fix(autosize): not updating when window is resized (#8619)

Fixes the autosize textarea not recalculating its height when the viewport size has changed.

Fixes #8610.

src/lib/input/autosize.spec.ts

@@ -1,12 +1,13 @@
 import {Component, ViewChild} from '@angular/core';
 import {FormsModule} from '@angular/forms';
-import {ComponentFixture, TestBed, async, fakeAsync, flushMicrotasks} from '@angular/core/testing';
+import {ComponentFixture, TestBed, async, fakeAsync, flush, tick} from '@angular/core/testing';
 import {By} from '@angular/platform-browser';
 import {MatInputModule} from './index';
 import {MatTextareaAutosize} from './autosize';
 import {MatStepperModule} from '@angular/material/stepper';
 import {MatTabsModule} from '@angular/material/tabs';
 import {NoopAnimationsModule} from '@angular/platform-browser/animations';
+import {dispatchFakeEvent} from '@angular/cdk/testing';
 
 
 describe('MatTextareaAutosize', () => {
@@ -185,14 +186,14 @@ describe('MatTextareaAutosize', () => {
     autosize = fixtureWithPlaceholder.debugElement.query(
       By.directive(MatTextareaAutosize)).injector.get<MatTextareaAutosize>(MatTextareaAutosize);
 
-    triggerTextareaResize();
+    autosize.resizeToFitContent(true);
 
     const heightWithLongPlaceholder = textarea.clientHeight;
 
     fixtureWithPlaceholder.componentInstance.placeholder = 'Short';
     fixtureWithPlaceholder.detectChanges();
 
-    triggerTextareaResize();
+    autosize.resizeToFitContent(true);
 
     expect(textarea.clientHeight).toBe(heightWithLongPlaceholder,
         'Expected the textarea height to be the same with a long placeholder.');
@@ -213,7 +214,7 @@ describe('MatTextareaAutosize', () => {
     Some late visitor entreating entrance at my chamber door;—
                 This it is and nothing more.” `;
     fixtureWithForms.detectChanges();
-    flushMicrotasks();
+    flush();
     fixtureWithForms.detectChanges();
 
     expect(textarea.clientHeight)
@@ -229,7 +230,7 @@ describe('MatTextareaAutosize', () => {
     `;
 
     fixture.detectChanges();
-    flushMicrotasks();
+    flush();
     fixture.detectChanges();
 
     expect(textarea.clientHeight)
@@ -250,16 +251,14 @@ describe('MatTextareaAutosize', () => {
     expect(textarea.getBoundingClientRect().height).toBeGreaterThan(1);
   });
 
-  /** Triggers a textarea resize to fit the content. */
-  function triggerTextareaResize() {
-    // To be able to trigger a new calculation of the height with a short placeholder, the
-    // textarea value needs to be changed.
-    textarea.value = '1';
-    autosize.resizeToFitContent();
+  it('should trigger a resize when the window is resized', fakeAsync(() => {
+    spyOn(autosize, 'resizeToFitContent');
 
-    textarea.value = '';
-    autosize.resizeToFitContent();
-  }
+    dispatchFakeEvent(window, 'resize');
+    tick(16);
+
+    expect(autosize.resizeToFitContent).toHaveBeenCalled();
+  }));
 });
 
 // Styles to reset padding and border to make measurement comparisons easier.

src/lib/input/autosize.ts

@@ -6,8 +6,20 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-import {Directive, ElementRef, Input, AfterViewInit, DoCheck} from '@angular/core';
+import {
+  Directive,
+  ElementRef,
+  Input,
+  AfterViewInit,
+  DoCheck,
+  OnDestroy,
+  NgZone,
+} from '@angular/core';
 import {Platform} from '@angular/cdk/platform';
+import {fromEvent} from 'rxjs/observable/fromEvent';
+import {auditTime} from 'rxjs/operators/auditTime';
+import {takeUntil} from 'rxjs/operators/takeUntil';
+import {Subject} from 'rxjs/Subject';
 
 
 /**
@@ -23,9 +35,10 @@ import {Platform} from '@angular/cdk/platform';
     'rows': '1',
   },
 })
-export class MatTextareaAutosize implements AfterViewInit, DoCheck {
+export class MatTextareaAutosize implements AfterViewInit, DoCheck, OnDestroy {
   /** Keep track of the previous textarea value to avoid resizing when the value hasn't changed. */
   private _previousValue: string;
+  private _destroyed = new Subject<void>();
 
   private _minRows: number;
   private _maxRows: number;
@@ -49,7 +62,12 @@ export class MatTextareaAutosize implements AfterViewInit, DoCheck {
   /** Cached height of a textarea with a single row. */
   private _cachedLineHeight: number;
 
-  constructor(private _elementRef: ElementRef, private _platform: Platform) {}
+  constructor(
+    private _elementRef: ElementRef,
+    private _platform: Platform,
+    private _ngZone?: NgZone) {}
+
+  // TODO(crisbeto): make the `_ngZone` a required param in the next major version.
 
   /** Sets the minimum height of the textarea as determined by minRows. */
   _setMinHeight(): void {
@@ -74,9 +92,22 @@ export class MatTextareaAutosize implements AfterViewInit, DoCheck {
   ngAfterViewInit() {
     if (this._platform.isBrowser) {
       this.resizeToFitContent();
+
+      if (this._ngZone) {
+        this._ngZone.runOutsideAngular(() => {
+          fromEvent(window, 'resize')
+            .pipe(auditTime(16), takeUntil(this._destroyed))
+            .subscribe(() => this.resizeToFitContent(true));
+        });
+      }
     }
   }
 
+  ngOnDestroy() {
+    this._destroyed.next();
+    this._destroyed.complete();
+  }
+
   /** Sets a style property on the textarea element. */
   private _setTextareaStyle(property: string, value: string): void {
     const textarea = this._elementRef.nativeElement as HTMLTextAreaElement;
@@ -134,8 +165,12 @@ export class MatTextareaAutosize implements AfterViewInit, DoCheck {
     }
   }
 
-  /** Resize the textarea to fit its content. */
-  resizeToFitContent() {
+  /**
+   * Resize the textarea to fit its content.
+   * @param force Whether to force a height recalculation. By default the height will be
+   *    recalculated only if the value changed since the last call.
+   */
+  resizeToFitContent(force = false) {
     this._cacheTextareaLineHeight();
 
     // If we haven't determined the line-height yet, we know we're still hidden and there's no point
@@ -148,7 +183,7 @@ export class MatTextareaAutosize implements AfterViewInit, DoCheck {
     const value = textarea.value;
 
     // Only resize of the value changed since these calculations can be expensive.
-    if (value === this._previousValue) {
+    if (value === this._previousValue && !force) {
       return;
     }