feat(badge): allow badge to be disabled (#13196)

Adds the `matBadgeDisabled` input that allows for a badge to be styled as if it was disabled. This allows it to blend in when it's attached to an element that is also disabled.

Fixes #13191.

src/demo-app/badge/badge-demo.html

@@ -48,6 +48,14 @@
       <mat-icon color="primary">home</mat-icon>
     </button>
 
+    <button mat-raised-button [matBadge]="badgeContent" matBadgeDisabled>
+      <mat-icon color="primary">home</mat-icon>
+    </button>
+
+    <button disabled mat-raised-button [matBadge]="badgeContent" matBadgeDisabled>
+      <mat-icon color="primary">home</mat-icon>
+    </button>
+
     <button mat-raised-button matBadge="22" matBadgePosition="below before">
       <mat-icon color="primary">home</mat-icon>
     </button>

src/lib/badge/_badge-theme.scss

@@ -96,6 +96,8 @@ $mat-badge-large-size: $mat-badge-default-size + 6;
   $accent: map-get($theme, accent);
   $warn: map-get($theme, warn);
   $primary: map-get($theme, primary);
+  $background: map-get($theme, background);
+  $foreground: map-get($theme, foreground);
 
   .mat-badge-content {
     color: mat-color($primary, default-contrast);
@@ -126,6 +128,20 @@ $mat-badge-large-size: $mat-badge-default-size + 6;
     }
   }
 
+  .mat-badge-disabled {
+    .mat-badge-content {
+      // The disabled color usually has some kind of opacity, but because the badge is overlayed
+      // on top of something else, it won't look good if it's opaque. We convert it into a solid
+      // color by taking the opacity from the rgba value and using the value to determine the
+      // percentage of the background to put into foreground when mixing the colors together.
+      $app-background: mat-color($background, 'background');
+      $badge-color: mat-color($foreground, disabled-button);
+      $badge-opacity: opacity($badge-color);
+      background: mix($app-background, rgba($badge-color, 1), (1 - $badge-opacity) * 100%);
+      color: mat-color($foreground, disabled-text);
+    }
+  }
+
   .mat-badge-content {
     position: absolute;
     text-align: center;

src/lib/badge/badge.spec.ts

@@ -154,6 +154,17 @@ describe('MatBadge', () => {
     expect(encapsulationAttr).toBeTruthy();
   });
 
+  it('should toggle a class depending on the badge disabled state', () => {
+    const element: HTMLElement = badgeDebugElement.nativeElement;
+
+    expect(element.classList).not.toContain('mat-badge-disabled');
+
+    testComponent.badgeDisabled = true;
+    fixture.detectChanges();
+
+    expect(element.classList).toContain('mat-badge-disabled');
+  });
+
 });
 
 /** Test component that contains a MatBadge. */
@@ -168,7 +179,8 @@ describe('MatBadge', () => {
           [matBadgeHidden]="badgeHidden"
           [matBadgeSize]="badgeSize"
           [matBadgeOverlap]="badgeOverlap"
-          [matBadgeDescription]="badgeDescription">
+          [matBadgeDescription]="badgeDescription"
+          [matBadgeDisabled]="badgeDisabled">
       home
     </span>
   `
@@ -181,4 +193,5 @@ class BadgeTestApp {
   badgeSize = 'medium';
   badgeOverlap = false;
   badgeDescription: string;
+  badgeDisabled = false;
 }

src/lib/badge/badge.ts

@@ -19,17 +19,25 @@ import {
   Optional,
   Renderer2,
 } from '@angular/core';
-import {ThemePalette} from '@angular/material/core';
+import {ThemePalette, mixinDisabled, CanDisableCtor, CanDisable} from '@angular/material/core';
 
 
 let nextId = 0;
 
+// Boilerplate for applying mixins to MatBadge.
+/** @docs-private */
+export class MatBadgeBase {}
+
+export const _MatBadgeMixinBase:
+    CanDisableCtor & typeof MatBadgeBase = mixinDisabled(MatBadgeBase);
+
 export type MatBadgePosition = 'above after' | 'above before' | 'below before' | 'below after';
 export type MatBadgeSize = 'small' | 'medium' | 'large';
 
 /** Directive to display a text badge. */
 @Directive({
   selector: '[matBadge]',
+  inputs: ['disabled: matBadgeDisabled'],
   host: {
     'class': 'mat-badge',
     '[class.mat-badge-overlap]': 'overlap',
@@ -41,9 +49,10 @@ export type MatBadgeSize = 'small' | 'medium' | 'large';
     '[class.mat-badge-medium]': 'size === "medium"',
     '[class.mat-badge-large]': 'size === "large"',
     '[class.mat-badge-hidden]': 'hidden || !_hasContent',
+    '[class.mat-badge-disabled]': 'disabled',
   },
 })
-export class MatBadge implements OnDestroy {
+export class MatBadge extends _MatBadgeMixinBase implements OnDestroy, CanDisable {
   /** Whether the badge has any content. */
   _hasContent = false;
 
@@ -113,7 +122,9 @@ export class MatBadge implements OnDestroy {
       private _elementRef: ElementRef<HTMLElement>,
       private _ariaDescriber: AriaDescriber,
       /** @breaking-change 8.0.0 Make _renderer a required param and remove _document. */
-      private _renderer?: Renderer2) {}
+      private _renderer?: Renderer2) {
+        super();
+      }
 
   /** Whether the badge is above the host or not */
   isAbove(): boolean {