View (engine/view)

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

class

Editor's view controller class. Its main responsibility is DOM - View management for editing purposes, to provide abstraction over the DOM structure and events and hide all browsers quirks.

View controller renders view document to DOM whenever view structure changes. To determine when view can be rendered, all changes need to be done using the change method, using DowncastWriter:

view.change( writer => {
    writer.insert( position, writer.createText( 'foo' ) );
} );

View controller also register observers which observes changes on DOM and fire events on the Document. Note that the following observers are added by the class constructor and are always available:

This class also bind DOM and View elements.

If you do not need full DOM - View management, and want to only transform the tree of view elements to the DOM elements you do not need this controller, you can use the DomConverter.

Filtering

Public
Inherited
Mixed
Protected
Private
Deprecated

Properties

document : Document

readonly

Instance of the Document associated with this view controller.
domConverter : DomConverter

readonly

Instance of the domConverter use by renderer and observers.
domRoots : Map

readonly

Roots of the DOM tree. Map on the HTMLElements with roots names as keys.
_renderingDisabled : Boolean

protected

Internal flag to temporary disable rendering. See usage in the editing controller.
renderer : Renderer

protected

Instance of the renderer.
_observers : Map.<Function, Observer>

private

Map of registered observers.
_ongoingChange : Boolean

private

Is set to true when view changes are currently in progress.
_renderingInProgress : Boolean

private

Used to prevent calling render and change during rendering view to the DOM.
_writer : DowncastWriter

private

DowncastWriter instance used in {@link #change change method) callbacks.

Methods

addObserver( Observer ) → Observer

Creates observer of the given type if not yet created, enables it and attaches to all existing and future DOM roots.

Note: Observers are recognized by their constructor (classes). A single observer will be instantiated and used only when registered for the first time. This means that features and other components can register a single observer multiple times without caring whether it has been already added or not.

Parameters

Observer : function

The constructor of an observer to add. Should create an instance inheriting from Observer.

Returns

Observer

Added observer instance.
attachDomRoot( domRoot, [ name ] )

Attaches DOM root element to the view element and enable all observers on that element. Also mark element to be synchronized with the view what means that all child nodes will be removed and replaced with content of the view root.

This method also will change view element name as the same as tag name of given dom root. Name is always transformed to lower case.

Parameters

domRoot : Element

DOM root element.

[ name ] : String

Name of the root.

Defaults to 'main'
bind( bindProperties ) → Object
Binds observable properties to another objects implementing Observable interface (like Model).
Once bound, the observable will immediately share the current state of properties of the observable it is bound to and react to the changes to these properties in the future.

Note: To release the binding use unbind.

Using bind().to() chain:
```
A.bind( 'a' ).to( B );
A.bind( 'a' ).to( B, 'b' );
A.bind( 'a', 'b' ).to( B, 'c', 'd' );
A.bind( 'a' ).to( B, 'b', C, 'd', ( b, d ) => b + d );
```
It is also possible to bind to the same property in a observables collection using bind().toMany() chain:
```
A.bind( 'a' ).toMany( [ B, C, D ], 'x', ( a, b, c ) => a + b + c );
A.bind( 'a' ).toMany( [ B, C, D ], 'x', ( ...x ) => x.every( x => x ) );
```
Parameters

bindProperties : String

Observable properties that will be bound to another observable(s).

Returns

Object

The bind chain with the to() and toMany() methods.
change( callback )
Change method is the primary way of changing the view. You should use it to modify any node in the view tree. It makes sure that after all changes are made view is rendered to DOM. It prevents situations when DOM is updated when view state is not yet correct. It allows to nest calls one inside another and still perform single rendering after all changes are applied.
```
view.change( writer => {
    writer.insert( position1, writer.createText( 'foo' ) );

    view.change( writer => {
        writer.insert( position2, writer.createText( 'bar' ) );
    } );

    writer.remove( range );
} );
```
Change block is executed immediately.

When the outermost change block is done and rendering to DOM is over it fires event-render event.

Throws CKEditorError applying-view-changes-on-rendering when change block is used after rendering to DOM has started.

Parameters

callback : function

Callback function which may modify the view.
decorate( methodName )
Turns the given methods of this object into event-based ones. This means that the new method will fire an event (named after the method) and the original action will be plugged as a listener to that event.
This is a very simplified method decoration. Itself it doesn't change the behavior of a method (expect adding the event), but it allows to modify it later on by listening to the method's event.

For example, in order to cancel the method execution one can stop the event:
```
class Foo {
    constructor() {
        this.decorate( 'method' );
    }

    method() {
        console.log( 'called!' );
    }
}

const foo = new Foo();
foo.on( 'method', ( evt ) => {
    evt.stop();
}, { priority: 'high' } );

foo.method(); // Nothing is logged.
```
Note: we used a high priority listener here to execute this callback before the one which calls the original method (which used the default priority).

It's also possible to change the return value:
```
foo.on( 'method', ( evt ) => {
    evt.return = 'Foo!';
} );

foo.method(); // -> 'Foo'
```
Finally, it's possible to access and modify the parameters:
```
method( a, b ) {
    console.log( `${ a }, ${ b }`  );
}

// ...

foo.on( 'method', ( evt, args ) => {
    args[ 0 ] = 3;

    console.log( args[ 1 ] ); // -> 2
}, { priority: 'high' } );

foo.method( 1, 2 ); // -> '3, 2'
```
Parameters

methodName : String

Name of the method to decorate.
delegate( events ) → EmitterMixinDelegateChain
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 : String

Event names that will be delegated to another emitter.

Returns

EmitterMixinDelegateChain
destroy()

Destroys this instance. Makes sure that all observers are destroyed and listeners removed.
disableObservers()

Disables all added observers.
enableObservers()

Enables all added observers.
fire( eventOrInfo, [ args ] ) → *

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.

Parameters

eventOrInfo : String | EventInfo

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

[ args ] : *

Additional arguments to be passed to the callbacks.

Returns

*

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).
focus()

It will focus DOM element representing EditableElement that is currently having selection inside.
getDomRoot( [ name ] ) → Element

Gets DOM root element.

Parameters

[ name ] : String

Name of the root.

Defaults to 'main'

Returns

Element

DOM root element instance.
getObserver( Observer ) → Observer | undefined

Returns observer of the given type or undefined if such observer has not been added yet.

Parameters

Observer : function

The constructor of an observer to get.

Returns

Observer | undefined

Observer instance or undefined.
listenTo( emitter, event, callback, [ options ] = { [options.priority] } )
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.

Parameters

emitter : Emitter

The object that fires the event.

event : String

The name of the event.

callback : function

The function to be called on event.

[ options ] : Object

Additional options.

Properties

[ options.priority ] : PriorityString | Number

The priority of this event callback. The higher the priority value the sooner the callback will be fired. Events having the same priority are called in the order they were added.

Defaults to 'normal'

Defaults to {}
off( event, callback )

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.
on( event, callback, [ options ] = { [options.priority] } )

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).

Parameters

event : String

The name of the event.

callback : function

The function to be called on event.

[ options ] : Object

Additional options.

Properties

[ options.priority ] : PriorityString | Number

The priority of this event callback. The higher the priority value the sooner the callback will be fired. Events having the same priority are called in the order they were added.

Defaults to 'normal'

Defaults to {}
once( event, callback, [ options ] = { [options.priority] } )

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.

Parameters

event : String

The name of the event.

callback : function

The function to be called on event.

[ options ] : Object

Additional options.

Properties

[ options.priority ] : PriorityString | Number

The priority of this event callback. The higher the priority value the sooner the callback will be fired. Events having the same priority are called in the order they were added.

Defaults to 'normal'

Defaults to {}
render()

Renders view document to DOM. If any view changes are currently in progress, rendering will start after all change blocks are processed.

Throws CKEditorError applying-view-changes-on-rendering when trying to re-render when rendering to DOM has already started.
scrollToTheSelection()

Scrolls the page viewport and domRoots with their ancestors to reveal the caret, if not already visible to the user.
set( name, [ value ] )

Creates and sets the value of an observable property of this object. Such an property becomes a part of the state and is be observable.

It accepts also a single object literal containing key/value pairs with properties to be set.

This method throws the observable-set-cannot-override error if the observable instance already have a property with the given property name. This prevents from mistakenly overriding existing properties and methods, but means that foo.set( 'bar', 1 ) may be slightly slower than foo.bar = 1.

Parameters

name : String | Object

The property's name or object with name=>value pairs.

[ value ] : *

The property's value (if name was passed in the first parameter).
stopDelegating( [ event ], [ emitter ] )
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.
stopListening( [ emitter ], [ event ], [ callback ] )
Stops listening for events. It can be used at different levels:
- 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 ] : 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.
unbind( [ unbindProperties ] )
Removes the binding created with bind.
```
A.unbind( 'a' );
A.unbind();
```
Parameters

[ unbindProperties ] : String

Observable properties to be unbound. All the bindings will be released if no properties provided.
_render()

private

Renders all changes. In order to avoid triggering the observers (e.g. mutations) all observers are disabled before rendering and re-enabled after that.

Events

change:{property}( eventInfo, name, value, oldValue )
Fired when a property changed value.
```
observable.set( 'prop', 1 );

observable.on( 'change:prop', ( evt, propertyName, newValue, oldValue ) => {
    console.log( `${ propertyName } has changed from ${ oldValue } to ${ newValue }` );
} );

observable.prop = 2; // -> 'prop has changed from 1 to 2'
```
Parameters

eventInfo : EventInfo

An object containing information about the fired event.

name : String

The property name.

value : *

The new property value.

oldValue : *

The previous property value.
render( eventInfo )
Fired after a topmost change block and all post-fixers are executed.
Actual rendering is performed as a first listener on 'normal' priority.
```
view.on( 'render', () => {
    // Rendering to the DOM is complete.
} );
```
This event is useful when you want to update interface elements after the rendering, e.g. position of the balloon panel. If you wants to change view structure use post-fixers.

Parameters

eventInfo : EventInfo

An object containing information about the fired event.
set:{property}( eventInfo, name, value, oldValue )
Fired when a property value is going to be set but is not set yet (before the change event is fired).
You can control the final value of the property by using the event's return property.
```
observable.set( 'prop', 1 );

observable.on( 'set:prop', ( evt, propertyName, newValue, oldValue ) => {
    console.log( `Value is going to be changed from ${ oldValue } to ${ newValue }` );
    console.log( `Current property value is ${ observable[ propertyName ] }` );

    // Let's override the value.
    evt.return = 3;
} );

observable.on( 'change:prop', ( evt, propertyName, newValue, oldValue ) => {
    console.log( `Value has changed from ${ oldValue } to ${ newValue }` );
} );

observable.prop = 2; // -> 'Value is going to be changed from 1 to 2'
                     // -> 'Current property value is 1'
                     // -> 'Value has changed from 1 to 3'
```
Note: Event is fired even when the new value is the same as the old value.

Parameters

eventInfo : EventInfo

An object containing information about the fired event.

name : String

The property name.

value : *

The new property value.

oldValue : *

The previous property value.

View (engine/view)

Filtering

Properties

document : Documentmodule:engine/view/view~View#document

domConverter : DomConvertermodule:engine/view/view~View#domConverter

domRoots : Mapmodule:engine/view/view~View#domRoots

_renderingDisabled : Booleanmodule:engine/view/view~View#_renderingDisabled

renderer : Renderermodule:engine/view/view~View#renderer

_observers : Map.<Function, Observer>module:engine/view/view~View#_observers

_ongoingChange : Booleanmodule:engine/view/view~View#_ongoingChange

_renderingInProgress : Booleanmodule:engine/view/view~View#_renderingInProgress

_writer : DowncastWritermodule:engine/view/view~View#_writer

Methods

addObserver( Observer ) → Observermodule:engine/view/view~View#addObserver

Parameters

Returns

attachDomRoot( domRoot, [ name ] )module:engine/view/view~View#attachDomRoot

Parameters

bind( bindProperties ) → Objectmodule:engine/view/view~View#bind

Parameters

Returns

change( callback )module:engine/view/view~View#change

Parameters

decorate( methodName )module:engine/view/view~View#decorate

Parameters

delegate( events ) → EmitterMixinDelegateChainmodule:engine/view/view~View#delegate

Parameters

Returns

destroy()module:engine/view/view~View#destroy

disableObservers()module:engine/view/view~View#disableObservers

enableObservers()module:engine/view/view~View#enableObservers

fire( eventOrInfo, [ args ] ) → *module:engine/view/view~View#fire

Parameters

Returns

focus()module:engine/view/view~View#focus

getDomRoot( [ name ] ) → Elementmodule:engine/view/view~View#getDomRoot

Parameters

Returns

getObserver( Observer ) → Observer | undefinedmodule:engine/view/view~View#getObserver

Parameters

Returns

listenTo( emitter, event, callback, [ options ] = { [options.priority] } )module:engine/view/view~View#listenTo

Parameters

off( event, callback )module:engine/view/view~View#off

Parameters

on( event, callback, [ options ] = { [options.priority] } )module:engine/view/view~View#on

Parameters

once( event, callback, [ options ] = { [options.priority] } )module:engine/view/view~View#once

Parameters

render()module:engine/view/view~View#render

scrollToTheSelection()module:engine/view/view~View#scrollToTheSelection

set( name, [ value ] )module:engine/view/view~View#set

Parameters

stopDelegating( [ event ], [ emitter ] )module:engine/view/view~View#stopDelegating

Parameters

stopListening( [ emitter ], [ event ], [ callback ] )module:engine/view/view~View#stopListening

Parameters

unbind( [ unbindProperties ] )module:engine/view/view~View#unbind

Parameters

_render()module:engine/view/view~View#_render

Events

change:{property}( eventInfo, name, value, oldValue )module:engine/view/view~View#event:change:{property}

Parameters

render( eventInfo )module:engine/view/view~View#event:render

Parameters

set:{property}( eventInfo, name, value, oldValue )module:engine/view/view~View#event:set:{property}

Parameters

`document : Document`

`domConverter : DomConverter`

`domRoots : Map`

`_renderingDisabled : Boolean`

`renderer : Renderer`

`_observers : Map.<Function, Observer>`

`_ongoingChange : Boolean`

`_renderingInProgress : Boolean`

`_writer : DowncastWriter`

`addObserver( Observer ) → Observer`

`attachDomRoot( domRoot, [ name ] )`

`bind( bindProperties ) → Object`

`change( callback )`

`decorate( methodName )`

`delegate( events ) → EmitterMixinDelegateChain`

`destroy()`

`disableObservers()`

`enableObservers()`

`fire( eventOrInfo, [ args ] ) → *`

`focus()`

`getDomRoot( [ name ] ) → Element`

`getObserver( Observer ) → Observer | undefined`

`listenTo( emitter, event, callback, [ options ] = { [options.priority] } )`

`off( event, callback )`

`on( event, callback, [ options ] = { [options.priority] } )`

`once( event, callback, [ options ] = { [options.priority] } )`

`render()`

`scrollToTheSelection()`

`set( name, [ value ] )`

`stopDelegating( [ event ], [ emitter ] )`

`stopListening( [ emitter ], [ event ], [ callback ] )`

`unbind( [ unbindProperties ] )`

`_render()`

`change:{property}( eventInfo, name, value, oldValue )`

`render( eventInfo )`

`set:{property}( eventInfo, name, value, oldValue )`