src/vs/editor/browser/viewParts/glyphMargin/glyphMargin.ts/GlyphMarginOverlay/constructor
class GlyphMarginOverlay:	constructor(context: ViewContext) {
		super();
		this._context = context;

		const options = this._context.configuration.options;
		const layoutInfo = options.get(EditorOption.layoutInfo);

		this._lineHeight = options.get(EditorOption.lineHeight);
		this._glyphMargin = options.get(EditorOption.glyphMargin);
		this._glyphMarginLeft = layoutInfo.glyphMarginLeft;
		this._glyphMarginWidth = layoutInfo.glyphMarginWidth;
		this._renderResult = null;
		this._context.addEventHandler(this);
	}