feat(button): add soft-disabled attribute for focusable disabled buttons

PiperOrigin-RevId: 651854744

Author: zelliott

button/demo/demo.ts

@@ -22,6 +22,7 @@ const collection = new MaterialCollection<KnobTypesToKnobs<StoryKnobs>>(
   [
     new Knob('label', {ui: textInput(), defaultValue: ''}),
     new Knob('disabled', {ui: boolInput(), defaultValue: false}),
+    new Knob('softDisabled', {ui: boolInput(), defaultValue: false}),
   ],
 );
 

button/demo/stories.ts

@@ -18,6 +18,7 @@ import {css, html} from 'lit';
 export interface StoryKnobs {
   label: string;
   disabled: boolean;
+  softDisabled: boolean;
 }
 
 const styles = css`
@@ -38,61 +39,74 @@ const styles = css`
 const buttons: MaterialStoryInit<StoryKnobs> = {
   name: 'Button variants',
   styles,
-  render({label, disabled}) {
+  render({label, disabled, softDisabled}) {
     return html`
       <div class="column">
         <div class="row">
-          <md-filled-button ?disabled=${disabled}>
+          <md-filled-button
+            ?disabled=${disabled}
+            ?soft-disabled=${softDisabled}>
             ${label || 'Filled'}
           </md-filled-button>
 
-          <md-outlined-button ?disabled=${disabled}>
+          <md-outlined-button
+            ?disabled=${disabled}
+            ?soft-disabled=${softDisabled}>
             ${label || 'Outlined'}
           </md-outlined-button>
 
-          <md-elevated-button ?disabled=${disabled}>
+          <md-elevated-button
+            ?disabled=${disabled}
+            ?soft-disabled=${softDisabled}>
             ${label || 'Elevated'}
           </md-elevated-button>
 
-          <md-filled-tonal-button ?disabled=${disabled}>
+          <md-filled-tonal-button
+            ?disabled=${disabled}
+            ?soft-disabled=${softDisabled}>
             ${label || 'Tonal'}
           </md-filled-tonal-button>
 
-          <md-text-button ?disabled=${disabled}>
+          <md-text-button ?disabled=${disabled} ?soft-disabled=${softDisabled}>
             ${label || 'Text'}
           </md-text-button>
         </div>
         <div class="row">
           <md-filled-button
             ?disabled=${disabled}
+            ?soft-disabled=${softDisabled}
             aria-label="${label || 'Filled'} button with icon">
             <md-icon slot="icon">upload</md-icon>
             ${label || 'Filled'}
           </md-filled-button>
 
           <md-outlined-button
             ?disabled=${disabled}
+            ?soft-disabled=${softDisabled}
             aria-label="${label || 'Outlined'} button with icon">
             <md-icon slot="icon">upload</md-icon>
             ${label || 'Outlined'}
           </md-outlined-button>
 
           <md-elevated-button
             ?disabled=${disabled}
+            ?soft-disabled=${softDisabled}
             aria-label="${label || 'Elevated'} button with icon">
             <md-icon slot="icon">upload</md-icon>
             ${label || 'Elevated'}
           </md-elevated-button>
 
           <md-filled-tonal-button
             ?disabled=${disabled}
+            ?soft-disabled=${softDisabled}
             aria-label="${label || 'Tonal'} button with icon">
             <md-icon slot="icon">upload</md-icon>
             ${label || 'Tonal'}
           </md-filled-tonal-button>
 
           <md-text-button
             ?disabled=${disabled}
+            ?soft-disabled=${softDisabled}
             aria-label="${label || 'Text'} button with icon">
             <md-icon slot="icon">upload</md-icon>
             ${label || 'Text'}

button/internal/_elevation.scss

@@ -20,7 +20,7 @@ $_md-sys-motion: tokens.md-sys-motion-values();
     transition-timing-function: map.get($_md-sys-motion, 'emphasized-easing');
   }
 
-  :host([disabled]) md-elevation {
+  :host(:is([disabled], [soft-disabled])) md-elevation {
     transition: none;
   }
 
@@ -59,7 +59,7 @@ $_md-sys-motion: tokens.md-sys-motion-values();
     );
   }
 
-  :host([disabled]) md-elevation {
+  :host(:is([disabled], [soft-disabled])) md-elevation {
     @include elevation.theme(
       (
         'level': var(--_disabled-container-elevation),

button/internal/_icon.scss

@@ -31,7 +31,7 @@
     color: var(--_pressed-icon-color);
   }
 
-  :host([disabled]) ::slotted([slot='icon']) {
+  :host(:is([disabled], [soft-disabled])) ::slotted([slot='icon']) {
     color: var(--_disabled-icon-color);
     opacity: var(--_disabled-icon-opacity);
   }

button/internal/_outlined-button.scss

@@ -57,20 +57,20 @@
     border-color: var(--_pressed-outline-color);
   }
 
-  :host([disabled]) .outline {
+  :host(:is([disabled], [soft-disabled])) .outline {
     border-color: var(--_disabled-outline-color);
     opacity: var(--_disabled-outline-opacity);
   }
 
   @media (forced-colors: active) {
-    :host([disabled]) .background {
+    :host(:is([disabled], [soft-disabled])) .background {
       // Only outlined buttons change their border when disabled to distinguish
       // them from other buttons that add a border for increased visibility in
       // HCM.
       border-color: GrayText;
     }
 
-    :host([disabled]) .outline {
+    :host(:is([disabled], [soft-disabled])) .outline {
       opacity: 1;
     }
   }

button/internal/_shared.scss

@@ -71,7 +71,7 @@
     );
   }
 
-  :host([disabled]) {
+  :host(:is([disabled], [soft-disabled])) {
     cursor: default;
     pointer-events: none;
   }
@@ -139,12 +139,12 @@
     text-overflow: inherit;
   }
 
-  :host([disabled]) .label {
+  :host(:is([disabled], [soft-disabled])) .label {
     color: var(--_disabled-label-text-color);
     opacity: var(--_disabled-label-text-opacity);
   }
 
-  :host([disabled]) .background {
+  :host(:is([disabled], [soft-disabled])) .background {
     background-color: var(--_disabled-container-color);
     opacity: var(--_disabled-container-opacity);
   }
@@ -157,7 +157,7 @@
       border: 1px solid CanvasText;
     }
 
-    :host([disabled]) {
+    :host(:is([disabled], [soft-disabled])) {
       --_disabled-icon-color: GrayText;
       --_disabled-icon-opacity: 1;
       --_disabled-container-opacity: 1;

button/internal/button.ts

@@ -51,6 +51,17 @@ export abstract class Button extends buttonBaseClass implements FormSubmitter {
    */
   @property({type: Boolean, reflect: true}) disabled = false;
 
+  /**
+   * Whether or not the button is "soft-disabled" (disabled but still
+   * focusable).
+   *
+   * Use this when a button needs increased visibility when disabled. See
+   * https://www.w3.org/WAI/ARIA/apg/practices/keyboard-interface/#kbd_disabled_controls
+   * for more guidance on when this is needed.
+   */
+  @property({type: Boolean, attribute: 'soft-disabled', reflect: true})
+  softDisabled = false;
+
   /**
    * The URL that the link button points to.
    */
@@ -111,7 +122,7 @@ export abstract class Button extends buttonBaseClass implements FormSubmitter {
   constructor() {
     super();
     if (!isServer) {
-      this.addEventListener('click', this.handleActivationClick);
+      this.addEventListener('click', this.handleClick.bind(this));
     }
   }
 
@@ -125,7 +136,7 @@ export abstract class Button extends buttonBaseClass implements FormSubmitter {
 
   protected override render() {
     // Link buttons may not be disabled
-    const isDisabled = this.disabled && !this.href;
+    const isRippleDisabled = !this.href && (this.disabled || this.softDisabled);
     const buttonOrLink = this.href ? this.renderLink() : this.renderButton();
     // TODO(b/310046938): due to a limitation in focus ring/ripple, we can't use
     // the same ID for different elements, so we change the ID instead.
@@ -137,7 +148,7 @@ export abstract class Button extends buttonBaseClass implements FormSubmitter {
       <md-ripple
         part="ripple"
         for=${buttonId}
-        ?disabled="${isDisabled}"></md-ripple>
+        ?disabled="${isRippleDisabled}"></md-ripple>
       ${buttonOrLink}
     `;
   }
@@ -155,6 +166,7 @@ export abstract class Button extends buttonBaseClass implements FormSubmitter {
       id="button"
       class="button"
       ?disabled=${this.disabled}
+      aria-disabled=${this.softDisabled || nothing}
       aria-label="${ariaLabel || nothing}"
       aria-haspopup="${ariaHasPopup || nothing}"
       aria-expanded="${ariaExpanded || nothing}">
@@ -190,13 +202,22 @@ export abstract class Button extends buttonBaseClass implements FormSubmitter {
     `;
   }
 
-  private readonly handleActivationClick = (event: MouseEvent) => {
+  private handleClick(event: MouseEvent) {
+    // If the button is soft-disabled, we need to explicitly prevent the click
+    // from propagating to other event listeners as well as prevent the default
+    // action.
+    if (!this.href && this.softDisabled) {
+      event.stopImmediatePropagation();
+      event.preventDefault();
+      return;
+    }
+
     if (!isActivationClick(event) || !this.buttonElement) {
       return;
     }
     this.focus();
     dispatchActivationClick(this.buttonElement);
-  };
+  }
 
   private handleSlotChange() {
     this.hasIcon = this.assignedIcons.length > 0;

button/internal/button_test.ts

@@ -0,0 +1,88 @@
+/**
+ * @license
+ * Copyright 2024 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+// import 'jasmine'; (google3-only)
+
+import {html} from 'lit';
+import {customElement} from 'lit/decorators.js';
+
+import {Environment} from '../../testing/environment.js';
+import {ButtonHarness} from '../harness.js';
+import {Button} from './button.js';
+
+@customElement('test-button')
+class TestButton extends Button {}
+
+describe('Button', () => {
+  const env = new Environment();
+
+  async function setupTest() {
+    const button = new TestButton();
+    env.render(html`${button}`);
+    await env.waitForStability();
+    return {button, harness: new ButtonHarness(button)};
+  }
+
+  it('should not be focusable when disabled', async () => {
+    // Arrange
+    const {button} = await setupTest();
+    button.disabled = true;
+    await env.waitForStability();
+
+    // Act
+    button.focus();
+
+    // Assert
+    expect(document.activeElement)
+      .withContext('disabled button should not be focused')
+      .not.toBe(button);
+  });
+
+  it('should be focusable when soft-disabled', async () => {
+    // Arrange
+    const {button} = await setupTest();
+    button.softDisabled = true;
+    await env.waitForStability();
+
+    // Act
+    button.focus();
+
+    // Assert
+    expect(document.activeElement)
+      .withContext('soft-disabled button should be focused')
+      .toBe(button);
+  });
+
+  it('should not be clickable when disabled', async () => {
+    // Arrange
+    const clickListener = jasmine.createSpy('clickListener');
+    const {button} = await setupTest();
+    button.disabled = true;
+    button.addEventListener('click', clickListener);
+    await env.waitForStability();
+
+    // Act
+    button.click();
+
+    // Assert
+    expect(clickListener).not.toHaveBeenCalled();
+  });
+
+  it('should not be clickable when soft-disabled', async () => {
+    // Arrange
+    const clickListener = jasmine.createSpy('clickListener');
+    const {button} = await setupTest();
+    button.softDisabled = true;
+    button.addEventListener('click', clickListener);
+    await env.waitForStability();
+
+    // Act
+    button.click();
+
+    // Assert
+    expect(clickListener).not.toHaveBeenCalled();
+  });
+});

testing/templates.ts

@@ -24,6 +24,7 @@ export enum State {
   HOVER = 'Hover',
   PRESSED = 'Pressed',
   SELECTED = 'Selected',
+  SOFT_DISABLED = 'Soft disabled',
 }
 
 /**