feat(focus-monitor): support monitoring ElementRef (#12712)

Allows for an `ElementRef` to be monitored by the `FocusMonitor`. This makes it more convenient, because most of the time we're dealing with `ElementRef` anyway.

src/cdk/a11y/focus-monitor/focus-monitor.ts

@@ -88,14 +88,29 @@ export class FocusMonitor implements OnDestroy {
    * @returns An observable that emits when the focus state of the element changes.
    *     When the element is blurred, null will be emitted.
    */
-  monitor(element: HTMLElement, checkChildren: boolean = false): Observable<FocusOrigin> {
+  monitor(element: HTMLElement, checkChildren?: boolean): Observable<FocusOrigin>;
+
+  /**
+   * Monitors focus on an element and applies appropriate CSS classes.
+   * @param element The element to monitor
+   * @param checkChildren Whether to count the element as focused when its children are focused.
+   * @returns An observable that emits when the focus state of the element changes.
+   *     When the element is blurred, null will be emitted.
+   */
+  monitor(element: ElementRef<HTMLElement>, checkChildren?: boolean): Observable<FocusOrigin>;
+
+  monitor(element: HTMLElement | ElementRef<HTMLElement>,
+          checkChildren: boolean = false): Observable<FocusOrigin> {
     // Do nothing if we're not on the browser platform.
     if (!this._platform.isBrowser) {
       return observableOf(null);
     }
+
+    const nativeElement = this._getNativeElement(element);
+
     // Check if we're already monitoring this element.
-    if (this._elementInfo.has(element)) {
-      let cachedInfo = this._elementInfo.get(element);
+    if (this._elementInfo.has(nativeElement)) {
+      let cachedInfo = this._elementInfo.get(nativeElement);
       cachedInfo!.checkChildren = checkChildren;
       return cachedInfo!.subject.asObservable();
     }
@@ -106,21 +121,21 @@ export class FocusMonitor implements OnDestroy {
       checkChildren: checkChildren,
       subject: new Subject<FocusOrigin>()
     };
-    this._elementInfo.set(element, info);
+    this._elementInfo.set(nativeElement, info);
     this._incrementMonitoredElementCount();
 
     // Start listening. We need to listen in capture phase since focus events don't bubble.
-    let focusListener = (event: FocusEvent) => this._onFocus(event, element);
-    let blurListener = (event: FocusEvent) => this._onBlur(event, element);
+    let focusListener = (event: FocusEvent) => this._onFocus(event, nativeElement);
+    let blurListener = (event: FocusEvent) => this._onBlur(event, nativeElement);
     this._ngZone.runOutsideAngular(() => {
-      element.addEventListener('focus', focusListener, true);
-      element.addEventListener('blur', blurListener, true);
+      nativeElement.addEventListener('focus', focusListener, true);
+      nativeElement.addEventListener('blur', blurListener, true);
     });
 
     // Create an unlisten function for later.
     info.unlisten = () => {
-      element.removeEventListener('focus', focusListener, true);
-      element.removeEventListener('blur', blurListener, true);
+      nativeElement.removeEventListener('focus', focusListener, true);
+      nativeElement.removeEventListener('blur', blurListener, true);
     };
 
     return info.subject.asObservable();
@@ -130,15 +145,24 @@ export class FocusMonitor implements OnDestroy {
    * Stops monitoring an element and removes all focus classes.
    * @param element The element to stop monitoring.
    */
-  stopMonitoring(element: HTMLElement): void {
-    const elementInfo = this._elementInfo.get(element);
+  stopMonitoring(element: HTMLElement): void;
+
+  /**
+   * Stops monitoring an element and removes all focus classes.
+   * @param element The element to stop monitoring.
+   */
+  stopMonitoring(element: ElementRef<HTMLElement>): void;
+
+  stopMonitoring(element: HTMLElement | ElementRef<HTMLElement>): void {
+    const nativeElement = this._getNativeElement(element);
+    const elementInfo = this._elementInfo.get(nativeElement);
 
     if (elementInfo) {
       elementInfo.unlisten();
       elementInfo.subject.complete();
 
-      this._setClasses(element);
-      this._elementInfo.delete(element);
+      this._setClasses(nativeElement);
+      this._elementInfo.delete(nativeElement);
       this._decrementMonitoredElementCount();
     }
   }
@@ -370,6 +394,10 @@ export class FocusMonitor implements OnDestroy {
       this._unregisterGlobalListeners = () => {};
     }
   }
+
+  private _getNativeElement(element: HTMLElement | ElementRef<HTMLElement>): HTMLElement {
+    return element instanceof ElementRef ? element.nativeElement : element;
+  }
 }
 
 
@@ -391,13 +419,13 @@ export class CdkMonitorFocus implements OnDestroy {
 
   constructor(private _elementRef: ElementRef, private _focusMonitor: FocusMonitor) {
     this._monitorSubscription = this._focusMonitor.monitor(
-        this._elementRef.nativeElement,
+        this._elementRef,
         this._elementRef.nativeElement.hasAttribute('cdkMonitorSubtreeFocus'))
         .subscribe(origin => this.cdkFocusChange.emit(origin));
   }
 
   ngOnDestroy() {
-    this._focusMonitor.stopMonitoring(this._elementRef.nativeElement);
+    this._focusMonitor.stopMonitoring(this._elementRef);
     this._monitorSubscription.unsubscribe();
   }
 }

src/lib/button-toggle/button-toggle.ts

@@ -433,11 +433,11 @@ export class MatButtonToggle extends _MatButtonToggleMixinBase implements OnInit
       this.checked = true;
     }
 
-    this._focusMonitor.monitor(this._elementRef.nativeElement, true);
+    this._focusMonitor.monitor(this._elementRef, true);
   }
 
   ngOnDestroy() {
-    this._focusMonitor.stopMonitoring(this._elementRef.nativeElement);
+    this._focusMonitor.stopMonitoring(this._elementRef);
   }
 
   /** Focuses the button. */

src/lib/button/button.ts

@@ -106,15 +106,15 @@ export class MatButton extends _MatButtonMixinBase
       }
     }
 
-    this._focusMonitor.monitor(this._elementRef.nativeElement, true);
+    this._focusMonitor.monitor(this._elementRef, true);
 
     if (this.isRoundButton) {
       this.color = DEFAULT_ROUND_BUTTON_COLOR;
     }
   }
 
   ngOnDestroy() {
-    this._focusMonitor.stopMonitoring(this._elementRef.nativeElement);
+    this._focusMonitor.stopMonitoring(this._elementRef);
   }
 
   /** Focuses the button. */

src/lib/checkbox/checkbox.ts

@@ -197,12 +197,12 @@ export class MatCheckbox extends _MatCheckboxMixinBase implements ControlValueAc
 
   ngAfterViewInit() {
     this._focusMonitor
-      .monitor(this._inputElement.nativeElement)
+      .monitor(this._inputElement)
       .subscribe(focusOrigin => this._onInputFocusChange(focusOrigin));
   }
 
   ngOnDestroy() {
-    this._focusMonitor.stopMonitoring(this._inputElement.nativeElement);
+    this._focusMonitor.stopMonitoring(this._inputElement);
   }
 
   /**

src/lib/expansion/expansion-panel-header.ts

@@ -83,7 +83,7 @@ export class MatExpansionPanelHeader implements OnDestroy {
     )
     .subscribe(() => this._changeDetectorRef.markForCheck());
 
-    _focusMonitor.monitor(_element.nativeElement);
+    _focusMonitor.monitor(_element);
   }
 
   /** Height of the header while the panel is expanded. */
@@ -133,7 +133,7 @@ export class MatExpansionPanelHeader implements OnDestroy {
 
   ngOnDestroy() {
     this._parentChangeSubscription.unsubscribe();
-    this._focusMonitor.stopMonitoring(this._element.nativeElement);
+    this._focusMonitor.stopMonitoring(this._element);
   }
 }
 

src/lib/menu/menu-item.ts

@@ -82,7 +82,7 @@ export class MatMenuItem extends _MatMenuItemMixinBase
       // Start monitoring the element so it gets the appropriate focused classes. We want
       // to show the focus style for menu items only when the focus was not caused by a
       // mouse or touch interaction.
-      _focusMonitor.monitor(this._getHostElement(), false);
+      _focusMonitor.monitor(this._elementRef, false);
     }
 
     if (_parentMenu && _parentMenu.addItem) {
@@ -103,7 +103,7 @@ export class MatMenuItem extends _MatMenuItemMixinBase
 
   ngOnDestroy() {
     if (this._focusMonitor) {
-      this._focusMonitor.stopMonitoring(this._getHostElement());
+      this._focusMonitor.stopMonitoring(this._elementRef);
     }
 
     if (this._parentMenu && this._parentMenu.removeItem) {

src/lib/radio/radio.ts

@@ -518,12 +518,12 @@ export class MatRadioButton extends _MatRadioButtonMixinBase
 
   ngAfterViewInit() {
     this._focusMonitor
-      .monitor(this._inputElement.nativeElement)
+      .monitor(this._inputElement)
       .subscribe(focusOrigin => this._onInputFocusChange(focusOrigin));
   }
 
   ngOnDestroy() {
-    this._focusMonitor.stopMonitoring(this._inputElement.nativeElement);
+    this._focusMonitor.stopMonitoring(this._inputElement);
     this._removeUniqueSelectionListener();
   }
 

src/lib/slide-toggle/slide-toggle.ts

@@ -194,7 +194,7 @@ export class MatSlideToggle extends _MatSlideToggleMixinBase implements OnDestro
 
   ngAfterContentInit() {
     this._focusMonitor
-      .monitor(this._elementRef.nativeElement, true)
+      .monitor(this._elementRef, true)
       .subscribe(focusOrigin => {
         if (!focusOrigin) {
           // When a focused element becomes disabled, the browser *immediately* fires a blur event.
@@ -208,7 +208,7 @@ export class MatSlideToggle extends _MatSlideToggleMixinBase implements OnDestro
   }
 
   ngOnDestroy() {
-    this._focusMonitor.stopMonitoring(this._elementRef.nativeElement);
+    this._focusMonitor.stopMonitoring(this._elementRef);
   }
 
   /** Method being called whenever the underlying input emits a change event. */

src/lib/slider/slider.ts

@@ -465,7 +465,7 @@ export class MatSlider extends _MatSliderMixinBase
 
   ngOnInit() {
     this._focusMonitor
-        .monitor(this._elementRef.nativeElement, true)
+        .monitor(this._elementRef, true)
         .subscribe((origin: FocusOrigin) => {
           this._isActive = !!origin && origin !== 'keyboard';
           this._changeDetectorRef.detectChanges();
@@ -478,7 +478,7 @@ export class MatSlider extends _MatSliderMixinBase
   }
 
   ngOnDestroy() {
-    this._focusMonitor.stopMonitoring(this._elementRef.nativeElement);
+    this._focusMonitor.stopMonitoring(this._elementRef);
     this._dirChangeSubscription.unsubscribe();
   }
 

src/lib/stepper/step-header.ts

@@ -64,13 +64,13 @@ export class MatStepHeader implements OnDestroy {
     private _focusMonitor: FocusMonitor,
     private _element: ElementRef,
     changeDetectorRef: ChangeDetectorRef) {
-    _focusMonitor.monitor(_element.nativeElement, true);
+    _focusMonitor.monitor(_element, true);
     this._intlSubscription = _intl.changes.subscribe(() => changeDetectorRef.markForCheck());
   }
 
   ngOnDestroy() {
     this._intlSubscription.unsubscribe();
-    this._focusMonitor.stopMonitoring(this._element.nativeElement);
+    this._focusMonitor.stopMonitoring(this._element);
   }
 
   /** Returns string label of given step if it is a text label. */

src/lib/tabs/tab-nav-bar/tab-nav-bar.ts

@@ -247,15 +247,15 @@ export class MatTabLink extends _MatTabLinkMixinBase
     }
 
     if (_focusMonitor) {
-      _focusMonitor.monitor(_elementRef.nativeElement);
+      _focusMonitor.monitor(_elementRef);
     }
   }
 
   ngOnDestroy() {
     this._tabLinkRipple._removeTriggerEvents();
 
     if (this._focusMonitor) {
-      this._focusMonitor.stopMonitoring(this._elementRef.nativeElement);
+      this._focusMonitor.stopMonitoring(this._elementRef);
     }
   }
 

src/lib/tooltip/tooltip.ts

@@ -234,7 +234,7 @@ export class MatTooltip implements OnDestroy {
       element.style['webkitUserDrag'] = '';
     }
 
-    _focusMonitor.monitor(element).pipe(takeUntil(this._destroyed)).subscribe(origin => {
+    _focusMonitor.monitor(_elementRef).pipe(takeUntil(this._destroyed)).subscribe(origin => {
       // Note that the focus monitor runs outside the Angular zone.
       if (!origin) {
         _ngZone.run(() => this.hide(0));
@@ -265,7 +265,7 @@ export class MatTooltip implements OnDestroy {
     this._destroyed.complete();
 
     this._ariaDescriber.removeDescription(this._elementRef.nativeElement, this.message);
-    this._focusMonitor.stopMonitoring(this._elementRef.nativeElement);
+    this._focusMonitor.stopMonitoring(this._elementRef);
   }
 
   /** Shows the tooltip after the delay in ms, defaults to tooltip-delay-show or 0ms if no input */

src/material-examples/focus-monitor-focus-via/focus-monitor-focus-via-example.ts

@@ -25,15 +25,15 @@ export class FocusMonitorFocusViaExample implements OnDestroy, OnInit {
               private ngZone: NgZone) {}
 
   ngOnInit() {
-    this.focusMonitor.monitor(this.monitoredEl.nativeElement)
+    this.focusMonitor.monitor(this.monitoredEl)
         .subscribe(origin => this.ngZone.run(() => {
           this.origin = this.formatOrigin(origin);
           this.cdr.markForCheck();
         }));
   }
 
   ngOnDestroy() {
-    this.focusMonitor.stopMonitoring(this.monitoredEl.nativeElement);
+    this.focusMonitor.stopMonitoring(this.monitoredEl);
   }
 
   formatOrigin(origin: FocusOrigin): string {

src/material-examples/focus-monitor-overview/focus-monitor-overview-example.ts

@@ -27,21 +27,21 @@ export class FocusMonitorOverviewExample implements OnDestroy, OnInit {
               private ngZone: NgZone) {}
 
   ngOnInit() {
-    this.focusMonitor.monitor(this.element.nativeElement)
+    this.focusMonitor.monitor(this.element)
         .subscribe(origin => this.ngZone.run(() => {
           this.elementOrigin = this.formatOrigin(origin);
           this.cdr.markForCheck();
         }));
-    this.focusMonitor.monitor(this.subtree.nativeElement, true)
+    this.focusMonitor.monitor(this.subtree, true)
         .subscribe(origin => this.ngZone.run(() => {
           this.subtreeOrigin = this.formatOrigin(origin);
           this.cdr.markForCheck();
         }));
   }
 
   ngOnDestroy() {
-    this.focusMonitor.stopMonitoring(this.element.nativeElement);
-    this.focusMonitor.stopMonitoring(this.subtree.nativeElement);
+    this.focusMonitor.stopMonitoring(this.element);
+    this.focusMonitor.stopMonitoring(this.subtree);
   }
 
   formatOrigin(origin: FocusOrigin): string {

src/material-examples/form-field-custom-control/form-field-custom-control-example.ts

@@ -88,15 +88,15 @@ export class MyTelInput implements MatFormFieldControl<MyTel>, OnDestroy {
       subscriber: '',
     });
 
-    fm.monitor(elRef.nativeElement, true).subscribe(origin => {
+    fm.monitor(elRef, true).subscribe(origin => {
       this.focused = !!origin;
       this.stateChanges.next();
     });
   }
 
   ngOnDestroy() {
     this.stateChanges.complete();
-    this.fm.stopMonitoring(this.elRef.nativeElement);
+    this.fm.stopMonitoring(this.elRef);
   }
 
   setDescribedByIds(ids: string[]) {