Used for touch events.
type field will be one of gdk_touch_begin, gdk_touch_update
, gdk_touch_end or gdk_touch_cancel.
Touch events are grouped into sequences by means of the sequence field, which can also be obtained with
get_event_sequence. Each sequence begins with a
gdk_touch_begin event, followed by any number of gdk_touch_update events, and ends with a
gdk_touch_end (or gdk_touch_cancel) event. With multitouch devices,
there may be several active sequences at the same time.