[Differential] [Request, 1,110 lines] D3402: Drop OpenGL based color correction from KWin

[graesslin (Martin Gräßlin)]

graesslin created this revision.
graesslin added reviewers: KWin, Plasma.
Restricted Application added a project: KWin.
Restricted Application added subscribers: kwin, plasma-devel.

REVISION SUMMARY
  The feature has always been considered experimental. Unfortunately it is
  completely unmaintained and hasn't seen any commits in years. It
  requires kolor-manager to function, but that has not seen a release
  based on frameworks yet. This makes it difficult to maintain. In fact I
  have never been able from the introduction till now to setup a color
  corrected system. One needs kolor-manager and oyranos and especially the
  latter is hardly available on any linux distribution (e.g. not on the
  Debian/Ubuntu systems).
  
  Due to being unmaintained color correction in KWin did not keep up with
  recent changes. Neither did it see any updates during the xlib->xcb
  port, nor during the Wayland port. Especially the Wayland port with the
  rendering changes make it unlikely to function correctly. E.g. Wayland
  introduced a proper per-screen rendering, while color correction did a
  "fake" per screen rendering. How that is going to work in combination is
  something nobody ever tried. Now after the introduction of proper
  per-screen rendering the solution would be to port color correction to
  the new api, but that never happened.
  
  Color correction also modified the shaders, but a newer shader API got
  introduced some time ago. Whether the color correction shader support
  that or not, is unknown to me. Also which shader language versions are
  supported. I know it was based on 3d texture support, which back on
  introduction was partially lacking in OpenGL ES. Nowadays that changed,
  but color correction didn't update.
  
  Last but not least it is completely X11 based and there is no work on
  how to make it work with Wayland.
  
  Given all the problems, especially the fact that it is unmaintained and
  cannot be setup on my system, means to me that the only solution is to
  remove it.
  
  I'm open to having it reintroduced in future, but only if the
  availability on Linux distributions gets addressed before. As long as
  major linux distributions do not ship this feature, it should not be in
  KWin. Given that I must say that it was a mistake to add it in the first
  place and I need to point out that I was against the merge back then.

REPOSITORY
  rKWIN KWin

BRANCH
  drop-color-correction

REVISION DETAIL
  https://phabricator.kde.org/D3402

AFFECTED FILES
  kcmkwin/kwincompositing/compositing.cpp
  kcmkwin/kwincompositing/compositing.h
  kcmkwin/kwincompositing/compositing.ui
  kcmkwin/kwincompositing/main.cpp
  kwin.kcfg
  libkwineffects/CMakeLists.txt
  libkwineffects/kwinglcolorcorrection.cpp
  libkwineffects/kwinglcolorcorrection.h
  libkwineffects/kwinglcolorcorrection_p.h
  libkwineffects/kwinglutils.cpp
  libkwineffects/kwinglutils.h
  options.cpp
  options.h
  scene_opengl.cpp
  scene_opengl.h

EMAIL PREFERENCES
  https://phabricator.kde.org/settings/panel/emailpreferences/

To: graesslin, #kwin, #plasma
Cc: plasma-devel, kwin, lesliezhai, ali-mohamed, hardening, jensreuterberg, abetts, sebas
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