feat: add soft-disabled property to button and iconbutton

Fixes #5672.

PiperOrigin-RevId: 651409230

Author: zelliott

button/internal/_elevation.scss

@@ -20,7 +20,8 @@ $_md-sys-motion: tokens.md-sys-motion-values();
     transition-timing-function: map.get($_md-sys-motion, 'emphasized-easing');
   }
 
-  :host([disabled]) md-elevation {
+  :host([disabled]) md-elevation,
+  :host([soft-disabled]) md-elevation {
     transition: none;
   }
 
@@ -59,7 +60,8 @@ $_md-sys-motion: tokens.md-sys-motion-values();
     );
   }
 
-  :host([disabled]) md-elevation {
+  :host([disabled]) md-elevation,
+  :host([soft-disabled]) md-elevation {
     @include elevation.theme(
       (
         'level': var(--_disabled-container-elevation),

button/internal/_icon.scss

@@ -31,7 +31,8 @@
     color: var(--_pressed-icon-color);
   }
 
-  :host([disabled]) ::slotted([slot='icon']) {
+  :host([disabled]) ::slotted([slot='icon']),
+  :host([soft-disabled]) ::slotted([slot='icon']) {
     color: var(--_disabled-icon-color);
     opacity: var(--_disabled-icon-opacity);
   }

button/internal/_outlined-button.scss

@@ -57,20 +57,23 @@
     border-color: var(--_pressed-outline-color);
   }
 
-  :host([disabled]) .outline {
+  :host([disabled]) .outline,
+  :host([soft-disabled]) .outline {
     border-color: var(--_disabled-outline-color);
     opacity: var(--_disabled-outline-opacity);
   }
 
   @media (forced-colors: active) {
-    :host([disabled]) .background {
+    :host([disabled]) .background,
+    :host([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([disabled]) .outline,
+    :host([soft-disabled]) .outline {
       opacity: 1;
     }
   }

button/internal/_shared.scss

@@ -71,7 +71,8 @@
     );
   }
 
-  :host([disabled]) {
+  :host([disabled]),
+  :host([soft-disabled]) {
     cursor: default;
     pointer-events: none;
   }
@@ -139,12 +140,14 @@
     text-overflow: inherit;
   }
 
-  :host([disabled]) .label {
+  :host([disabled]) .label,
+  :host([soft-disabled]) .label {
     color: var(--_disabled-label-text-color);
     opacity: var(--_disabled-label-text-opacity);
   }
 
-  :host([disabled]) .background {
+  :host([disabled]) .background,
+  :host([soft-disabled]) .background {
     background-color: var(--_disabled-container-color);
     opacity: var(--_disabled-container-opacity);
   }
@@ -157,7 +160,8 @@
       border: 1px solid CanvasText;
     }
 
-    :host([disabled]) {
+    :host([disabled]),
+    :host([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);
     }
   }
 
@@ -123,9 +134,19 @@ export abstract class Button extends buttonBaseClass implements FormSubmitter {
     this.buttonElement?.blur();
   }
 
+  /**
+   * Link buttons cannot be disabled or soft-disabled.
+   */
+  protected override willUpdate() {
+    if (this.href) {
+      this.disabled = false;
+      this.softDisabled = false;
+    }
+  }
+
   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 +158,7 @@ export abstract class Button extends buttonBaseClass implements FormSubmitter {
       <md-ripple
         part="ripple"
         for=${buttonId}
-        ?disabled="${isDisabled}"></md-ripple>
+        ?disabled="${isRippleDisabled}"></md-ripple>
       ${buttonOrLink}
     `;
   }
@@ -155,6 +176,7 @@ export abstract class Button extends buttonBaseClass implements FormSubmitter {
       id="button"
       class="button"
       ?disabled=${this.disabled}
+      aria-disabled=${this.softDisabled ? 'true' : nothing}
       aria-label="${ariaLabel || nothing}"
       aria-haspopup="${ariaHasPopup || nothing}"
       aria-expanded="${ariaExpanded || nothing}">
@@ -190,7 +212,16 @@ export abstract class Button extends buttonBaseClass implements FormSubmitter {
     `;
   }
 
-  private readonly handleActivationClick = (event: MouseEvent) => {
+  private readonly 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;
     }

button/internal/button_test.ts

@@ -0,0 +1,69 @@
+/**
+ * @license
+ * Copyright 2023 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 () => {
+    const {button} = await setupTest();
+    button.disabled = true;
+    await env.waitForStability();
+
+    button.focus();
+    expect(document.activeElement).toEqual(document.body);
+  });
+
+  it('should be focusable when soft-disabled', async () => {
+    const {button} = await setupTest();
+    button.softDisabled = true;
+    await env.waitForStability();
+
+    button.focus();
+    expect(document.activeElement).toEqual(button);
+  });
+
+  it('should not be clickable when disabled', async () => {
+    const clickListener = jasmine.createSpy('clickListener');
+    const {button} = await setupTest();
+    button.disabled = true;
+    button.addEventListener('click', clickListener);
+    await env.waitForStability();
+
+    button.click();
+    expect(clickListener).not.toHaveBeenCalled();
+  });
+
+  it('should not be clickable when soft-disabled', async () => {
+    const clickListener = jasmine.createSpy('clickListener');
+    const {button} = await setupTest();
+    button.softDisabled = true;
+    button.addEventListener('click', clickListener);
+    await env.waitForStability();
+
+    button.click();
+    expect(clickListener).not.toHaveBeenCalled();
+  });
+});

docs/components/button.md

@@ -236,6 +236,28 @@ attribute to buttons whose labels need a more descriptive label.
 <md-elevated-button aria-label="Add a new contact">Add</md-elevated-button>
 ```
 
+### Focusable and disabled
+
+By default, disabled buttons are not focusable with the keyboard, while
+soft-disabled buttons are. Some use cases encourage focusability of disabled
+toolbar items to increase their discoverability.
+
+See the
+[ARIA guidelines on focusability of disabled controls](https://www.w3.org/WAI/ARIA/apg/practices/keyboard-interface/#kbd_disabled_controls)<!-- {.external} -->
+for guidance on when this is recommended.
+
+```html
+<div role="toolbar">
+  <md-text-button>Copy</md-text-button>
+  <md-text-button>Cut</md-text-button>
+  <!--
+    This button is disabled but kept focusable to improve its discoverability
+    in the toolbar.
+  -->
+  <md-text-button soft-disabled>Paste</md-text-button>
+</div>
+```
+
 ## Elevated button
 
 <!-- go/md-elevated-button -->
@@ -703,7 +725,6 @@ Token                               | Default value
 
 ## API
 
-
 ### MdElevatedButton <code>&lt;md-elevated-button&gt;</code>
 
 #### Properties
@@ -713,6 +734,7 @@ Token                               | Default value
 | Property | Attribute | Type | Default | Description |
 | --- | --- | --- | --- | --- |
 | `disabled` | `disabled` | `boolean` | `false` | Whether or not the button is disabled. |
+| `softDisabled` | `soft-disabled` | `boolean` | `false` | Whether the button is "soft-disabled" (disabled but still focusable). |
 | `href` | `href` | `string` | `''` | The URL that the link button points to. |
 | `target` | `target` | `string` | `''` | Where to display the linked `href` URL for a link button. Common options include `_blank` to open in a new tab. |
 | `trailingIcon` | `trailing-icon` | `boolean` | `false` | Whether to render the icon at the inline end of the label rather than the inline start.<br>_Note:_ Link buttons cannot have trailing icons. |

docs/components/icon-button.md

@@ -182,6 +182,28 @@ attribute to icon buttons whose labels need a more descriptive label.
 </md-icon-button>
 ```
 
+### Focusable and disabled
+
+By default, disabled icon buttons are not focusable with the keyboard, while
+soft-disabled icon buttons are. Some use cases encourage focusability of
+disabled toolbar items to increase their discoverability.
+
+See the
+[ARIA guidelines on focusability of disabled controls](https://www.w3.org/WAI/ARIA/apg/practices/keyboard-interface/#kbd_disabled_controls)<!-- {.external} -->
+for guidance on when this is recommended.
+
+```html
+<div role="toolbar">
+  <md-icon-button><md-icon>copy</md-icon></md-icon-button>
+  <md-icon-button><md-icon>cut</md-icon></md-icon-button>
+  <!--
+    This icon button is disabled but kept focusable to improve its
+    discoverability in the toolbar.
+  -->
+  <md-icon-button soft-disabled><md-icon>paste</md-icon></md-icon-button>
+</div>
+```
+
 ### Toggle
 
 Add an `aria-label-selected` attribute to toggle buttons whose labels need a
@@ -319,7 +341,7 @@ Token                                | Default value
 ### Filled Icon Button tokens
 
 Token                                              | Default value
--------------------------------------------------- | ------------------------
+-------------------------------------------------- | -------------
 `--md-filled-icon-button-selected-container-color` | `--md-sys-color-primary`
 `--md-filled-icon-button-container-shape`          | `--md-sys-shape-corner-full`
 `--md-filled-icon-button-container-width`          | `40px`
@@ -391,7 +413,7 @@ Token                                                    | Default value
 ### Outlined Icon Button tokens
 
 Token                                        | Default value
--------------------------------------------- | ------------------------
+-------------------------------------------- | ----------------------------
 `--md-outlined-icon-button-outline-color`    | `--md-sys-color-outline`
 `--md-outlined-icon-button-outline-width`    | `1px`
 `--md-outlined-icon-button-container-shape`  | `--md-sys-shape-corner-full`
@@ -428,7 +450,6 @@ Token                                        | Default value
 
 ## API
 
-
 ### MdIconButton <code>&lt;md-icon-button&gt;</code>
 
 #### Properties
@@ -472,6 +493,7 @@ Token                                        | Default value
 | Property | Attribute | Type | Default | Description |
 | --- | --- | --- | --- | --- |
 | `disabled` | `disabled` | `boolean` | `false` | Disables the icon button and makes it non-interactive. |
+| `softDisabled` | `soft-disabled` | `boolean` | `false` | "Soft-disables" the icon button (disabled but still focusable). |
 | `flipIconInRtl` | `flip-icon-in-rtl` | `boolean` | `false` | Flips the icon if it is in an RTL context at startup. |
 | `href` | `href` | `string` | `''` | Sets the underlying `HTMLAnchorElement`'s `href` resource attribute. |
 | `target` | `target` | `string` | `''` | Sets the underlying `HTMLAnchorElement`'s `target` attribute. |