On Fri, 07 Nov 2014 11:32:04 -0800 Eric Anholt <e...@anholt.net> wrote:
> Pekka Paalanen <ppaala...@gmail.com> writes: > > > On Thu, 06 Nov 2014 13:01:03 -0800 > > Ian Romanick <i...@freedesktop.org> wrote: > > > >> I thought Eric and Chad already NAKed it in bugzilla. The problem is > >> that applications ask for an RGBA visual for GL blending. They use the > >> alpha channel to generate their images, but the final alpha values are, > >> basically, random... and the composited result would be pure garbage. > > > > Reading > > https://bugs.freedesktop.org/show_bug.cgi?id=67676#c5 > > "We should certainly be exposing EGLConfigs that match up to the rgba > > visual, though, so you can find it when you try." - Eric > > > > To me that sounds like Eric would accept having the visuals there > > in additional configs (as long as they are sorted after the otherwise > > equivalent xRGB configs?). Eric, would you like to confirm your current > > opinion? > > What I believe we want: > > Somebody just requesting RGBA with ChooseConfig doesn't end up forced > into the depth-32 (blending) X visual. This is the most important. > > There is some mechanism for somebody that does want the depth 32 visual > to get an EGL config to draw to it. This is important but secondary to > not breaking everything else, and them having to jump through hoops is > reasonable but probably avoidable. I think that is exactly what everybody already agrees on. The remaining question seems to be, should we add new configs with the blending X visual, or wait for an EGL extension to allow to request blending in generic terms (*and* add configs with the blending X visual, since that is essentially required for making, say, a new value for EGL_TRANSPARENT_TYPE to work on X11). Can you imagine other reasonable mechanisms? Btw. I noticed that EGL_TRANSPARENT_TYPE defaults to EGL_NONE for eglChooseConfig, not DONT_CARE (which is not even allowed in EGL 1.4). So if we add only configs now, and add the EGL_TRANSPARENT_TYPE=alpha extension later, apps using eglChooseConfig for initial config filtering and wanting a blending config will be broken yet again. I suppose one might even claim, that exposing bleding configs when EGL_TRANSPARENT_TYPE=NONE is a violation of the spirit of the spec. EGL 1.4 says that EGL_TRANSPARENT_TYPE is not a sorting key at all, but NATIVE_VISUAL_ID is with an implementation specified order. Thanks, pq _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/mesa-dev
