The global "mtouch" is non-nil when a working multi-touch device is available on the user's system.
- on_begin ( mtouch, id, x, y )
Called when the user contacts the multi-touch device.
Each individual contact point has an id and position.
- on_cancel ( mtouch, id )
Called when an input motion is canceled
- on_end ( mtouch, id, x, y )
Called when the user lifts his finger from the multi-touch device
- on_move ( mtouch, id, x, y )
Called continually while the user moves his finger across the multi-touch device
x and y show the new position of the contact point