# OpenLayers.Event

Utility functions for event handling.

Summary

OpenLayers.Event | Utility functions for event handling.
Constants |
KEY_SPACE | {int}
KEY_BACKSPACE | {int}
KEY_TAB | {int}
KEY_RETURN | {int}
KEY_ESC | {int}
KEY_LEFT | {int}
KEY_UP | {int}
KEY_RIGHT | {int}
KEY_DOWN | {int}
KEY_DELETE | {int}
OpenLayers.Events |
Constants |
BROWSER_EVENTS | {Array(String)} supported events
Properties |
fallThrough | {Boolean}
includeXY | {Boolean} Should the .xy property automatically be created for browser mouse events?
extensions | {Object} Event extensions registered with this instance.
Constructor |
OpenLayers.Events | Construct an OpenLayers.Events object.
Functions |
destroy |
addEventType | Deprecated.
on | Convenience method for registering listeners with a common scope.
register | Register an event on the events object.
registerPriority | Same as register() but adds the new listener to the front of the events queue instead of to the end.
un | Convenience method for unregistering listeners with a common scope.
unregister |
triggerEvent | Trigger a specified registered event.
clearMouseCache | Clear cached data about the mouse position.

### Constants

### KEY_SPACE

{int}

### KEY_BACKSPACE

{int}

### KEY_TAB

{int}

### KEY_RETURN

{int}

### KEY_ESC

{int}

### KEY_LEFT

{int}

### KEY_UP

{int}

### KEY_RIGHT

{int}

### KEY_DOWN

{int}

### KEY_DELETE

{int}

## OpenLayers.Events

Summary

Constants |
BROWSER_EVENTS | {Array(String)} supported events
Properties |
fallThrough | {Boolean}
includeXY | {Boolean} Should the .xy property automatically be created for browser mouse events?
extensions | {Object} Event extensions registered with this instance.
Constructor |
OpenLayers.Events | Construct an OpenLayers.Events object.
Functions |
destroy |
addEventType | Deprecated.
on | Convenience method for registering listeners with a common scope.
register | Register an event on the events object.
registerPriority | Same as register() but adds the new listener to the front of the events queue instead of to the end.
un | Convenience method for unregistering listeners with a common scope.
unregister |
triggerEvent | Trigger a specified registered event.
clearMouseCache | Clear cached data about the mouse position.

### Constants

### BROWSER_EVENTS

{Array(String)} supported events

### Properties

### fallThrough

{Boolean}

### includeXY

{Boolean} Should the .xy property automatically be created for browser mouse events? In general, this should be false. If it is true, then mouse events will automatically generate a ‘.xy’ property on the event object that is passed. (Prior to OpenLayers 2.7, this was true by default.) Otherwise, you can call the getMousePosition on the relevant events handler on the object available via the ‘evt.object’ property of the evt object. So, for most events, you can call: function named(evt) { this.xy = this.object.events.getMousePosition(evt) }

#### This option typically defaults to false for performance reasons

when creating an events object whose primary purpose is to manage relatively positioned mouse events within a div, it may make sense to set it to true.

This option is also used to control whether the events object caches offsets. If this is false, it will not: the reason for this is that it is only expected to be called many times if the includeXY property is set to true. If you set this to true, you are expected to clear the offset cache manually (using this.clearMouseCache()) if: the border of the element changes the location of the element in the page changes

### extensions

{Object} Event extensions registered with this instance. Keys are event types, values are {OpenLayers.Events.*} extension instances or {Boolean} for events that an instantiated extension provides in addition to the one it was created for.

Extensions create an event in addition to browser events, which usually fires when a sequence of browser events is completed. Extensions are automatically instantiated when a listener is registered for an event provided by an extension.

Extensions are created in the OpenLayers.Events namespace using OpenLayers.Class, and named after the event they provide. The constructor receives the target OpenLayers.Events instance as argument. Extensions that need to capture browser events before they propagate can register their listeners events using register, with {extension: true} as 4th argument.

If an extension creates more than one event, an alias for each event type should be created and reference the same class. The constructor should set a reference in the target’s extensions registry to itself.

Below is a minimal extension that provides the “foostart” and “fooend” event types, which replace the native “click” event type if clicked on an element with the css class “foo”:

>     OpenLayers.Events.foostart = OpenLayers.Class({
>         initialize: function(target) {
>             this.target = target;
>             this.target.register("click", this, this.doStuff, {extension: true});
>             // only required if extension provides more than one event type
>             this.target.extensions["foostart"] = true;
>             this.target.extensions["fooend"] = true;
>         },
>         destroy: function() {
>             var target = this.target;
>             target.unregister("click", this, this.doStuff);
>             delete this.target;
>             // only required if extension provides more than one event type
>             delete target.extensions["foostart"];
>             delete target.extensions["fooend"];
>         },
>         doStuff: function(evt) {
>             var propagate = true;
>             if (OpenLayers.Event.element(evt).className === "foo") {
>                 propagate = false;
>                 var target = this.target;
>                 target.triggerEvent("foostart");
>                 window.setTimeout(function() {
>                     target.triggerEvent("fooend");
>                 }, 1000);
>             }
>             return propagate;
>         }
>     });
>     // only required if extension provides more than one event type
>     OpenLayers.Events.fooend = OpenLayers.Events.foostart;

### Constructor

### OpenLayers.Events

Construct an OpenLayers.Events object.

#### Parameters

object | {Object} The js object to which this Events object is being added
element | {DOMElement} A dom element to respond to browser events
eventTypes | {Array(String)} Deprecated. Array of custom application events. A listener may be registered for any named event, regardless of the values provided here.
fallThrough | {Boolean} Allow events to fall through after these have been handled?
options | {Object} Options for the events object.

### Functions

### destroy

> destroy: function ()

### addEventType

> addEventType: function( | eventName | )

Deprecated. Any event can be triggered without adding it first.

#### Parameters

eventName | {String}

### on

> on: function( | object | )

Convenience method for registering listeners with a common scope. Internally, this method calls register as shown in the examples below.

#### Example use

>     // register a single listener for the "loadstart" event
>     events.on({"loadstart": loadStartListener});

>     // this is equivalent to the following
>     events.register("loadstart", undefined, loadStartListener);

>     // register multiple listeners to be called with the same `this` object
>     events.on({
>         "loadstart": loadStartListener,
>         "loadend": loadEndListener,
>         scope: object
>     });

>     // this is equivalent to the following
>     events.register("loadstart", object, loadStartListener);
>     events.register("loadend", object, loadEndListener);

#### Parameters

object | {Object}

### register

> register: function ( | type,
> | obj,
> | func,
> | priority | )

Register an event on the events object.

When the event is triggered, the ‘func’ function will be called, in the context of ‘obj’. Imagine we were to register an event, specifying an OpenLayers.Bounds Object as ‘obj’. When the event is triggered, the context in the callback function will be our Bounds object. This means that within our callback function, we can access the properties and methods of the Bounds object through the “this” variable. So our callback could execute something like:

>     leftStr = "Left: " + this.left;

or

>     centerStr = "Center: " + this.getCenterLonLat();

#### Parameters

type | {String} Name of the event to register
obj | {Object} The object to bind the context to for the callback#. If no object is specified, default is the Events’s ‘object’ property.
func | {Function} The callback function. If no callback is specified, this function does nothing.
priority | {Boolean|Object} If true, adds the new listener to the front of the events queue instead of to the end.

#### Valid options for priority

extension | {Boolean} If true, then the event will be registered as extension event. Extension events are handled before all other events.

### registerPriority

> registerPriority: function ( | type,
> | obj,
> | func | )

Same as register() but adds the new listener to the front of the events queue instead of to the end.

TODO: get rid of this in 3.0 | Decide whether listeners should be called in the order they were registered or in reverse order.

#### Parameters

type | {String} Name of the event to register
obj | {Object} The object to bind the context to for the callback#. If no object is specified, default is the Events’s ‘object’ property.
func | {Function} The callback function. If no callback is specified, this function does nothing.

### un

> un: function( | object | )

Convenience method for unregistering listeners with a common scope. Internally, this method calls unregister as shown in the examples below.

#### Example use

>     // unregister a single listener for the "loadstart" event
>     events.un({"loadstart": loadStartListener});

>     // this is equivalent to the following
>     events.unregister("loadstart", undefined, loadStartListener);

>     // unregister multiple listeners with the same `this` object
>     events.un({
>         "loadstart": loadStartListener,
>         "loadend": loadEndListener,
>         scope: object
>     });

>     // this is equivalent to the following
>     events.unregister("loadstart", object, loadStartListener);
>     events.unregister("loadend", object, loadEndListener);

### unregister

> unregister: function ( | type,
> | obj,
> | func | )

#### Parameters

type | {String}
obj | {Object} If none specified, defaults to this.object
func | {Function}

### triggerEvent

> triggerEvent: function ( | type,
> | evt | )

Trigger a specified registered event.

#### Parameters

type | {String}
evt | {Event}

#### Returns

{Boolean} The last listener return. If a listener returns false, the chain of listeners will stop getting called.

### clearMouseCache

> clearMouseCache: function()

Clear cached data about the mouse position. This should be called any time the element that events are registered on changes position within the page.

> destroy: function ()

> addEventType: function( | eventName | )

Deprecated.

> on: function( | object | )

Convenience method for registering listeners with a common scope.

> register: function ( | type,
> | obj,
> | func,
> | priority | )

Register an event on the events object.

> registerPriority: function ( | type,
> | obj,
> | func | )

Same as register() but adds the new listener to the front of the events queue instead of to the end.

> un: function( | object | )

Convenience method for unregistering listeners with a common scope.

> unregister: function ( | type,
> | obj,
> | func | )

> triggerEvent: function ( | type,
> | evt | )

Trigger a specified registered event.

> clearMouseCache: function()

Clear cached data about the mouse position.
Construct an OpenLayers.Events object.
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