D23947: [platforms/x11] Get rid of some code duplication in windowed backend

zzag created this revision.
zzag added a reviewer: KWin.
Herald added a project: KWin.
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zzag requested review of this revision.

REVISION SUMMARY
  We repeat quite a lot code that finds an output by xcb_window_t and
  translates global X11 screen coordinates to output coordinates.

TEST PLAN
  Compiles.

REPOSITORY
  R108 KWin

BRANCH
  x11-find-output

REVISION DETAIL
  https://phabricator.kde.org/D23947

AFFECTED FILES
  plugins/platforms/x11/windowed/x11windowed_backend.cpp
  plugins/platforms/x11/windowed/x11windowed_backend.h
  plugins/platforms/x11/windowed/x11windowed_output.cpp
  plugins/platforms/x11/windowed/x11windowed_output.h

To: zzag, #kwin
Cc: kwin, LeGast00n, The-Feren-OS-Dev, sbergeron, jraleigh, fbampaloukas, GB_2, mkulinski, ragreen, jackyalcine, Pitel, iodelay, crozbo, bwowk, ZrenBot, ngraham, alexeymin, himcesjf, lesliezhai, ali-mohamed, hardening, romangg, jensreuterberg, abetts, sebas, apol, mart