Class TreePattern

src/aria/private/tree/tree.ts:150–488

/** Controls the state and interactions of a tree view. */
export class TreePattern<V> implements TreeInputs<V> {
  /** The tree behavior for the tree. */
  readonly treeBehavior: Tree<TreeItemPattern<V>, V>;

  /** Whether the tree has been interacted with. */
  readonly hasBeenInteracted = signal(false);

  /** The root level is 0. */
  readonly level = () => 0;

  /** The root is always expanded. */
  readonly expanded = () => true;

  /** The root is always visible. */
  readonly visible = () => true;

  /** The tab index of the tree. */
  readonly tabIndex: SignalLike<-1 | 0> = computed(() => this.treeBehavior.tabIndex());

  /** The id of the current active item. */
  readonly activeDescendant = computed(() => this.treeBehavior.activeDescendant());

  /** The direct children of the root (top-level tree items). */
  readonly children = computed(() =>
    this.inputs.items().filter(item => item.level() === this.level() + 1),
  );

  /** Whether the tree selection follows focus. */
  readonly followFocus = computed(() => this.inputs.selectionMode() === 'follow');

  /** Whether the tree direction is RTL. */
  readonly isRtl = computed(() => this.textDirection() === 'rtl');

  /** The key for navigating to the previous item. */
  readonly prevKey = computed(() => {
    if (this.inputs.orientation() === 'vertical') {
      return 'ArrowUp';
    }
    return this.isRtl() ? 'ArrowRight' : 'ArrowLeft';
  });

  /** The key for navigating to the next item. */
  readonly nextKey = computed(() => {
    if (this.inputs.orientation() === 'vertical') {
      return 'ArrowDown';
    }
    return this.isRtl() ? 'ArrowLeft' : 'ArrowRight';
  });

  /** The key for collapsing an item or moving to its parent. */
  readonly collapseKey = computed(() => {
    if (this.inputs.orientation() === 'horizontal') {
      return 'ArrowUp';
    }
    return this.isRtl() ? 'ArrowRight' : 'ArrowLeft';
  });

  /** The key for expanding an item or moving to its first child. */