Refreshing a CKEditor5 widget upon model changes - widget

Question

I have a custom schema element with a text attribute node that renders as a widget for the editingDowncast:
conversion.for( 'editingDowncast' )
.add( downcastElementToElement({
model: 'myModelElement',
view: (modelElement, viewWriter) => {
return createMyModelWidget( modelElement, viewWriter, 'Label' );
}
} )
);
function createMyModelWidget( modelElement, writer, label ) {
const content = modelElement.getAttribute('content')
const placeholder = writer.createText( content );
const container = writer.createContainerElement( 'div', { class: 'my-model-element--widget' } );
writer.insert( ViewPosition.createAt( container ), placeholder );
return toWidget( container, writer, label );
}
Through some external event (e.g., result from an external modal that configures the widget), the attribute is updated using model.change.
model.change(writer => {
writer.setAttribute( 'attribute', 'whatever', widget );
writer.setAttribute( 'content', 'new content', widget );
});
Now since its attribute changed, I would expect the widget to be re-rendered, however that is not the case. How can I manually trigger a refresh to ensure it is up-to-date?

Answer 1

The refreshing of an view widget on model changes is handled by downcast conversion. I can see that you want convert a model attribute to a text contents of a <div>. I assume that the "attribute" attribute is a <div>s element attribute (like data-attribute). In such case you'll need set of converters:
Upcast
a single element to element upcast converter that will create myModelElement model element instance.
Downcast
an element to element downcast converter that will create div for newly inserted myModelElment into a model
a custom attribute converter that will update div contents on attribute content changes
A two-way converter that will cover simple attribute to attribute conversion (both upcast & downcast).
ps.: I've used "downcast" instead of "editingDowncast" to not define the downcast conversion for "editingDowncast" and "dataDowncast" separately.
// Required imports:
// import { toWidget } from '#ckeditor/ckeditor5-widget/src/utils';
// import { downcastElementToElement } from '#ckeditor/ckeditor5-engine/src/conversion/downcast-converters';
// import { upcastElementToElement } from '#ckeditor/ckeditor5-engine/src/conversion/upcast-converters';
// import ViewPosition from '#ckeditor/ckeditor5-engine/src/view/position';
// import ViewRange from '#ckeditor/ckeditor5-engine/src/view/range';
const conversion = editor.conversion;
const model = editor.model;
const schema = model.schema;
// Define model element and allow attributes on it.
schema.register( 'myModelElement', {
allowWhere: '$block',
allowAttributes: [ 'content', 'attribute' ],
isObject: true
} );
// Simple attribute to attribute converter two-way converter
// - for upcast it will read "data-attribute" property of div and put it into model's "attribute" attribute
// - for downcast it will update "data-attribute" on changes in "attribute".
conversion.attributeToAttribute( {
model: {
name: 'myModelElement',
key: 'attribute'
},
view: {
key: 'data-attribute'
}
} );
// Define upcast conversion:
conversion.for( 'upcast' ).add( upcastElementToElement( {
model: ( viewElement, modelWriter ) => {
const firstChild = viewElement.getChild( 0 );
const text = firstChild.is( 'text' ) ? firstChild.data : '(empty)';
return modelWriter.createElement( 'myModelElement', { content: text } );
},
view: {
name: 'div',
classes: 'my-model-element--widget'
}
} ) );
// Define downcast conversion:
conversion.for( 'downcast' )
.add( downcastElementToElement( {
model: 'myModelElement',
view: ( modelElement, viewWriter ) => {
return createMyModelWidget( modelElement, viewWriter, 'Label' );
}
} ) )
// Special conversion of attribute "content":
.add( dispatcher => dispatcher.on( 'attribute:content', ( evt, data, conversionApi ) => {
const myModelElement = data.item;
// Mark element as consumed by conversion.
conversionApi.consumable.consume( data.item, evt.name );
// Get mapped view element to update.
const viewElement = conversionApi.mapper.toViewElement( myModelElement );
// Remove current <div> element contents.
conversionApi.writer.remove( ViewRange.createOn( viewElement.getChild( 0 ) ) );
// Set current content
setContent( conversionApi.writer, data.attributeNewValue, viewElement );
} ) );
function createMyModelWidget( modelElement, writer, label ) {
const content = modelElement.getAttribute( 'content' );
const container = writer.createContainerElement( 'div', { class: 'my-model-element--widget' } );
setContent( writer, content, container );
return toWidget( container, writer, label );
}
function setContent( writer, content, container ) {
const placeholder = writer.createText( content || '' );
writer.insert( ViewPosition.createAt( container ), placeholder );
}