fix(material/tabs): avoid timeouts in background tabs

The tabs have a couple of `requestAnimationFrame` calls when checking for the size/position of elements which can cause tests to hang when they're in a background tab. The problem is that browsers block `requestAnimationFrame` when the browser is out of focus and test harnesses will wait for the call to resolve.

These changes switch to `NgZone.onStable` in an attempt to resolve the issue.

Fixes #23964.

Author: crisbeto

src/material-experimental/mdc-tabs/ink-bar.ts

@@ -80,7 +80,9 @@ export class MatInkBarFoundation {
       }
     },
     setContentStyleProperty: (propName, value) => {
-      this._inkBarContentElement.style.setProperty(propName, value);
+      if (!this._destroyed) {
+        this._inkBarContentElement.style.setProperty(propName, value);
+      }
     },
     computeContentClientRect: () => {
       // `getBoundingClientRect` isn't available on the server.

src/material-experimental/mdc-tabs/tab-header.spec.ts

@@ -23,25 +23,18 @@ import {MatRippleModule} from '@angular/material-experimental/mdc-core';
 import {By} from '@angular/platform-browser';
 import {MatTabHeader} from './tab-header';
 import {MatTabLabelWrapper} from './tab-label-wrapper';
-import {Subject} from 'rxjs';
 import {ObserversModule, MutationObserverFactory} from '@angular/cdk/observers';
 
 describe('MDC-based MatTabHeader', () => {
-  let dir: Direction = 'ltr';
-  let change = new Subject();
   let fixture: ComponentFixture<SimpleTabHeaderApp>;
   let appComponent: SimpleTabHeaderApp;
 
   beforeEach(
     waitForAsync(() => {
-      dir = 'ltr';
       TestBed.configureTestingModule({
         imports: [CommonModule, PortalModule, MatRippleModule, ScrollingModule, ObserversModule],
         declarations: [MatTabHeader, MatTabLabelWrapper, SimpleTabHeaderApp],
-        providers: [
-          ViewportRuler,
-          {provide: Directionality, useFactory: () => ({value: dir, change: change})},
-        ],
+        providers: [ViewportRuler],
       });
 
       TestBed.compileComponents();
@@ -238,11 +231,10 @@ describe('MDC-based MatTabHeader', () => {
   describe('pagination', () => {
     describe('ltr', () => {
       beforeEach(() => {
-        dir = 'ltr';
         fixture = TestBed.createComponent(SimpleTabHeaderApp);
-        fixture.detectChanges();
-
         appComponent = fixture.componentInstance;
+        appComponent.dir = 'ltr';
+        fixture.detectChanges();
       });
 
       it('should show width when tab list width exceeds container', () => {
@@ -322,11 +314,9 @@ describe('MDC-based MatTabHeader', () => {
 
     describe('rtl', () => {
       beforeEach(() => {
-        dir = 'rtl';
         fixture = TestBed.createComponent(SimpleTabHeaderApp);
         appComponent = fixture.componentInstance;
         appComponent.dir = 'rtl';
-
         fixture.detectChanges();
       });
 
@@ -607,9 +597,9 @@ describe('MDC-based MatTabHeader', () => {
 
       fixture.detectChanges();
 
-      change.next();
+      fixture.componentInstance.dir = 'rtl';
       fixture.detectChanges();
-      tick(20); // Angular turns rAF calls into 16.6ms timeouts in tests.
+      tick();
 
       expect(inkBar.alignToElement).toHaveBeenCalled();
     }));

src/material/tabs/ink-bar.ts

@@ -8,6 +8,7 @@
 
 import {Directive, ElementRef, Inject, InjectionToken, NgZone, Optional} from '@angular/core';
 import {ANIMATION_MODULE_TYPE} from '@angular/platform-browser/animations';
+import {take} from 'rxjs/operators';
 
 /**
  * Interface for a a MatInkBar positioner method, defining the positioning and width of the ink
@@ -65,14 +66,12 @@ export class MatInkBar {
    */
   alignToElement(element: HTMLElement) {
     this.show();
-
-    if (typeof requestAnimationFrame !== 'undefined') {
-      this._ngZone.runOutsideAngular(() => {
-        requestAnimationFrame(() => this._setStyles(element));
-      });
-    } else {
-      this._setStyles(element);
-    }
+    this._ngZone.onStable.pipe(take(1)).subscribe(() => {
+      const positions = this._inkBarPositioner(element);
+      const inkBar: HTMLElement = this._elementRef.nativeElement;
+      inkBar.style.left = positions.left;
+      inkBar.style.width = positions.width;
+    });
   }
 
   /** Shows the ink bar. */
@@ -84,16 +83,4 @@ export class MatInkBar {
   hide(): void {
     this._elementRef.nativeElement.style.visibility = 'hidden';
   }
-
-  /**
-   * Sets the proper styles to the ink bar element.
-   * @param element
-   */
-  private _setStyles(element: HTMLElement) {
-    const positions = this._inkBarPositioner(element);
-    const inkBar: HTMLElement = this._elementRef.nativeElement;
-
-    inkBar.style.left = positions.left;
-    inkBar.style.width = positions.width;
-  }
 }

src/material/tabs/paginated-tab-header.ts

@@ -27,7 +27,7 @@ import {ViewportRuler} from '@angular/cdk/scrolling';
 import {FocusKeyManager, FocusableOption} from '@angular/cdk/a11y';
 import {ENTER, SPACE, hasModifierKey} from '@angular/cdk/keycodes';
 import {merge, of as observableOf, Subject, timer, fromEvent} from 'rxjs';
-import {takeUntil} from 'rxjs/operators';
+import {take, takeUntil} from 'rxjs/operators';
 import {Platform, normalizePassiveListenerOptions} from '@angular/cdk/platform';
 import {ANIMATION_MODULE_TYPE} from '@angular/platform-browser/animations';
 
@@ -201,7 +201,9 @@ export abstract class MatPaginatedTabHeader
 
     // Defer the first call in order to allow for slower browsers to lay out the elements.
     // This helps in cases where the user lands directly on a page with paginated tabs.
-    typeof requestAnimationFrame !== 'undefined' ? requestAnimationFrame(realign) : realign();
+    // Note that we use `onStable` instead of `requestAnimationFrame`, because the latter
+    // can hold up tests that are in a background tab.
+    this._ngZone.onStable.pipe(take(1)).subscribe(realign);
 
     // On dir change or window resize, realign the ink bar and update the orientation of
     // the key manager if the direction has changed.

src/material/tabs/tab-header.spec.ts

@@ -28,21 +28,15 @@ import {Subject} from 'rxjs';
 import {ObserversModule, MutationObserverFactory} from '@angular/cdk/observers';
 
 describe('MatTabHeader', () => {
-  let dir: Direction = 'ltr';
-  let change = new Subject();
   let fixture: ComponentFixture<SimpleTabHeaderApp>;
   let appComponent: SimpleTabHeaderApp;
 
   beforeEach(
     waitForAsync(() => {
-      dir = 'ltr';
       TestBed.configureTestingModule({
         imports: [CommonModule, PortalModule, MatRippleModule, ScrollingModule, ObserversModule],
         declarations: [MatTabHeader, MatInkBar, MatTabLabelWrapper, SimpleTabHeaderApp],
-        providers: [
-          ViewportRuler,
-          {provide: Directionality, useFactory: () => ({value: dir, change: change})},
-        ],
+        providers: [ViewportRuler],
       });
 
       TestBed.compileComponents();
@@ -239,11 +233,10 @@ describe('MatTabHeader', () => {
   describe('pagination', () => {
     describe('ltr', () => {
       beforeEach(() => {
-        dir = 'ltr';
         fixture = TestBed.createComponent(SimpleTabHeaderApp);
-        fixture.detectChanges();
-
         appComponent = fixture.componentInstance;
+        appComponent.dir = 'ltr';
+        fixture.detectChanges();
       });
 
       it('should show width when tab list width exceeds container', () => {
@@ -319,11 +312,9 @@ describe('MatTabHeader', () => {
 
     describe('rtl', () => {
       beforeEach(() => {
-        dir = 'rtl';
         fixture = TestBed.createComponent(SimpleTabHeaderApp);
         appComponent = fixture.componentInstance;
         appComponent.dir = 'rtl';
-
         fixture.detectChanges();
       });
 
@@ -603,9 +594,9 @@ describe('MatTabHeader', () => {
 
       fixture.detectChanges();
 
-      change.next();
+      fixture.componentInstance.dir = 'rtl';
       fixture.detectChanges();
-      tick(20); // Angular turns rAF calls into 16.6ms timeouts in tests.
+      tick();
 
       expect(inkBar.alignToElement).toHaveBeenCalled();
     }));