The grabbed key events inside TabBox are forwarded to the declarative
view which passes it to the normal keyPressedEvent() method. This
allows the QML files to handle keyboard navigation themselves.
The views support key navigation natively, though this cannot be
used as we need to update the ModelIndex when a new item is selected.
Also there seems to be a problem if the tabbox is shown again, in
that case the focus seems to be somehow lost. Because of that the
navigation is handled in the Item embedding the list.
REVIEW: 104357
FEATURE: 291916
FIXED-IN: 4.9.0
This layout is intended to replace the TabBox mode in Present
Windows effect.
The advantages of a layout over the effect are:
* works without compositing
* supports multi-screen in a better way (windows don't move)
* is an overlay on top of the windows instead of reusing the windows
* is not a hack inside the actual effect
* visually consistent with other layouts
