feat(focus-classes): expose focus origin changes through observable (#2974)

* return observable from registerElementForFocusClasses

* added tests

* restore focus origin on window focus

* addressed comments

* rebased

src/lib/core/style/focus-classes.spec.ts

@@ -1,15 +1,16 @@
 import {async, ComponentFixture, TestBed, inject} from '@angular/core/testing';
-import {Component, Renderer} from '@angular/core';
+import {Component, Renderer, ViewChild} from '@angular/core';
 import {StyleModule} from './index';
 import {By} from '@angular/platform-browser';
 import {TAB} from '../keyboard/keycodes';
-import {FocusOriginMonitor} from './focus-classes';
+import {FocusOriginMonitor, FocusOrigin, CdkFocusClasses} from './focus-classes';
 
 describe('FocusOriginMonitor', () => {
   let fixture: ComponentFixture<PlainButton>;
   let buttonElement: HTMLElement;
   let buttonRenderer: Renderer;
   let focusOriginMonitor: FocusOriginMonitor;
+  let changeHandler: (origin: FocusOrigin) => void;
 
   beforeEach(async(() => {
     TestBed.configureTestingModule({
@@ -30,7 +31,9 @@ describe('FocusOriginMonitor', () => {
     buttonRenderer = fixture.componentInstance.renderer;
     focusOriginMonitor = fom;
 
-    focusOriginMonitor.registerElementForFocusClasses(buttonElement, buttonRenderer);
+    changeHandler = jasmine.createSpy('focus origin change handler');
+    focusOriginMonitor.registerElementForFocusClasses(buttonElement, buttonRenderer)
+        .subscribe(changeHandler);
 
     // Patch the element focus to properly emit focus events when the browser is blurred.
     patchElementFocus(buttonElement);
@@ -45,6 +48,7 @@ describe('FocusOriginMonitor', () => {
 
       expect(buttonElement.classList.contains('cdk-focused'))
           .toBe(true, 'button should have cdk-focused class');
+      expect(changeHandler).toHaveBeenCalledTimes(1);
     }, 0);
   }));
 
@@ -63,6 +67,7 @@ describe('FocusOriginMonitor', () => {
           .toBe(true, 'button should have cdk-focused class');
       expect(buttonElement.classList.contains('cdk-keyboard-focused'))
           .toBe(true, 'button should have cdk-keyboard-focused class');
+      expect(changeHandler).toHaveBeenCalledWith('keyboard');
     }, 0);
   }));
 
@@ -81,6 +86,7 @@ describe('FocusOriginMonitor', () => {
           .toBe(true, 'button should have cdk-focused class');
       expect(buttonElement.classList.contains('cdk-mouse-focused'))
           .toBe(true, 'button should have cdk-mouse-focused class');
+      expect(changeHandler).toHaveBeenCalledWith('mouse');
     }, 0);
   }));
 
@@ -98,6 +104,7 @@ describe('FocusOriginMonitor', () => {
           .toBe(true, 'button should have cdk-focused class');
       expect(buttonElement.classList.contains('cdk-program-focused'))
           .toBe(true, 'button should have cdk-program-focused class');
+      expect(changeHandler).toHaveBeenCalledWith('program');
     }, 0);
   }));
 
@@ -114,6 +121,7 @@ describe('FocusOriginMonitor', () => {
           .toBe(true, 'button should have cdk-focused class');
       expect(buttonElement.classList.contains('cdk-keyboard-focused'))
           .toBe(true, 'button should have cdk-keyboard-focused class');
+      expect(changeHandler).toHaveBeenCalledWith('keyboard');
     }, 0);
   }));
 
@@ -130,6 +138,7 @@ describe('FocusOriginMonitor', () => {
           .toBe(true, 'button should have cdk-focused class');
       expect(buttonElement.classList.contains('cdk-mouse-focused'))
           .toBe(true, 'button should have cdk-mouse-focused class');
+      expect(changeHandler).toHaveBeenCalledWith('mouse');
     }, 0);
   }));
 
@@ -146,6 +155,27 @@ describe('FocusOriginMonitor', () => {
           .toBe(true, 'button should have cdk-focused class');
       expect(buttonElement.classList.contains('cdk-program-focused'))
           .toBe(true, 'button should have cdk-program-focused class');
+      expect(changeHandler).toHaveBeenCalledWith('program');
+    }, 0);
+  }));
+
+  it('should remove focus classes on blur', async(() => {
+    buttonElement.focus();
+    fixture.detectChanges();
+
+    setTimeout(() => {
+      fixture.detectChanges();
+
+      expect(buttonElement.classList.length)
+          .toBe(2, 'button should have exactly 2 focus classes');
+      expect(changeHandler).toHaveBeenCalledWith('program');
+
+      buttonElement.blur();
+      fixture.detectChanges();
+
+      expect(buttonElement.classList.length)
+          .toBe(0, 'button should not have any focus classes');
+      expect(changeHandler).toHaveBeenCalledWith(null);
     }, 0);
   }));
 });
@@ -154,6 +184,7 @@ describe('FocusOriginMonitor', () => {
 describe('cdkFocusClasses', () => {
   let fixture: ComponentFixture<ButtonWithFocusClasses>;
   let buttonElement: HTMLElement;
+  let changeHandler: (origin: FocusOrigin) => void;
 
   beforeEach(async(() => {
     TestBed.configureTestingModule({
@@ -170,6 +201,8 @@ describe('cdkFocusClasses', () => {
     fixture = TestBed.createComponent(ButtonWithFocusClasses);
     fixture.detectChanges();
 
+    changeHandler = jasmine.createSpy('focus origin change handler');
+    fixture.componentInstance.cdkFocusClasses.changes.subscribe(changeHandler);
     buttonElement = fixture.debugElement.query(By.css('button')).nativeElement;
 
     // Patch the element focus to properly emit focus events when the browser is blurred.
@@ -195,6 +228,7 @@ describe('cdkFocusClasses', () => {
           .toBe(true, 'button should have cdk-focused class');
       expect(buttonElement.classList.contains('cdk-keyboard-focused'))
           .toBe(true, 'button should have cdk-keyboard-focused class');
+      expect(changeHandler).toHaveBeenCalledWith('keyboard');
     }, 0);
   }));
 
@@ -213,6 +247,7 @@ describe('cdkFocusClasses', () => {
           .toBe(true, 'button should have cdk-focused class');
       expect(buttonElement.classList.contains('cdk-mouse-focused'))
           .toBe(true, 'button should have cdk-mouse-focused class');
+      expect(changeHandler).toHaveBeenCalledWith('mouse');
     }, 0);
   }));
 
@@ -230,6 +265,27 @@ describe('cdkFocusClasses', () => {
           .toBe(true, 'button should have cdk-focused class');
       expect(buttonElement.classList.contains('cdk-program-focused'))
           .toBe(true, 'button should have cdk-program-focused class');
+      expect(changeHandler).toHaveBeenCalledWith('program');
+    }, 0);
+  }));
+
+  it('should remove focus classes on blur', async(() => {
+    buttonElement.focus();
+    fixture.detectChanges();
+
+    setTimeout(() => {
+      fixture.detectChanges();
+
+      expect(buttonElement.classList.length)
+          .toBe(2, 'button should have exactly 2 focus classes');
+      expect(changeHandler).toHaveBeenCalledWith('program');
+
+      buttonElement.blur();
+      fixture.detectChanges();
+
+      expect(buttonElement.classList.length)
+          .toBe(0, 'button should not have any focus classes');
+      expect(changeHandler).toHaveBeenCalledWith(null);
     }, 0);
   }));
 });
@@ -242,7 +298,9 @@ class PlainButton {
 
 
 @Component({template: `<button cdkFocusClasses>focus me!</button>`})
-class ButtonWithFocusClasses {}
+class ButtonWithFocusClasses {
+  @ViewChild(CdkFocusClasses) cdkFocusClasses: CdkFocusClasses;
+}
 
 // TODO(devversion): move helper functions into a global utility file. See #2902
 
@@ -273,14 +331,21 @@ function dispatchFocusEvent(element: Node, type = 'focus') {
   element.dispatchEvent(event);
 }
 
-/** Patches an elements focus method to properly emit focus events when the browser is blurred. */
+/**
+ * Patches an elements focus and blur methods to properly emit focus events when the browser is
+ * blurred.
+ */
 function patchElementFocus(element: HTMLElement) {
   // On Saucelabs, browsers will run simultaneously and therefore can't focus all browser windows
   // at the same time. This is problematic when testing focus states. Chrome and Firefox
   // only fire FocusEvents when the window is focused. This issue also appears locally.
   let _nativeButtonFocus = element.focus.bind(element);
+  let _nativeButtonBlur = element.blur.bind(element);
 
   element.focus = () => {
     document.hasFocus() ? _nativeButtonFocus() : dispatchFocusEvent(element);
   };
+  element.blur = () => {
+    document.hasFocus() ? _nativeButtonBlur() : dispatchFocusEvent(element, 'blur');
+  };
 }

src/lib/core/style/focus-classes.ts

@@ -1,4 +1,6 @@
 import {Directive, Injectable, Optional, SkipSelf, Renderer, ElementRef} from '@angular/core';
+import {Observable} from 'rxjs/Observable';
+import {Subject} from 'rxjs/Subject';
 
 
 export type FocusOrigin = 'mouse' | 'keyboard' | 'program';
@@ -10,6 +12,12 @@ export class FocusOriginMonitor {
   /** The focus origin that the next focus event is a result of. */
   private _origin: FocusOrigin = null;
 
+  /** The FocusOrigin of the last focus event tracked by the FocusOriginMonitor. */
+  private _lastFocusOrigin: FocusOrigin;
+
+  /** Whether the window has just been focused. */
+  private _windowFocused = false;
+
   constructor() {
     // Listen to keydown and mousedown in the capture phase so we can detect them even if the user
     // stops propagation.
@@ -18,12 +26,21 @@ export class FocusOriginMonitor {
         'keydown', () => this._setOriginForCurrentEventQueue('keyboard'), true);
     document.addEventListener(
         'mousedown', () => this._setOriginForCurrentEventQueue('mouse'), true);
+
+    // Make a note of when the window regains focus, so we can restore the origin info for the
+    // focused element.
+    window.addEventListener('focus', () => {
+      this._windowFocused = true;
+      setTimeout(() => this._windowFocused = false, 0);
+    });
   }
 
   /** Register an element to receive focus classes. */
-  registerElementForFocusClasses(element: Element, renderer: Renderer) {
-    renderer.listen(element, 'focus', () => this._onFocus(element, renderer));
-    renderer.listen(element, 'blur', () => this._onBlur(element, renderer));
+  registerElementForFocusClasses(element: Element, renderer: Renderer): Observable<FocusOrigin> {
+    let subject = new Subject<FocusOrigin>();
+    renderer.listen(element, 'focus', () => this._onFocus(element, renderer, subject));
+    renderer.listen(element, 'blur', () => this._onBlur(element, renderer, subject));
+    return subject.asObservable();
   }
 
   /** Focuses the element via the specified focus origin. */
@@ -39,21 +56,37 @@ export class FocusOriginMonitor {
   }
 
   /** Handles focus events on a registered element. */
-  private _onFocus(element: Element, renderer: Renderer) {
+  private _onFocus(element: Element, renderer: Renderer, subject: Subject<FocusOrigin>) {
+    // If we couldn't detect a cause for the focus event, it's due to one of two reasons:
+    // 1) The window has just regained focus, in which case we want to restore the focused state of
+    //    the element from before the window blurred.
+    // 2) The element was programmatically focused, in which case we should mark the origin as
+    //    'program'.
+    if (!this._origin) {
+      if (this._windowFocused && this._lastFocusOrigin) {
+        this._origin = this._lastFocusOrigin;
+      } else {
+        this._origin = 'program';
+      }
+    }
+
     renderer.setElementClass(element, 'cdk-focused', true);
     renderer.setElementClass(element, 'cdk-keyboard-focused', this._origin == 'keyboard');
     renderer.setElementClass(element, 'cdk-mouse-focused', this._origin == 'mouse');
-    renderer.setElementClass(element, 'cdk-program-focused',
-        !this._origin || this._origin == 'program');
+    renderer.setElementClass(element, 'cdk-program-focused', this._origin == 'program');
+
+    subject.next(this._origin);
+    this._lastFocusOrigin = this._origin;
     this._origin = null;
   }
 
   /** Handles blur events on a registered element. */
-  private _onBlur(element: Element, renderer: Renderer) {
+  private _onBlur(element: Element, renderer: Renderer, subject: Subject<FocusOrigin>) {
     renderer.setElementClass(element, 'cdk-focused', false);
     renderer.setElementClass(element, 'cdk-keyboard-focused', false);
     renderer.setElementClass(element, 'cdk-mouse-focused', false);
     renderer.setElementClass(element, 'cdk-program-focused', false);
+    subject.next(null);
   }
 }
 
@@ -66,8 +99,11 @@ export class FocusOriginMonitor {
   selector: '[cdkFocusClasses]',
 })
 export class CdkFocusClasses {
+  changes: Observable<FocusOrigin>;
+
   constructor(elementRef: ElementRef, focusOriginMonitor: FocusOriginMonitor, renderer: Renderer) {
-    focusOriginMonitor.registerElementForFocusClasses(elementRef.nativeElement, renderer);
+    this.changes =
+        focusOriginMonitor.registerElementForFocusClasses(elementRef.nativeElement, renderer);
   }
 }