feat(cdk-experimental/ui-patterns): listbox ui pattern (#30495)

* feat(cdk-experimental/ui-patterns): listbox ui pattern

* refactor(cdk-experimental/ui-patterns): remove controllers & lazy-loading

* refactor: event managers

* fixup! refactor: event managers

* fixup! feat(cdk-experimental/ui-patterns): listbox ui pattern

* fixup! feat(cdk-experimental/ui-patterns): listbox ui pattern

* fixup! feat(cdk-experimental/ui-patterns): listbox ui pattern

* fixup! feat(cdk-experimental/ui-patterns): listbox ui pattern

* fixup! feat(cdk-experimental/ui-patterns): listbox ui pattern

* fixup! feat(cdk-experimental/ui-patterns): listbox ui pattern

* fixup! feat(cdk-experimental/ui-patterns): listbox ui pattern

---------

Co-authored-by: Jeremy Elbourn <jelbourn@google.com>

.ng-dev/commit-message.mts

@@ -11,10 +11,12 @@ export const commitMessage: CommitMessageConfig = {
     'multiple', // For when a commit applies to multiple components.
     'cdk-experimental/column-resize',
     'cdk-experimental/combobox',
+    'cdk-experimental/listbox',
     'cdk-experimental/popover-edit',
     'cdk-experimental/scrolling',
     'cdk-experimental/selection',
     'cdk-experimental/table-scroll-container',
+    'cdk-experimental/ui-patterns',
     'cdk/a11y',
     'cdk/accordion',
     'cdk/bidi',

src/cdk-experimental/config.bzl

@@ -2,10 +2,12 @@
 CDK_EXPERIMENTAL_ENTRYPOINTS = [
     "column-resize",
     "combobox",
+    "listbox",
     "popover-edit",
     "scrolling",
     "selection",
     "table-scroll-container",
+    "ui-patterns",
 ]
 
 # List of all entry-point targets of the Angular cdk-experimental package.

src/cdk-experimental/listbox/BUILD.bazel

@@ -0,0 +1,16 @@
+load("//tools:defaults.bzl", "ng_module")
+
+package(default_visibility = ["//visibility:public"])
+
+ng_module(
+    name = "listbox",
+    srcs = glob(
+        ["**/*.ts"],
+        exclude = ["**/*.spec.ts"],
+    ),
+    deps = [
+        "//src/cdk-experimental/ui-patterns",
+        "//src/cdk/a11y",
+        "//src/cdk/bidi",
+    ],
+)

src/cdk-experimental/listbox/index.ts

@@ -0,0 +1,9 @@
+/**
+ * @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.dev/license
+ */
+
+export * from './public-api';

src/cdk-experimental/listbox/listbox.ts

@@ -0,0 +1,158 @@
+/**
+ * @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.dev/license
+ */
+
+import {
+  booleanAttribute,
+  computed,
+  contentChildren,
+  Directive,
+  ElementRef,
+  inject,
+  input,
+  model,
+} from '@angular/core';
+import {ListboxPattern, OptionPattern} from '@angular/cdk-experimental/ui-patterns';
+import {Directionality} from '@angular/cdk/bidi';
+import {toSignal} from '@angular/core/rxjs-interop';
+import {_IdGenerator} from '@angular/cdk/a11y';
+
+/**
+ * A listbox container.
+ *
+ * Listboxes are used to display a list of items for a user to select from. The CdkListbox is meant
+ * to be used in conjunction with CdkOption as follows:
+ *
+ * ```html
+ * <ul cdkListbox>
+ *   <li cdkOption>Item 1</li>
+ *   <li cdkOption>Item 2</li>
+ *   <li cdkOption>Item 3</li>
+ * </ul>
+ * ```
+ */
+@Directive({
+  selector: '[cdkListbox]',
+  exportAs: 'cdkListbox',
+  host: {
+    'role': 'listbox',
+    'class': 'cdk-listbox',
+    '[attr.tabindex]': 'pattern.tabindex()',
+    '[attr.aria-disabled]': 'pattern.disabled()',
+    '[attr.aria-orientation]': 'pattern.orientation()',
+    '[attr.aria-multiselectable]': 'pattern.multiselectable()',
+    '[attr.aria-activedescendant]': 'pattern.activedescendant()',
+    '(keydown)': 'pattern.onKeydown($event)',
+    '(pointerdown)': 'pattern.onPointerdown($event)',
+  },
+})
+export class CdkListbox {
+  /** The directionality (LTR / RTL) context for the application (or a subtree of it). */
+  private readonly _directionality = inject(Directionality);
+
+  /** The CdkOptions nested inside of the CdkListbox. */
+  private readonly _cdkOptions = contentChildren(CdkOption, {descendants: true});
+
+  /** A signal wrapper for directionality. */
+  protected textDirection = toSignal(this._directionality.change, {
+    initialValue: this._directionality.value,
+  });
+
+  /** The Option UIPatterns of the child CdkOptions. */
+  protected items = computed(() => this._cdkOptions().map(option => option.pattern));
+
+  /** Whether the list is vertically or horizontally oriented. */
+  orientation = input<'vertical' | 'horizontal'>('vertical');
+
+  /** Whether multiple items in the list can be selected at once. */
+  multiselectable = input(false, {transform: booleanAttribute});
+
+  /** Whether focus should wrap when navigating. */
+  wrap = input(true, {transform: booleanAttribute});
+
+  /** Whether disabled items in the list should be skipped when navigating. */
+  skipDisabled = input(true, {transform: booleanAttribute});
+
+  /** The focus strategy used by the list. */
+  focusMode = input<'roving' | 'activedescendant'>('roving');
+
+  /** The selection strategy used by the list. */
+  selectionMode = input<'follow' | 'explicit'>('follow');
+
+  /** The amount of time before the typeahead search is reset. */
+  typeaheadDelay = input<number>(0.5); // Picked arbitrarily.
+
+  /** Whether the listbox is disabled. */
+  disabled = input(false, {transform: booleanAttribute});
+
+  // TODO(wagnermaciel): Figure out how we want to expose control over the current listbox value.
+  /** The ids of the current selected items. */
+  selectedIds = model<string[]>([]);
+
+  /** The current index that has been navigated to. */
+  activeIndex = model<number>(0);
+
+  /** The Listbox UIPattern. */
+  pattern: ListboxPattern = new ListboxPattern({
+    ...this,
+    items: this.items,
+    textDirection: this.textDirection,
+  });
+}
+
+/** A selectable option in a CdkListbox. */
+@Directive({
+  selector: '[cdkOption]',
+  exportAs: 'cdkOption',
+  host: {
+    'role': 'option',
+    'class': 'cdk-option',
+    '[attr.tabindex]': 'pattern.tabindex()',
+    '[attr.aria-selected]': 'pattern.selected()',
+    '[attr.aria-disabled]': 'pattern.disabled()',
+  },
+})
+export class CdkOption {
+  /** A reference to the option element. */
+  private readonly _elementRef = inject(ElementRef);
+
+  /** The parent CdkListbox. */
+  private readonly _cdkListbox = inject(CdkListbox);
+
+  /** A unique identifier for the option. */
+  private readonly _generatedId = inject(_IdGenerator).getId('cdk-option-');
+
+  // TODO(wagnermaciel): https://github.com/angular/components/pull/30495#discussion_r1972601144.
+  /** A unique identifier for the option. */
+  protected id = computed(() => this._generatedId);
+
+  // TODO(wagnermaciel): See if we want to change how we handle this since textContent is not
+  // reactive. See https://github.com/angular/components/pull/30495#discussion_r1961260216.
+  /** The text used by the typeahead search. */
+  protected searchTerm = computed(() => this.label() ?? this.element().textContent);
+
+  /** The parent Listbox UIPattern. */
+  protected listbox = computed(() => this._cdkListbox.pattern);
+
+  /** A reference to the option element to be focused on navigation. */
+  protected element = computed(() => this._elementRef.nativeElement);
+
+  /** Whether an item is disabled. */
+  disabled = input(false, {transform: booleanAttribute});
+
+  /** The text used by the typeahead search. */
+  label = input<string>();
+
+  /** The Option UIPattern. */
+  pattern = new OptionPattern({
+    ...this,
+    id: this.id,
+    listbox: this.listbox,
+    element: this.element,
+    searchTerm: this.searchTerm,
+  });
+}

src/cdk-experimental/listbox/public-api.ts

@@ -0,0 +1,9 @@
+/**
+ * @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.dev/license
+ */
+
+export {CdkListbox, CdkOption} from './listbox';

src/cdk-experimental/ui-patterns/BUILD.bazel

@@ -0,0 +1,15 @@
+load("//tools:defaults.bzl", "ts_library")
+
+package(default_visibility = ["//visibility:public"])
+
+ts_library(
+    name = "ui-patterns",
+    srcs = glob(
+        ["**/*.ts"],
+        exclude = ["**/*.spec.ts"],
+    ),
+    deps = [
+        "//src/cdk-experimental/ui-patterns/listbox",
+        "@npm//@angular/core",
+    ],
+)

src/cdk-experimental/ui-patterns/behaviors/event-manager/BUILD.bazel

@@ -0,0 +1,12 @@
+load("//tools:defaults.bzl", "ts_library")
+
+package(default_visibility = ["//visibility:public"])
+
+ts_library(
+    name = "event-manager",
+    srcs = glob(
+        ["**/*.ts"],
+        exclude = ["**/*.spec.ts"],
+    ),
+    deps = ["@npm//@angular/core"],
+)

src/cdk-experimental/ui-patterns/behaviors/event-manager/event-manager.ts

@@ -0,0 +1,103 @@
+/**
+ * @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.dev/license
+ */
+
+/**
+ * An event that supports modifier keys.
+ *
+ * Matches the native KeyboardEvent, MouseEvent, and TouchEvent.
+ */
+export interface EventWithModifiers extends Event {
+  ctrlKey: boolean;
+  shiftKey: boolean;
+  altKey: boolean;
+  metaKey: boolean;
+}
+
+/**
+ * Options that are applicable to all event handlers.
+ *
+ * This library has not yet had a need for stopPropagationImmediate.
+ */
+export interface EventHandlerOptions {
+  stopPropagation: boolean;
+  preventDefault: boolean;
+}
+
+/** A basic event handler. */
+export type EventHandler<T extends Event> = (event: T) => void;
+
+/** A function that determines whether an event is to be handled. */
+export type EventMatcher<T extends Event> = (event: T) => boolean;
+
+/** A config that specifies how to handle a particular event. */
+export interface EventHandlerConfig<T extends Event> extends EventHandlerOptions {
+  matcher: EventMatcher<T>;
+  handler: EventHandler<T>;
+}
+
+/** Bit flag representation of the possible modifier keys that can be present on an event. */
+export enum ModifierKey {
+  None = 0,
+  Ctrl = 0b1,
+  Shift = 0b10,
+  Alt = 0b100,
+  Meta = 0b1000,
+}
+
+export type ModifierInputs = ModifierKey | ModifierKey[];
+
+/**
+ * Abstract base class for all event managers.
+ *
+ * Event managers are designed to normalize how event handlers are authored and create a safety net
+ * for common event handling gotchas like remembering to call preventDefault or stopPropagation.
+ */
+export abstract class EventManager<T extends Event> {
+  protected configs: EventHandlerConfig<T>[] = [];
+  abstract options: EventHandlerOptions;
+
+  /** Runs the handlers that match with the given event. */
+  handle(event: T): void {
+    for (const config of this.configs) {
+      if (config.matcher(event)) {
+        config.handler(event);
+
+        if (config.preventDefault) {
+          event.preventDefault();
+        }
+
+        if (config.stopPropagation) {
+          event.stopPropagation();
+        }
+      }
+    }
+  }
+
+  /** Configures the event manager to handle specific events. (See subclasses for more). */
+  abstract on(...args: [...unknown[]]): this;
+}
+
+/** Gets bit flag representation of the modifier keys present on the given event. */
+export function getModifiers(event: EventWithModifiers): number {
+  return (
+    (+event.ctrlKey && ModifierKey.Ctrl) |
+    (+event.shiftKey && ModifierKey.Shift) |
+    (+event.altKey && ModifierKey.Alt) |
+    (+event.metaKey && ModifierKey.Meta)
+  );
+}
+
+/**
+ * Checks if the given event has modifiers that are an exact match for any of the given modifier
+ * flag combinations.
+ */
+export function hasModifiers(event: EventWithModifiers, modifiers: ModifierInputs): boolean {
+  const eventModifiers = getModifiers(event);
+  const modifiersList = Array.isArray(modifiers) ? modifiers : [modifiers];
+  return modifiersList.some(modifiers => eventModifiers === modifiers);
+}