feat(tree): improve screen reader support

packages/elements/src/list/index.ts

@@ -103,6 +103,12 @@ export class List<T extends DataItem = ItemData> extends ControlElement {
   @property({ type: Boolean })
   public stateless = false;
 
+  /**
+   * Aria indicating that list supports multiple selection
+   */
+  @property({ type: String, reflect: true, attribute: 'aria-multiselectable' })
+  public ariaMultiselectable = 'false';
+
   /**
    * Allow multiple selections
    */

packages/elements/src/tree/__snapshots__/Tree.md

@@ -7,7 +7,7 @@
 ```html
 <ef-tree
   aria-multiselectable="false"
-  role="listbox"
+  role="tree"
 >
 </ef-tree>
 

packages/elements/src/tree/elements/tree-item.ts

@@ -34,6 +34,8 @@ export class TreeItem<T extends TreeDataItem = TreeDataItem> extends ControlElem
     return VERSION;
   }
 
+  protected readonly defaultRole: string | null = 'treeitem';
+
   /**
    * Checked state of the item
    */
@@ -61,7 +63,7 @@ export class TreeItem<T extends TreeDataItem = TreeDataItem> extends ControlElem
   /**
    * Depth of the item
    */
-  @property({ reflect: true, type: Number })
+  @property({ type: Number, reflect: true })
   public depth = 0;
 
   /**
@@ -103,10 +105,7 @@ export class TreeItem<T extends TreeDataItem = TreeDataItem> extends ControlElem
    */
   protected get toggleTemplate (): TemplateResult {
     return html`
-    <div
-    expand-toggle
-    part="toggle"
-    style="pointer-events:all;visibility:${this.parent ? 'visible' : 'hidden'}">
+    <div expand-toggle part="toggle" style="pointer-events:all;visibility:${this.parent ? 'visible' : 'hidden'}">
       <ef-icon part="toggle-icon${this.expanded ? ' toggle-icon-expanded' : ''}" icon="right"></ef-icon>
     </div>
     `;
@@ -119,23 +118,25 @@ export class TreeItem<T extends TreeDataItem = TreeDataItem> extends ControlElem
     if (!this.multiple) {
       return emptyTemplate;
     }
+
     return html`
     <ef-checkbox
-    part="checkbox"
-    tabindex="-1"
-    .disabled="${this.disabled}"
-    .readonly="${this.readonly}"
-    .indeterminate="${this.indeterminate}"
-    .checked="${this.checked}"
-    style="pointer-events:none"></ef-checkbox>
+      part="checkbox"
+      tabindex="-1"
+      .disabled="${this.disabled}"
+      .readonly="${this.readonly}"
+      .indeterminate="${this.indeterminate}"
+      .checked="${this.checked}"
+      style="pointer-events:none">
+    </ef-checkbox>
     `;
   }
 
   /**
    * Template for rendering the icon
    */
   protected get iconTemplate (): TemplateResult {
-    if(typeof this.icon === 'undefined') {
+    if (typeof this.icon === 'undefined') {
       return emptyTemplate;
     }
 
@@ -156,24 +157,93 @@ export class TreeItem<T extends TreeDataItem = TreeDataItem> extends ControlElem
     return this.checkedState === CheckedState.INDETERMINATE;
   }
 
+  /**
+   * Handles aria-checked and aria-selected when mode changes
+   * aria-checked is used for multiple mode due to tri-state support
+   * @returns {void}
+   **/
+  private multipleChanged (): void {
+    this.removeAttribute(this.multiple ? 'aria-selected' : 'aria-checked');
+    this.checkedChanged();
+  }
+
+  /**
+   * Handles selected and aria attribute changes
+   * @returns {void}
+   */
+  private checkedChanged (): void {
+    switch (this.checkedState) {
+      case CheckedState.CHECKED:
+        this.setAttribute('selected', '');
+        this.setAttribute(this.multiple ? 'aria-checked' : 'aria-selected', 'true');
+        break;
+      case CheckedState.INDETERMINATE:
+        this.setAttribute('selected', 'indeterminate');
+        this.setAttribute('aria-checked', 'mixed');
+        break;
+      default:
+        this.removeAttribute('selected');
+
+        // In single mode, only children nodes are selectable
+        if (this.parent && !this.multiple) {
+          this.removeAttribute('aria-selected');
+        }
+        else {
+          this.setAttribute(this.multiple ? 'aria-checked' : 'aria-selected', 'false');
+        }
+
+        break;
+    }
+  }
+
+  /**
+   * Handles aria-expanded when expanded state changes
+   * @returns {void}
+   */
+  private expandedChanged () :void {
+    if (this.parent) {
+      this.setAttribute('aria-expanded', this.expanded ? 'true' : 'false');
+    }
+  }
+
+  /**
+   * Called after the component is first rendered
+   * @param changedProperties Properties which have changed
+   * @returns {void}
+   */
+  protected firstUpdated (changedProperties: PropertyValues): void {
+    super.firstUpdated(changedProperties);
+    this.setAttribute('aria-level', String(this.depth + 1));
+  }
+
+  /**
+   * Invoked whenever the element is updated
+   * @param changedProperties Map of changed properties with old values
+   * @returns {void}
+   */
   protected update (changedProperties: PropertyValues): void {
     super.update(changedProperties);
+
     if (changedProperties.has('checkedState')) {
-      switch (this.checkedState) {
-        case CheckedState.CHECKED:
-          this.setAttribute('selected', '');
-          break;
-        case CheckedState.INDETERMINATE:
-          this.setAttribute('selected', 'indeterminate');
-          break;
-        default:
-          this.removeAttribute('selected');
-      }
+      this.checkedChanged();
+    }
+
+    if (changedProperties.has('multiple') && changedProperties.get('multiple') !== undefined) {
+      this.multipleChanged();
+    }
+
+    if (changedProperties.has('expanded')) {
+      this.expandedChanged();
     }
   }
 
+  /**
+   * A `TemplateResult` that will be used
+   * to render the updated internal template.
+   * @returns Render template
+   */
   protected render (): TemplateResult {
-    return html `
+    return html`
       ${this.indentTemplate}
       ${this.toggleTemplate}
       ${this.checkboxTemplate}

packages/elements/src/tree/elements/tree.ts

@@ -37,6 +37,8 @@ export class Tree<T extends TreeDataItem = TreeDataItem> extends List<T> {
     return VERSION;
   }
 
+  protected readonly defaultRole: string | null = 'tree';
+
   /**
    * Tree manager used for manipulation
    */

packages/elements/src/tree/helpers/renderer.ts

@@ -12,6 +12,7 @@ type RendererScope = {
 
 export class TreeRenderer extends Renderer {
   constructor (scope?: unknown) {
+
     let manager: TreeManager<TreeDataItem>;
     let currentMode: TreeManagerMode;
     let currentComposer: CollectionComposer<TreeDataItem>;
@@ -36,6 +37,7 @@ export class TreeRenderer extends Renderer {
       el.disabled = composer.getItemPropertyValue(item, 'disabled') === true;
       el.readonly = composer.getItemPropertyValue(item, 'readonly') === true;
       el.highlighted = composer.getItemPropertyValue(item, 'highlighted') === true;
+
       return el;
     });
   }

packages/elements/src/tree/managers/tree-manager.ts

@@ -439,5 +439,4 @@ export class TreeManager<T extends TreeDataItem> {
   public uncheckAllItems (): void {
     this.editableItems.forEach(item => this.uncheckItem(item));
   }
-
 }