refactor: Make INavigable extend IFocusableNode. (#9033)

core/interfaces/i_navigable.ts

@@ -4,24 +4,12 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
+import type {IFocusableNode} from './i_focusable_node.js';
+
 /**
  * Represents a UI element which can be navigated to using the keyboard.
  */
-export interface INavigable<T> {
-  /**
-   * Returns whether or not this specific instance should be reachable via
-   * keyboard navigation.
-   *
-   * Implementors should generally return true, unless there are circumstances
-   * under which this item should be skipped while using keyboard navigation.
-   * Common examples might include being disabled, invalid, readonly, or purely
-   * a visual decoration. For example, while Fields are navigable, non-editable
-   * fields return false, since they cannot be interacted with when focused.
-   *
-   * @returns True if this element should be included in keyboard navigation.
-   */
-  isNavigable(): boolean;
-
+export interface INavigable<T> extends IFocusableNode {
   /**
    * Returns the class of this instance.
    *

core/interfaces/i_navigation_policy.ts

@@ -43,4 +43,18 @@ export interface INavigationPolicy<T> {
    *     there is none.
    */
   getPreviousSibling(current: T): INavigable<any> | null;
+
+  /**
+   * Returns whether or not the given instance should be reachable via keyboard
+   * navigation.
+   *
+   * Implementors should generally return true, unless there are circumstances
+   * under which this item should be skipped while using keyboard navigation.
+   * Common examples might include being disabled, invalid, readonly, or purely
+   * a visual decoration. For example, while Fields are navigable, non-editable
+   * fields return false, since they cannot be interacted with when focused.
+   *
+   * @returns True if this element should be included in keyboard navigation.
+   */
+  isNavigable(current: T): boolean;
 }