D29010: Wayland: Allow to take single screen screenshots using scale factor without loss

meven created this revision.
meven added reviewers: davidedmundson, KWin.
Herald added a project: KWin.
Herald added a subscriber: kwin.
meven requested review of this revision.

REVISION SUMMARY
  The screenshot made on screens with scale factor were downscaled by their scale factor making them blurry.
  It prevents taking screenshots of missing Hidpi related bugs showing the issues under Wayland.
  
  This fix the case of a single screenshot, but not the rest:
  Multiscreen screenshot downscales the screen using scale factor.
  Spectacle rectangular selection screenshot is broken as soon as some scale factor different than 1 is used on any screen.

TEST PLAN
  Under Wayland with a scale factor on a screen, take a screenshot using spectacle.
  The output image is not downscaled and has the same size as the screen resolution.
  
  No other change to any other screenshot mode, or under X.

REPOSITORY
  R108 KWin

BRANCH
  screenshot

REVISION DETAIL
  https://phabricator.kde.org/D29010

AFFECTED FILES
  effects/screenshot/screenshot.cpp
  effects/screenshot/screenshot.h
  libkwineffects/kwineffects.cpp
  libkwineffects/kwineffects.h
  plugins/scenes/opengl/scene_opengl.cpp
  scene.cpp
  scene.h

To: meven, davidedmundson, #kwin
Cc: kwin, Orage, cacarry, LeGast00n, The-Feren-OS-Dev, cblack, jraleigh, zachus, fbampaloukas, mkulinski, ragreen, jackyalcine, iodelay, crozbo, bwowk, ZrenBot, ngraham, alexeymin, himcesjf, lesliezhai, ali-mohamed, hardening, romangg, jensreuterberg, abetts, sebas, apol, ahiemstra, mart