Improve selection mode when selection ends cross (#1013)

Emptying the selection with the spacebar slider puts the selection mode
in an unexpected state. This checks that this doesn't happen.

The selection ends can now cross each other, reversing the selection
order. Special care is made to make sure that the sliders go in the
expected direction.

Pointers is changed to send a `onPointerDown` for the first slider event
instead of a `onPointerHold`. This event is detected in
`KeyEventHandler` and the selection ends are reordered if needed when
sliding again.

0 files changed, 0 insertions, 0 deletions