|
| 1 | +# UI Patterns |
| 2 | + |
| 3 | +## Conceptual Description |
| 4 | + |
| 5 | +Accessibility patterns are established, reusable solutions for creating accessible web content and |
| 6 | +applications. Some common accessibility patterns include the Tree View, Switch, Listbox, and Grid. |
| 7 | + |
| 8 | +Behaviors are TypeScript classes that encapsulate the common behaviors of Accessibility Patterns. |
| 9 | +Some common behaviors include navigation and selection. |
| 10 | + |
| 11 | +UI Patterns are TypeScript classes that encapsulate Accessibility Patterns. UI Patterns are built |
| 12 | +by utilizing multiple Behavior classes to implement the complete functionality of an Accessibility |
| 13 | +Pattern. |
| 14 | + |
| 15 | +## Authoring Guidelines |
| 16 | + |
| 17 | +### License Header |
| 18 | + |
| 19 | +All .ts files should begin with an @license comment. |
| 20 | + |
| 21 | +```ts |
| 22 | +/** |
| 23 | + * @license |
| 24 | + * Copyright Google LLC All Rights Reserved. |
| 25 | + * |
| 26 | + * Use of this source code is governed by an MIT-style license that can be |
| 27 | + * found in the LICENSE file at https://angular.dev/license |
| 28 | + */ |
| 29 | +``` |
| 30 | + |
| 31 | +### Imports |
| 32 | + |
| 33 | +- Imports should be at the top of the file and kept in alphabetical order. |
| 34 | +- The only allowed external APIs are `signal`, and `computed` from `@angular/core`. |
| 35 | +- All other dependencies must come from inside of the ui-patterns folder. |
| 36 | + |
| 37 | +### Type Definition |
| 38 | + |
| 39 | +Each UI Pattern defines a type for it's constructor arguments. |
| 40 | + |
| 41 | +All inputs must be signals. Inputs must not use the `Signal` or `WritableSignal` types from |
| 42 | +`@angular/core`. Instead, they must use the `SignalLike` and `WritableSignalLike` types from |
| 43 | +`ui-patterns/behaviors/signal-like`. |
| 44 | + |
| 45 | +```ts |
| 46 | +export interface ExampleInputs extends Behavior1Inputs, Behavior2Inputs { |
| 47 | + // Additional inputs. |
| 48 | +} |
| 49 | +``` |
| 50 | + |
| 51 | +### Class Definition |
| 52 | + |
| 53 | +#### How to instantiate Behaviors |
| 54 | + |
| 55 | +All Behaviors are defined as class variables and instantiated in the constructor of the UI Pattern. |
| 56 | + |
| 57 | +#### Core Methods |
| 58 | + |
| 59 | +Each UI Pattern implements the following core methods: |
| 60 | + |
| 61 | +- `validate()` |
| 62 | +- `setDefaultState()` |
| 63 | +- `onKeydown()` |
| 64 | +- `onPointerdown()` |
| 65 | + |
| 66 | +```ts |
| 67 | +// License... |
| 68 | + |
| 69 | +// Imports... |
| 70 | + |
| 71 | +// Type Definition... |
| 72 | + |
| 73 | +export class ExamplePattern { |
| 74 | + /** Controls behavior1 for the accessiblity pattern. */ |
| 75 | + behavior1: Behavior1; |
| 76 | + |
| 77 | + /** Controls behavior2 for the accessiblity pattern. */ |
| 78 | + behavior2: Behavior2; |
| 79 | + |
| 80 | + constructor(inputs: ExampleInputs) { |
| 81 | + this.behavior1 = new Behavior1(inputs); |
| 82 | + this.behavior2 = new Behavior2(inputs); |
| 83 | + } |
| 84 | + |
| 85 | + /** Checks that the internal state of the pattern is valid. */ |
| 86 | + validate(): string[] {} |
| 87 | + |
| 88 | + /** Sets the default initial state of the accessibility pattern. */ |
| 89 | + setDefaultState(): void {} |
| 90 | + |
| 91 | + /** Handles keydown events for the accessibility pattern. */ |
| 92 | + onKeydown(event: KeyboardEvent) {} |
| 93 | + |
| 94 | + /** Handles pointer events for the accessibility pattern. */ |
| 95 | + onPointerdown(event: PointerEvent) {} |
| 96 | +} |
| 97 | +``` |
| 98 | + |
| 99 | +#### Event Handlers |
| 100 | + |
| 101 | +Event handlers for UI Patterns are authored utilizing the EventManager system from |
| 102 | +`ui-patterns/behaviors/event-manager`. The event-manager system exposes two primary event manager |
| 103 | +classes: `KeyboardEventManager` and `PointerEventManager`. |
| 104 | + |
| 105 | +```ts |
| 106 | +// License... |
| 107 | + |
| 108 | +// Imports... |
| 109 | + |
| 110 | +// Type Definition... |
| 111 | + |
| 112 | +export class ExamplePattern { |
| 113 | + // Behaviors... |
| 114 | + |
| 115 | + /** The keydown event manager for the accessibility pattern. */ |
| 116 | + keydown = computed(() => { |
| 117 | + return new KeyboardEventManager() |
| 118 | + .on('ArrowUp', () => { /* Arrow up logic. */ }) |
| 119 | + .on('ArrowDown', () => { /* Arrow down logic. */ }); |
| 120 | + }); |
| 121 | + |
| 122 | + /** The pointerdown event manager for the listbox. */ |
| 123 | + pointerdown = computed(() => { |
| 124 | + return new PointerEventManager().on(() => {/* Pointerdown logic. */}); |
| 125 | + }); |
| 126 | + |
| 127 | + // Constructor... |
| 128 | + |
| 129 | + // Core Methods... |
| 130 | + |
| 131 | + /** Handles keydown events for the accessibility pattern. */ |
| 132 | + onKeydown(event: KeyboardEvent) { |
| 133 | + this.keydown().handle(event); |
| 134 | + } |
| 135 | + |
| 136 | + /** Handles pointer events for the accessibility pattern. */ |
| 137 | + onPointerdown(event: PointerEvent) { |
| 138 | + this.pointerdown().handle(event); |
| 139 | + } |
| 140 | +} |
| 141 | +``` |
| 142 | + |
| 143 | +##### KeyboardEventManager Expanded |
| 144 | + |
| 145 | +The `KeyboardEventManager` class can accept strings, signals, and regular expressions as keys. |
| 146 | + |
| 147 | +```ts |
| 148 | + /** The key used to navigate to the next item in the list. */ |
| 149 | + nextKey = computed(() => { .. }); |
| 150 | + |
| 151 | + /** The key used to navigate to the next item in the list. */ |
| 152 | + prevKey = computed(() => { ... }); |
| 153 | + |
| 154 | + /** The keydown event manager for the accessibility pattern. */ |
| 155 | + keydown = computed(() => { |
| 156 | + return new KeyboardEventManager() |
| 157 | + .on(prevKey, () => { /* Navigate prev logic. */ }) |
| 158 | + .on(nextKey, () => { /* Navigate next logic. */ }); |
| 159 | + }); |
| 160 | +``` |
| 161 | + |
| 162 | +The `KeyboardEventManager` can also accept a `Modifier` argument for handling modifier keys. |
| 163 | + |
| 164 | +```ts |
| 165 | + /** The keydown event manager for the accessibility pattern. */ |
| 166 | + keydown = computed(() => { |
| 167 | + return new KeyboardEventManager() |
| 168 | + .on(Modifier.Shift, 'ArrowUp', () => { |
| 169 | + /* Arrow up while holding shift logic. */ |
| 170 | + }); |
| 171 | + }); |
| 172 | +``` |
| 173 | + |
| 174 | +The `Modifier` argument can be an array of modifier keys for defining the same behavior with |
| 175 | +multiple different modifier keys. |
| 176 | + |
| 177 | +```ts |
| 178 | + /** The keydown event manager for the accessibility pattern. */ |
| 179 | + keydown = computed(() => { |
| 180 | + return new KeyboardEventManager() |
| 181 | + .on([Modifier.Ctrl, Modifier.Meta], 'ArrowUp', () => { |
| 182 | + /* Arrow up while holding ctrl OR meta logic. */ |
| 183 | + }); |
| 184 | + }); |
| 185 | +``` |
| 186 | + |
| 187 | +Holding multiple `Modifier` keys when performing a keydown event can be represented by using the |
| 188 | +bitwise OR operator. |
| 189 | + |
| 190 | +```ts |
| 191 | + /** The keydown event manager for the accessibility pattern. */ |
| 192 | + keydown = computed(() => { |
| 193 | + return new KeyboardEventManager() |
| 194 | + .on(Modifier.Ctrl | Modifier.Shift, 'ArrowUp', () => { |
| 195 | + /* Arrow up while holding ctrl + shift logic. */ |
| 196 | + }); |
| 197 | + }); |
| 198 | +``` |
| 199 | + |
| 200 | +##### PointerEventManager Expanded |
| 201 | + |
| 202 | +The `PointerEventManager` can also accept a `Modifier` argument for handling modifier keys. |
| 203 | + |
| 204 | +```ts |
| 205 | + /** The pointerdown event manager for the accessibility pattern. */ |
| 206 | + pointerdown = computed(() => { |
| 207 | + return new PointerEventManager() |
| 208 | + .on(Modifier.Shift, (e) => { |
| 209 | + /* Pointerdown while holding shift logic. */ |
| 210 | + }); |
| 211 | + }); |
| 212 | +``` |
| 213 | + |
| 214 | +The `Modifier` argument can be an array of modifier keys for defining the same behavior with |
| 215 | +multiple different modifier keys. |
| 216 | + |
| 217 | +```ts |
| 218 | + /** The pointerdown event manager for the accessibility pattern. */ |
| 219 | + pointerdown = computed(() => { |
| 220 | + return new PointerEventManager() |
| 221 | + .on([Modifier.Ctrl, Modifier.Meta], () => { |
| 222 | + /* Pointerdown while holding ctrl OR meta logic. */ |
| 223 | + }); |
| 224 | + }); |
| 225 | +``` |
| 226 | + |
| 227 | +Holding multiple `Modifier` keys when performing a pointerdown event can be represented by using the |
| 228 | +bitwise OR operator. |
| 229 | + |
| 230 | +```ts |
| 231 | + /** The pointerdown event manager for the accessibility pattern. */ |
| 232 | + pointerdown = computed(() => { |
| 233 | + return new PointerEventManager() |
| 234 | + .on(Modifier.Ctrl | Modifier.Shift, () => { |
| 235 | + /* Pointerdown while holding ctrl + shift logic. */ |
| 236 | + }); |
| 237 | + }); |
| 238 | +``` |
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