feat(ripple): expose ripple directive in template (#3165)

* When programmatically calling `launch` on the ripple element the developer can specifiy a configuration object.
  Since the `launch` method is part of the directive and all the associated `@Input`s. The given configuration should be used as default.

 * Exposes the ripple component instance to the Angular template.

src/lib/core/ripple/ripple.spec.ts

@@ -75,6 +75,7 @@ describe('MdRipple', () => {
   }
 
   describe('basic ripple', () => {
+    let rippleDirective: MdRipple;
 
     const TARGET_HEIGHT = 200;
     const TARGET_WIDTH = 300;
@@ -83,7 +84,8 @@ describe('MdRipple', () => {
       fixture = TestBed.createComponent(BasicRippleContainer);
       fixture.detectChanges();
 
-      rippleTarget = fixture.debugElement.nativeElement.querySelector('[mat-ripple]');
+      rippleTarget = fixture.nativeElement.querySelector('[mat-ripple]');
+      rippleDirective = fixture.componentInstance.ripple;
     });
 
     it('creates ripple on mousedown', () => {
@@ -111,15 +113,29 @@ describe('MdRipple', () => {
     }));
 
     it('creates ripples when manually triggered', () => {
-      let rippleComponent = fixture.debugElement.componentInstance.ripple as MdRipple;
-
       expect(rippleTarget.querySelectorAll('.mat-ripple-element').length).toBe(0);
 
-      rippleComponent.launch(0, 0);
+      rippleDirective.launch(0, 0);
 
       expect(rippleTarget.querySelectorAll('.mat-ripple-element').length).toBe(1);
     });
 
+    it('creates manual ripples with the default ripple config', () => {
+      expect(rippleTarget.querySelectorAll('.mat-ripple-element').length).toBe(0);
+
+      // Calculate the diagonal distance and divide it by two for the center radius.
+      let radius = Math.sqrt(TARGET_HEIGHT * TARGET_HEIGHT + TARGET_WIDTH * TARGET_WIDTH) / 2;
+
+      rippleDirective.centered = true;
+      rippleDirective.launch(0, 0);
+
+      let rippleElement = rippleTarget.querySelector('.mat-ripple-element') as HTMLElement;
+
+      expect(rippleElement).toBeTruthy();
+      expect(parseFloat(rippleElement.style.left)).toBeCloseTo(TARGET_WIDTH / 2 - radius, 1);
+      expect(parseFloat(rippleElement.style.top)).toBeCloseTo(TARGET_HEIGHT / 2 - radius, 1);
+    });
+
     it('sizes ripple to cover element', () => {
       let elementRect = rippleTarget.getBoundingClientRect();
 
@@ -382,13 +398,13 @@ describe('MdRipple', () => {
 
 @Component({
   template: `
-    <div id="container" mat-ripple [mdRippleSpeedFactor]="0"
+    <div id="container" #ripple="mdRipple" mat-ripple [mdRippleSpeedFactor]="0"
          style="position: relative; width:300px; height:200px;">
     </div>
   `,
 })
 class BasicRippleContainer {
-  @ViewChild(MdRipple) ripple: MdRipple;
+  @ViewChild('ripple') ripple: MdRipple;
 }
 
 @Component({

src/lib/core/ripple/ripple.ts

@@ -17,6 +17,7 @@ import {SCROLL_DISPATCHER_PROVIDER} from '../overlay/scroll/scroll-dispatcher';
 
 @Directive({
   selector: '[md-ripple], [mat-ripple]',
+  exportAs: 'mdRipple',
   host: {
     '[class.mat-ripple]': 'true',
     '[class.mat-ripple-unbounded]': 'unbounded'
@@ -77,7 +78,7 @@ export class MdRipple implements OnChanges, OnDestroy {
     }
 
     this._rippleRenderer.rippleDisabled = this.disabled;
-    this._updateRippleConfig();
+    this._rippleRenderer.rippleConfig = this.rippleConfig;
   }
 
   ngOnDestroy() {
@@ -86,13 +87,13 @@ export class MdRipple implements OnChanges, OnDestroy {
   }
 
   /** Launches a manual ripple at the specified position. */
-  launch(pageX: number, pageY: number, config?: RippleConfig) {
+  launch(pageX: number, pageY: number, config = this.rippleConfig) {
     this._rippleRenderer.fadeInRipple(pageX, pageY, config);
   }
 
-  /** Updates the ripple configuration with the input values. */
-  private _updateRippleConfig() {
-    this._rippleRenderer.rippleConfig = {
+  /** Ripple configuration from the directive's input values. */
+  get rippleConfig(): RippleConfig {
+    return {
       centered: this.centered,
       speedFactor: this.speedFactor,
       radius: this.radius,