[CL-427] Add skeleton loading components to the CL

apps/browser/src/platform/popup/layout/popup-layout.stories.ts

@@ -29,6 +29,9 @@ import {
   SearchModule,
   SectionComponent,
   ScrollLayoutDirective,
+  SkeletonComponent,
+  SkeletonTextComponent,
+  SkeletonGroupComponent,
 } from "@bitwarden/components";
 
 import { PopupRouterCacheService } from "../view-cache/popup-router-cache.service";
@@ -335,6 +338,9 @@ export default {
         SectionComponent,
         IconButtonModule,
         BadgeModule,
+        SkeletonComponent,
+        SkeletonTextComponent,
+        SkeletonGroupComponent,
       ],
       providers: [
         {
@@ -594,6 +600,34 @@ export const Loading: Story = {
   }),
 };
 
+export const SkeletonLoading: Story = {
+  render: (args) => ({
+    props: { ...args, data: Array(8) },
+    template: /* HTML */ `
+      <extension-container>
+        <popup-tab-navigation>
+          <popup-page>
+            <popup-header slot="header" pageTitle="Page Header"></popup-header>
+            <div>
+              <div class="tw-sr-only" role="status">Loading...</div>
+              <div class="tw-flex tw-flex-col tw-gap-4">
+                <bit-skeleton-text class="tw-w-1/3"></bit-skeleton-text>
+                @for (num of data; track $index) {
+                <bit-skeleton-group>
+                  <bit-skeleton class="tw-size-8" slot="start"></bit-skeleton>
+                  <bit-skeleton-text [lines]="2" class="tw-w-1/2"></bit-skeleton-text>
+                </bit-skeleton-group>
+                <bit-skeleton class="tw-w-full tw-h-[1px]"></bit-skeleton>
+                }
+              </div>
+            </div>
+          </popup-page>
+        </popup-tab-navigation>
+      </extension-container>
+    `,
+  }),
+};
+
 export const TransparentHeader: Story = {
   render: (args) => ({
     props: args,

libs/components/src/index.ts

@@ -36,6 +36,7 @@ export * from "./search";
 export * from "./section";
 export * from "./select";
 export * from "./shared/compact-mode.service";
+export * from "./skeleton";
 export * from "./table";
 export * from "./tabs";
 export * from "./toast";

libs/components/src/skeleton/index.ts

@@ -0,0 +1,3 @@
+export * from "./skeleton.component";
+export * from "./skeleton-text.component";
+export * from "./skeleton-group.component";

libs/components/src/skeleton/skeleton-group.component.html

@@ -0,0 +1,7 @@
+<div class="tw-flex tw-flex-row tw-justify-between tw-gap-2">
+  <div class="tw-flex tw-gap-2 tw-w-full">
+    <ng-content select="[slot=start]"></ng-content>
+    <ng-content></ng-content>
+  </div>
+  <ng-content select="[slot=end]"></ng-content>
+</div>

libs/components/src/skeleton/skeleton-group.component.ts

@@ -0,0 +1,18 @@
+import { CommonModule } from "@angular/common";
+import { Component } from "@angular/core";
+
+/**
+ * Arranges skeleton loaders into a pre-arranged group that mimics the table and item components.
+ *
+ * Pass skeleton loaders into the start, default, and end content slots. The content within each slot
+ * is fully customizable.
+ */
+@Component({
+  selector: "bit-skeleton-group",
+  templateUrl: "./skeleton-group.component.html",
+  imports: [CommonModule],
+  host: {
+    class: "tw-block",
+  },
+})
+export class SkeletonGroupComponent {}

libs/components/src/skeleton/skeleton-group.stories.ts

@@ -0,0 +1,73 @@
+import { Meta, moduleMetadata, StoryObj } from "@storybook/angular";
+
+import { SharedModule } from "../shared/shared.module";
+
+import { SkeletonGroupComponent } from "./skeleton-group.component";
+import { SkeletonTextComponent } from "./skeleton-text.component";
+import { SkeletonComponent } from "./skeleton.component";
+
+export default {
+  title: "Component Library/Skeleton/Skeleton Group",
+  component: SkeletonGroupComponent,
+  decorators: [
+    moduleMetadata({
+      imports: [SharedModule, SkeletonTextComponent, SkeletonComponent],
+    }),
+  ],
+} as Meta<SkeletonGroupComponent>;
+
+type Story = StoryObj<SkeletonGroupComponent>;
+
+export const Default: Story = {
+  render: (args) => ({
+    props: args,
+    template: /*html*/ `
+      <bit-skeleton-group>
+        <bit-skeleton class="tw-size-8" slot="start"></bit-skeleton>
+        <bit-skeleton-text [lines]="2" class="tw-w-1/2"></bit-skeleton-text>
+        <bit-skeleton-text [lines]="1" slot="end" class="tw-w-1/4"></bit-skeleton-text>
+      </bit-skeleton-group>
+    `,
+  }),
+};
+
+export const NoEndSlot: Story = {
+  render: (args) => ({
+    props: args,
+    template: /*html*/ `
+      <bit-skeleton-group>
+        <bit-skeleton class="tw-size-8" slot="start"></bit-skeleton>
+        <bit-skeleton-text [lines]="2" class="tw-w-1/2"></bit-skeleton-text>
+      </bit-skeleton-group>
+    `,
+  }),
+};
+
+export const NoStartSlot: Story = {
+  render: (args) => ({
+    props: args,
+    template: /*html*/ `
+      <bit-skeleton-group>
+        <bit-skeleton-text [lines]="2" class="tw-w-1/2"></bit-skeleton-text>
+        <bit-skeleton-text [lines]="1" slot="end" class="tw-w-1/4"></bit-skeleton-text>
+      </bit-skeleton-group>
+    `,
+  }),
+};
+
+export const CustomContent: Story = {
+  render: (args) => ({
+    props: args,
+    template: /*html*/ `
+      <bit-skeleton-group>
+        <bit-skeleton class="tw-size-12" slot="start" edgeShape="circle"></bit-skeleton>
+        <bit-skeleton-text [lines]="3" class="tw-w-full"></bit-skeleton-text>
+        <div slot="end" class="tw-flex tw-flex-row tw-gap-1">
+          <bit-skeleton class="tw-size-4" slot="start"></bit-skeleton>
+          <bit-skeleton class="tw-size-4" slot="start"></bit-skeleton>
+          <bit-skeleton class="tw-size-4" slot="start"></bit-skeleton>
+        </div>
+      </bit-skeleton-group>
+    `,
+  }),
+};

libs/components/src/skeleton/skeleton-text.component.html

@@ -0,0 +1,12 @@
+<div class="tw-w-full tw-flex tw-flex-col tw-gap-2">
+  @for (line of this.linesArray(); track $index; let last = $last, first = $first) {
+    <bit-skeleton
+      edgeShape="circle"
+      class="tw-h-3"
+      [ngClass]="{
+        'tw-w-full': first || !last,
+        'tw-w-1/3': !first && last,
+      }"
+    ></bit-skeleton>
+  }
+</div>

libs/components/src/skeleton/skeleton-text.component.ts

@@ -0,0 +1,31 @@
+import { CommonModule } from "@angular/common";
+import { Component, computed, input } from "@angular/core";
+
+import { SkeletonComponent } from "./skeleton.component";
+
+/**
+ * Specific skeleton component used to represent lines of text. It uses the `bit-skeleton`
+ * under the hood.
+ *
+ * Customize the number of lines represented with the `lines` input. Customize the width
+ * by applying a class to the `bit-skeleton-text` element (i.e. `tw-w-1/2`).
+ */
+@Component({
+  selector: "bit-skeleton-text",
+  templateUrl: "./skeleton-text.component.html",
+  imports: [CommonModule, SkeletonComponent],
+  host: {
+    class: "tw-block",
+  },
+})
+export class SkeletonTextComponent {
+  /**
+   * The number of text lines to display
+   */
+  readonly lines = input<number>(1);
+
+  /**
+   * Array-transformed version of the `lines` to loop over
+   */
+  protected linesArray = computed(() => Array.from(Array(this.lines()).keys()));
+}

libs/components/src/skeleton/skeleton-text.stories.ts

@@ -0,0 +1,46 @@
+import { Meta, moduleMetadata, StoryObj } from "@storybook/angular";
+
+import { SharedModule } from "../shared/shared.module";
+
+import { SkeletonTextComponent } from "./skeleton-text.component";
+
+export default {
+  title: "Component Library/Skeleton/Skeleton Text",
+  component: SkeletonTextComponent,
+  decorators: [
+    moduleMetadata({
+      imports: [SharedModule],
+    }),
+  ],
+  args: {
+    lines: 1,
+  },
+  argTypes: {
+    lines: {
+      control: { type: "number", min: 1 },
+    },
+  },
+} as Meta<SkeletonTextComponent>;
+
+type Story = StoryObj<SkeletonTextComponent>;
+
+export const Text: Story = {
+  render: (args) => ({
+    props: args,
+    template: /*html*/ `
+      <bit-skeleton-text [lines]="lines"></bit-skeleton-text>
+    `,
+  }),
+};
+
+export const TextMultiline: Story = {
+  render: (args) => ({
+    props: args,
+    template: /*html*/ `
+      <bit-skeleton-text [lines]="lines"></bit-skeleton-text>
+    `,
+  }),
+  args: {
+    lines: 5,
+  },
+};

libs/components/src/skeleton/skeleton.component.html

@@ -0,0 +1,8 @@
+<div
+  class="tw-size-full tw-bg-secondary-100 tw-animate-pulse"
+  [ngClass]="{
+    'tw-rounded': edgeShape() === 'box',
+    'tw-rounded-full': edgeShape() === 'circle',
+  }"
+  aria-hidden="true"
+></div>

libs/components/src/skeleton/skeleton.component.ts

@@ -0,0 +1,26 @@
+import { CommonModule } from "@angular/common";
+import { Component, input } from "@angular/core";
+
+/**
+ * Basic skeleton loading component that can be used to represent content that is loading.
+ * Use for layout-level elements and text, not for interactive elements.
+ *
+ * Customize the shape's edges with the `edgeShape` input. Customize the shape's size by
+ * applying classes to the `bit-skeleton` element (i.e. `tw-w-40 tw-h-8`).
+ *
+ * If you're looking to represent lines of text, use the `bit-skeleton-text` helper component.
+ */
+@Component({
+  selector: "bit-skeleton",
+  templateUrl: "./skeleton.component.html",
+  imports: [CommonModule],
+  host: {
+    class: "tw-block",
+  },
+})
+export class SkeletonComponent {
+  /**
+   * The shape of the corners of the skeleton element
+   */
+  readonly edgeShape = input<"box" | "circle">("box");
+}

libs/components/src/skeleton/skeleton.mdx

@@ -0,0 +1,74 @@
+import { Meta, Canvas, Source } from "@storybook/addon-docs";
+
+import * as skeletonStories from "./skeleton.stories";
+import * as skeletonTextStories from "./skeleton-text.stories";
+import * as skeletonGroupStories from "./skeleton-group.stories";
+
+<Meta title="Component Library/Skeleton" />
+
+# Skeleton Loading
+
+The skeleton component can be used as an alternative loading indicator to the spinner by mimicking
+the content that will be loaded such as text, images, or video. It can be used to represent layout
+components as well, but should not be used for interactive elements like form controls or buttons.
+
+## Skeleton Loading Components
+
+There are three components that can be used to create a skeleton loading page.
+
+### Skeleton
+
+Basic skeleton loading component that can be used to represent content that is loading. The shape of
+the edges is configurable to be either squared or round. Use for non-text shapes.
+
+<Canvas of={skeletonStories.Square} />
+<Canvas of={skeletonStories.Circle} />
+
+### Skeleton Text
+
+Specific skeleton component used to represent lines of text. The number of lines is configurable.
+
+<Canvas of={skeletonTextStories.Text} />
+<Canvas of={skeletonTextStories.TextMultiline} />
+
+### Skeleton Group
+
+Arranges skeleton loaders into a pre-arranged group that mimics the table and item components. It
+uses start, default, and end slots to allow any skeleton content to be rendered.
+
+<Canvas of={skeletonGroupStories.Default} />
+
+## Display Considerations
+
+For pages that load quickly, we want to avoid the skeleton flashing in and out. To avoid this, we
+recommend the following display guidelines:
+
+- After the loading is initiated (by page load or by user action), wait 1 second to display the
+  skeleton loader.
+- After waiting 1s, render the loading skeleton.
+- Ideally the skeleton disappears after 10 seconds, but we do not enforce a max duration. Add a max
+  duration at your discretion.
+
+## Accessibility
+
+Because there are typically multiple skeleton loaders present on a page that is using skeleton
+loading, the individual skeleton loaders should not announce themselves or be present to
+screenreaders, as this would overwhelm the user with multiple identical announcements. Thus, the
+skeleton components are hidden from screenreaders.
+
+Instead, the recommended strategy is to use a page-level announcement for screenreaders:
+
+- We recommend using the
+  [Angular CDK LiveAnnouncer](https://material.angular.dev/cdk/a11y/overview#liveannouncer) to first
+  announce that content is loading when the skeleton loader is displayed, and then to announce that
+  content has loaded. The announcements should be localized, and the politeness level should be set
+  to `polite`.
+
+- Alternatively, you may wish to render your own `role="status"` element or a custom `aria-live`
+  region in the template to accomplish the announcements detailed above.
+
+## Example with Browser Extension
+
+To see a full-page example of what skeleton loading might look like using all three skeleton
+components, check the
+[Popup Layout Skeleton Loading story](?path=/docs/browser-popup-layout--skeleton-loading).