UpcastDispatcher

class

Upcast dispatcher is a central point of the view-to-model conversion, which is a process of converting a given view document fragment or view element into a correct model structure.

During the conversion process, the dispatcher fires events for all view nodes from the converted view document fragment. Special callbacks called "converters" should listen to these events in order to convert the view nodes.

The second parameter of the callback is the data object with the following properties:

data.viewItem contains a view node or a view document fragment that is converted at the moment and might be handled by the callback.
data.modelRange is used to point to the result of the current conversion (e.g. the element that is being inserted) and is always a ModelRange when the conversion succeeds.
data.modelCursor is a position on which the converter should insert the newly created items.

The third parameter of the callback is an instance of UpcastConversionApi which provides additional tools for converters.

You can read more about conversion in the Upcast conversion guide.

Examples of event-based converters:

// A converter for links (<a>).
editor.data.upcastDispatcher.on( 'element:a', ( evt, data, conversionApi ) => {
	if ( conversionApi.consumable.consume( data.viewItem, { name: true, attributes: [ 'href' ] } ) ) {
		// The <a> element is inline and is represented by an attribute in the model.
		// This is why you need to convert only children.
		const { modelRange } = conversionApi.convertChildren( data.viewItem, data.modelCursor );

		for ( let item of modelRange.getItems() ) {
			if ( conversionApi.schema.checkAttribute( item, 'linkHref' ) ) {
				conversionApi.writer.setAttribute( 'linkHref', data.viewItem.getAttribute( 'href' ), item );
			}
		}
	}
} );

// Convert <p> element's font-size style.
// Note: You should use a low-priority observer in order to ensure that
// it is executed after the element-to-element converter.
editor.data.upcastDispatcher.on( 'element:p', ( evt, data, conversionApi ) => {
	const { consumable, schema, writer } = conversionApi;

	if ( !consumable.consume( data.viewItem, { style: 'font-size' } ) ) {
		return;
	}

	const fontSize = data.viewItem.getStyle( 'font-size' );

	// Do not go for the model element after data.modelCursor because it might happen
	// that a single view element was converted to multiple model elements. Get all of them.
	for ( const item of data.modelRange.getItems( { shallow: true } ) ) {
		if ( schema.checkAttribute( item, 'fontSize' ) ) {
			writer.setAttribute( 'fontSize', fontSize, item );
		}
	}
}, { priority: 'low' } );

// Convert all elements which have no custom converter into a paragraph (autoparagraphing).
editor.data.upcastDispatcher.on( 'element', ( evt, data, conversionApi ) => {
	// Check if an element can be converted.
	if ( !conversionApi.consumable.test( data.viewItem, { name: data.viewItem.name } ) ) {
		// When an element is already consumed by higher priority converters, do nothing.
		return;
	}

	const paragraph = conversionApi.writer.createElement( 'paragraph' );

	// Try to safely insert a paragraph at the model cursor - it will find an allowed parent for the current element.
	if ( !conversionApi.safeInsert( paragraph, data.modelCursor ) ) {
		// When an element was not inserted, it means that you cannot insert a paragraph at this position.
		return;
	}

	// Consume the inserted element.
	conversionApi.consumable.consume( data.viewItem, { name: data.viewItem.name } ) );

	// Convert the children to a paragraph.
	const { modelRange } = conversionApi.convertChildren( data.viewItem,  paragraph ) );

	// Update `modelRange` and `modelCursor` in the `data` as a conversion result.
	conversionApi.updateConversionResult( paragraph, data );
}, { priority: 'low' } );

See source

Properties

conversionApi : UpcastConversionApi

An interface passed by the dispatcher to the event callbacks.

See source (with github icon)
_cursorParents : Map<ModelNode, ModelElement | ModelDocumentFragment>
private

The list of cursor parent elements that were created during splitting.

After the conversion process the list is cleared.

See source (with github icon)
_emptyElementsToKeep : Set<ModelElement>
private

The list of elements that were created during the splitting but should not get removed on conversion end even if they are empty.

The list is cleared after the conversion process.

See source (with github icon)
_modelCursor : null | ModelPosition
private

The position in the temporary structure where the converted content is inserted. The structure reflects the context of the target position where the content will be inserted. This property is built based on the context parameter of the convert method.

See source (with github icon)
_splitParts : Map<ModelElement, Array<ModelElement>>
private

The list of elements that were created during splitting.

After the conversion process, the list is cleared.

See source (with github icon)

Methods

constructor( conversionApi )

module:engine/conversion/upcastdispatcher~UpcastDispatcher#constructor
Creates an upcast dispatcher that operates using the passed API.

See source (with github icon)

Parameters

conversionApi : Pick<UpcastConversionApi, 'schema'>

Additional properties for an interface that will be passed to events fired by the upcast dispatcher.

Related:
- UpcastConversionApi
convert( viewElement, writer, context ) → ModelDocumentFragment

module:engine/conversion/upcastdispatcher~UpcastDispatcher#convert
Starts the conversion process. The entry point for the conversion.

See source (with github icon)

Parameters

viewElement : ViewElement | ViewDocumentFragment

The part of the view to be converted.

writer : ModelWriter

An instance of the model writer.

context : ModelSchemaContextDefinition

Elements will be converted according to this context.

Defaults to ...

Returns

ModelDocumentFragment

Model data that is the result of the conversion process wrapped in DocumentFragment. Converted marker elements will be set as the document fragment's static markers map.

Fires
delegate( events ) → EmitterMixinDelegateChain
inherited

module:engine/conversion/upcastdispatcher~UpcastDispatcher#delegate
Delegates selected events to another Emitter. For instance:
```
emitterA.delegate( 'eventX' ).to( emitterB );
emitterA.delegate( 'eventX', 'eventY' ).to( emitterC );
```
Copy code
then eventX is delegated (fired by) emitterB and emitterC along with data:
```
emitterA.fire( 'eventX', data );
```
Copy code
and eventY is delegated (fired by) emitterC along with data:
```
emitterA.fire( 'eventY', data );
```
Copy code
See source (with github icon)

Parameters

events : Array<string>

Event names that will be delegated to another emitter.

Returns

EmitterMixinDelegateChain
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 object, followed by the optional args provided in the fire() method call.

See source (with github icon)

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

module:engine/conversion/upcastdispatcher~UpcastDispatcher#listenTo:BASE_EMITTER
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' );
```
Copy code
An event callback can stop the event and set the return value of the fire method.

See source (with github icon)

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
off( event, callback ) → void
inherited

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

See source (with github icon)

Parameters

event : string

The name of the event.

callback : Function

The function to stop being called.

Returns

void
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 ) (it makes the emitter listen on itself).

See source (with github icon)

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
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 followed by off in the callback.

See source (with github icon)

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

module:engine/conversion/upcastdispatcher~UpcastDispatcher#stopDelegating
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 (with github icon)

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

module:engine/conversion/upcastdispatcher~UpcastDispatcher#stopListening:BASE_STOP
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 (with github icon)

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
_convertChildren( viewItem, elementOrModelCursor ) → object
private

module:engine/conversion/upcastdispatcher~UpcastDispatcher#_convertChildren
See source (with github icon)

Parameters

viewItem : ViewElement | ViewDocumentFragment

elementOrModelCursor : ModelElement | ModelPosition

Returns

object

Related:
- UpcastConversionApi#convertChildren
_convertItem( viewItem, modelCursor ) → object
private

module:engine/conversion/upcastdispatcher~UpcastDispatcher#_convertItem
See source (with github icon)

Parameters

viewItem : ViewDocumentFragment | ViewItem

modelCursor : ModelPosition

Returns

object

Related:
- UpcastConversionApi#convertItem
_getSplitParts( element ) → Array<ModelElement>
private

module:engine/conversion/upcastdispatcher~UpcastDispatcher#_getSplitParts
See source (with github icon)

Parameters

element : ModelElement

Returns

Array<ModelElement>

Related:
- UpcastConversionApi#getSplitParts
_keepEmptyElement( element ) → void
private

Mark an element that were created during the splitting to not get removed on conversion end even if it is empty.

See source (with github icon)

Parameters

element : ModelElement

Returns

void
_registerSplitPair( originalPart, splitPart ) → void
private

Registers that a splitPart element is a split part of the originalPart element.

The data set by this method is used by _getSplitParts and _removeEmptyElements.

See source (with github icon)

Parameters

originalPart : ModelElement

splitPart : ModelElement

Returns

void
_removeEmptyElements() → void
private

Checks if there are any empty elements created while splitting and removes them.

This method works recursively to re-check empty elements again after at least one element was removed in the initial call, as some elements might have become empty after other empty elements were removed from them.

See source (with github icon)

Returns

void
_safeInsert( modelNode, position ) → boolean
private

module:engine/conversion/upcastdispatcher~UpcastDispatcher#_safeInsert
See source (with github icon)

Parameters

modelNode : ModelNode

position : ModelPosition

Returns

boolean

Related:
- UpcastConversionApi#safeInsert
_splitToAllowedParent( node, modelCursor ) → null | object
private

module:engine/conversion/upcastdispatcher~UpcastDispatcher#_splitToAllowedParent
See source (with github icon)

Parameters

node : ModelNode

modelCursor : ModelPosition

Returns

null | object

Related:
- UpcastConversionApi#splitToAllowedParent
_updateConversionResult( modelElement, data ) → void
private

module:engine/conversion/upcastdispatcher~UpcastDispatcher#_updateConversionResult
See source (with github icon)

Parameters

modelElement : ModelElement

data : UpcastConversionData

Returns

void

Related:
- UpcastConversionApi#updateConversionResult

Events

documentFragment( eventInfo, data, conversionApi )

module:engine/conversion/upcastdispatcher~UpcastDispatcher#event:documentFragment
Fired when a ViewDocumentFragment is converted.

See source (with github icon)

Parameters

eventInfo : EventInfo

An object containing information about the fired event.

data : UpcastConversionData<TItem>

conversionApi : UpcastConversionApi

Related:
- UpcastDispatcher#event:element
element( eventInfo, data, conversionApi )

Fired when an ViewElement is converted.

element is a namespace event for a class of events. Names of actually called events follow the pattern of element:<elementName> where elementName is the name of the converted element. This way listeners may listen to a conversion of all or just specific elements.

See source (with github icon)

Parameters

eventInfo : EventInfo

An object containing information about the fired event.

data : UpcastConversionData<TItem>

The conversion data. Keep in mind that this object is shared by reference between all callbacks that will be called. This means that callbacks can override values if needed, and these values will be available in other callbacks.

conversionApi : UpcastConversionApi

Conversion utilities to be used by the callback.
text( eventInfo, data, conversionApi )

module:engine/conversion/upcastdispatcher~UpcastDispatcher#event:text
Fired when a ViewText is converted.

See source (with github icon)

Parameters

eventInfo : EventInfo

An object containing information about the fired event.

data : UpcastConversionData<TItem>

conversionApi : UpcastConversionApi

Related:
- UpcastDispatcher#event:element
viewCleanup( eventInfo, viewItem )

Fired before the first conversion event, at the beginning of the upcast (view-to-model conversion) process.

See source (with github icon)

Parameters

eventInfo : EventInfo

An object containing information about the fired event.

viewItem : ViewElement | ViewDocumentFragment

A part of the view to be converted.

UpcastDispatcher

Properties

conversionApi : UpcastConversionApi

_cursorParents : Map<ModelNode, ModelElement | ModelDocumentFragment> Lock icon private

_emptyElementsToKeep : Set<ModelElement> Lock icon private

_modelCursor : null | ModelPosition Lock icon private

_splitParts : Map<ModelElement, Array<ModelElement>> Lock icon private

Methods

constructor( conversionApi )

Parameters

Related:

convert( viewElement, writer, context ) → ModelDocumentFragment

Parameters

Returns

Fires

delegate( events ) → EmitterMixinDelegateChain inherited

Parameters

Returns

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

Type parameters

Parameters

Returns

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

Type parameters

Parameters

Returns

off( event, callback ) → void inherited

Parameters

Returns

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

Type parameters

Parameters

Returns

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

Type parameters

Parameters

Returns

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

Parameters

Returns

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

Parameters

Returns

_convertChildren( viewItem, elementOrModelCursor ) → object Lock icon private

Parameters

Returns

Related:

_convertItem( viewItem, modelCursor ) → object Lock icon private

Parameters

Returns

Related:

_getSplitParts( element ) → Array<ModelElement> Lock icon private

Parameters

Returns

Related:

_keepEmptyElement( element ) → void Lock icon private

Parameters

Returns

_registerSplitPair( originalPart, splitPart ) → void Lock icon private

Parameters

Returns

_removeEmptyElements() → void Lock icon private

Returns

_safeInsert( modelNode, position ) → boolean Lock icon private

Parameters

Returns

Related:

_splitToAllowedParent( node, modelCursor ) → null | object Lock icon private

Parameters

Returns

Related:

_updateConversionResult( modelElement, data ) → void Lock icon private

Parameters

Returns

Related:

Events

documentFragment( eventInfo, data, conversionApi )

Parameters

Related:

element( eventInfo, data, conversionApi )

`conversionApi : UpcastConversionApi`

`_cursorParents : Map<ModelNode, ModelElement | ModelDocumentFragment>`
private

`_emptyElementsToKeep : Set<ModelElement>`
private

`_modelCursor : null | ModelPosition`
private

`_splitParts : Map<ModelElement, Array<ModelElement>>`
private

`constructor( conversionApi )`

`convert( viewElement, writer, context ) → ModelDocumentFragment`

`delegate( events ) → EmitterMixinDelegateChain`
inherited

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

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

`off( event, callback ) → void`
inherited

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

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

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

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

`_convertChildren( viewItem, elementOrModelCursor ) → object`
private

`_convertItem( viewItem, modelCursor ) → object`
private

`_getSplitParts( element ) → Array<ModelElement>`
private

`_keepEmptyElement( element ) → void`
private

`_registerSplitPair( originalPart, splitPart ) → void`
private

`_removeEmptyElements() → void`
private

`_safeInsert( modelNode, position ) → boolean`
private

`_splitToAllowedParent( node, modelCursor ) → null | object`
private

`_updateConversionResult( modelElement, data ) → void`
private

`documentFragment( eventInfo, data, conversionApi )`

`element( eventInfo, data, conversionApi )`

`text( eventInfo, data, conversionApi )`

`viewCleanup( eventInfo, viewItem )`