src/vs/editor/contrib/hover/hoverWidgets.ts/GlyphHoverWidget/constructor
class GlyphHoverWidget:	constructor(id: string, editor: ICodeEditor) {
		super();
		this._id = id;
		this._editor = editor;
		this._isVisible = false;

		this._domNode = document.createElement('div');
		this._domNode.className = 'monaco-hover hidden';
		this._domNode.setAttribute('aria-hidden', 'true');
		this._domNode.setAttribute('role', 'tooltip');

		this._showAtLineNumber = -1;

		this._register(this._editor.onDidChangeConfiguration((e: ConfigurationChangedEvent) => {
			if (e.hasChanged(EditorOption.fontInfo)) {
				this.updateFont();
			}
		}));

		this._editor.addOverlayWidget(this);
	}