Replace timeout interval with MutationObserver for monaco editor AutoLayout

src/vs/editor/browser/config/elementSizeObserver.ts

@@ -9,18 +9,18 @@ import { IDimension } from 'vs/editor/common/editorCommon';
 export class ElementSizeObserver extends Disposable {
 
 	private readonly referenceDomElement: HTMLElement | null;
-	private measureReferenceDomElementToken: any;
 	private readonly changeCallback: () => void;
 	private width: number;
 	private height: number;
+	private resizeObserver: any;
 
 	constructor(referenceDomElement: HTMLElement | null, dimension: IDimension | undefined, changeCallback: () => void) {
 		super();
 		this.referenceDomElement = referenceDomElement;
 		this.changeCallback = changeCallback;
-		this.measureReferenceDomElementToken = -1;
 		this.width = -1;
 		this.height = -1;
+		this.resizeObserver = null;
 		this.measureReferenceDomElement(false, dimension);
 	}
 
@@ -38,15 +38,23 @@ export class ElementSizeObserver extends Disposable {
 	}
 
 	public startObserving(): void {
-		if (this.measureReferenceDomElementToken === -1) {
-			this.measureReferenceDomElementToken = setInterval(() => this.measureReferenceDomElement(true), 100);
+		if (this.resizeObserver === null) {
+			this.resizeObserver = new MutationObserver(this.mutationObserve.bind(this));
+			this.resizeObserver.observe(this.referenceDomElement, {
+				attributes: true,
+				childList: true,
+				characterData: true,
+				subtree: true
+			});
+			window.addEventListener('resize', this.windowObserve.bind(this));
 		}
 	}
 
 	public stopObserving(): void {
-		if (this.measureReferenceDomElementToken !== -1) {
-			clearInterval(this.measureReferenceDomElementToken);
-			this.measureReferenceDomElementToken = -1;
+		if (this.resizeObserver !== null) {
+			this.resizeObserver.disconnect();
+			this.resizeObserver = null;
+			window.removeEventListener('resize', this.windowObserve.bind(this));
 		}
 	}
 
@@ -54,6 +62,14 @@ export class ElementSizeObserver extends Disposable {
 		this.measureReferenceDomElement(true, dimension);
 	}
 
+	private mutationObserve(mutations: MutationRecord[], observer: MutationObserver): void {
+		this.measureReferenceDomElement(true);
+	}
+
+	private windowObserve(): void {
+		this.measureReferenceDomElement(true);
+	}
+
 	private measureReferenceDomElement(callChangeCallback: boolean, dimension?: IDimension): void {
 		let observedWidth = 0;
 		let observedHeight = 0;