# ViewRenderer

class

Renderer is responsible for updating the DOM structure and the DOM selection based on the [information about updated view nodes](#function-markToSync). In other words, it renders the view to the DOM.

Its main responsibility is to make only the necessary, minimal changes to the DOM. However, unlike in many virtual DOM implementations, the primary reason for doing minimal changes is not the performance but ensuring that native editing features such as text composition, autocompletion, spell checking, selection's x-index are affected as little as possible.

Renderer uses [`ViewDomConverter`](module_engine_view_domconverter-ViewDomConverter.md) to transform view nodes and positions to and from the DOM.

[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-engine/src/view/renderer.ts#L60)

<a id="properties">

## Properties

<a id="member-domConverter">

### `domConverter: ViewDomConverter` _(readonly)_

Converter instance.

[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-engine/src/view/renderer.ts#L69)

<a id="member-domDocuments">

### `domDocuments: Set<Document>` _(readonly)_

Set of DOM Documents instances.

[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-engine/src/view/renderer.ts#L64)

<a id="member-isComposing">

### `isComposing: boolean` _(readonly)_

True if composition is in progress inside the document.

This property is bound to the [`Document#isComposing`](module_engine_view_document-ViewDocument.md#member-isComposing) property.

[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-engine/src/view/renderer.ts#L118)

<a id="member-isFocused">

### `isFocused: boolean` _(readonly)_

Indicates if the view document is focused and selection can be rendered. Selection will not be rendered if this is set to `false`.

[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-engine/src/view/renderer.ts#L97)

<a id="member-isSelecting">

### `isSelecting: boolean` _(readonly)_

Indicates whether the user is making a selection in the document (e.g. holding the mouse button and moving the cursor). When they stop selecting, the property goes back to `false`.

Note: In some browsers, the renderer will stop rendering the selection and inline fillers while the user is making a selection to avoid glitches in DOM selection (https\://github.com/ckeditor/ckeditor5/issues/10562, https\://github.com/ckeditor/ckeditor5/issues/10723).

[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-engine/src/view/renderer.ts#L109)

<a id="member-markedAttributes">

### `markedAttributes: Set<ViewElement>` _(readonly)_

Set of nodes which attributes changed and may need to be rendered.

[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-engine/src/view/renderer.ts#L74)

<a id="member-markedChildren">

### `markedChildren: Set<ViewElement>` _(readonly)_

Set of elements which child lists changed and may need to be rendered.

[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-engine/src/view/renderer.ts#L79)

<a id="member-markedTexts">

### `markedTexts: Set<ViewNode>` _(readonly)_

Set of text nodes which text data changed and may need to be rendered.

[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-engine/src/view/renderer.ts#L84)

<a id="member-selection">

### `selection: ViewDocumentSelection` _(readonly)_

View selection. Renderer updates DOM selection based on the view selection.

[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-engine/src/view/renderer.ts#L89)

<a id="member-_fakeSelectionContainer">

### `_fakeSelectionContainer: HTMLElement | null` _(private)_

DOM element containing fake selection.

[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-engine/src/view/renderer.ts#L128)

<a id="member-_inlineFiller">

### `_inlineFiller: Text | null` _(private)_

The text node in which the inline filler was rendered.

[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-engine/src/view/renderer.ts#L123)

<a id="methods">

## Methods

<a id="function-constructor">

### `constructor( domConverter, selection )`

Creates a renderer instance.

[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-engine/src/view/renderer.ts#L136)

#### Parameters

* `domConverter: ViewDomConverter`

  Converter instance.

* `selection: ViewDocumentSelection`

  View selection.

<a id="function-bind:MANY_BIND">

### `bind( bindProperties ) → ObservableMultiBindChain` _(inherited)_

Binds [observable properties](#function-set:KEY_VALUE) to other objects implementing the [`Observable`](module_utils_observablemixin-Observable.md) interface.

Read more in the [dedicated](../framework/deep-dive/observables.md#property-bindings) guide covering the topic of property bindings with some additional examples.

Consider two objects: a `button` and an associated `command` (both `Observable`).

A simple property binding could be as follows:

```typescript
button.bind( 'isEnabled' ).to( command, 'isEnabled' );
```

or even shorter:

```typescript
button.bind( 'isEnabled' ).to( command );
```

which works in the following way:

* `button.isEnabled` **instantly equals** `command.isEnabled`,
* whenever `command.isEnabled` changes, `button.isEnabled` will immediately reflect its value.

**Note**: To release the binding, use [`unbind`](module_utils_observablemixin-Observable.md#function-unbind).

You can also "rename" the property in the binding by specifying the new name in the `to()` chain:

```typescript
button.bind( 'isEnabled' ).to( command, 'isWorking' );
```

It is possible to bind more than one property at a time to shorten the code:

```typescript
button.bind( 'isEnabled', 'value' ).to( command );
```

which corresponds to:

```typescript
button.bind( 'isEnabled' ).to( command );
button.bind( 'value' ).to( command );
```

The binding can include more than one observable, combining multiple data sources in a custom callback:

```typescript
button.bind( 'isEnabled' ).to( command, 'isEnabled', ui, 'isVisible',
	( isCommandEnabled, isUIVisible ) => isCommandEnabled && isUIVisible );
```

Using a custom callback allows processing the value before passing it to the target property:

```typescript
button.bind( 'isEnabled' ).to( command, 'value', value => value === 'heading1' );
```

It is also possible to bind to the same property in an array of observables. To bind a `button` to multiple commands (also `Observables`) so that each and every one of them must be enabled for the button to become enabled, use the following code:

```typescript
button.bind( 'isEnabled' ).toMany( [ commandA, commandB, commandC ], 'isEnabled',
	( isAEnabled, isBEnabled, isCEnabled ) => isAEnabled && isBEnabled && isCEnabled );
```

[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-utils/src/observablemixin.ts#L1074)

#### Parameters

* `bindProperties: Array<'off' | 'set' | 'bind' | 'unbind' | 'decorate' | 'stopListening' | 'on' | 'once' | 'listenTo' | 'fire' | 'delegate' | 'stopDelegating' | 'isFocused' | 'selection' | 'isSelecting' | 'isComposing' | 'domDocuments' | 'domConverter' | 'markedAttributes' | 'markedChildren' | 'markedTexts' | 'markToSync' | 'render'>`

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

#### Returns

* `ObservableMultiBindChain`

  The bind chain with the `to()` and `toMany()` methods.

<a id="function-bind:DUAL_BIND">

### `bind( bindProperty1, bindProperty2 ) → ObservableDualBindChain<K1, ViewRenderer[ K1 ], K2, ViewRenderer[ K2 ]>` _(inherited)_

Binds [observable properties](#function-set:KEY_VALUE) to other objects implementing the [`Observable`](module_utils_observablemixin-Observable.md) interface.

Read more in the [dedicated](../framework/deep-dive/observables.md#property-bindings) guide covering the topic of property bindings with some additional examples.

Consider two objects: a `button` and an associated `command` (both `Observable`).

A simple property binding could be as follows:

```typescript
button.bind( 'isEnabled' ).to( command, 'isEnabled' );
```

or even shorter:

```typescript
button.bind( 'isEnabled' ).to( command );
```

which works in the following way:

* `button.isEnabled` **instantly equals** `command.isEnabled`,
* whenever `command.isEnabled` changes, `button.isEnabled` will immediately reflect its value.

**Note**: To release the binding, use [`unbind`](module_utils_observablemixin-Observable.md#function-unbind).

You can also "rename" the property in the binding by specifying the new name in the `to()` chain:

```typescript
button.bind( 'isEnabled' ).to( command, 'isWorking' );
```

It is possible to bind more than one property at a time to shorten the code:

```typescript
button.bind( 'isEnabled', 'value' ).to( command );
```

which corresponds to:

```typescript
button.bind( 'isEnabled' ).to( command );
button.bind( 'value' ).to( command );
```

The binding can include more than one observable, combining multiple data sources in a custom callback:

```typescript
button.bind( 'isEnabled' ).to( command, 'isEnabled', ui, 'isVisible',
	( isCommandEnabled, isUIVisible ) => isCommandEnabled && isUIVisible );
```

Using a custom callback allows processing the value before passing it to the target property:

```typescript
button.bind( 'isEnabled' ).to( command, 'value', value => value === 'heading1' );
```

It is also possible to bind to the same property in an array of observables. To bind a `button` to multiple commands (also `Observables`) so that each and every one of them must be enabled for the button to become enabled, use the following code:

```typescript
button.bind( 'isEnabled' ).toMany( [ commandA, commandB, commandC ], 'isEnabled',
	( isAEnabled, isBEnabled, isCEnabled ) => isAEnabled && isBEnabled && isCEnabled );
```

[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-utils/src/observablemixin.ts#L996)

#### Type parameters

* * `K1`
  * `K2`

#### Parameters

* `bindProperty1: K1`

  Observable property that will be bound to other observable(s).

* `bindProperty2: K2`

  Observable property that will be bound to other observable(s).

#### Returns

* `ObservableDualBindChain<K1, ViewRenderer[ K1 ], K2, ViewRenderer[ K2 ]>`

  The bind chain with the `to()` and `toMany()` methods.

<a id="function-bind:SINGLE_BIND">

### `bind( bindProperty ) → ObservableSingleBindChain<K, ViewRenderer[ K ]>` _(inherited)_

Binds [observable properties](#function-set:KEY_VALUE) to other objects implementing the [`Observable`](module_utils_observablemixin-Observable.md) interface.

Read more in the [dedicated](../framework/deep-dive/observables.md#property-bindings) guide covering the topic of property bindings with some additional examples.

Consider two objects: a `button` and an associated `command` (both `Observable`).

A simple property binding could be as follows:

```typescript
button.bind( 'isEnabled' ).to( command, 'isEnabled' );
```

or even shorter:

```typescript
button.bind( 'isEnabled' ).to( command );
```

which works in the following way:

* `button.isEnabled` **instantly equals** `command.isEnabled`,
* whenever `command.isEnabled` changes, `button.isEnabled` will immediately reflect its value.

**Note**: To release the binding, use [`unbind`](module_utils_observablemixin-Observable.md#function-unbind).

You can also "rename" the property in the binding by specifying the new name in the `to()` chain:

```typescript
button.bind( 'isEnabled' ).to( command, 'isWorking' );
```

It is possible to bind more than one property at a time to shorten the code:

```typescript
button.bind( 'isEnabled', 'value' ).to( command );
```

which corresponds to:

```typescript
button.bind( 'isEnabled' ).to( command );
button.bind( 'value' ).to( command );
```

The binding can include more than one observable, combining multiple data sources in a custom callback:

```typescript
button.bind( 'isEnabled' ).to( command, 'isEnabled', ui, 'isVisible',
	( isCommandEnabled, isUIVisible ) => isCommandEnabled && isUIVisible );
```

Using a custom callback allows processing the value before passing it to the target property:

```typescript
button.bind( 'isEnabled' ).to( command, 'value', value => value === 'heading1' );
```

It is also possible to bind to the same property in an array of observables. To bind a `button` to multiple commands (also `Observables`) so that each and every one of them must be enabled for the button to become enabled, use the following code:

```typescript
button.bind( 'isEnabled' ).toMany( [ commandA, commandB, commandC ], 'isEnabled',
	( isAEnabled, isBEnabled, isCEnabled ) => isAEnabled && isBEnabled && isCEnabled );
```

[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-utils/src/observablemixin.ts#L918)

#### Type parameters

* `K`

#### Parameters

* `bindProperty: K`

  Observable property that will be bound to other observable(s).

#### Returns

* `ObservableSingleBindChain<K, ViewRenderer[ K ]>`

  The bind chain with the `to()` and `toMany()` methods.

<a id="function-decorate">

### `decorate( methodName ) → void` _(inherited)_

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.

Read more in the [dedicated](../framework/deep-dive/observables.md#decorating-object-methods) guide covering the topic of decorating methods with some additional examples.

Decorating the method does not change its behavior (it only adds an event), but it allows to modify it later on by listening to the method's event.

For example, to cancel the method execution the event can be [stopped](module_utils_eventinfo-EventInfo.md#member-stop):

```typescript
class Foo extends ObservableMixin() {
	constructor() {
		super();
		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**: The high [priority](module_utils_priorities-PriorityString.md) listener has been used to execute this particular callback before the one which calls the original method (which uses the "normal" priority).

It is also possible to change the returned value:

```typescript
foo.on( 'method', ( evt ) => {
	evt.return = 'Foo!';
} );

foo.method(); // -> 'Foo'
```

Finally, it is possible to access and modify the arguments the method is called with:

```typescript
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'
```

[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-utils/src/observablemixin.ts#L1159)

#### Parameters

* `methodName: 'off' | 'set' | 'bind' | 'unbind' | 'decorate' | 'stopListening' | 'on' | 'once' | 'listenTo' | 'fire' | 'delegate' | 'stopDelegating' | 'isFocused' | 'selection' | 'isSelecting' | 'isComposing' | 'domDocuments' | 'domConverter' | 'markedAttributes' | 'markedChildren' | 'markedTexts' | 'markToSync' | 'render'`

  Name of the method to decorate.

#### Returns

* `void`

<a id="function-delegate">

### `delegate( events ) → EmitterMixinDelegateChain` _(inherited)_

Delegates selected events to another [`Emitter`](module_utils_emittermixin-Emitter.md). For instance:

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

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

```typescript
emitterA.fire( 'eventX', data );
```

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

```typescript
emitterA.fire( 'eventY', data );
```

[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-utils/src/emittermixin.ts#L539)

#### Parameters

* `events: Array<string>`

  Event names that will be delegated to another emitter.

#### Returns

* `EmitterMixinDelegateChain`

<a id="function-fire">

### `fire( eventOrInfo, args ) → GetEventInfo<TEvent>[ 'return' ]` _(inherited)_

Fires an event, executing all callbacks registered for it.

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

[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-utils/src/emittermixin.ts#L512)

#### Type parameters

* `TEvent: extends BaseEvent`

  The type describing the event. See [`BaseEvent`](module_utils_emittermixin-BaseEvent.md).

#### 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`](module_utils_eventinfo-EventInfo.md#member-return)'s property (the event info is the first param of every callback).

<a id="function-listenTo:BASE_EMITTER">

### `listenTo( emitter, event, callback, options? ) → void` _(inherited)_

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.

```typescript
// 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](module_utils_eventinfo-EventInfo.md#member-stop) and set the [return value](module_utils_eventinfo-EventInfo.md#member-return) of the [`fire`](#function-fire) method.

[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-utils/src/emittermixin.ts#L475)

#### Type parameters

* `TEvent: extends BaseEvent`

  The type describing the event. See [`BaseEvent`](module_utils_emittermixin-BaseEvent.md).

#### 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?: GetCallbackOptions<TEvent>`

  Additional options.

#### Returns

* `void`

<a id="function-markToSync">

### `markToSync( type, node ) → void`

Marks a view node to be updated in the DOM by [`render()`](#function-render).

Note that only view nodes whose parents have corresponding DOM elements need to be marked to be synchronized.

[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-engine/src/view/renderer.ts#L171)

#### Parameters

* `type: ViewDocumentChangeType`

  Type of the change.

* `node: ViewNode`

  ViewNode to be marked.

#### Returns

* `void`

#### Related:

* [ViewRenderer#markedAttributes](#member-markedAttributes)
* [ViewRenderer#markedChildren](#member-markedChildren)
* [ViewRenderer#markedTexts](#member-markedTexts)

<a id="function-off">

### `off( event, callback ) → void` _(inherited)_

Stops executing the callback on the given event. Shorthand for [`this.stopListening( this, event, callback )`](#function-stopListening:BASE_STOP).

[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-utils/src/emittermixin.ts#L444)

#### Parameters

* `event: string`

  The name of the event.

* `callback: Function`

  The function to stop being called.

#### Returns

* `void`

<a id="function-on">

### `on( event, callback, options? ) → void` _(inherited)_

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

Shorthand for [`this.listenTo( this, event, callback, options )`](#function-listenTo:BASE_EMITTER) (it makes the emitter listen on itself).

[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-utils/src/emittermixin.ts#L416)

#### Type parameters

* `TEvent: extends BaseEvent`

  The type descibing the event. See [`BaseEvent`](module_utils_emittermixin-BaseEvent.md).

#### 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`

<a id="function-once">

### `once( event, callback, options? ) → void` _(inherited)_

Registers a callback function to be executed on the next time the event is fired only. This is similar to calling [`on`](#function-on) followed by [`off`](#function-off) in the callback.

[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-utils/src/emittermixin.ts#L431)

#### Type parameters

* `TEvent: extends BaseEvent`

  The type descibing the event. See [`BaseEvent`](module_utils_emittermixin-BaseEvent.md).

#### 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`

<a id="function-render">

### `render() → void`

Renders all buffered changes ([`markedAttributes`](#member-markedAttributes), [`markedChildren`](#member-markedChildren) and [`markedTexts`](#member-markedTexts)) and the current view selection (if needed) to the DOM by applying a minimal set of changes to it.

Renderer tries not to break the text composition (e.g. IME) and x-index of the selection, so it does as little as it is needed to update the DOM.

Renderer also handles [fillers](module_engine_view_filler.md). Especially, it checks if the inline filler is needed at the selection position and adds or removes it. To prevent breaking text composition inline filler will not be removed as long as the selection is in the text node which needed it at first.

[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-engine/src/view/renderer.ts#L212)

#### Returns

* `void`

<a id="function-set:OBJECT">

### `set( values ) → void` _(inherited)_

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

It accepts 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 has 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`.

In TypeScript, those properties should be declared in class using `declare` keyword. In example:

```typescript
public declare myProp1: number;
public declare myProp2: string;

constructor() {
	this.set( {
		'myProp1: 2,
		'myProp2: 'foo'
	} );
}
```

[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-utils/src/observablemixin.ts#L843)

#### Parameters

* `values: object & object`

  An object with `name=>value` pairs.

#### Returns

* `void`

<a id="function-set:KEY_VALUE">

### `set( name, value ) → void` _(inherited)_

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

This method throws the `observable-set-cannot-override` error if the observable instance already has 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`.

In TypeScript, those properties should be declared in class using `declare` keyword. In example:

```typescript
public declare myProp: number;

constructor() {
	this.set( 'myProp', 2 );
}
```

[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-utils/src/observablemixin.ts#L815)

#### Type parameters

* `K`

#### Parameters

* `name: K`

  The property's name.

* `value: ViewRenderer[ K ]`

  The property's value.

#### Returns

* `void`

<a id="function-stopDelegating">

### `stopDelegating( event?, emitter? ) → void` _(inherited)_

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.

[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-utils/src/emittermixin.ts#L552)

#### 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`

<a id="function-stopListening:BASE_STOP">

### `stopListening( emitter?, event?, callback? ) → void` _(inherited)_

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.

[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-utils/src/emittermixin.ts#L497)

#### 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`.

#### Returns

* `void`

<a id="function-unbind">

### `unbind( unbindProperties ) → void` _(inherited)_

Removes the binding created with [`bind`](#function-bind:SINGLE_BIND).

```typescript
// Removes the binding for the 'a' property.
A.unbind( 'a' );

// Removes bindings for all properties.
A.unbind();
```

[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-utils/src/observablemixin.ts#L1090)

#### Parameters

* `unbindProperties: Array<'off' | 'set' | 'bind' | 'unbind' | 'decorate' | 'stopListening' | 'on' | 'once' | 'listenTo' | 'fire' | 'delegate' | 'stopDelegating' | 'isFocused' | 'selection' | 'isSelecting' | 'isComposing' | 'domDocuments' | 'domConverter' | 'markedAttributes' | 'markedChildren' | 'markedTexts' | 'markToSync' | 'render'>`

  Observable properties to be unbound. All the bindings will be released if no properties are provided.

#### Returns

* `void`

<a id="function-_diffNodeLists">

### `_diffNodeLists( actualDomChildren, expectedDomChildren ) → Array<DiffResult>` _(private)_

Shorthand for diffing two arrays or node lists of DOM nodes.

[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-engine/src/view/renderer.ts#L795)

#### Parameters

* `actualDomChildren: Array<Node> | NodeList`

  Actual DOM children

* `expectedDomChildren: Array<Node> | NodeList`

  Expected DOM children.

#### Returns

* `Array<DiffResult>`

  The list of actions based on the [`diff`](module_utils_diff.md#constant-diff) function.

<a id="function-_domSelectionNeedsUpdate">

### `_domSelectionNeedsUpdate( domSelection ) → boolean` _(private)_

Checks whether a given DOM selection needs to be updated.

[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-engine/src/view/renderer.ts#L1127)

#### Parameters

* `domSelection: Selection`

  The DOM selection to check.

#### Returns

* `boolean`

<a id="function-_fakeSelectionNeedsUpdate">

### `_fakeSelectionNeedsUpdate( domEditable ) → boolean` _(private)_

Checks whether the fake selection needs to be updated.

[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-engine/src/view/renderer.ts#L1154)

#### Parameters

* `domEditable: HTMLElement`

  A valid DOM editable where a new fake selection container should be added.

#### Returns

* `boolean`

<a id="function-_findUpdateActions">

### `_findUpdateActions( actions, actualDom, expectedDom, comparator ) → Array<DiffResult | 'update'>` _(private)_

Finds DOM nodes that were replaced with the similar nodes (same tag name) in the view. All nodes are compared within one `insert`/`delete` action group, for example:

```
Actual DOM:		<p><b>Foo</b>Bar<i>Baz</i><b>Bax</b></p>
Expected DOM:	<p>Bar<b>123</b><i>Baz</i><b>456</b></p>
Input actions:	[ insert, insert, delete, delete, equal, insert, delete ]
Output actions:	[ insert, replace, delete, equal, replace ]
```

[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-engine/src/view/renderer.ts#L819)

#### Parameters

* `actions: Array<DiffResult>`

  Actions array which is a result of the [`diff`](module_utils_diff.md#constant-diff) function.

* `actualDom: Array<Node> | NodeList`

  Actual DOM children

* `expectedDom: Array<Node>`

  Expected DOM children.

* `comparator: ( a: Node, b: Node ) => boolean`

  A comparator function that should return `true` if the given node should be reused (either by the update of a text node data or an element children list for similar elements).

#### Returns

* `Array<DiffResult | 'update'>`

  Actions array modified with the `update` actions.

<a id="function-_getInlineFillerPosition">

### `_getInlineFillerPosition() → ViewPosition` _(private)_

Gets the position of the inline filler based on the current selection. Here, we assume that we know that the filler is needed and [is at the selection position](#function-_isSelectionInInlineFiller), and, since it is needed, it is somewhere at the selection position.

Note: The filler position cannot be restored based on the filler's DOM text node, because when this method is called (before rendering), the bindings will often be broken. View-to-DOM bindings are only dependable after rendering.

[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-engine/src/view/renderer.ts#L432)

#### Returns

* `ViewPosition`

<a id="function-_isSelectionInInlineFiller">

### `_isSelectionInInlineFiller() → boolean` _(private)_

Returns `true` if the selection has not left the inline filler's text node. If it is `true`, it means that the filler had been added for a reason and the selection did not leave the filler's text node. For example, the user can be in the middle of a composition so it should not be touched.

[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-engine/src/view/renderer.ts#L449)

#### Returns

* `boolean`

  `true` if the inline filler and selection are in the same place.

<a id="function-_markDescendantTextToSync">

### `_markDescendantTextToSync( viewNode ) → void` _(private)_

Marks text nodes to be synchronized.

If a text node is passed, it will be marked. If an element is passed, all descendant text nodes inside it will be marked.

[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-engine/src/view/renderer.ts#L946)

#### Parameters

* `viewNode: ViewNode | undefined`

  View node to sync.

#### Returns

* `void`

<a id="function-_needsInlineFillerAtSelection">

### `_needsInlineFillerAtSelection() → boolean` _(private)_

Checks if the inline [filler](module_engine_view_filler.md) should be added.

[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-engine/src/view/renderer.ts#L513)

#### Returns

* `boolean`

  `true` if the inline filler should be added.

<a id="function-_removeDomSelection">

### `_removeDomSelection() → void` _(private)_

Removes the DOM selection.

[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-engine/src/view/renderer.ts#L1175)

#### Returns

* `void`

<a id="function-_removeFakeSelection">

### `_removeFakeSelection() → void` _(private)_

Removes the fake selection.

[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-engine/src/view/renderer.ts#L1193)

#### Returns

* `void`

<a id="function-_removeInlineFiller">

### `_removeInlineFiller() → void` _(private)_

Removes the inline filler.

[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-engine/src/view/renderer.ts#L476)

#### Returns

* `void`

<a id="function-_updateAttrs">

### `_updateAttrs( viewElement ) → void` _(private)_

Checks if attribute list needs to be updated and possibly updates it.

[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-engine/src/view/renderer.ts#L594)

#### Parameters

* `viewElement: ViewElement`

  The view element to update.

#### Returns

* `void`

<a id="function-_updateChildren">

### `_updateChildren( viewElement, options = { options.inlineFillerPosition } ) → void` _(private)_

Checks if elements child list needs to be updated and possibly updates it.

Note that on Android, to reduce the risk of composition breaks, it tries to update data of an existing child text nodes instead of replacing them completely.

[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-engine/src/view/renderer.ts#L636)

#### Parameters

* `viewElement: ViewElement`

  View element to update.

* `options: object`

  Properties

  * `options.inlineFillerPosition: ViewPosition | null`

    The position where the inline filler should be rendered.

#### Returns

* `void`

<a id="function-_updateChildrenMappings">

### `_updateChildrenMappings( viewElement ) → void` _(private)_

Updates mappings of view element's children.

Children that were replaced in the view structure by similar elements (same tag name) are treated as 'replaced'. This means that their mappings can be updated so the new view elements are mapped to the existing DOM elements. Thanks to that these elements do not need to be re-rendered completely.

[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-engine/src/view/renderer.ts#L346)

#### Parameters

* `viewElement: ViewElement`

  The view element whose children mappings will be updated.

#### Returns

* `void`

<a id="function-_updateDomSelection">

### `_updateDomSelection( domEditable ) → void` _(private)_

Updates the DOM selection.

[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-engine/src/view/renderer.ts#L1083)

#### Parameters

* `domEditable: HTMLElement`

  A valid DOM editable where the DOM selection should be rendered.

#### Returns

* `void`

<a id="function-_updateElementMappings">

### `_updateElementMappings( viewElement, domElement ) → void` _(private)_

Updates mappings of a given view element.

[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-engine/src/view/renderer.ts#L401)

#### Parameters

* `viewElement: ViewElement`

  The view element whose mappings will be updated.

* `domElement: HTMLElement`

  The DOM element representing the given view element.

#### Returns

* `void`

<a id="function-_updateFakeSelection">

### `_updateFakeSelection( domEditable ) → void` _(private)_

Updates the fake selection.

[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-engine/src/view/renderer.ts#L1042)

#### Parameters

* `domEditable: HTMLElement`

  A valid DOM editable where the fake selection container should be added.

#### Returns

* `void`

<a id="function-_updateFocus">

### `_updateFocus() → void` _(private)_

Checks if focus needs to be updated and possibly updates it.

[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-engine/src/view/renderer.ts#L1204)

#### Returns

* `void`

<a id="function-_updateSelection">

### `_updateSelection() → void` _(private)_

Checks if the selection needs to be updated and possibly updates it.

[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-engine/src/view/renderer.ts#L963)

#### Returns

* `void`

<a id="function-_updateText">

### `_updateText( viewText, options = { options.inlineFillerPosition? } ) → void` _(private)_

Checks if text needs to be updated and possibly updates it.

[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-engine/src/view/renderer.ts#L564)

#### Parameters

* `viewText: ViewText`

  View text to update.

* `options: object`

  Properties

  * `options.inlineFillerPosition?: ViewPosition | null`

    The position where the inline filler should be rendered.

#### Returns

* `void`

<a id="function-_updateTextNode">

### `_updateTextNode( domText, expectedText ) → void` _(private)_

Checks if text needs to be updated and possibly updates it by removing and inserting only parts of the data from the existing text node to reduce impact on the IME composition.

[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-engine/src/view/renderer.ts#L869)

#### Parameters

* `domText: Text`

  DOM text node to update.

* `expectedText: string`

  The expected data of a text node.

#### Returns

* `void`

<a id="function-_updateTextNodeInternal">

### `_updateTextNodeInternal( domText, expectedText ) → void` _(private)_

Part of the `_updateTextNode` method extracted for easier testing.

[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-engine/src/view/renderer.ts#L927)

#### Parameters

* `domText: Text`
* `expectedText: string`

#### Returns

* `void`

<a id="events">

## Events

<a id="event-change:isComposing">

### `change:isComposing( eventInfo, name, value, oldValue )`

Fired when the `isComposing` property changed value.

[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-engine/src/view/renderer.ts#L118)

#### Parameters

* `eventInfo: EventInfo`

  An object containing information about the fired event.

* `name: string`

  Name of the changed property (`isComposing`).

* `value: boolean`

  New value of the `isComposing` property with given key or `null`, if operation should remove property.

* `oldValue: boolean`

  Old value of the `isComposing` property with given key or `null`, if property was not set before.

<a id="event-change:isFocused">

### `change:isFocused( eventInfo, name, value, oldValue )`

Fired when the `isFocused` property changed value.

[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-engine/src/view/renderer.ts#L97)

#### Parameters

* `eventInfo: EventInfo`

  An object containing information about the fired event.

* `name: string`

  Name of the changed property (`isFocused`).

* `value: boolean`

  New value of the `isFocused` property with given key or `null`, if operation should remove property.

* `oldValue: boolean`

  Old value of the `isFocused` property with given key or `null`, if property was not set before.

<a id="event-change:isSelecting">

### `change:isSelecting( eventInfo, name, value, oldValue )`

Fired when the `isSelecting` property changed value.

[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-engine/src/view/renderer.ts#L109)

#### Parameters

* `eventInfo: EventInfo`

  An object containing information about the fired event.

* `name: string`

  Name of the changed property (`isSelecting`).

* `value: boolean`

  New value of the `isSelecting` property with given key or `null`, if operation should remove property.

* `oldValue: boolean`

  Old value of the `isSelecting` property with given key or `null`, if property was not set before.

<a id="event-change:%7Bproperty%7D">

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

Fired when a property changed value.

```typescript
observable.set( 'prop', 1 );

observable.on<ObservableChangeEvent<number>>( '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'
```

[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-utils/src/observablemixin.ts#L1190)

#### Parameters

* `eventInfo: EventInfo`

  An object containing information about the fired event.

* `name: string`

  The property name.

* `value: TValue`

  The new property value.

* `oldValue: TValue`

  The previous property value.

<a id="event-set:isComposing">

### `set:isComposing( eventInfo, name, value, oldValue )`

Fired when the `isComposing` property is going to be set but is not set yet (before the `change` event is fired).

[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-engine/src/view/renderer.ts#L118)

#### Parameters

* `eventInfo: EventInfo`

  An object containing information about the fired event.

* `name: string`

  Name of the changed property (`isComposing`).

* `value: boolean`

  New value of the `isComposing` property with given key or `null`, if operation should remove property.

* `oldValue: boolean`

  Old value of the `isComposing` property with given key or `null`, if property was not set before.

<a id="event-set:isFocused">

### `set:isFocused( eventInfo, name, value, oldValue )`

Fired when the `isFocused` property is going to be set but is not set yet (before the `change` event is fired).

[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-engine/src/view/renderer.ts#L97)

#### Parameters

* `eventInfo: EventInfo`

  An object containing information about the fired event.

* `name: string`

  Name of the changed property (`isFocused`).

* `value: boolean`

  New value of the `isFocused` property with given key or `null`, if operation should remove property.

* `oldValue: boolean`

  Old value of the `isFocused` property with given key or `null`, if property was not set before.

<a id="event-set:isSelecting">

### `set:isSelecting( eventInfo, name, value, oldValue )`

Fired when the `isSelecting` property is going to be set but is not set yet (before the `change` event is fired).

[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-engine/src/view/renderer.ts#L109)

#### Parameters

* `eventInfo: EventInfo`

  An object containing information about the fired event.

* `name: string`

  Name of the changed property (`isSelecting`).

* `value: boolean`

  New value of the `isSelecting` property with given key or `null`, if operation should remove property.

* `oldValue: boolean`

  Old value of the `isSelecting` property with given key or `null`, if property was not set before.

<a id="event-set:%7Bproperty%7D">

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

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](module_utils_eventinfo-EventInfo.md#member-return).

```typescript
observable.set( 'prop', 1 );

observable.on<ObservableSetEvent<number>>( '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<ObservableChangeEvent<number>>( '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:** The event is fired even when the new value is the same as the old value.

[See source](https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-utils/src/observablemixin.ts#L1228)

#### Parameters

* `eventInfo: EventInfo`

  An object containing information about the fired event.

* `name: string`

  The property name.

* `value: TValue`

  The new property value.

* `oldValue: TValue`

  The previous property value.

---

Full index of the CKEditor 5 API reference: [llms.txt](llms.txt)