When the threshold-trigger-edge property was introduced in
GestureAction, it was late in the cycle and I elected to keep it
private, given the fact that nobody was subclassing GestureAction
outside of Clutter itself.
These days, people are experimenting more with the GestureAction API, so
they will need access to the various knobs that control the class
default behaviour.
https://bugzilla.gnome.org/show_bug.cgi?id=710227
Use G_GNUC_INTERNAL instead of the leading underscore, as we may make
the accessor functions public at some point. Also, clean up the
documentation.
https://bugzilla.gnome.org/show_bug.cgi?id=710227
Let gesture subclasses override how the drag threshold should
be handled:
• CLUTTER_GESTURE_TRIGGER_NONE tells GestureAction that the gesture
must begin immediately and there's no drag limit that will cause
its cancellation;
• CLUTTER_GESTURE_TRIGGER_AFTER is the default GestureAction behaviour,
where it needs to wait until the drag threshold has been exceeded
before considering the gesture valid;
• CLUTTER_GESTURE_TRIGGER_BEFORE will make GestureAction cancel
the gesture once the drag exceed the configured threshold.
For example, ZoomAction and RotateAction could set
CLUTTER_GESTURE_TRIGGER_NONE since the use of two fingers makes the
begin of the action more self-evident, while an hypothetical Tap
gesture may use CLUTTER_GESTURE_TRIGGER_BEFORE to cancel the tap if
the pointer moves too much.
https://bugzilla.gnome.org/show_bug.cgi?id=685028
