BookStack/resources/js/wysiwyg/fixes.js

/**
 * Handle alignment for embed (iframe/video) content.
 * TinyMCE built-in handling doesn't work well for these when classes are used for
 * alignment, since the editor wraps these elements in a non-editable preview span
 * which looses tracking and setting of alignment options.
 * Here we manually manage these properties and formatting events, by effectively
 * syncing the alignment classes to the parent preview span.
 * @param {Editor} editor
 */
export function handleEmbedAlignmentChanges(editor) {
    function updateClassesForPreview(previewElem) {
        const mediaTarget = previewElem.querySelector('iframe, video');
        if (!mediaTarget) {
            return;
        }

        const alignmentClasses = [...mediaTarget.classList.values()].filter(c => c.startsWith('align-'));
        const previewAlignClasses = [...previewElem.classList.values()].filter(c => c.startsWith('align-'));
        previewElem.classList.remove(...previewAlignClasses);
        previewElem.classList.add(...alignmentClasses);
    }

    editor.on('SetContent', () => {
        const previewElems = editor.dom.select('span.mce-preview-object');
        for (const previewElem of previewElems) {
            updateClassesForPreview(previewElem);
        }
    });

    editor.on('FormatApply', event => {
        const isAlignment = event.format.startsWith('align');
        if (!event.node || !event.node.matches('.mce-preview-object')) {
            return;
        }

        const realTarget = event.node.querySelector('iframe, video');
        if (isAlignment && realTarget) {
            const className = (editor.formatter.get(event.format)[0]?.classes || [])[0];
            const toAdd = !realTarget.classList.contains(className);

            const wrapperClasses = (event.node.getAttribute('data-mce-p-class') || '').split(' ');
            const wrapperClassesFiltered = wrapperClasses.filter(c => !c.startsWith('align-'));
            if (toAdd) {
                wrapperClassesFiltered.push(className);
            }

            const classesToApply = wrapperClassesFiltered.join(' ');
            event.node.setAttribute('data-mce-p-class', classesToApply);

            realTarget.setAttribute('class', classesToApply);
            editor.formatter.apply(event.format, {}, realTarget);
            updateClassesForPreview(event.node);
        }
    });
}