OpenLayers Event model

Every object has predefined event types, which can be assigned to particular function in defined scope. When you write your custom code, you can define your own events and register them, using

this.events = new OpenLayers.Events(this, this.div,
                                    ["event1","event2"]);

For example object OpenLayers.Map, has several predefined events:

preaddlayer

triggered before a layer has been added. The event object will include a layer property that references the layer to be added.

addlayer

triggered after a layer has been added. The event object

will include a layer property that references the added layer.

removelayer

triggered after a layer has been removed. The event object will include a layer property that references the removed layer.

changelayer

triggered after a layer name change, order change, or visibility change (due to resolution thresholds). Listeners will receive an event object with layer and property properties. The layer property will be a reference to the changed layer. The property property will be a key to the changed property (name, visibility, or order).

movestart

triggered after the start of a drag, pan, or zoom

move

triggered after each drag, pan, or zoom

moveend

triggered after a drag, pan, or zoom completes

zoomend

triggered after a zoom completes

addmarker

triggered after a marker has been added

removemarker

triggered after a marker has been removed

clearmarkers

triggered after markers have been cleared

mouseover

triggered after mouseover the map

mouseout triggered after mouseout the map

mousemove

triggered after mousemove the map

dragstart

Does not work. Register for movestart instead.

drag

Does not work. Register for move instead.

dragend

Does not work. Register for moveend instead.

changebaselayer

triggered after the base layer changes

OpenLayers.Layer has:

loadstart Triggered when layer loading starts.

loadend Triggered when layer loading ends.

loadcancel Triggered when layer loading is canceled.

visibilitychanged Triggered when layer visibility is changed.

move Triggered when layer moves (triggered with every mousemove

during a drag).

moveend Triggered when layer is done moving, object passed as

argument has a zoomChanged boolean property which tells that the zoom has changed.

and OpenLayers.Layer.Vector adds:

beforefeatureadded Triggered before a feature is added. Listeners

will receive an object with a feature property referencing the feature to be added. To stop the feature from being added, a listener should return false.

beforefeaturesadded Triggered before an array of features is added.

Listeners will receive an object with a features property referencing the feature to be added. To stop the features from being added, a listener should return false.

featureadded Triggered after a feature is added. The event

object passed to listeners will have a feature property with a reference to the added feature.

featuresadded Triggered after features are added. The event

object passed to listeners will have a features property with a reference to an array of added features.

beforefeatureremoved Triggered before a feature is removed. Listeners

will receive an object with a feature property referencing the feature to be removed.

featureremoved Triggerd after a feature is removed. The event

object passed to listeners will have a feature property with a reference to the removed feature.

featuresremoved Triggered after features are removed. The event

object passed to listeners will have a features property with a reference to an array of removed features.

featureselected Triggered after a feature is selected. Listeners

will receive an object with a feature property referencing the selected feature.

featureunselected Triggered after a feature is unselected.

Listeners will receive an object with a feature property referencing the unselected feature.

beforefeaturemodified Triggered when a feature is selected to

be modified. Listeners will receive an object with a feature property referencing the selected feature.

featuremodified Triggered when a feature has been modified.

Listeners will receive an object with a feature property referencing the modified feature.

afterfeaturemodified Triggered when a feature is finished being modified.

Listeners will receive an object with a feature property referencing the modified feature.

vertexmodified Triggered when a vertex within any feature geometry

has been modified. Listeners will receive an object with a feature property referencing the modified feature, a vertex property referencing the vertex modified (always a point geometry), and a pixel property referencing the pixel location of the modification.

sketchstarted Triggered when a feature sketch bound for this layer

is started. Listeners will receive an object with a feature property referencing the new sketch feature and a vertex property referencing the creation point.

sketchmodified Triggered when a feature sketch bound for this layer

is modified. Listeners will receive an object with a vertex property referencing the modified vertex and a feature property referencing the sketch feature.

sketchcomplete Triggered when a feature sketch bound for this layer

is complete. Listeners will receive an object with a feature property referencing the sketch feature. By returning false, a listener can stop the sketch feature from being added to the layer.

refresh Triggered when something wants a strategy to ask the protocol

for a new set of features.

and so on. If we want to do something, when new feature is added to the vector layer, it is simple:

var vlayer = new OpenLayers.Layer.Vector("Vector layer");

var onFeatureAdd = function(e) {
    // do something
    // 'this' (scope) is {self: object, layer: vector layer}
};

vlayer.events.register("featureadded",{"self":this,layer:vlayer},onFeatureAdd);