[Differential] [Request, 46 lines] D2347: Use a Timer to switch on hover event handling and do the initial geo export.

[hein (Eike Hein)]

hein created this revision.
hein added reviewers: Plasma, mart.
hein added a subscriber: plasma-devel.
Restricted Application added a project: Plasma.

REVISION SUMMARY
  Different versions of Qt (or maybe it's the position of Jupiter-vs-
  Saturn) seem to behave differently with regard to whether delegates
  in a Repeater+Flow package initially appear at 0,0 and then get moved
  into position, or directly appear at target geometry. This is despite
  the fact that we already layout before changing delegate visibility
  to true.
  
  The former behavior causes various problems. One of them is that after
  clicking a launcher, a new task delegate can be under the mouse cursor
  initially (even though it never shows up in a rendered frame - this
  only matters for event checks) causing containsMouse to be true and
  then never to go false as the item is moved from under the cursor
  (which Qt Quick's hover handling famously can't handle). Another is
  that we export delegate geometry in global coordinates to kwin so it
  knows where to animate window minimization to, and this needs to be
  the correct (i.e. 'final-initial') geometry.
  
  Previously, we tried to handle this by only enabling hover event
  handling and doing the initial geometry export on two triggers:
  
  - onVisibleChanged(true) && index == 0 + boolean fence=false
  - onXChanged + boolean fence=false
  
  This worked, but breaks the case where an item actually appears at
  the desired final-initial geometry directly, so not causing an
  onXChanged.
  
  After brainstorming we couldn't come up with a better alternative
  than a trigger. Exploiting Flow's add transition seems to error-
  prone given various gotchas mentioned in the docs, and delaying
  things by one event loop iteration is too brittle, since we don't
  know exactly how this interacts with scene graph positioning.
  
  So this changes things to a singleshot timer, which is created and
  started whenever a task is completed or changes its type to window
  (the latter for the geo export). The duration matches what the
  Flow move animation is set to (now ported to units) to make sure
  it can't interfere.

REPOSITORY
  rPLASMADESKTOP Plasma Desktop

BRANCH
  Plasma/5.7

REVISION DETAIL
  https://phabricator.kde.org/D2347

AFFECTED FILES
  applets/taskmanager/package/contents/ui/Task.qml
  applets/taskmanager/package/contents/ui/TaskList.qml

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

To: hein, #plasma, mart
Cc: plasma-devel, ali-mohamed, jensreuterberg, abetts, sebas
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