src/vs/editor/browser/viewParts/selections/selections.ts/SelectionsOverlay/constructor
class SelectionsOverlay:	constructor(context: ViewContext) {
		super();
		this._context = context;
		const options = this._context.configuration.options;
		this._lineHeight = options.get(EditorOption.lineHeight);
		this._roundedSelection = options.get(EditorOption.roundedSelection);
		this._typicalHalfwidthCharacterWidth = options.get(EditorOption.fontInfo).typicalHalfwidthCharacterWidth;
		this._selections = [];
		this._renderResult = null;
		this._context.addEventHandler(this);
	}