refactor(cdk-experimental/ui-patterns): track focus by item not index

src/cdk-experimental/accordion/accordion.ts

@@ -177,9 +177,9 @@ export class CdkAccordionGroup {
   /** The UI pattern instance for this accordion group. */
   readonly pattern: AccordionGroupPattern = new AccordionGroupPattern({
     ...this,
-    // TODO(ok7sai): Consider making `activeIndex` an internal state in the pattern and call
+    // TODO(ok7sai): Consider making `activeItem` an internal state in the pattern and call
     // `setDefaultState` in the CDK.
-    activeIndex: signal(0),
+    activeItem: signal(undefined),
     items: computed(() => this._triggers().map(trigger => trigger.pattern)),
     expandedIds: this.value,
     // TODO(ok7sai): Investigate whether an accordion should support horizontal mode.

src/cdk-experimental/listbox/listbox.ts

@@ -103,7 +103,7 @@ export class CdkListbox<V> {
   pattern: ListboxPattern<V> = new ListboxPattern<V>({
     ...this,
     items: this.items,
-    activeIndex: signal(0), // TODO: Use linkedSignal to ensure this doesn't get fked up.
+    activeItem: signal(undefined),
     textDirection: this.textDirection,
   });
 

src/cdk-experimental/radio-group/radio-group.ts

@@ -129,7 +129,7 @@ export class CdkRadioGroup<V> {
     ...this,
     items: this.items,
     value: this._value,
-    activeIndex: signal(0),
+    activeItem: signal(undefined),
     textDirection: this.textDirection,
   });
 

src/cdk-experimental/tabs/tabs.ts

@@ -173,7 +173,7 @@ export class CdkTabList implements OnInit, OnDestroy {
     ...this,
     items: this.tabs,
     value: this._selection,
-    activeIndex: signal(0),
+    activeItem: signal(undefined),
   });
 
   /** Whether the tree has received focus yet. */

src/cdk-experimental/tree/tree.ts

@@ -126,7 +126,7 @@ export class CdkTree<V> {
     allItems: computed(() =>
       [...this._unorderedItems()].sort(sortDirectives).map(item => item.pattern),
     ),
-    activeIndex: signal(0),
+    activeItem: signal(undefined),
   });
 
   /** Whether the tree has received focus yet. */

src/cdk-experimental/ui-patterns/accordion/accordion.spec.ts

@@ -61,7 +61,7 @@ describe('Accordion Pattern', () => {
     groupInputs = {
       orientation: signal('vertical'),
       textDirection: signal('ltr'),
-      activeIndex: signal(0),
+      activeItem: signal(undefined),
       disabled: signal(false),
       multiExpandable: signal(true),
       items: signal([]),
@@ -104,6 +104,8 @@ describe('Accordion Pattern', () => {
       new AccordionTriggerPattern(triggerInputs[2]),
     ];
 
+    groupPattern.inputs.activeItem.set(triggerPatterns[0]);
+
     // Initiate a list of AccordionPanelPattern.
     panelInputs = [
       {
@@ -167,15 +169,15 @@ describe('Accordion Pattern', () => {
     });
 
     it('navigates to first accordion trigger with home key.', () => {
-      groupInputs.activeIndex.set(2);
+      groupInputs.activeItem.set(groupInputs.items()[2]);
       expect(triggerPatterns[2].active()).toBeTrue();
       triggerPatterns[2].onKeydown(home());
       expect(triggerPatterns[2].active()).toBeFalse();
       expect(triggerPatterns[0].active()).toBeTrue();
     });
 
     it('navigates to last accordion trigger with end key.', () => {
-      groupInputs.activeIndex.set(0);
+      groupInputs.activeItem.set(groupInputs.items()[0]);
       expect(triggerPatterns[0].active()).toBeTrue();
       triggerPatterns[0].onKeydown(end());
       expect(triggerPatterns[0].active()).toBeFalse();
@@ -184,7 +186,7 @@ describe('Accordion Pattern', () => {
 
     describe('Vertical Orientation (orientation=vertical)', () => {
       it('navigates to the next trigger with down key.', () => {
-        groupInputs.activeIndex.set(0);
+        groupInputs.activeItem.set(groupInputs.items()[0]);
         expect(triggerPatterns[0].active()).toBeTrue();
         expect(triggerPatterns[1].active()).toBeFalse();
         triggerPatterns[0].onKeydown(down());
@@ -193,7 +195,7 @@ describe('Accordion Pattern', () => {
       });
 
       it('navigates to the previous trigger with up key.', () => {
-        groupInputs.activeIndex.set(1);
+        groupInputs.activeItem.set(groupInputs.items()[1]);
         expect(triggerPatterns[0].active()).toBeFalse();
         expect(triggerPatterns[1].active()).toBeTrue();
         triggerPatterns[1].onKeydown(up());
@@ -207,7 +209,7 @@ describe('Accordion Pattern', () => {
         });
 
         it('navigates to the last trigger with up key from first trigger.', () => {
-          groupInputs.activeIndex.set(0);
+          groupInputs.activeItem.set(groupInputs.items()[0]);
           expect(triggerPatterns[0].active()).toBeTrue();
           expect(triggerPatterns[2].active()).toBeFalse();
           triggerPatterns[0].onKeydown(up());
@@ -216,7 +218,7 @@ describe('Accordion Pattern', () => {
         });
 
         it('navigates to the first trigger with down key from last trigger.', () => {
-          groupInputs.activeIndex.set(2);
+          groupInputs.activeItem.set(groupInputs.items()[2]);
           expect(triggerPatterns[0].active()).toBeFalse();
           expect(triggerPatterns[2].active()).toBeTrue();
           triggerPatterns[2].onKeydown(down());
@@ -231,14 +233,14 @@ describe('Accordion Pattern', () => {
         });
 
         it('stays on the first trigger with up key from first trigger.', () => {
-          groupInputs.activeIndex.set(0);
+          groupInputs.activeItem.set(groupInputs.items()[0]);
           expect(triggerPatterns[0].active()).toBeTrue();
           triggerPatterns[0].onKeydown(up());
           expect(triggerPatterns[0].active()).toBeTrue();
         });
 
         it('stays on the last trigger with down key from last trigger.', () => {
-          groupInputs.activeIndex.set(2);
+          groupInputs.activeItem.set(groupInputs.items()[2]);
           expect(triggerPatterns[2].active()).toBeTrue();
           triggerPatterns[2].onKeydown(down());
           expect(triggerPatterns[2].active()).toBeTrue();
@@ -252,7 +254,7 @@ describe('Accordion Pattern', () => {
       });
 
       it('navigates to the next trigger with right key.', () => {
-        groupInputs.activeIndex.set(0);
+        groupInputs.activeItem.set(groupInputs.items()[0]);
         expect(triggerPatterns[0].active()).toBeTrue();
         expect(triggerPatterns[1].active()).toBeFalse();
         triggerPatterns[0].onKeydown(right());
@@ -261,7 +263,7 @@ describe('Accordion Pattern', () => {
       });
 
       it('navigates to the previous trigger with left key.', () => {
-        groupInputs.activeIndex.set(1);
+        groupInputs.activeItem.set(groupInputs.items()[1]);
         expect(triggerPatterns[0].active()).toBeFalse();
         expect(triggerPatterns[1].active()).toBeTrue();
         triggerPatterns[1].onKeydown(left());
@@ -275,7 +277,7 @@ describe('Accordion Pattern', () => {
         });
 
         it('navigates to the last trigger with left key from first trigger.', () => {
-          groupInputs.activeIndex.set(0);
+          groupInputs.activeItem.set(groupInputs.items()[0]);
           expect(triggerPatterns[0].active()).toBeTrue();
           expect(triggerPatterns[2].active()).toBeFalse();
           triggerPatterns[0].onKeydown(left());
@@ -284,7 +286,7 @@ describe('Accordion Pattern', () => {
         });
 
         it('navigates to the first trigger with right key from last trigger.', () => {
-          groupInputs.activeIndex.set(2);
+          groupInputs.activeItem.set(groupInputs.items()[2]);
           expect(triggerPatterns[2].active()).toBeTrue();
           expect(triggerPatterns[0].active()).toBeFalse();
           triggerPatterns[2].onKeydown(right());
@@ -299,14 +301,14 @@ describe('Accordion Pattern', () => {
         });
 
         it('stays on the first trigger with left key from first trigger.', () => {
-          groupInputs.activeIndex.set(0);
+          groupInputs.activeItem.set(groupInputs.items()[0]);
           expect(triggerPatterns[0].active()).toBeTrue();
           triggerPatterns[0].onKeydown(left());
           expect(triggerPatterns[0].active()).toBeTrue();
         });
 
         it('stays on the last trigger with right key from last trigger.', () => {
-          groupInputs.activeIndex.set(2);
+          groupInputs.activeItem.set(groupInputs.items()[2]);
           expect(triggerPatterns[2].active()).toBeTrue();
           triggerPatterns[2].onKeydown(right());
           expect(triggerPatterns[2].active()).toBeTrue();

src/cdk-experimental/ui-patterns/accordion/accordion.ts

@@ -48,7 +48,7 @@ export class AccordionGroupPattern {
     this.wrap = inputs.wrap;
     this.orientation = inputs.orientation;
     this.textDirection = inputs.textDirection;
-    this.activeIndex = inputs.activeIndex;
+    this.activeItem = inputs.activeItem;
     this.disabled = inputs.disabled;
     this.multiExpandable = inputs.multiExpandable;
     this.items = inputs.items;
@@ -70,8 +70,7 @@ export class AccordionGroupPattern {
 }
 
 /** Inputs for the AccordionTriggerPattern. */
-export type AccordionTriggerInputs = ListNavigationItem &
-  ListFocusItem &
+export type AccordionTriggerInputs = Omit<ListNavigationItem & ListFocusItem, 'index'> &
   Omit<ExpansionItem, 'expansionId' | 'expandable'> & {
     /** A local unique identifier for the trigger. */
     value: SignalLike<string>;
@@ -99,7 +98,7 @@ export class AccordionTriggerPattern {
   expansionControl: ExpansionControl;
 
   /** Whether the trigger is active. */
-  active = computed(() => this.inputs.accordionGroup().focusManager.activeItem() === this);
+  active = computed(() => this.inputs.accordionGroup().activeItem() === this);
 
   /** Id of the accordion panel controlled by the trigger. */
   controls = computed(() => this.inputs.accordionPanel()?.id());
@@ -110,6 +109,9 @@ export class AccordionTriggerPattern {
   /** Whether the trigger is disabled. Disabling an accordion group disables all the triggers. */
   disabled = computed(() => this.inputs.disabled() || this.inputs.accordionGroup().disabled());
 
+  /** The index of the trigger within its accordion group. */
+  index = computed(() => this.inputs.accordionGroup().items().indexOf(this));
+
   constructor(readonly inputs: AccordionTriggerInputs) {
     this.id = inputs.id;
     this.element = inputs.element;

src/cdk-experimental/ui-patterns/behaviors/list-focus/list-focus.spec.ts

@@ -18,12 +18,13 @@ type TestInputs = Partial<ListFocusInputs<ListFocusItem>> & {
 };
 
 export function getListFocus(inputs: TestInputs = {}): ListFocus<ListFocusItem> {
+  const items = inputs.items || getItems(inputs.numItems ?? 5);
   return new ListFocus({
-    activeIndex: signal(0),
+    activeItem: signal(items()[0]),
     disabled: signal(false),
     skipDisabled: signal(false),
     focusMode: signal('roving'),
-    items: getItems(inputs.numItems ?? 5),
+    items: items,
     ...inputs,
   });
 }
@@ -35,6 +36,7 @@ function getItems(length: number): Signal<ListFocusItem[]> {
         id: signal(`${i}`),
         disabled: signal(false),
         element: signal({focus: () => {}} as HTMLElement),
+        index: signal(i),
       };
     }),
   );
@@ -58,7 +60,7 @@ describe('List Focus', () => {
 
     it('should set the tabindex based on the active index', () => {
       const items = focusManager.inputs.items() as TestItem[];
-      focusManager.inputs.activeIndex.set(2);
+      focusManager.inputs.activeItem.set(focusManager.inputs.items()[2]);
       expect(focusManager.getItemTabindex(items[0])).toBe(-1);
       expect(focusManager.getItemTabindex(items[1])).toBe(-1);
       expect(focusManager.getItemTabindex(items[2])).toBe(0);
@@ -84,7 +86,7 @@ describe('List Focus', () => {
 
     it('should set the tabindex of all items to -1', () => {
       const items = focusManager.inputs.items() as TestItem[];
-      focusManager.inputs.activeIndex.set(0);
+      focusManager.inputs.activeItem.set(focusManager.inputs.items()[0]);
       expect(focusManager.getItemTabindex(items[0])).toBe(-1);
       expect(focusManager.getItemTabindex(items[1])).toBe(-1);
       expect(focusManager.getItemTabindex(items[2])).toBe(-1);
@@ -93,7 +95,7 @@ describe('List Focus', () => {
     });
 
     it('should update the activedescendant of the list when navigating', () => {
-      focusManager.inputs.activeIndex.set(1);
+      focusManager.inputs.activeItem.set(focusManager.inputs.items()[1]);
       expect(focusManager.getActiveDescendant()).toBe(focusManager.inputs.items()[1].id());
     });
   });

src/cdk-experimental/ui-patterns/behaviors/list-focus/list-focus.ts

@@ -19,6 +19,9 @@ export interface ListFocusItem {
 
   /** Whether an item is disabled. */
   disabled: SignalLike<boolean>;
+
+  /** The index of the item in the list. */
+  index: SignalLike<number>;
 }
 
 /** Represents the required inputs for a collection that contains focusable items. */
@@ -32,20 +35,23 @@ export interface ListFocusInputs<T extends ListFocusItem> {
   /** The items in the list. */
   items: SignalLike<T[]>;
 
-  /** The index of the current active item. */
-  activeIndex: WritableSignalLike<number>;
+  /** The active item. */
+  activeItem: WritableSignalLike<T | undefined>;
 
   /** Whether disabled items in the list should be skipped when navigating. */
   skipDisabled: SignalLike<boolean>;
 }
 
 /** Controls focus for a list of items. */
 export class ListFocus<T extends ListFocusItem> {
-  /** The last index that was active. */
-  prevActiveIndex = signal(0);
+  /** The last item that was active. */
+  prevActiveItem = signal<T | undefined>(undefined);
+
+  /** The index of the last item that was active. */
+  prevActiveIndex = computed(() => this.prevActiveItem()?.index() ?? -1);
 
-  /** The current active item. */
-  activeItem = computed(() => this.inputs.items()[this.inputs.activeIndex()]);
+  /** The current active index in the list. */
+  activeIndex = computed(() => this.inputs.activeItem()?.index() ?? -1);
 
   constructor(readonly inputs: ListFocusInputs<T>) {}
 
@@ -62,7 +68,7 @@ export class ListFocus<T extends ListFocusItem> {
     if (this.inputs.focusMode() === 'roving') {
       return undefined;
     }
-    return this.inputs.items()[this.inputs.activeIndex()].id();
+    return this.inputs.activeItem()?.id() ?? undefined;
   }
 
   /** The tabindex for the list. */
@@ -81,7 +87,7 @@ export class ListFocus<T extends ListFocusItem> {
     if (this.inputs.focusMode() === 'activedescendant') {
       return -1;
     }
-    return this.activeItem() === item ? 0 : -1;
+    return this.inputs.activeItem() === item ? 0 : -1;
   }
 
   /** Moves focus to the given item if it is focusable. */
@@ -90,9 +96,8 @@ export class ListFocus<T extends ListFocusItem> {
       return false;
     }
 
-    this.prevActiveIndex.set(this.inputs.activeIndex());
-    const index = this.inputs.items().indexOf(item);
-    this.inputs.activeIndex.set(index);
+    this.prevActiveItem.set(this.inputs.activeItem());
+    this.inputs.activeItem.set(item);
 
     if (this.inputs.focusMode() === 'roving') {
       item.element().focus();