fix(tabs): fix tab headers resize/scroll issue

Author: yinglejia

package-lock.json

@@ -94,6 +94,7 @@
     "@storybook/theming": "5.3.19",
     "@types/jasmine": "2.8.2",
     "@types/node": "11.13.0",
+    "@types/resize-observer-browser": "^0.1.7",
     "babel-loader": "8.0.5",
     "carbon-components": "10.58.3",
     "chai": "4.2.0",

package.json

@@ -11,6 +11,7 @@ import {
 	TemplateRef,
 	OnChanges,
 	SimpleChanges,
+	OnDestroy,
 	OnInit,
 	ChangeDetectorRef
 } from "@angular/core";
@@ -33,7 +34,8 @@ import { Tab } from "./tab.component";
 			}"
 			role="navigation"
 			[attr.aria-label]="ariaLabel"
-			[attr.aria-labelledby]="ariaLabelledby">
+			[attr.aria-labelledby]="ariaLabelledby"
+			#tabsScrollable>
 			<button
 				#leftOverflowNavButton
 				type="button"
@@ -132,7 +134,7 @@ import { Tab } from "./tab.component";
 	`
 })
 
-export class TabHeaders implements AfterContentInit, OnChanges, OnInit {
+export class TabHeaders implements AfterContentInit, OnChanges, OnDestroy, OnInit {
 	/**
 	 * List of `Tab` components.
 	 */
@@ -172,6 +174,8 @@ export class TabHeaders implements AfterContentInit, OnChanges, OnInit {
 	 * Gets the Unordered List element that holds the `Tab` headings from the view DOM.
 	 */
 	// @ts-ignore
+	@ViewChild("tabsScrollable", { static: true }) tabsScrollable: ElementRef<HTMLElement>;
+	// @ts-ignore
 	@ViewChild("tabList", { static: true }) headerContainer;
 	// @ts-ignore
 	@ViewChild("rightOverflowNavButton", { static: true }) rightOverflowNavButton;
@@ -199,8 +203,9 @@ export class TabHeaders implements AfterContentInit, OnChanges, OnInit {
 	public currentSelectedTab: number;
 
 	public get hasHorizontalOverflow() {
-		const tabList = this.headerContainer.nativeElement;
-		return tabList.scrollWidth > tabList.clientWidth;
+		const scrollWidth = this.headerContainer.nativeElement.scrollWidth;
+		const availableWidth = this.tabsScrollable.nativeElement.clientWidth;
+		return scrollWidth > availableWidth;
 	}
 
 	public get leftOverflowNavButtonHidden() {
@@ -217,6 +222,7 @@ export class TabHeaders implements AfterContentInit, OnChanges, OnInit {
 	// width of the overflow buttons
 	OVERFLOW_BUTTON_OFFSET = 40;
 
+	private resizeObserver: ResizeObserver;
 	private overflowNavInterval;
 
 	constructor(
@@ -290,8 +296,17 @@ export class TabHeaders implements AfterContentInit, OnChanges, OnInit {
 		}
 	}
 
-	ngOnInit() {
-		this.eventService.on(window as any, "resize", () => this.handleScroll());
+	ngOnInit(): void {
+		// Update scroll on resize
+		this.resizeObserver = new ResizeObserver(() => {
+			// Need to explicitly trigger change detection since this runs outside Angular zone
+			this.changeDetectorRef.detectChanges();
+		});
+		this.resizeObserver.observe(this.tabsScrollable.nativeElement);
+	}
+
+	ngOnDestroy(): void {
+		this.resizeObserver.unobserve(this.tabsScrollable.nativeElement);
 	}
 
 	ngAfterContentInit() {

src/tabs/tab-headers.component.ts

@@ -22,7 +22,8 @@
 		],
 		"types": [
 			"jasmine",
-			"node"
+			"node",
+			"resize-observer-browser"
 		],
 		"paths": {
 			"carbon-components-angular": [