[Development] [QtQuick] Mouse/Touch handling from Qt CS

[Alan Alpert]

Qt CS had a discussion on how to handle mouse and touch event
conflicts in QtQuick going forwards.

An interesting idea came up that the existing model might be
salvageable if we fix multi-cursor support. Some investigation will
occur to see whether having multiple mouse grabs automatically solves
the multitouch problems the current model has with converting touch
events to mouse events. Also necessary is some sort of grab stack so
that when a multi-finger gesture moves the mouse events to a different
item, the grab for single fingers can return to where it was should
the other fingers lift.

If this approach works, then we'll have multi-touch and multi-cursor
support without having to redesign the pointer interaction model in
QtQuick. Otherwise we'll just have to implement separate touch and
mouse handlers in all QtQuick items until we come up with a better
idea.

--
Alan Alpert