src/vs/editor/browser/viewParts/editorScrollbar/editorScrollbar.ts/EditorScrollbar/constructor
class EditorScrollbar:	constructor(
		context: ViewContext,
		linesContent: FastDomNode<HTMLElement>,
		viewDomNode: FastDomNode<HTMLElement>,
		overflowGuardDomNode: FastDomNode<HTMLElement>
	) {
		super(context);


		const options = this._context.configuration.options;
		const scrollbar = options.get(EditorOption.scrollbar);
		const mouseWheelScrollSensitivity = options.get(EditorOption.mouseWheelScrollSensitivity);
		const fastScrollSensitivity = options.get(EditorOption.fastScrollSensitivity);
		const scrollPredominantAxis = options.get(EditorOption.scrollPredominantAxis);

		const scrollbarOptions: ScrollableElementCreationOptions = {
			listenOnDomNode: viewDomNode.domNode,
			className: 'editor-scrollable' + ' ' + getThemeTypeSelector(context.theme.type),
			useShadows: false,
			lazyRender: true,

			vertical: scrollbar.vertical,
			horizontal: scrollbar.horizontal,
			verticalHasArrows: scrollbar.verticalHasArrows,
			horizontalHasArrows: scrollbar.horizontalHasArrows,
			verticalScrollbarSize: scrollbar.verticalScrollbarSize,
			verticalSliderSize: scrollbar.verticalSliderSize,
			horizontalScrollbarSize: scrollbar.horizontalScrollbarSize,
			horizontalSliderSize: scrollbar.horizontalSliderSize,
			handleMouseWheel: scrollbar.handleMouseWheel,
			alwaysConsumeMouseWheel: scrollbar.alwaysConsumeMouseWheel,
			arrowSize: scrollbar.arrowSize,
			mouseWheelScrollSensitivity: mouseWheelScrollSensitivity,
			fastScrollSensitivity: fastScrollSensitivity,
			scrollPredominantAxis: scrollPredominantAxis,
			scrollByPage: scrollbar.scrollByPage,
		};

		this.scrollbar = this._register(new SmoothScrollableElement(linesContent.domNode, scrollbarOptions, this._context.viewLayout.getScrollable()));
		PartFingerprints.write(this.scrollbar.getDomNode(), PartFingerprint.ScrollableElement);

		this.scrollbarDomNode = createFastDomNode(this.scrollbar.getDomNode());
		this.scrollbarDomNode.setPosition('absolute');
		this._setLayout();

		// When having a zone widget that calls .focus() on one of its dom elements,
		// the browser will try desperately to reveal that dom node, unexpectedly
		// changing the .scrollTop of this.linesContent

		const onBrowserDesperateReveal = (domNode: HTMLElement, lookAtScrollTop: boolean, lookAtScrollLeft: boolean) => {
			const newScrollPosition: INewScrollPosition = {};

			if (lookAtScrollTop) {
				const deltaTop = domNode.scrollTop;
				if (deltaTop) {
					newScrollPosition.scrollTop = this._context.viewLayout.getCurrentScrollTop() + deltaTop;
					domNode.scrollTop = 0;
				}
			}

			if (lookAtScrollLeft) {
				const deltaLeft = domNode.scrollLeft;
				if (deltaLeft) {
					newScrollPosition.scrollLeft = this._context.viewLayout.getCurrentScrollLeft() + deltaLeft;
					domNode.scrollLeft = 0;
				}
			}

			this._context.viewModel.viewLayout.setScrollPosition(newScrollPosition, ScrollType.Immediate);
		};

		// I've seen this happen both on the view dom node & on the lines content dom node.
		this._register(dom.addDisposableListener(viewDomNode.domNode, 'scroll', (e: Event) => onBrowserDesperateReveal(viewDomNode.domNode, true, true)));
		this._register(dom.addDisposableListener(linesContent.domNode, 'scroll', (e: Event) => onBrowserDesperateReveal(linesContent.domNode, true, false)));
		this._register(dom.addDisposableListener(overflowGuardDomNode.domNode, 'scroll', (e: Event) => onBrowserDesperateReveal(overflowGuardDomNode.domNode, true, false)));
		this._register(dom.addDisposableListener(this.scrollbarDomNode.domNode, 'scroll', (e: Event) => onBrowserDesperateReveal(this.scrollbarDomNode.domNode, true, false)));
	}