A handler_group
object is a collection of recogniser
objects (hence, a better name would be recogniser_group;
this might change). It provides a means to combine a set of recognisers,
each dealing with some detailed UI behaviour into one object dealing
with many UI behaviours. Handler groups may be nested. This process may
be repeated to get more complex event-recognisers.
It is common practice to combine recognisers. Suppose the user
interface contains a (large) number of icons that should be movable and
double-click should open the icon.. In this case a
recogniser would be declared as:
:- pce_global(@icon_recogniser, new(handler_group(
new(move_gesture),
new(click_gesture(left, '', double,
message(@receiver, open)))))).
Bugs: Should be called recogniser_group
->event
on each of the
handler_group<-members until this message
succeeds. If no recogniser accepts the event it fails.
<-members.
See object<-_arg.<-members.
See object<-_arity.