well.
IIRC it was removed due to issues around ARB_texture_rectangle using non normalised co-ords (adding complexity's to things making shaders work everywhere), lack of mipmap support, issues around repeating and other oddities. I believe ARB_texture_rectangle is regarded as 'legacy' in the GL world with use of ARB_texture_non_power_of_two being much preferred and more modern approach (with less issues). > > Unfortunately, that's not the case - in particular Radeon r3xx and r5xx > don't have full hardware support for NPOT textures; they are pretty > much restricted to supporting only ARB_texture_rectangle. On these > cards mutter performs poorly using the GetImage fallback. I could be wrong here, but I thought ATI did actually support npots sized regular textures, they just did not advertise the fact. Worth checking. > > In addition, there seem to be a wide variety of driver/hardware > combinations where compiz works but mutter badly misbehaves (anything > but the very latest Intel drivers, some versions of the nVidia > proprietary drivers, etc.) It's pure speculation that using > ARB_texture_rectangle would resolve these issues, but it's at least > something I want to try. > > So, anyways, the conclusion is that I need ARB_texture_rectangle > support. I have a hacked up version of GLXPixmapTexture that does this > by either using cogl_texture or directly using a GL texture, but this > runs into some problems because mutter uses CloneTexture and otherwise > expects to be able to get the cogl_texture and draw with it. > > I see two basic routes I could take: > > 1) I could add support for ARB_texture_rectangle into cogl_texture. > Presumably this would look like cogl_texture_new_rectangle() > or something ... you'd have to explicitly ask to get a rectangular > texture, since they do behave significantly different. > > (Though more different than a sliced up texture? Not sure...) > > The main downside here, assuming I could get a change like this > into clutter, would by tying gnome-shell to the devel branch > of clutter. 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. == Matthew -- Matthew Allum, Intel Open Source Technology Center -- To unsubscribe send a mail to [EMAIL PROTECTED]
