chore(ckeditor5-mermaid): port source code

packages/ckeditor5-mermaid/src/mermaidtoolbar.ts

@@ -0,0 +1,43 @@
+/**
+ * @module mermaid/mermaidtoolbar
+ */
+
+import { Plugin, ViewDocumentSelection, ViewElement, WidgetToolbarRepository } from "ckeditor5";
+
+
+export default class MermaidToolbar extends Plugin {
+
+	static get requires() {
+		return [ WidgetToolbarRepository ];
+	}
+
+	static get pluginName() {
+		return 'MermaidToolbar' as const;
+	}
+
+	afterInit() {
+		const editor = this.editor;
+		const t = editor.t;
+
+		const widgetToolbarRepository = editor.plugins.get( WidgetToolbarRepository );
+		const mermaidToolbarItems = [ 'mermaidSourceView', 'mermaidSplitView', 'mermaidPreview', '|', 'mermaidInfo' ];
+
+		if ( mermaidToolbarItems ) {
+			widgetToolbarRepository.register( 'mermaidToolbar', {
+				ariaLabel: t( 'Mermaid toolbar' ),
+				items: mermaidToolbarItems,
+				getRelatedElement: selection => getSelectedElement( selection )
+			} );
+		}
+	}
+}
+
+function getSelectedElement( selection: ViewDocumentSelection ) {
+	const viewElement = selection.getSelectedElement() as unknown as ViewElement;
+
+	if ( viewElement && viewElement.hasClass( 'ck-mermaid__wrapper' ) ) {
+		return viewElement;
+	}
+
+	return null;
+}