Class

UpcastDispatcher (engine/conversion)

@ckeditor/ckeditor5-engine/src/conversion/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 Range 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 following guides:

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' } );

Filtering

Properties

  • conversionApi : UpcastConversionApi

    An interface passed by the dispatcher to the event callbacks.

  • _cursorParents : Map.<Element, Element>>

    private

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

    After the conversion process the list is cleared.

  • _modelCursor : Position | null

    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.

  • _splitParts : Map.<Element, Element>>

    private

    The list of elements that were created during splitting.

    After the conversion process the list is cleared.

Methods

  • constructor( [ conversionApi ] )

    Creates an upcast dispatcher that operates using the passed API.

    Parameters

    [ conversionApi ] : Object

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

    Related:

  • convert( viewItem, writer, [ context ] ) → DocumentFragment

    Starts the conversion process. The entry point for the conversion.

    Parameters

    viewItem : DocumentFragment | Element

    The part of the view to be converted.

    writer : Writer

    An instance of the model writer.

    [ context ] : SchemaContextDefinition

    Elements will be converted according to this context.

    Defaults to ['$root']

    Returns

    DocumentFragment

    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

    mixed

    Delegates selected events to another Emitter. For instance:

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

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

    emitterA.fire( 'eventX', data );
    

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

    emitterA.fire( 'eventY', data );

    Parameters

    events : String

    Event names that will be delegated to another emitter.

    Returns

    EmitterMixinDelegateChain
  • fire( eventOrInfo, [ args ] ) → *

    mixed

    Fires an event, executing all callbacks registered for it.

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

    Parameters

    eventOrInfo : String | EventInfo

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

    [ args ] : *

    Additional arguments to be passed to the callbacks.

    Returns

    *

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

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

    mixed

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

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

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

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

    Parameters

    emitter : Emitter

    The object that fires the event.

    event : String

    The name of the event.

    callback : function

    The function to be called on event.

    [ options ] : Object

    Additional options.

    Properties
    [ options.priority ] : PriorityString | Number

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

    Defaults to 'normal'

    Defaults to {}

  • off( event, callback )

    mixed

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

    Parameters

    event : String

    The name of the event.

    callback : function

    The function to stop being called.

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

    mixed

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

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

    Parameters

    event : String

    The name of the event.

    callback : function

    The function to be called on event.

    [ options ] : Object

    Additional options.

    Properties
    [ options.priority ] : PriorityString | Number

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

    Defaults to 'normal'

    Defaults to {}

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

    mixed

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

    Parameters

    event : String

    The name of the event.

    callback : function

    The function to be called on event.

    [ options ] : Object

    Additional options.

    Properties
    [ options.priority ] : PriorityString | Number

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

    Defaults to 'normal'

    Defaults to {}

  • stopDelegating( [ event ], [ emitter ] )

    mixed

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

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

    Parameters

    [ event ] : String

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

    [ emitter ] : Emitter

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

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

    mixed

    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.

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

    protected mixed

    Adds callback to emitter for given event.

    Parameters

    event : String

    The name of the event.

    callback : function

    The function to be called on event.

    [ options ] : Object

    Additional options.

    Properties
    [ options.priority ] : PriorityString | Number

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

    Defaults to 'normal'

    Defaults to {}

  • _removeEventListener( event, callback )

    protected mixed

    Removes callback from emitter for given event.

    Parameters

    event : String

    The name of the event.

    callback : function

    The function to stop being called.

  • _convertChildren()

    private

  • _convertItem()

    private

  • _getSplitParts()

    private

  • _registerSplitPair( originalPart, splitPart )

    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.

    Parameters

    originalPart : Element
    splitPart : Element
  • _removeEmptyElements()

    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.

  • _safeInsert()

    private

  • _splitToAllowedParent()

    private

  • _updateConversionResult()

    private

Events

  • documentFragment( eventInfo )

    Fired when a DocumentFragment is converted.

    Parameters

    eventInfo : EventInfo

    An object containing information about the fired event.

    Related:

  • element( eventInfo, data, conversionApi )

    Fired when an Element 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.

    Parameters

    eventInfo : EventInfo

    An object containing information about the fired event.

    data : UpcastConversionData

    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 )

    Fired when a Text is converted.

    Parameters

    eventInfo : EventInfo

    An object containing information about the fired event.

    Related:

  • viewCleanup( eventInfo, viewItem )

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

    Parameters

    eventInfo : EventInfo

    An object containing information about the fired event.

    viewItem : DocumentFragment | Element

    A part of the view to be converted.