D7096: Only send active window changes to X11 root window if the X11 window changed

[Martin Flöser]

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

REVISION SUMMARY
  So far KWin always updated the active window property even if the actual
  window id hasn't changed. E.g. if a Wayland window was active and another
  Wayland window gets activated the window id was and stays 0.
  
  Nevertheless KWin updated the property causing wakeups in X server and
  any application listening to property changes on the root window.
  
  Futhermore this situation is an information leak: we leak when a Wayland
  window gets activated to X11.
  
  To solve this problem RootInfo caches the active window id and only
  updates if it changes.

TEST PLAN
  Verified with xev -root that the active window does not get
  updated needlessly.

REPOSITORY
  R108 KWin

BRANCH
  root-info-only-on-change

REVISION DETAIL
  https://phabricator.kde.org/D7096

AFFECTED FILES
  activation.cpp
  netinfo.cpp
  netinfo.h

To: graesslin, #kwin, #plasma
Cc: plasma-devel, kwin, ZrenBot, progwolff, lesliezhai, ali-mohamed, hardening, jensreuterberg, abetts, sebas, apol, mart, lukas
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