Releasing a mouse button was delivered as a plain mouse-move (hover)
event: the release processing resets dragState to NOT_DRAGGING, after
which the event fell into the NOT_DRAGGING branch. Views therefore had
no way of telling that a drag gesture ended, which the upcoming
drag-based features (range selection, commit reordering) need.
Deliver the release as a real mouse event with the MouseRelease key
and normalize its modifiers to ModNone, so release bindings also match
modified drags. Make recordClickInfo ignore it: a release is the end of
a click, not a click of its own, and must not break double-click
detection.
When the left button is pressed and the pointer then moves, the event
that made the MAYBE_DRAGGING -> DRAGGING transition fell through the
switch without being assigned a key or modifier, so the first cell of
every drag arrived at handlers as a MouseRelease event without the
motion modifier and was effectively lost. Give it the same
MouseLeft/ModMotion identity as all subsequent drag events.
Held-button motion events that stay within the pressed cell carry no
information at all; swallow them instead of letting them through as
further release-shaped events (which used to clobber the double-click
state when the pointer jittered within a cell between two clicks).
