1 """Provides classes and interfaces for the inheritable event model. The model
2 supports inheritable events and a flexible way of registering and unregistering
3 event listeners. It's a fundamental building block of Muntjac, and as it is
4 included in L{muntjac.ui.abstract_component.AbstractComponent}, all UI
5 components automatically support it.
6
7 Package Specification
8 =====================
9
10 The core of the event model is the inheritable event class hierarchy, and the
11 L{EventRouter} which provide a simple, ubiquitous mechanism to transport events
12 to all interested parties.
13
14 The power of the event inheritance arises from the possibility of receiving not
15 only the events of the registered type, I{but also the ones which are inherited
16 from it}. For example, let's assume that there are the events C{GeneralEvent}
17 and C{SpecializedEvent} so that the latter inherits the former. Furthermore we
18 have an object C{A} which registers to receive C{GeneralEvent} type events from
19 the object C{B}. C{A} would of course receive all C{GeneralEvent}s generated by
20 C{B}, but in addition to this, C{A} would also receive all C{SpecializedEvent}s
21 generated by C{B}. However, if C{B} generates some other events that do not
22 have C{GeneralEvent} as an ancestor, C{A} would not receive them unless it
23 registers to listen for them, too.
24
25 The interface to attaching and detaching listeners to and from an object
26 works with methods. One specifies the event that should trigger the listener,
27 the trigger method that should be called when a suitable event occurs and the
28 object owning the method. From these a new listener is constructed and added
29 to the event router of the specified component.
30
31 The interface is defined in L{MethodEventSource}, and a straightforward
32 implementation of it is defined in L{EventRouter} which also includes a method
33 to actually fire the events.
34
35 All fired events are passed to all registered listeners, which are of type
36 L{ListenerMethod}. The listener then checks if the event type matches with the
37 specified event type and calls the specified trigger method if it does."""
38