ckeditor/ckeditor5-basic-styles

/**
 * @license Copyright (c) 2003-2020, CKSource - Frederico Knabben. All rights reserved.
 * For licensing, see LICENSE.md or https://ckeditor.com/legal/ckeditor-oss-license
 */

/**
 * @module basic-styles/subscript/subscriptediting
 */

import Plugin from '@ckeditor/ckeditor5-core/src/plugin';
import AttributeCommand from '../attributecommand';

const SUBSCRIPT = 'subscript';

/**
 * The subscript editing feature.
 *
 * It registers the `sub` command and introduces the `sub` attribute in the model which renders to the view
 * as a `<sub>` element.
 *
 * @extends module:core/plugin~Plugin
 */
export default class SubscriptEditing extends Plugin {
    /**
     * @inheritDoc
     */
    static get pluginName() {
        return 'SubscriptEditing';
    }

    /**
     * @inheritDoc
     */
    init() {
        const editor = this.editor;
        // Allow sub attribute on text nodes.
        editor.model.schema.extend( '$text', { allowAttributes: SUBSCRIPT } );
        editor.model.schema.setAttributeProperties( SUBSCRIPT, {
            isFormatting: true,
            copyOnEnter: true
        } );

        // Build converter from model to view for data and editing pipelines.

        editor.conversion.attributeToElement( {
            model: SUBSCRIPT,
            view: 'sub',
            upcastAlso: [
                {
                    styles: {
                        'vertical-align': 'sub'
                    }
                }
            ]
        } );

        // Create sub command.
        editor.commands.add( SUBSCRIPT, new AttributeCommand( editor, SUBSCRIPT ) );
    }
}