D17982: [kcmkwin/kwindecoration] Fix visuals of KCM decorations' buttons tab

vpilo created this revision.
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vpilo requested review of this revision.

REVISION SUMMARY
  BUG: 346222
  FIXED-IN: 5.16
  
  The QML changes make the tab look and feel less awful:
  
  - make the fake window borders stand out less
  - add margins to drop area to make it easier to drop buttons on the title bar (fixing 346222)
  - change cursor to a non-pointing one [1]
  
  [1] Drag&drop: When dropping, we receive the position of the button being dropped,
  not of the cursor. The two can be far (when starting drag by moving the cursor fast):
  which makes the whole experience very confusing, as the user means to drop at cursor location.

TEST PLAN
  Tested drag/drop: same (messy) behavior as before, but can now drop more loosely around titlebar items

REPOSITORY
  R108 KWin

BRANCH
  vpilo/decorations_fixes (branched from master)

REVISION DETAIL
  https://phabricator.kde.org/D17982

AFFECTED FILES
  kcmkwin/kwindecoration/kcm.cpp
  kcmkwin/kwindecoration/qml/ButtonGroup.qml
  kcmkwin/kwindecoration/qml/Buttons.qml

To: vpilo
Cc: kwin, kvanton, jraleigh, GB_2, mkulinski, ragreen, jackyalcine, Pitel, iodelay, bwowk, ZrenBot, ngraham, lesliezhai, ali-mohamed, hardening, jensreuterberg, abetts, sebas, apol, mart