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Class

Observer (engine/view/observer)

@ckeditor/ckeditor5-engine/src/view/observer/observer

class
See source

Abstract base observer class. Observers are classes which listen to DOM events, do the preliminary processing and fire events on the Document objects. Observers can also add features to the view, for instance by updating its status or marking elements which need a refresh on DOM events.

Filtering

Properties

  • readonly

    document : Document

    See source

    A reference to the Document object.

  • readonly

    isEnabled : boolean

    See source

    The state of the observer. If it is disabled, no events will be fired.

  • readonly

    view : View

    See source

    An instance of the view controller.

  • private

    _isEnabled : boolean

    See source

    The state of the observer. If it is disabled, no events will be fired.

Methods

  • constructor( view )

    See source

    Creates an instance of the observer.

    Parameters

    view : View

  • checkShouldIgnoreEventFromTarget( domTarget ) → boolean

    See source

    Checks whether a given DOM event should be ignored (should not be turned into a synthetic view document event).

    Currently, an event will be ignored only if its target or any of its ancestors has the data-cke-ignore-events attribute. This attribute can be used inside the structures generated by DowncastWriter#createUIElement() to ignore events fired within a UI that should be excluded from CKEditor 5's realms.

    Parameters

    domTarget : null | Node

    The DOM event target to check (usually an element, sometimes a text node and potentially sometimes a document, too).

    Returns

    boolean

    Whether this event should be ignored by the observer.

  • inherited

    delegate( events ) → EmitterMixinDelegateChain

    See source

    Delegates selected events to another Emitter. For instance:

    emitterA.delegate( 'eventX' ).to( emitterB );
emitterA.delegate( 'eventX', 'eventY' ).to( emitterC );

    then eventX is delegated (fired by) emitterB and emitterC along with data:

    emitterA.fire( 'eventX', data );

    and eventY is delegated (fired by) emitterC along with data:

    emitterA.fire( 'eventY', data );

    Parameters

    events : Array<string>

    Event names that will be delegated to another emitter.

    Returns

    EmitterMixinDelegateChain

  • destroy() → void

    See source

    Disables and destroys the observer, among others removes event listeners created by the observer.

    Returns

    void

  • disable() → void

    See source

    Disables the observer. This method is called before rendering to prevent firing events during rendering.

    Returns

    void

    Related:

  • enable() → void

    See source

    Enables the observer. This method is called when the observer is registered to the View and after rendering (all observers are disabled before rendering).

    A typical use case for disabling observers is that mutation observers need to be disabled for the rendering. However, a child class may not need to be disabled, so it can implement an empty method.

    Returns

    void

    Related:

  • inherited

    fire( eventOrInfo, args ) → GetEventInfo<TEvent>[ 'return' ]

    See source

    Fires an event, executing all callbacks registered for it.

    The first parameter passed to callbacks is an EventInfo object, followed by the optional args provided in the fire() method call.

    Type parameters

    TEvent : extends BaseEvent

    The type describing the event. See BaseEvent.

    Parameters

    eventOrInfo : GetNameOrEventInfo<TEvent>

    The name of the event or EventInfo object if event is delegated.

    args : TEvent[ 'args' ]

    Additional arguments to be passed to the callbacks.

    Returns

    GetEventInfo<TEvent>[ 'return' ]

    By default the method returns undefined. However, the return value can be changed by listeners through modification of the evt.return's property (the event info is the first param of every callback).

  • inherited

    listenTo( emitter, event, callback, [ options ] ) → void

    See source

    Registers a callback function to be executed when an event is fired in a specific (emitter) object.

    Events can be grouped in namespaces using :. When namespaced event is fired, it additionally fires all callbacks for that namespace.

    // myEmitter.on( ... ) is a shorthand for myEmitter.listenTo( myEmitter, ... ).
myEmitter.on( 'myGroup', genericCallback );
myEmitter.on( 'myGroup:myEvent', specificCallback );

// genericCallback is fired.
myEmitter.fire( 'myGroup' );
// both genericCallback and specificCallback are fired.
myEmitter.fire( 'myGroup:myEvent' );
// genericCallback is fired even though there are no callbacks for "foo".
myEmitter.fire( 'myGroup:foo' );

    An event callback can stop the event and set the return value of the fire method.

    Type parameters

    TEvent : extends BaseEvent

    The type describing the event. See BaseEvent.

    Parameters

    emitter : Emitter

    The object that fires the event.

    event : TEvent[ 'name' ]

    The name of the event.

    callback : GetCallback<TEvent>

    The function to be called on event.

    [ options ] : CallbackOptions

    Additional options.

    Returns

    void

  • inherited

    listenTo( emitter, event, callback, [ options ] ) → void

    See source

    Registers a callback function to be executed when an event is fired in a specific Emitter or DOM Node. It is backwards compatible with listenTo.

    Type parameters

    K : extends keyof DomEventMap

    Parameters

    emitter : Window | Node

    The object that fires the event.

    event : K

    The name of the event.

    callback : ( Observer, EventInfo<string, unknown>, DomEventMap[ K ] ) => void

    The function to be called on event.

    [ options ] : object

    Additional options.

    Returns

    void

  • observe( domElement, name ) → void

    See source

    Starts observing given DOM element.

    Parameters

    domElement : HTMLElement

    DOM element to observe.

    name : string

    The name of the related root element.

    Returns

    void

  • inherited

    off( event, callback ) → void

    See source

    Stops executing the callback on the given event. Shorthand for this.stopListening( this, event, callback ).

    Parameters

    event : string

    The name of the event.

    callback : Function

    The function to stop being called.

    Returns

    void

  • inherited

    on( event, callback, [ options ] ) → void

    See source

    Registers a callback function to be executed when an event is fired.

    Shorthand for this.listenTo( this, event, callback, options ) (it makes the emitter listen on itself).

    Type parameters

    TEvent : extends BaseEvent

    The type descibing the event. See BaseEvent.

    Parameters

    event : TEvent[ 'name' ]

    The name of the event.

    callback : GetCallback<TEvent>

    The function to be called on event.

    [ options ] : GetCallbackOptions<TEvent>

    Additional options.

    Returns

    void

  • inherited

    once( event, callback, [ options ] ) → void

    See source

    Registers a callback function to be executed on the next time the event is fired only. This is similar to calling on followed by off in the callback.

    Type parameters

    TEvent : extends BaseEvent

    The type descibing the event. See BaseEvent.

    Parameters

    event : TEvent[ 'name' ]

    The name of the event.

    callback : GetCallback<TEvent>

    The function to be called on event.

    [ options ] : GetCallbackOptions<TEvent>

    Additional options.

    Returns

    void

  • inherited

    stopDelegating( [ event ], [ emitter ] ) → void

    See source

    Stops delegating events. It can be used at different levels:

    • To stop delegating all events.
    • To stop delegating a specific event to all emitters.
    • To stop delegating a specific event to a specific emitter.

    Parameters

    [ event ] : string

    The name of the event to stop delegating. If omitted, stops it all delegations.

    [ emitter ] : Emitter

    (requires event) The object to stop delegating a particular event to. If omitted, stops delegation of event to all emitters.

    Returns

    void

  • inherited

    stopListening( [ emitter ], [ event ], [ callback ] ) → void

    See source

    Stops listening for events. It can be used at different levels: It is backwards compatible with listenTo.

    • To stop listening to a specific callback.
    • To stop listening to a specific event.
    • To stop listening to all events fired by a specific object.
    • To stop listening to all events fired by all objects.

    Parameters

    [ emitter ] : Window | Node | Emitter

    The object to stop listening to. If omitted, stops it for all objects.

    [ event ] : string

    (Requires the emitter) The name of the event to stop listening to. If omitted, stops it for all events from emitter.

    [ callback ] : Function

    (Requires the event) The function to be removed from the call list for the given event.

    Returns

    void

  • stopObserving( domElement ) → void

    See source

    Stops observing given DOM element.

    Parameters

    domElement : HTMLElement

    Returns

    void