feat(material/button): make button ripples lazy

src/material/button/button-base.ts

@@ -16,7 +16,6 @@ import {
   NgZone,
   OnDestroy,
   OnInit,
-  ViewChild,
 } from '@angular/core';
 import {
   CanColor,
@@ -27,6 +26,7 @@ import {
   mixinDisabled,
   mixinDisableRipple,
 } from '@angular/material/core';
+import {MAT_BUTTON_RIPPLE_UNINITIALIZED, MatButtonLazyLoader} from './button-lazy-loader';
 
 /** Inputs common to all buttons. */
 export const MAT_BUTTON_INPUTS = ['disabled', 'disableRipple', 'color'];
@@ -42,6 +42,9 @@ export const MAT_BUTTON_HOST = {
   // Add a class that applies to all buttons. This makes it easier to target if somebody
   // wants to target all Material buttons.
   '[class.mat-mdc-button-base]': 'true',
+  [MAT_BUTTON_RIPPLE_UNINITIALIZED]: '',
+  '[attr.mat-button-disabled]': '_isRippleDisabled()',
+  '[attr.mat-button-is-fab]': '_isFab',
 };
 
 /** List of classes to add to buttons instances based on host attribute selector. */
@@ -96,11 +99,32 @@ export class MatButtonBase
 {
   private readonly _focusMonitor = inject(FocusMonitor);
 
+  /**
+   * Handles the lazy creation of the MatButton ripple.
+   * Used to improve initial load time of large applications.
+   */
+  _rippleLoader: MatButtonLazyLoader = inject(MatButtonLazyLoader);
+
   /** Whether this button is a FAB. Used to apply the correct class on the ripple. */
   _isFab = false;
 
-  /** Reference to the MatRipple instance of the button. */
-  @ViewChild(MatRipple) ripple: MatRipple;
+  /**
+   * Reference to the MatRipple instance of the button.
+   * @deprecated Considered an implementation detail. To be removed.
+   * @breaking-change 17.0.0
+   */
+  get ripple(): MatRipple {
+    if (!this._ripple && this._rippleLoader) {
+      this._ripple = this._rippleLoader._createMatRipple(this._elementRef.nativeElement);
+    }
+    return this._ripple!;
+  }
+  set ripple(v: MatRipple) {
+    this._ripple = v;
+  }
+
+  /** @docs-private Reference to the MatRipple instance of the button. */
+  protected _ripple?: MatRipple;
 
   constructor(
     elementRef: ElementRef,
@@ -146,7 +170,9 @@ export class MatButtonBase
   }
 
   _isRippleDisabled() {
-    return this.disableRipple || this.disabled;
+    if (this._ripple) {
+      this._ripple.disabled = this.disableRipple || this.disabled;
+    }
   }
 }
 
@@ -170,6 +196,9 @@ export const MAT_ANCHOR_HOST = {
   // Add a class that applies to all buttons. This makes it easier to target if somebody
   // wants to target all Material buttons.
   '[class.mat-mdc-button-base]': 'true',
+  [MAT_BUTTON_RIPPLE_UNINITIALIZED]: '',
+  '[attr.mat-button-disabled]': '_isRippleDisabled()',
+  '[attr.mat-button-is-fab]': '_isFab',
 };
 
 /**

src/material/button/button-lazy-loader.ts

@@ -0,0 +1,151 @@
+/**
+ * @license
+ * Copyright Google LLC All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+
+import {DOCUMENT} from '@angular/common';
+import {
+  ANIMATION_MODULE_TYPE,
+  ElementRef,
+  Injectable,
+  NgZone,
+  OnDestroy,
+  inject,
+} from '@angular/core';
+import {
+  MAT_RIPPLE_GLOBAL_OPTIONS,
+  MatRipple,
+  RippleConfig,
+  RippleGlobalOptions,
+  RippleRenderer,
+  RippleTarget,
+} from '@angular/material/core';
+import {Platform} from '@angular/cdk/platform';
+
+/** The options for the MatButtonRippleLoader's event listeners. */
+const eventListenerOptions = {capture: true};
+
+/** The events that should trigger the initialization of the ripple. */
+const rippleInteractionEvents = ['focus', 'click', 'mouseenter', 'touchstart'];
+
+/** The attribute attached to a mat-button whose ripple has not yet been initialized. */
+export const MAT_BUTTON_RIPPLE_UNINITIALIZED = 'mat-button-ripple-uninitialized';
+
+/**
+ * Handles attaching the MatButton's ripple on demand.
+ *
+ * This service allows us to avoid eagerly creating & attaching the MatButton's ripple.
+ * It works by creating & attaching the ripple only when a MatButton is first interacted with.
+ */
+@Injectable({providedIn: 'root'})
+export class MatButtonLazyLoader implements OnDestroy {
+  private _document = inject(DOCUMENT, {optional: true});
+  private _animationMode = inject(ANIMATION_MODULE_TYPE, {optional: true});
+  private _globalRippleOptions = inject(MAT_RIPPLE_GLOBAL_OPTIONS, {optional: true});
+  private _platform = inject(Platform);
+  private _ngZone = inject(NgZone);
+
+  constructor() {
+    this._ngZone.runOutsideAngular(() => {
+      for (const event of rippleInteractionEvents) {
+        this._document?.addEventListener(event, this._onInteraction, eventListenerOptions);
+      }
+    });
+  }
+
+  ngOnDestroy() {
+    for (const event of rippleInteractionEvents) {
+      this._document?.removeEventListener(event, this._onInteraction, eventListenerOptions);
+    }
+  }
+
+  /** Handles creating and attaching button internals when a button is initially interacted with. */
+  private _onInteraction = (event: Event) => {
+    if (event.target === this._document) {
+      return;
+    }
+    const eventTarget = event.target as Element;
+
+    // TODO(wagnermaciel): Consider batching these events to improve runtime performance.
+
+    const button = eventTarget.closest(`[${MAT_BUTTON_RIPPLE_UNINITIALIZED}]`);
+    if (button) {
+      button.removeAttribute(MAT_BUTTON_RIPPLE_UNINITIALIZED);
+      this._appendRipple(button as HTMLElement);
+    }
+  };
+
+  /** Creates a MatButtonRipple and appends it to the given button element. */
+  private _appendRipple(button: HTMLElement): void {
+    if (!this._document) {
+      return;
+    }
+    const ripple = this._document.createElement('span');
+    ripple.classList.add('mat-mdc-button-ripple');
+
+    const target = new MatButtonRippleTarget(
+      button,
+      this._globalRippleOptions ? this._globalRippleOptions : undefined,
+      this._animationMode ? this._animationMode : undefined,
+    );
+    target.rippleConfig.centered = button.hasAttribute('mat-icon-button');
+
+    const rippleRenderer = new RippleRenderer(target, this._ngZone, ripple, this._platform);
+    rippleRenderer.setupTriggerEvents(button);
+    button.append(ripple);
+  }
+
+  _createMatRipple(button: HTMLElement): MatRipple | undefined {
+    if (!this._document) {
+      return;
+    }
+    button.querySelector('.mat-mdc-button-ripple')?.remove();
+    button.removeAttribute(MAT_BUTTON_RIPPLE_UNINITIALIZED);
+    const rippleEl = this._document!.createElement('span');
+    rippleEl.classList.add('mat-mdc-button-ripple');
+    const ripple = new MatRipple(
+      new ElementRef(rippleEl),
+      this._ngZone,
+      this._platform,
+      this._globalRippleOptions ? this._globalRippleOptions : undefined,
+      this._animationMode ? this._animationMode : undefined,
+    );
+    ripple._isInitialized = true;
+    ripple.trigger = button;
+    button.append(rippleEl);
+    return ripple;
+  }
+}
+
+/**
+ * The RippleTarget for the lazily rendered MatButton ripple.
+ * It handles ripple configuration and disabled state for ripples interactions.
+ *
+ * Note that this configuration is usually handled by the MatRipple, but the MatButtonLazyLoader does not use the
+ * MatRipple Directive. In order to create & attach a ripple on demand, it uses the "lower level" RippleRenderer.
+ */
+class MatButtonRippleTarget implements RippleTarget {
+  rippleConfig: RippleConfig & RippleGlobalOptions;
+
+  constructor(
+    private _button: HTMLElement,
+    private _globalRippleOptions?: RippleGlobalOptions,
+    animationMode?: string,
+  ) {
+    this._setRippleConfig(_globalRippleOptions, animationMode);
+  }
+
+  private _setRippleConfig(globalRippleOptions?: RippleGlobalOptions, animationMode?: string) {
+    this.rippleConfig = globalRippleOptions || {};
+    if (animationMode === 'NoopAnimations') {
+      this.rippleConfig.animation = {enterDuration: 0, exitDuration: 0};
+    }
+  }
+
+  get rippleDisabled(): boolean {
+    return this._button.hasAttribute('disabled') || !!this._globalRippleOptions?.disabled;
+  }
+}

src/material/button/button.html

@@ -17,8 +17,4 @@
 -->
 <span class="mat-mdc-focus-indicator"></span>
 
-<span matRipple class="mat-mdc-button-ripple"
-     [matRippleDisabled]="_isRippleDisabled()"
-     [matRippleTrigger]="_elementRef.nativeElement"></span>
-
 <span class="mat-mdc-button-touch-target"></span>

src/material/button/button.scss

@@ -92,6 +92,12 @@
   }
 }
 
+// This style used to be applied by the MatRipple
+// directive, which is no longer attached to this element.
+.mat-mdc-button-ripple {
+  overflow: hidden;
+}
+
 // Since the stroked button has has an actual border that reduces the available space for
 // child elements such as the ripple container or focus overlay, an inherited border radius
 // for the absolute-positioned child elements does not work properly. This is because the

src/material/button/button.spec.ts

@@ -4,6 +4,7 @@ import {By} from '@angular/platform-browser';
 import {MatButtonModule, MatButton, MatFabDefaultOptions, MAT_FAB_DEFAULT_OPTIONS} from './index';
 import {MatRipple, ThemePalette} from '@angular/material/core';
 import {createMouseEvent, dispatchEvent} from '@angular/cdk/testing/private';
+import {MAT_BUTTON_RIPPLE_UNINITIALIZED} from './button-lazy-loader';
 
 describe('MDC-based MatButton', () => {
   beforeEach(waitForAsync(() => {
@@ -267,10 +268,8 @@ describe('MDC-based MatButton', () => {
     let fixture: ComponentFixture<TestApp>;
     let testComponent: TestApp;
     let buttonDebugElement: DebugElement;
-    let buttonRippleDebugElement: DebugElement;
     let buttonRippleInstance: MatRipple;
     let anchorDebugElement: DebugElement;
-    let anchorRippleDebugElement: DebugElement;
     let anchorRippleInstance: MatRipple;
 
     beforeEach(() => {
@@ -280,12 +279,10 @@ describe('MDC-based MatButton', () => {
       testComponent = fixture.componentInstance;
 
       buttonDebugElement = fixture.debugElement.query(By.css('button[mat-button]'))!;
-      buttonRippleDebugElement = buttonDebugElement.query(By.directive(MatRipple))!;
-      buttonRippleInstance = buttonRippleDebugElement.injector.get<MatRipple>(MatRipple);
+      buttonRippleInstance = buttonDebugElement.componentInstance.ripple;
 
       anchorDebugElement = fixture.debugElement.query(By.css('a[mat-button]'))!;
-      anchorRippleDebugElement = anchorDebugElement.query(By.directive(MatRipple))!;
-      anchorRippleInstance = anchorRippleDebugElement.injector.get<MatRipple>(MatRipple);
+      anchorRippleInstance = anchorDebugElement.componentInstance.ripple;
     });
 
     it('should disable the ripple if matRippleDisabled input is set', () => {
@@ -315,6 +312,43 @@ describe('MDC-based MatButton', () => {
         'Expected a disabled a[mat-button] not to have an enabled ripple',
       );
     });
+
+    it('should render the ripple once it is referenced', () => {
+      const fab = fixture.debugElement.query(By.css('button[mat-fab]'))!;
+      let ripple = fab.nativeElement.querySelector('.mat-mdc-button-ripple');
+      expect(ripple).withContext('Expect ripple to be absent before user interaction').toBeNull();
+      expect(fab.nativeElement.hasAttribute(MAT_BUTTON_RIPPLE_UNINITIALIZED))
+        .withContext('Expect mat-button to have the "uninitialized" attr before user interaction')
+        .toBeTrue();
+
+      // Referencing the ripple should instantiate the ripple.
+      expect(fab.componentInstance.ripple).toBeDefined();
+
+      ripple = fab.nativeElement.querySelector('.mat-mdc-button-ripple');
+      expect(ripple)
+        .withContext('Expect ripple to be present after user interaction')
+        .not.toBeNull();
+      expect(fab.nativeElement.hasAttribute(MAT_BUTTON_RIPPLE_UNINITIALIZED))
+        .withContext(
+          'Expect mat-button NOT to have the "uninitialized" attr after user interaction',
+        )
+        .toBeFalse();
+    });
+
+    // Ensure each of these events triggers the initialization of the button ripple.
+    for (const event of ['click', 'touchstart', 'mouseenter', 'focus']) {
+      it(`should render the ripple once a button has received a "${event}" event`, () => {
+        const fab = fixture.debugElement.query(By.css('button[mat-fab]'))!;
+        let ripple = fab.nativeElement.querySelector('.mat-mdc-button-ripple');
+        expect(ripple).toBeNull();
+        expect(fab.nativeElement.hasAttribute(MAT_BUTTON_RIPPLE_UNINITIALIZED)).toBeTrue();
+
+        dispatchEvent(fab.nativeElement, createMouseEvent(event));
+        ripple = fab.nativeElement.querySelector('.mat-mdc-button-ripple');
+        expect(ripple).not.toBeNull();
+        expect(fab.nativeElement.hasAttribute(MAT_BUTTON_RIPPLE_UNINITIALIZED)).toBeFalse();
+      });
+    }
   });
 
   it('should have a focus indicator', () => {

src/material/button/icon-button.html

@@ -8,9 +8,4 @@
 -->
 <span class="mat-mdc-focus-indicator"></span>
 
-<span matRipple class="mat-mdc-button-ripple"
-      [matRippleDisabled]="_isRippleDisabled()"
-      [matRippleCentered]="true"
-      [matRippleTrigger]="_elementRef.nativeElement"></span>
-
 <span class="mat-mdc-button-touch-target"></span>

src/material/button/icon-button.scss

@@ -55,6 +55,12 @@
   @include button-base.mat-private-button-touch-target(true);
   @include private.private-animation-noop();
 
+  // This style used to be applied by the MatRipple
+  // directive, which is no longer attached to this element.
+  .mat-mdc-button-ripple {
+    overflow: hidden;
+  }
+
   .mat-mdc-button-persistent-ripple {
     border-radius: 50%;
   }

src/material/button/icon-button.ts

@@ -26,6 +26,7 @@ import {
   MatAnchorBase,
   MatButtonBase,
 } from './button-base';
+import {MatRipple} from '@angular/material/core';
 
 /**
  * Material Design icon button component. This type of button displays a single interactive icon for
@@ -43,6 +44,19 @@ import {
   changeDetection: ChangeDetectionStrategy.OnPush,
 })
 export class MatIconButton extends MatButtonBase {
+  /**
+   * Reference to the MatRipple instance of the button.
+   * @deprecated Considered an implementation detail. To be removed.
+   * @breaking-change 17.0.0
+   */
+  override get ripple(): MatRipple {
+    if (!this._ripple && this._rippleLoader) {
+      this._ripple = this._rippleLoader._createMatRipple(this._elementRef.nativeElement);
+      this._ripple!.centered = true;
+    }
+    return this._ripple!;
+  }
+
   constructor(
     elementRef: ElementRef,
     platform: Platform,

src/material/core/ripple/ripple.ts

@@ -121,8 +121,8 @@ export class MatRipple implements OnInit, OnDestroy, RippleTarget {
   /** Options that are set globally for all ripples. */
   private _globalOptions: RippleGlobalOptions;
 
-  /** Whether ripple directive is initialized and the input bindings are set. */
-  private _isInitialized: boolean = false;
+  /** @docs-private Whether ripple directive is initialized and the input bindings are set. */
+  _isInitialized: boolean = false;
 
   constructor(
     private _elementRef: ElementRef<HTMLElement>,