ViewRenderer

Converter instance.

Set of DOM Documents instances.

True if composition is in progress inside the document.

This property is bound to the Document#isComposing property.

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

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).

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

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

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

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

DOM element containing fake selection.

The text node in which the inline filler was rendered.

Creates a renderer instance.

Parameters

domConverter : ViewDomConverter

Converter instance.

selection : ViewDocumentSelection

View selection.

Binds observable properties to other objects implementing the Observable interface.

Read more in the dedicated 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:

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

or even shorter:

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.

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

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

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

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

which corresponds to:

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:

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:

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:

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

Parameters

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

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

Returns

ObservableMultiBindChain

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

Binds observable properties to other objects implementing the Observable interface.

Read more in the dedicated 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:

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

or even shorter:

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.

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

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

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

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

which corresponds to:

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:

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:

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:

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

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.

Binds observable properties to other objects implementing the Observable interface.

Read more in the dedicated 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:

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

or even shorter:

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.

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

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

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

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

which corresponds to:

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:

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:

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:

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

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.

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 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:

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 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:

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:

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

Name of the method to decorate.

Returns

void

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

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).

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 ] : GetCallbackOptions<TEvent>

Additional options.

Returns

void

Marks a view node to be updated in the DOM by render().

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

Parameters

type : ViewDocumentChangeType

Type of the change.

node : ViewNode

ViewNode to be marked.

Returns

void

Related:

• ViewRenderer#markedAttributes
• ViewRenderer#markedChildren
• ViewRenderer#markedTexts

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

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

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

Renders all buffered changes (markedAttributes, markedChildren and 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. 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.

Returns

void

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:

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

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

Parameters

values : object

An object with name=>value pairs.

Returns

void

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:

public declare myProp: number;

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

Type parameters

K

Parameters

name : K

The property's name.

value : ViewRenderer[ K ]

The property's value.

Returns

void

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

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.

Returns

void

Removes the binding created with bind.

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

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

Parameters

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

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

Returns

void

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

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 function.

Checks whether a given DOM selection needs to be updated.

Parameters

domSelection : Selection

The DOM selection to check.

Returns

boolean

Checks whether the fake selection needs to be updated.

Parameters

domEditable : HTMLElement

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

Returns

boolean

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 ]

Parameters

actions : Array<DiffResult>

Actions array which is a result of the 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.

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, 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.

Returns

ViewPosition

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.

Returns

boolean

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

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.

Parameters

viewNode : undefined | ViewNode

View node to sync.

Returns

void

Checks if the inline filler should be added.

Returns

boolean

true if the inline filler should be added.

Removes the DOM selection.

Returns

void

Removes the fake selection.

Returns

void

Removes the inline filler.

Returns

void

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

Parameters

viewElement : ViewElement

The view element to update.

Returns

void

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.

Parameters

viewElement : ViewElement

View element to update.

options : object

Properties

options.inlineFillerPosition : null | ViewPosition

The position where the inline filler should be rendered.

Returns

void

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.

Parameters

viewElement : ViewElement

The view element whose children mappings will be updated.

Returns

void

Updates the DOM selection.

Parameters

domEditable : HTMLElement

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

Returns

void

Updates mappings of a given view element.

Parameters

viewElement : ViewElement

The view element whose mappings will be updated.

domElement : HTMLElement

The DOM element representing the given view element.

Returns

void

Updates the fake selection.

Parameters

domEditable : HTMLElement

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

Returns

void

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

Returns

void

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

Returns

void

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

Parameters

viewText : ViewText

View text to update.

options : object

Properties

[ options.inlineFillerPosition ] : null | ViewPosition

The position where the inline filler should be rendered.

Returns

void

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.

Parameters

domText : Text

DOM text node to update.

expectedText : string

The expected data of a text node.

Returns

void

Part of the _updateTextNode method extracted for easier testing.

Parameters

domText : Text

expectedText : string

Returns

void

Fired when the isComposing property changed value.

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.

Fired when the isFocused property changed value.

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.

Fired when the isSelecting property changed value.

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.

Fired when a property changed value.

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'

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.

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

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.

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

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.

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

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.

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<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.

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.