FRAME

The touch frame, consisting of a set of simultaneous contacts.

CONTACT

The current MT contact configuration. Changes whenever an id changes.

TOUCH

The current touch configuration. Changes whenever the number of contacts
changes. A touch frame is well-defined a time T after the last
configuration change. This allows for simultaneous touches being
handled. It also allows for a very quick change of one finger to
another. Such an action changes the CONTACT state, but it does not change
the TOUCH state.

DRAG/PINCH/ROTATE

A transformation based on the touch frame.

GESTURES

Two creation points may be grouped if they are close in space-time, and
they are always close within the same controlling entity. There can be only
one controlling entity per point, and that decision is made upon
creation. The window manager is a controlling entity. Ambiguities can occur
between close points, and are resolved either by state rule or by
priority. Relaxing the time closeness criteria has no effect within a
controlling entity, but creates a larger set of ambiguous and undesired
groupings, which is considered inferior.