application-specific events
GvaScript.fireEvent - application-specific events
MyConstructor = function (...) {...}; MyContructor.prototype = { fireEvent = GvaScript.fireEvent, // copy into the target object someMethod: function(...) { ... this.fireEvent(eventName, target1, target2, ...); // OR ... this.fireEvent({type: eventName, prop1: value1, ... }, target1, target2, ...); } };
Extension of the HTML event model with specific events.
Various GvaScript
controllers use this to manage interactions
between the DOM elements and the controller. Client code
can register a an event handler either within the
HTML code, or through Javascript.
Events have names specific to the controller
(for example choiceList
uses events Highlight
and Ping
;
treeNavigator
uses events Close
, Open
, BeforeLoadContent
, etc.).
If a class needs to fire specific events, it must
copy the GvaScript.fireEvent
method into its own
methods (so that "this" is properly bound to an instance
of that class).
The first argument to fireEvent
is usually an event name. This
can be any string, without the on
prefix :
this.fireEvent("Ping", this.htmlElement, otherElement1, ...);
The method will inspect all HTML elements supplied in
the argument list, trying to find an onPing
handler.
If none is found, the method also tries to find
an onPing
property within the calling object (this
).
If an event handler is found, that handler is called
with an event
argument as described below;
the return value of the handler becomes the
return value of fireEvent
. If not handler is found,
fireEvent
returns null
.
For more sophisticated needs, the first argument
to fireEvent
can be an object with several
properties. In that case, all properties will be copied
into the generated event structure. The type
property
should contain the event name, in order to be compatible
with the first syntax. So for example
this.fireEvent({type : "Ping", prop1 : "value1", prop2 : "value2"}, this.htmlElement, otherElement1, ...);
will generate "Ping" events with all default properties described
below, plus the properties prop1
and prop2
.
<div onEventName="doSomethingWith(this)"> <span onEventName="doSomethingMoreSpecificWith(this, controller)"> <span onEventName="doYetAnotherThing"> </div>
myController.onEventName = function(event){...};
There are three ways to register a handler:
This works as for ordinary HTML DOM events. The javascript statement will be evaluated in a context where the following variables are defined:
The object that registered the event handler.
The HTML element that first received the event.
The object that registered the event handler (equivalent to this
).
The GvaScript controller object that generated the event.
A structure containing various information about the generated event, described below.
The given function will be called with a single event
argument.
This works exactly like the previous case : the event handling
function receives a single event
argument.
The event
object passed to event handlers contains the
following properties :