On Fri, Feb 22, 2019 at 9:00 AM Pekka Paalanen <ppaala...@gmail.com> wrote: > > Hi Chris, > > that is some interesting background, but I feel like I didn't quite > catch the point. > > If the CRTC color management pipeline (LUT-CTM-LUT + maybe more) is > programmed according to the monitor's color profile, where would those > "conflicting video card LUTs" arise from?
A common offender were games. They'd try to access the video card LUT directly for effects, but then not reset it back to what it was, rather reset it to a hardwired assumption the game makes, e.g. all displays have gamma 2.2 so we'll just do that! A secondary offender were display calibration programs, user would upgrade or get a competing program and now you've got two startup applets that apply conflicting LUTs and it may be deterministically wrong or it may be subject to a race condition as to which applet applies. The later problem has mostly vanished with the advent of an OS API for reading the vcgt tag directly from the ICC profile set as the profile for a particular display. So who owns the pipeline? If it's shared, then anyone can use it and not set it back the way they found it. Or alternatively if they're going to mess with that pipeline, to have a kind of "reset" API for the thing that ought to be mostly responsible for such a thing, e.g. colord. -- Chris Murphy _______________________________________________ wayland-devel mailing list wayland-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/wayland-devel