When we miss button release events (eg. when they happen outside
of our window) we must ensure that the corresponding point is
removed from the array of tracked points, otherwise GestureAction
will get very confused and will cancel all subsequent gestures.
https://bugzilla.gnome.org/show_bug.cgi?id=683471
Add some accessors to simplify common tasks for GestureAction users:
• clutter_gesture_action_get_motion_delta() to get the delta
on the X and Y axis in stage coordinates since the last motion
event, and the scalar distance travelled;
• clutter_gesture_action_get_velocity() to get an estimate of the
speed of the last motion event along the X and Y axis and as a
scalar value in pixels per millisecond.
https://bugzilla.gnome.org/show_bug.cgi?id=681648
GestureAction supports a single device/touch point. We'll need touch
events supported in Clutter before adding the ability to set required
device/touch points on gestures.
http://bugzilla.clutter-project.org/show_bug.cgi?id=2585
The GestureAction is marked as abstract, but it has a constructor. It
should be possible to create simple gesture recognizers through signal
handling alone, so we might as well have GestureAction be a concrete
class from the start.
http://bugzilla.clutter-project.org/show_bug.cgi?id=2585
