refactor: Remove INavigable in favor of IFocusableNode. (#9037)

* refactor: Remove INavigable in favor of IFocusableNode.

* chore: Fix JSDoc.

* chore: Address review feedback.

core/block_svg.ts

@@ -47,7 +47,6 @@ import type {IDragStrategy, IDraggable} from './interfaces/i_draggable.js';
 import type {IFocusableNode} from './interfaces/i_focusable_node.js';
 import type {IFocusableTree} from './interfaces/i_focusable_tree.js';
 import {IIcon} from './interfaces/i_icon.js';
-import type {INavigable} from './interfaces/i_navigable.js';
 import * as internalConstants from './internal_constants.js';
 import {Msg} from './msg.js';
 import * as renderManagement from './render_management.js';
@@ -77,8 +76,7 @@ export class BlockSvg
     ICopyable<BlockCopyData>,
     IDraggable,
     IDeletable,
-    IFocusableNode,
+    IFocusableNode
-    INavigable<BlockSvg>
 {
   /**
    * Constant for identifying rows that are to be rendered inline.
@@ -1796,16 +1794,4 @@ export class BlockSvg
   canBeFocused(): boolean {
     return true;
   }
-
-  /**
-   * Returns this block's class.
-   *
-   * Used by keyboard navigation to look up the rules for navigating from this
-   * block.
-   *
-   * @returns This block's class.
-   */
-  getClass() {
-    return BlockSvg;
-  }
 }

core/blockly.ts

@@ -171,7 +171,7 @@ import {
 import {IVariableMap} from './interfaces/i_variable_map.js';
 import {IVariableModel, IVariableState} from './interfaces/i_variable_model.js';
 import * as internalConstants from './internal_constants.js';
-import {CursorOptions, LineCursor} from './keyboard_nav/line_cursor.js';
+import {LineCursor} from './keyboard_nav/line_cursor.js';
 import {Marker} from './keyboard_nav/marker.js';
 import type {LayerManager} from './layer_manager.js';
 import * as layers from './layers.js';
@@ -429,7 +429,7 @@ Names.prototype.populateProcedures = function (
 };
 // clang-format on
 
-export * from './interfaces/i_navigable.js';
+export * from './flyout_navigator.js';
 export * from './interfaces/i_navigation_policy.js';
 export * from './keyboard_nav/block_navigation_policy.js';
 export * from './keyboard_nav/connection_navigation_policy.js';
@@ -457,7 +457,6 @@ export {
   ContextMenuItems,
   ContextMenuRegistry,
   Css,
-  CursorOptions,
   DeleteArea,
   DragTarget,
   Events,

core/field.ts

@@ -26,7 +26,6 @@ import type {Input} from './inputs/input.js';
 import type {IFocusableNode} from './interfaces/i_focusable_node.js';
 import type {IFocusableTree} from './interfaces/i_focusable_tree.js';
 import type {IKeyboardAccessible} from './interfaces/i_keyboard_accessible.js';
-import type {INavigable} from './interfaces/i_navigable.js';
 import type {IRegistrable} from './interfaces/i_registrable.js';
 import {ISerializable} from './interfaces/i_serializable.js';
 import type {ConstantProvider} from './renderers/common/constants.js';
@@ -68,12 +67,7 @@ export type FieldValidator<T = any> = (newValue: T) => T | null | undefined;
  * @typeParam T - The value stored on the field.
  */
 export abstract class Field<T = any>
-  implements
+  implements IKeyboardAccessible, IRegistrable, ISerializable, IFocusableNode
-    IKeyboardAccessible,
-    IRegistrable,
-    ISerializable,
-    IFocusableNode,
-    INavigable<Field<T>>
 {
   /**
    * To overwrite the default value which is set in **Field**, directly update
@@ -1410,16 +1404,6 @@ export abstract class Field<T = any>
       `Attempted to instantiate a field from the registry that hasn't defined a 'fromJson' method.`,
     );
   }
-
-  /**
-   * Returns this field's class.
-   *
-   * Used by keyboard navigation to look up the rules for navigating from this
-   * field. Must be implemented by subclasses.
-   *
-   * @returns This field's class.
-   */
-  abstract getClass(): new (...args: any) => Field<T>;
 }
 
 /**

core/field_checkbox.ts

@@ -228,18 +228,6 @@ export class FieldCheckbox extends Field<CheckboxBool> {
     // 'override' the static fromJson method.
     return new this(options.checked, undefined, options);
   }
-
-  /**
-   * Returns this field's class.
-   *
-   * Used by keyboard navigation to look up the rules for navigating from this
-   * field.
-   *
-   * @returns This field's class.
-   */
-  getClass() {
-    return FieldCheckbox;
-  }
 }
 
 fieldRegistry.register('field_checkbox', FieldCheckbox);

core/field_dropdown.ts

@@ -796,18 +796,6 @@ export class FieldDropdown extends Field<string> {
       throw TypeError('Found invalid FieldDropdown options.');
     }
   }
-
-  /**
-   * Returns this field's class.
-   *
-   * Used by keyboard navigation to look up the rules for navigating from this
-   * field.
-   *
-   * @returns This field's class.
-   */
-  getClass() {
-    return FieldDropdown;
-  }
 }
 
 /**

core/field_image.ts

@@ -272,18 +272,6 @@ export class FieldImage extends Field<string> {
       options,
     );
   }
-
-  /**
-   * Returns this field's class.
-   *
-   * Used by keyboard navigation to look up the rules for navigating from this
-   * field.
-   *
-   * @returns This field's class.
-   */
-  getClass() {
-    return FieldImage;
-  }
 }
 
 fieldRegistry.register('field_image', FieldImage);

core/field_label.ts

@@ -126,18 +126,6 @@ export class FieldLabel extends Field<string> {
     // the static fromJson method.
     return new this(text, undefined, options);
   }
-
-  /**
-   * Returns this field's class.
-   *
-   * Used by keyboard navigation to look up the rules for navigating from this
-   * field.
-   *
-   * @returns This field's class.
-   */
-  getClass() {
-    return FieldLabel;
-  }
 }
 
 fieldRegistry.register('field_label', FieldLabel);

core/field_number.ts

@@ -341,18 +341,6 @@ export class FieldNumber extends FieldInput<number> {
       options,
     );
   }
-
-  /**
-   * Returns this field's class.
-   *
-   * Used by keyboard navigation to look up the rules for navigating from this
-   * field.
-   *
-   * @returns This field's class.
-   */
-  getClass() {
-    return FieldNumber;
-  }
 }
 
 fieldRegistry.register('field_number', FieldNumber);

core/field_textinput.ts

@@ -89,18 +89,6 @@ export class FieldTextInput extends FieldInput<string> {
     // override the static fromJson method.
     return new this(text, undefined, options);
   }
-
-  /**
-   * Returns this field's class.
-   *
-   * Used by keyboard navigation to look up the rules for navigating from this
-   * field.
-   *
-   * @returns This field's class.
-   */
-  getClass() {
-    return FieldTextInput;
-  }
 }
 
 fieldRegistry.register('field_input', FieldTextInput);

core/flyout_base.ts

@@ -20,6 +20,7 @@ import {EventType} from './events/type.js';
 import * as eventUtils from './events/utils.js';
 import {FlyoutItem} from './flyout_item.js';
 import {FlyoutMetricsManager} from './flyout_metrics_manager.js';
+import {FlyoutNavigator} from './flyout_navigator.js';
 import {FlyoutSeparator, SeparatorAxis} from './flyout_separator.js';
 import {getFocusManager} from './focus_manager.js';
 import {IAutoHideable} from './interfaces/i_autohideable.js';
@@ -243,6 +244,7 @@ export abstract class Flyout
     this.workspace_.internalIsFlyout = true;
     // Keep the workspace visibility consistent with the flyout's visibility.
     this.workspace_.setVisible(this.visible);
+    this.workspace_.setNavigator(new FlyoutNavigator(this));
 
     /**
      * The unique id for this component that is used to register with the

core/flyout_button.ts

@@ -16,7 +16,6 @@ import * as Css from './css.js';
 import type {IBoundedElement} from './interfaces/i_bounded_element.js';
 import type {IFocusableNode} from './interfaces/i_focusable_node.js';
 import type {IFocusableTree} from './interfaces/i_focusable_tree.js';
-import type {INavigable} from './interfaces/i_navigable.js';
 import type {IRenderedElement} from './interfaces/i_rendered_element.js';
 import {idGenerator} from './utils.js';
 import {Coordinate} from './utils/coordinate.js';
@@ -32,11 +31,7 @@ import type {WorkspaceSvg} from './workspace_svg.js';
  * Class for a button or label in the flyout.
  */
 export class FlyoutButton
-  implements
+  implements IBoundedElement, IRenderedElement, IFocusableNode
-    IBoundedElement,
-    IRenderedElement,
-    IFocusableNode,
-    INavigable<FlyoutButton>
 {
   /** The horizontal margin around the text in the button. */
   static TEXT_MARGIN_X = 5;
@@ -412,18 +407,6 @@ export class FlyoutButton
   canBeFocused(): boolean {
     return true;
   }
-
-  /**
-   * Returns this button's class.
-   *
-   * Used by keyboard navigation to look up the rules for navigating from this
-   * button.
-   *
-   * @returns This button's class.
-   */
-  getClass() {
-    return FlyoutButton;
-  }
 }
 
 /** CSS for buttons and labels. See css.js for use. */

core/flyout_item.ts

@@ -1,5 +1,6 @@
 import type {IBoundedElement} from './interfaces/i_bounded_element.js';
-import type {INavigable} from './interfaces/i_navigable.js';
+import type {IFocusableNode} from './interfaces/i_focusable_node.js';
+
 /**
  * Representation of an item displayed in a flyout.
  */
@@ -12,7 +13,7 @@ export class FlyoutItem {
    *     flyout inflater that created this object.
    */
   constructor(
-    private element: IBoundedElement & INavigable<any>,
+    private element: IBoundedElement & IFocusableNode,
     private type: string,
   ) {}
 

core/flyout_navigator.ts

@@ -0,0 +1,24 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import type {IFlyout} from './interfaces/i_flyout.js';
+import {FlyoutButtonNavigationPolicy} from './keyboard_nav/flyout_button_navigation_policy.js';
+import {FlyoutNavigationPolicy} from './keyboard_nav/flyout_navigation_policy.js';
+import {FlyoutSeparatorNavigationPolicy} from './keyboard_nav/flyout_separator_navigation_policy.js';
+import {Navigator} from './navigator.js';
+
+export class FlyoutNavigator extends Navigator {
+  constructor(flyout: IFlyout) {
+    super();
+    this.rules.push(
+      new FlyoutButtonNavigationPolicy(),
+      new FlyoutSeparatorNavigationPolicy(),
+    );
+    this.rules = this.rules.map(
+      (rule) => new FlyoutNavigationPolicy(rule, flyout),
+    );
+  }
+}

core/flyout_separator.ts

@@ -7,15 +7,12 @@
 import type {IBoundedElement} from './interfaces/i_bounded_element.js';
 import type {IFocusableNode} from './interfaces/i_focusable_node.js';
 import type {IFocusableTree} from './interfaces/i_focusable_tree.js';
-import type {INavigable} from './interfaces/i_navigable.js';
 import {Rect} from './utils/rect.js';
 
 /**
  * Representation of a gap between elements in a flyout.
  */
-export class FlyoutSeparator
+export class FlyoutSeparator implements IBoundedElement, IFocusableNode {
-  implements IBoundedElement, INavigable<FlyoutSeparator>, IFocusableNode
-{
   private x = 0;
   private y = 0;
 
@@ -66,18 +63,6 @@ export class FlyoutSeparator
     return false;
   }
 
-  /**
-   * Returns this separator's class.
-   *
-   * Used by keyboard navigation to look up the rules for navigating from this
-   * separator.
-   *
-   * @returns This separator's class.
-   */
-  getClass() {
-    return FlyoutSeparator;
-  }
-
   /** See IFocusableNode.getFocusableElement. */
   getFocusableElement(): HTMLElement | SVGElement {
     throw new Error('Cannot be focused');

core/interfaces/i_navigable.ts

@@ -1,19 +0,0 @@
-/**
- * @license
- * Copyright 2025 Google LLC
- * 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> extends IFocusableNode {
-  /**
-   * Returns the class of this instance.
-   *
-   * @returns This object's class.
-   */
-  getClass(): new (...args: any) => T;
-}

core/interfaces/i_navigation_policy.ts

@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import type {INavigable} from './i_navigable.js';
+import type {IFocusableNode} from './i_focusable_node.js';
 
 /**
  * A set of rules that specify where keyboard navigation should proceed.
@@ -16,7 +16,7 @@ export interface INavigationPolicy<T> {
    * @param current The element which the user is navigating into.
    * @returns The current element's first child, or null if it has none.
    */
-  getFirstChild(current: T): INavigable<any> | null;
+  getFirstChild(current: T): IFocusableNode | null;
 
   /**
    * Returns the parent element of the given element, if any.
@@ -24,7 +24,7 @@ export interface INavigationPolicy<T> {
    * @param current The element which the user is navigating out of.
    * @returns The parent element of the current element, or null if it has none.
    */
-  getParent(current: T): INavigable<any> | null;
+  getParent(current: T): IFocusableNode | null;
 
   /**
    * Returns the peer element following the given element, if any.
@@ -33,7 +33,7 @@ export interface INavigationPolicy<T> {
    * @returns The next peer element of the current element, or null if there is
    *     none.
    */
-  getNextSibling(current: T): INavigable<any> | null;
+  getNextSibling(current: T): IFocusableNode | null;
 
   /**
    * Returns the peer element preceding the given element, if any.
@@ -42,7 +42,7 @@ export interface INavigationPolicy<T> {
    * @returns The previous peer element of the current element, or null if
    *     there is none.
    */
-  getPreviousSibling(current: T): INavigable<any> | null;
+  getPreviousSibling(current: T): IFocusableNode | null;
 
   /**
    * Returns whether or not the given instance should be reachable via keyboard
@@ -57,4 +57,13 @@ export interface INavigationPolicy<T> {
    * @returns True if this element should be included in keyboard navigation.
    */
   isNavigable(current: T): boolean;
+
+  /**
+   * Returns whether or not this navigation policy corresponds to the type of
+   * the given object.
+   *
+   * @param current An instance to check whether this policy applies to.
+   * @returns True if the given object is of a type handled by this policy.
+   */
+  isApplicable(current: any): current is T;
 }

core/keyboard_nav/block_navigation_policy.ts

@@ -6,7 +6,7 @@
 
 import {BlockSvg} from '../block_svg.js';
 import type {Field} from '../field.js';
-import type {INavigable} from '../interfaces/i_navigable.js';
+import type {IFocusableNode} from '../interfaces/i_focusable_node.js';
 import type {INavigationPolicy} from '../interfaces/i_navigation_policy.js';
 import {WorkspaceSvg} from '../workspace_svg.js';
 
@@ -20,7 +20,7 @@ export class BlockNavigationPolicy implements INavigationPolicy<BlockSvg> {
    * @param current The block to return the first child of.
    * @returns The first field or input of the given block, if any.
    */
-  getFirstChild(current: BlockSvg): INavigable<unknown> | null {
+  getFirstChild(current: BlockSvg): IFocusableNode | null {
     for (const input of current.inputList) {
       for (const field of input.fieldRow) {
         return field;
@@ -39,7 +39,7 @@ export class BlockNavigationPolicy implements INavigationPolicy<BlockSvg> {
    * @returns The top block of the given block's stack, or the connection to
    *     which it is attached.
    */
-  getParent(current: BlockSvg): INavigable<unknown> | null {
+  getParent(current: BlockSvg): IFocusableNode | null {
     if (current.previousConnection?.targetBlock()) {
       const surroundParent = current.getSurroundParent();
       if (surroundParent) return surroundParent;
@@ -57,7 +57,7 @@ export class BlockNavigationPolicy implements INavigationPolicy<BlockSvg> {
    * @returns The first block of the next stack if the given block is a terminal
    *     block, or its next connection.
    */
-  getNextSibling(current: BlockSvg): INavigable<unknown> | null {
+  getNextSibling(current: BlockSvg): IFocusableNode | null {
     if (current.nextConnection?.targetBlock()) {
       return current.nextConnection?.targetBlock();
     }
@@ -101,7 +101,7 @@ export class BlockNavigationPolicy implements INavigationPolicy<BlockSvg> {
    * @returns The block's previous/output connection, or the last
    *     connection/block of the previous block stack if it is a root block.
    */
-  getPreviousSibling(current: BlockSvg): INavigable<unknown> | null {
+  getPreviousSibling(current: BlockSvg): IFocusableNode | null {
     if (current.previousConnection?.targetBlock()) {
       return current.previousConnection?.targetBlock();
     }
@@ -127,7 +127,7 @@ export class BlockNavigationPolicy implements INavigationPolicy<BlockSvg> {
     }
 
     const currentIndex = siblings.indexOf(current);
-    let result: INavigable<any> | null = null;
+    let result: IFocusableNode | null = null;
     if (currentIndex >= 1) {
       result = siblings[currentIndex - 1];
     } else if (currentIndex === 0 && navigatingCrossStacks) {
@@ -152,4 +152,14 @@ export class BlockNavigationPolicy implements INavigationPolicy<BlockSvg> {
   isNavigable(current: BlockSvg): boolean {
     return current.canBeFocused();
   }
+
+  /**
+   * Returns whether the given object can be navigated from by this policy.
+   *
+   * @param current The object to check if this policy applies to.
+   * @returns True if the object is a BlockSvg.
+   */
+  isApplicable(current: any): current is BlockSvg {
+    return current instanceof BlockSvg;
+  }
 }

core/keyboard_nav/connection_navigation_policy.ts

@@ -6,9 +6,9 @@
 
 import type {BlockSvg} from '../block_svg.js';
 import {ConnectionType} from '../connection_type.js';
-import type {INavigable} from '../interfaces/i_navigable.js';
+import type {IFocusableNode} from '../interfaces/i_focusable_node.js';
 import type {INavigationPolicy} from '../interfaces/i_navigation_policy.js';
-import type {RenderedConnection} from '../rendered_connection.js';
+import {RenderedConnection} from '../rendered_connection.js';
 
 /**
  * Set of rules controlling keyboard navigation from a connection.
@@ -22,7 +22,7 @@ export class ConnectionNavigationPolicy
    * @param current The connection to return the first child of.
    * @returns The connection's first child element, or null if not none.
    */
-  getFirstChild(current: RenderedConnection): INavigable<unknown> | null {
+  getFirstChild(current: RenderedConnection): IFocusableNode | null {
     if (current.getParentInput()) {
       return current.targetConnection;
     }
@@ -36,7 +36,7 @@ export class ConnectionNavigationPolicy
    * @param current The connection to return the parent of.
    * @returns The given connection's parent connection or block.
    */
-  getParent(current: RenderedConnection): INavigable<unknown> | null {
+  getParent(current: RenderedConnection): IFocusableNode | null {
     if (current.type === ConnectionType.OUTPUT_VALUE) {
       return current.targetConnection ?? current.getSourceBlock();
     } else if (current.getParentInput()) {
@@ -56,7 +56,7 @@ export class ConnectionNavigationPolicy
    * @param current The connection to navigate from.
    * @returns The field, input connection or block following this connection.
    */
-  getNextSibling(current: RenderedConnection): INavigable<unknown> | null {
+  getNextSibling(current: RenderedConnection): IFocusableNode | null {
     if (current.getParentInput()) {
       const parentInput = current.getParentInput();
       const block = parentInput?.getSourceBlock();
@@ -101,7 +101,7 @@ export class ConnectionNavigationPolicy
    * @param current The connection to navigate from.
    * @returns The field, input connection or block preceding this connection.
    */
-  getPreviousSibling(current: RenderedConnection): INavigable<unknown> | null {
+  getPreviousSibling(current: RenderedConnection): IFocusableNode | null {
     if (current.getParentInput()) {
       const parentInput = current.getParentInput();
       const block = parentInput?.getSourceBlock();
@@ -176,4 +176,14 @@ export class ConnectionNavigationPolicy
   isNavigable(current: RenderedConnection): boolean {
     return current.canBeFocused();
   }
+
+  /**
+   * Returns whether the given object can be navigated from by this policy.
+   *
+   * @param current The object to check if this policy applies to.
+   * @returns True if the object is a RenderedConnection.
+   */
+  isApplicable(current: any): current is RenderedConnection {
+    return current instanceof RenderedConnection;
+  }
 }

core/keyboard_nav/field_navigation_policy.ts

@@ -5,8 +5,8 @@
  */
 
 import type {BlockSvg} from '../block_svg.js';
-import type {Field} from '../field.js';
+import {Field} from '../field.js';
-import type {INavigable} from '../interfaces/i_navigable.js';
+import type {IFocusableNode} from '../interfaces/i_focusable_node.js';
 import type {INavigationPolicy} from '../interfaces/i_navigation_policy.js';
 
 /**
@@ -19,7 +19,7 @@ export class FieldNavigationPolicy implements INavigationPolicy<Field<any>> {
    * @param _current The field to navigate from.
    * @returns Null.
    */
-  getFirstChild(_current: Field<any>): INavigable<unknown> | null {
+  getFirstChild(_current: Field<any>): IFocusableNode | null {
     return null;
   }
 
@@ -29,7 +29,7 @@ export class FieldNavigationPolicy implements INavigationPolicy<Field<any>> {
    * @param current The field to navigate from.
    * @returns The given field's parent block.
    */
-  getParent(current: Field<any>): INavigable<unknown> | null {
+  getParent(current: Field<any>): IFocusableNode | null {
     return current.getSourceBlock() as BlockSvg;
   }
 
@@ -39,7 +39,7 @@ export class FieldNavigationPolicy implements INavigationPolicy<Field<any>> {
    * @param current The field to navigate from.
    * @returns The next field or input in the given field's block.
    */
-  getNextSibling(current: Field<any>): INavigable<unknown> | null {
+  getNextSibling(current: Field<any>): IFocusableNode | null {
     const input = current.getParentInput();
     const block = current.getSourceBlock();
     if (!block) return null;
@@ -64,7 +64,7 @@ export class FieldNavigationPolicy implements INavigationPolicy<Field<any>> {
    * @param current The field to navigate from.
    * @returns The preceding field or input in the given field's block.
    */
-  getPreviousSibling(current: Field<any>): INavigable<unknown> | null {
+  getPreviousSibling(current: Field<any>): IFocusableNode | null {
     const parentInput = current.getParentInput();
     const block = current.getSourceBlock();
     if (!block) return null;
@@ -106,4 +106,14 @@ export class FieldNavigationPolicy implements INavigationPolicy<Field<any>> {
       current.getParentInput().isVisible()
     );
   }
+
+  /**
+   * Returns whether the given object can be navigated from by this policy.
+   *
+   * @param current The object to check if this policy applies to.
+   * @returns True if the object is a Field.
+   */
+  isApplicable(current: any): current is Field {
+    return current instanceof Field;
+  }
 }

core/keyboard_nav/flyout_button_navigation_policy.ts

@@ -4,8 +4,8 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import type {FlyoutButton} from '../flyout_button.js';
+import {FlyoutButton} from '../flyout_button.js';
-import type {INavigable} from '../interfaces/i_navigable.js';
+import type {IFocusableNode} from '../interfaces/i_focusable_node.js';
 import type {INavigationPolicy} from '../interfaces/i_navigation_policy.js';
 
 /**
@@ -20,7 +20,7 @@ export class FlyoutButtonNavigationPolicy
    * @param _current The FlyoutButton instance to navigate from.
    * @returns Null.
    */
-  getFirstChild(_current: FlyoutButton): INavigable<unknown> | null {
+  getFirstChild(_current: FlyoutButton): IFocusableNode | null {
     return null;
   }
 
@@ -30,7 +30,7 @@ export class FlyoutButtonNavigationPolicy
    * @param current The FlyoutButton instance to navigate from.
    * @returns The given flyout button's parent workspace.
    */
-  getParent(current: FlyoutButton): INavigable<unknown> | null {
+  getParent(current: FlyoutButton): IFocusableNode | null {
     return current.getWorkspace();
   }
 
@@ -40,7 +40,7 @@ export class FlyoutButtonNavigationPolicy
    * @param _current The FlyoutButton instance to navigate from.
    * @returns Null.
    */
-  getNextSibling(_current: FlyoutButton): INavigable<unknown> | null {
+  getNextSibling(_current: FlyoutButton): IFocusableNode | null {
     return null;
   }
 
@@ -50,7 +50,7 @@ export class FlyoutButtonNavigationPolicy
    * @param _current The FlyoutButton instance to navigate from.
    * @returns Null.
    */
-  getPreviousSibling(_current: FlyoutButton): INavigable<unknown> | null {
+  getPreviousSibling(_current: FlyoutButton): IFocusableNode | null {
     return null;
   }
 
@@ -63,4 +63,14 @@ export class FlyoutButtonNavigationPolicy
   isNavigable(current: FlyoutButton): boolean {
     return current.canBeFocused();
   }
+
+  /**
+   * Returns whether the given object can be navigated from by this policy.
+   *
+   * @param current The object to check if this policy applies to.
+   * @returns True if the object is a FlyoutButton.
+   */
+  isApplicable(current: any): current is FlyoutButton {
+    return current instanceof FlyoutButton;
+  }
 }

core/keyboard_nav/flyout_navigation_policy.ts

@@ -5,7 +5,7 @@
  */
 
 import type {IFlyout} from '../interfaces/i_flyout.js';
-import type {INavigable} from '../interfaces/i_navigable.js';
+import type {IFocusableNode} from '../interfaces/i_focusable_node.js';
 import type {INavigationPolicy} from '../interfaces/i_navigation_policy.js';
 
 /**
@@ -29,7 +29,7 @@ export class FlyoutNavigationPolicy<T> implements INavigationPolicy<T> {
    * @param _current The flyout item to navigate from.
    * @returns Null to prevent navigating into flyout items.
    */
-  getFirstChild(_current: T): INavigable<unknown> | null {
+  getFirstChild(_current: T): IFocusableNode | null {
     return null;
   }
 
@@ -39,7 +39,7 @@ export class FlyoutNavigationPolicy<T> implements INavigationPolicy<T> {
    * @param current The flyout item to navigate from.
    * @returns The parent of the given flyout item.
    */
-  getParent(current: T): INavigable<unknown> | null {
+  getParent(current: T): IFocusableNode | null {
     return this.policy.getParent(current);
   }
 
@@ -49,7 +49,7 @@ export class FlyoutNavigationPolicy<T> implements INavigationPolicy<T> {
    * @param current The flyout item to navigate from.
    * @returns The flyout item following the given one.
    */
-  getNextSibling(current: T): INavigable<unknown> | null {
+  getNextSibling(current: T): IFocusableNode | null {
     const flyoutContents = this.flyout.getContents();
     if (!flyoutContents) return null;
 
@@ -72,7 +72,7 @@ export class FlyoutNavigationPolicy<T> implements INavigationPolicy<T> {
    * @param current The flyout item to navigate from.
    * @returns The flyout item preceding the given one.
    */
-  getPreviousSibling(current: T): INavigable<unknown> | null {
+  getPreviousSibling(current: T): IFocusableNode | null {
     const flyoutContents = this.flyout.getContents();
     if (!flyoutContents) return null;
 
@@ -98,4 +98,14 @@ export class FlyoutNavigationPolicy<T> implements INavigationPolicy<T> {
   isNavigable(current: T): boolean {
     return this.policy.isNavigable(current);
   }
+
+  /**
+   * Returns whether the given object can be navigated from by this policy.
+   *
+   * @param current The object to check if this policy applies to.
+   * @returns True if the object is a BlockSvg.
+   */
+  isApplicable(current: any): current is T {
+    return this.policy.isApplicable(current);
+  }
 }

core/keyboard_nav/flyout_separator_navigation_policy.ts

@@ -4,8 +4,8 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import type {FlyoutSeparator} from '../flyout_separator.js';
+import {FlyoutSeparator} from '../flyout_separator.js';
-import type {INavigable} from '../interfaces/i_navigable.js';
+import type {IFocusableNode} from '../interfaces/i_focusable_node.js';
 import type {INavigationPolicy} from '../interfaces/i_navigation_policy.js';
 
 /**
@@ -15,19 +15,19 @@ import type {INavigationPolicy} from '../interfaces/i_navigation_policy.js';
 export class FlyoutSeparatorNavigationPolicy
   implements INavigationPolicy<FlyoutSeparator>
 {
-  getFirstChild(_current: FlyoutSeparator): INavigable<unknown> | null {
+  getFirstChild(_current: FlyoutSeparator): IFocusableNode | null {
     return null;
   }
 
-  getParent(_current: FlyoutSeparator): INavigable<unknown> | null {
+  getParent(_current: FlyoutSeparator): IFocusableNode | null {
     return null;
   }
 
-  getNextSibling(_current: FlyoutSeparator): INavigable<unknown> | null {
+  getNextSibling(_current: FlyoutSeparator): IFocusableNode | null {
     return null;
   }
 
-  getPreviousSibling(_current: FlyoutSeparator): INavigable<unknown> | null {
+  getPreviousSibling(_current: FlyoutSeparator): IFocusableNode | null {
     return null;
   }
 
@@ -40,4 +40,14 @@ export class FlyoutSeparatorNavigationPolicy
   isNavigable(_current: FlyoutSeparator): boolean {
     return false;
   }
+
+  /**
+   * Returns whether the given object can be navigated from by this policy.
+   *
+   * @param current The object to check if this policy applies to.
+   * @returns True if the object is a FlyoutSeparator.
+   */
+  isApplicable(current: any): current is FlyoutSeparator {
+    return current instanceof FlyoutSeparator;
+  }
 }

core/keyboard_nav/line_cursor.ts

@@ -14,43 +14,12 @@
  */
 
 import {BlockSvg} from '../block_svg.js';
-import {FieldCheckbox} from '../field_checkbox.js';
-import {FieldDropdown} from '../field_dropdown.js';
-import {FieldImage} from '../field_image.js';
-import {FieldLabel} from '../field_label.js';
-import {FieldNumber} from '../field_number.js';
-import {FieldTextInput} from '../field_textinput.js';
-import {FlyoutButton} from '../flyout_button.js';
-import {FlyoutSeparator} from '../flyout_separator.js';
 import {getFocusManager} from '../focus_manager.js';
+import type {IFocusableNode} from '../interfaces/i_focusable_node.js';
 import {isFocusableNode} from '../interfaces/i_focusable_node.js';
-import type {INavigable} from '../interfaces/i_navigable.js';
 import * as registry from '../registry.js';
-import {RenderedConnection} from '../rendered_connection.js';
-import {Renderer} from '../renderers/zelos/renderer.js';
 import {WorkspaceSvg} from '../workspace_svg.js';
-import {BlockNavigationPolicy} from './block_navigation_policy.js';
-import {ConnectionNavigationPolicy} from './connection_navigation_policy.js';
-import {FieldNavigationPolicy} from './field_navigation_policy.js';
-import {FlyoutButtonNavigationPolicy} from './flyout_button_navigation_policy.js';
-import {FlyoutNavigationPolicy} from './flyout_navigation_policy.js';
-import {FlyoutSeparatorNavigationPolicy} from './flyout_separator_navigation_policy.js';
 import {Marker} from './marker.js';
-import {WorkspaceNavigationPolicy} from './workspace_navigation_policy.js';
-
-/** Options object for LineCursor instances. */
-export interface CursorOptions {
-  /**
-   * Can the cursor visit all stack connections (next/previous), or
-   * (if false) only unconnected next connections?
-   */
-  stackConnections: boolean;
-}
-
-/** Default options for LineCursor instances. */
-const defaultOptions: CursorOptions = {
-  stackConnections: true,
-};
 
 /**
  * Class for a line cursor.
@@ -58,76 +27,14 @@ const defaultOptions: CursorOptions = {
 export class LineCursor extends Marker {
   override type = 'cursor';
 
-  /** Options for this line cursor. */
-  private readonly options: CursorOptions;
-
   /** Locations to try moving the cursor to after a deletion. */
-  private potentialNodes: INavigable<any>[] | null = null;
+  private potentialNodes: IFocusableNode[] | null = null;
-
-  /** Whether the renderer is zelos-style. */
-  private isZelos = false;
 
   /**
    * @param workspace The workspace this cursor belongs to.
-   * @param options Cursor options.
    */
-  constructor(
+  constructor(protected readonly workspace: WorkspaceSvg) {
-    protected readonly workspace: WorkspaceSvg,
-    options?: Partial<CursorOptions>,
-  ) {
     super();
-    // Regularise options and apply defaults.
-    this.options = {...defaultOptions, ...options};
-
-    this.isZelos = workspace.getRenderer() instanceof Renderer;
-
-    this.registerNavigationPolicies();
-  }
-
-  /**
-   * Registers default navigation policies for Blockly's built-in types with
-   * this cursor's workspace.
-   */
-  protected registerNavigationPolicies() {
-    const navigator = this.workspace.getNavigator();
-
-    const blockPolicy = new BlockNavigationPolicy();
-    if (this.workspace.isFlyout) {
-      const flyout = this.workspace.targetWorkspace?.getFlyout();
-      if (flyout) {
-        navigator.set(
-          BlockSvg,
-          new FlyoutNavigationPolicy(blockPolicy, flyout),
-        );
-
-        const buttonPolicy = new FlyoutButtonNavigationPolicy();
-        navigator.set(
-          FlyoutButton,
-          new FlyoutNavigationPolicy(buttonPolicy, flyout),
-        );
-
-        navigator.set(
-          FlyoutSeparator,
-          new FlyoutNavigationPolicy(
-            new FlyoutSeparatorNavigationPolicy(),
-            flyout,
-          ),
-        );
-      }
-    } else {
-      navigator.set(BlockSvg, blockPolicy);
-    }
-
-    navigator.set(RenderedConnection, new ConnectionNavigationPolicy());
-    navigator.set(WorkspaceSvg, new WorkspaceNavigationPolicy());
-
-    const fieldPolicy = new FieldNavigationPolicy();
-    navigator.set(FieldCheckbox, fieldPolicy);
-    navigator.set(FieldDropdown, fieldPolicy);
-    navigator.set(FieldImage, fieldPolicy);
-    navigator.set(FieldLabel, fieldPolicy);
-    navigator.set(FieldNumber, fieldPolicy);
-    navigator.set(FieldTextInput, fieldPolicy);
   }
 
   /**
@@ -137,14 +44,14 @@ export class LineCursor extends Marker {
    * @returns The next node, or null if the current node is
    *     not set or there is no next value.
    */
-  next(): INavigable<any> | null {
+  next(): IFocusableNode | null {
     const curNode = this.getCurNode();
     if (!curNode) {
       return null;
     }
     const newNode = this.getNextNode(
       curNode,
-      (candidate: INavigable<any> | null) => {
+      (candidate: IFocusableNode | null) => {
         return (
           candidate instanceof BlockSvg &&
           !candidate.outputConnection?.targetBlock()
@@ -166,7 +73,7 @@ export class LineCursor extends Marker {
    * @returns The next node, or null if the current node is
    *     not set or there is no next value.
    */
-  in(): INavigable<any> | null {
+  in(): IFocusableNode | null {
     const curNode = this.getCurNode();
     if (!curNode) {
       return null;
@@ -186,14 +93,14 @@ export class LineCursor extends Marker {
    * @returns The previous node, or null if the current node
    *     is not set or there is no previous value.
    */
-  prev(): INavigable<any> | null {
+  prev(): IFocusableNode | null {
     const curNode = this.getCurNode();
     if (!curNode) {
       return null;
     }
     const newNode = this.getPreviousNode(
       curNode,
-      (candidate: INavigable<any> | null) => {
+      (candidate: IFocusableNode | null) => {
         return (
           candidate instanceof BlockSvg &&
           !candidate.outputConnection?.targetBlock()
@@ -215,7 +122,7 @@ export class LineCursor extends Marker {
    * @returns The previous node, or null if the current node
    *     is not set or there is no previous value.
    */
-  out(): INavigable<any> | null {
+  out(): IFocusableNode | null {
     const curNode = this.getCurNode();
     if (!curNode) {
       return null;
@@ -241,7 +148,7 @@ export class LineCursor extends Marker {
     const inNode = this.getNextNode(curNode, () => true, true);
     const nextNode = this.getNextNode(
       curNode,
-      (candidate: INavigable<any> | null) => {
+      (candidate: IFocusableNode | null) => {
         return (
           candidate instanceof BlockSvg &&
           !candidate.outputConnection?.targetBlock()
@@ -265,10 +172,10 @@ export class LineCursor extends Marker {
    * @returns The next node in the traversal.
    */
   private getNextNodeImpl(
-    node: INavigable<any> | null,
+    node: IFocusableNode | null,
-    isValid: (p1: INavigable<any> | null) => boolean,
+    isValid: (p1: IFocusableNode | null) => boolean,
-    visitedNodes: Set<INavigable<any>> = new Set<INavigable<any>>(),
+    visitedNodes: Set<IFocusableNode> = new Set<IFocusableNode>(),
-  ): INavigable<any> | null {
+  ): IFocusableNode | null {
     if (!node || visitedNodes.has(node)) return null;
     let newNode =
       this.workspace.getNavigator().getFirstChild(node) ||
@@ -301,10 +208,10 @@ export class LineCursor extends Marker {
    * @returns The next node in the traversal.
    */
   getNextNode(
-    node: INavigable<any> | null,
+    node: IFocusableNode | null,
-    isValid: (p1: INavigable<any> | null) => boolean,
+    isValid: (p1: IFocusableNode | null) => boolean,
     loop: boolean,
-  ): INavigable<any> | null {
+  ): IFocusableNode | null {
     if (!node || (!loop && this.getLastNode() === node)) return null;
 
     return this.getNextNodeImpl(node, isValid);
@@ -323,10 +230,10 @@ export class LineCursor extends Marker {
    *     exists.
    */
   private getPreviousNodeImpl(
-    node: INavigable<any> | null,
+    node: IFocusableNode | null,
-    isValid: (p1: INavigable<any> | null) => boolean,
+    isValid: (p1: IFocusableNode | null) => boolean,
-    visitedNodes: Set<INavigable<any>> = new Set<INavigable<any>>(),
+    visitedNodes: Set<IFocusableNode> = new Set<IFocusableNode>(),
-  ): INavigable<any> | null {
+  ): IFocusableNode | null {
     if (!node || visitedNodes.has(node)) return null;
 
     const newNode =
@@ -355,10 +262,10 @@ export class LineCursor extends Marker {
    *     exists.
    */
   getPreviousNode(
-    node: INavigable<any> | null,
+    node: IFocusableNode | null,
-    isValid: (p1: INavigable<any> | null) => boolean,
+    isValid: (p1: IFocusableNode | null) => boolean,
     loop: boolean,
-  ): INavigable<any> | null {
+  ): IFocusableNode | null {
     if (!node || (!loop && this.getFirstNode() === node)) return null;
 
     return this.getPreviousNodeImpl(node, isValid);
@@ -371,15 +278,15 @@ export class LineCursor extends Marker {
    * @returns The right most child of the given node, or the node if no child
    *     exists.
    */
-  getRightMostChild(
+  private getRightMostChild(
-    node: INavigable<any> | null,
+    node: IFocusableNode | null,
-    stopIfFound: INavigable<any>,
+    stopIfFound: IFocusableNode,
-  ): INavigable<any> | null {
+  ): IFocusableNode | null {
     if (!node) return node;
     let newNode = this.workspace.getNavigator().getFirstChild(node);
     if (!newNode || newNode === stopIfFound) return node;
     for (
-      let nextNode: INavigable<any> | null = newNode;
+      let nextNode: IFocusableNode | null = newNode;
       nextNode;
       nextNode = this.workspace.getNavigator().getNextSibling(newNode)
     ) {
@@ -414,7 +321,7 @@ export class LineCursor extends Marker {
   preDelete(deletedBlock: BlockSvg) {
     const curNode = this.getCurNode();
 
-    const nodes: INavigable<any>[] = curNode ? [curNode] : [];
+    const nodes: IFocusableNode[] = curNode ? [curNode] : [];
     // The connection to which the deleted block is attached.
     const parentConnection =
       deletedBlock.previousConnection?.targetConnection ??
@@ -466,7 +373,7 @@ export class LineCursor extends Marker {
    *
    * @returns The current field, connection, or block the cursor is on.
    */
-  override getCurNode(): INavigable<any> | null {
+  override getCurNode(): IFocusableNode | null {
     this.updateCurNodeFromFocus();
     return super.getCurNode();
   }
@@ -479,7 +386,7 @@ export class LineCursor extends Marker {
    *
    * @param newNode The new location of the cursor.
    */
-  override setCurNode(newNode: INavigable<any> | null) {
+  override setCurNode(newNode: IFocusableNode | null) {
     super.setCurNode(newNode);
 
     if (isFocusableNode(newNode)) {
@@ -513,7 +420,7 @@ export class LineCursor extends Marker {
    *
    * @returns The first navigable node on the workspace, or null.
    */
-  getFirstNode(): INavigable<any> | null {
+  getFirstNode(): IFocusableNode | null {
     return this.workspace.getNavigator().getFirstChild(this.workspace);
   }
 
@@ -522,7 +429,7 @@ export class LineCursor extends Marker {
    *
    * @returns The last navigable node on the workspace, or null.
    */
-  getLastNode(): INavigable<any> | null {
+  getLastNode(): IFocusableNode | null {
     const first = this.getFirstNode();
     return this.getPreviousNode(first, () => true, true);
   }

core/keyboard_nav/marker.ts

@@ -14,7 +14,7 @@
 
 import {BlockSvg} from '../block_svg.js';
 import {Field} from '../field.js';
-import type {INavigable} from '../interfaces/i_navigable.js';
+import type {IFocusableNode} from '../interfaces/i_focusable_node.js';
 import {RenderedConnection} from '../rendered_connection.js';
 
 /**
@@ -26,7 +26,7 @@ export class Marker {
   colour: string | null = null;
 
   /** The current location of the marker. */
-  protected curNode: INavigable<any> | null = null;
+  protected curNode: IFocusableNode | null = null;
 
   /** The type of the marker. */
   type = 'marker';
@@ -36,7 +36,7 @@ export class Marker {
    *
    * @returns The current field, connection, or block the marker is on.
    */
-  getCurNode(): INavigable<any> | null {
+  getCurNode(): IFocusableNode | null {
     return this.curNode;
   }
 
@@ -45,7 +45,7 @@ export class Marker {
    *
    * @param newNode The new location of the marker, or null to remove it.
    */
-  setCurNode(newNode: INavigable<any> | null) {
+  setCurNode(newNode: IFocusableNode | null) {
     this.curNode = newNode;
   }
 
@@ -59,7 +59,7 @@ export class Marker {
    *
    * @returns The parent block of the node if any, otherwise null.
    */
-  getSourceBlockFromNode(node: INavigable<any> | null): BlockSvg | null {
+  getSourceBlockFromNode(node: IFocusableNode | null): BlockSvg | null {
     if (node instanceof BlockSvg) {
       return node;
     } else if (node instanceof Field) {

core/keyboard_nav/workspace_navigation_policy.ts

@@ -4,9 +4,9 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import type {INavigable} from '../interfaces/i_navigable.js';
+import type {IFocusableNode} from '../interfaces/i_focusable_node.js';
 import type {INavigationPolicy} from '../interfaces/i_navigation_policy.js';
-import type {WorkspaceSvg} from '../workspace_svg.js';
+import {WorkspaceSvg} from '../workspace_svg.js';
 
 /**
  * Set of rules controlling keyboard navigation from a workspace.
@@ -20,7 +20,7 @@ export class WorkspaceNavigationPolicy
    * @param current The workspace to return the first child of.
    * @returns The top block of the first block stack, if any.
    */
-  getFirstChild(current: WorkspaceSvg): INavigable<unknown> | null {
+  getFirstChild(current: WorkspaceSvg): IFocusableNode | null {
     const blocks = current.getTopBlocks(true);
     return blocks.length ? blocks[0] : null;
   }
@@ -31,7 +31,7 @@ export class WorkspaceNavigationPolicy
    * @param _current The workspace to return the parent of.
    * @returns Null.
    */
-  getParent(_current: WorkspaceSvg): INavigable<unknown> | null {
+  getParent(_current: WorkspaceSvg): IFocusableNode | null {
     return null;
   }
 
@@ -41,7 +41,7 @@ export class WorkspaceNavigationPolicy
    * @param _current The workspace to return the next sibling of.
    * @returns Null.
    */
-  getNextSibling(_current: WorkspaceSvg): INavigable<unknown> | null {
+  getNextSibling(_current: WorkspaceSvg): IFocusableNode | null {
     return null;
   }
 
@@ -51,7 +51,7 @@ export class WorkspaceNavigationPolicy
    * @param _current The workspace to return the previous sibling of.
    * @returns Null.
    */
-  getPreviousSibling(_current: WorkspaceSvg): INavigable<unknown> | null {
+  getPreviousSibling(_current: WorkspaceSvg): IFocusableNode | null {
     return null;
   }
 
@@ -64,4 +64,14 @@ export class WorkspaceNavigationPolicy
   isNavigable(current: WorkspaceSvg): boolean {
     return current.canBeFocused();
   }
+
+  /**
+   * Returns whether the given object can be navigated from by this policy.
+   *
+   * @param current The object to check if this policy applies to.
+   * @returns True if the object is a WorkspaceSvg.
+   */
+  isApplicable(current: any): current is WorkspaceSvg {
+    return current instanceof WorkspaceSvg;
+  }
 }

core/navigator.ts

@@ -4,10 +4,14 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import type {INavigable} from './interfaces/i_navigable.js';
+import type {IFocusableNode} from './interfaces/i_focusable_node.js';
 import type {INavigationPolicy} from './interfaces/i_navigation_policy.js';
+import {BlockNavigationPolicy} from './keyboard_nav/block_navigation_policy.js';
+import {ConnectionNavigationPolicy} from './keyboard_nav/connection_navigation_policy.js';
+import {FieldNavigationPolicy} from './keyboard_nav/field_navigation_policy.js';
+import {WorkspaceNavigationPolicy} from './keyboard_nav/workspace_navigation_policy.js';
 
-type RuleMap<T> = Map<new (...args: any) => T, INavigationPolicy<T>>;
+type RuleList<T> = INavigationPolicy<T>[];
 
 /**
  * Class responsible for determining where focus should move in response to
@@ -18,35 +22,35 @@ export class Navigator {
    * Map from classes to a corresponding ruleset to handle navigation from
    * instances of that class.
    */
-  private rules: RuleMap<any> = new Map();
+  protected rules: RuleList<any> = [
+    new BlockNavigationPolicy(),
+    new FieldNavigationPolicy(),
+    new ConnectionNavigationPolicy(),
+    new WorkspaceNavigationPolicy(),
+  ];
 
   /**
-   * Associates a navigation ruleset with its corresponding class.
+   * Adds a navigation ruleset to this Navigator.
    *
-   * @param key The class whose object instances should have their navigation
-   *     controlled by the associated policy.
    * @param policy A ruleset that determines where focus should move starting
-   *     from an instance of the given class.
+   *     from an instance of its managed class.
    */
-  set<T extends INavigable<T>>(
+  addNavigationPolicy(policy: INavigationPolicy<any>) {
-    key: new (...args: any) => T,
+    this.rules.push(policy);
-    policy: INavigationPolicy<T>,
-  ) {
-    this.rules.set(key, policy);
   }
 
   /**
    * Returns the navigation ruleset associated with the given object instance's
    * class.
    *
-   * @param key An object to retrieve a navigation ruleset for.
+   * @param current An object to retrieve a navigation ruleset for.
    * @returns The navigation ruleset of objects of the given object's class, or
    *     undefined if no ruleset has been registered for the object's class.
    */
-  private get<T extends INavigable<T>>(
+  private get(
-    key: T,
+    current: IFocusableNode,
-  ): INavigationPolicy<T> | undefined {
+  ): INavigationPolicy<typeof current> | undefined {
-    return this.rules.get(key.getClass());
+    return this.rules.find((rule) => rule.isApplicable(current));
   }
 
   /**
@@ -55,7 +59,7 @@ export class Navigator {
    * @param current The object to retrieve the first child of.
    * @returns The first child node of the given object, if any.
    */
-  getFirstChild<T extends INavigable<T>>(current: T): INavigable<any> | null {
+  getFirstChild(current: IFocusableNode): IFocusableNode | null {
     const result = this.get(current)?.getFirstChild(current);
     if (!result) return null;
     // If the child isn't navigable, don't traverse into it; check its peers.
@@ -71,7 +75,7 @@ export class Navigator {
    * @param current The object to retrieve the parent of.
    * @returns The parent node of the given object, if any.
    */
-  getParent<T extends INavigable<T>>(current: T): INavigable<any> | null {
+  getParent(current: IFocusableNode): IFocusableNode | null {
     const result = this.get(current)?.getParent(current);
     if (!result) return null;
     if (!this.get(result)?.isNavigable(result)) return this.getParent(result);
@@ -84,7 +88,7 @@ export class Navigator {
    * @param current The object to retrieve the next sibling node of.
    * @returns The next sibling node of the given object, if any.
    */
-  getNextSibling<T extends INavigable<T>>(current: T): INavigable<any> | null {
+  getNextSibling(current: IFocusableNode): IFocusableNode | null {
     const result = this.get(current)?.getNextSibling(current);
     if (!result) return null;
     if (!this.get(result)?.isNavigable(result)) {
@@ -99,9 +103,7 @@ export class Navigator {
    * @param current The object to retrieve the previous sibling node of.
    * @returns The previous sibling node of the given object, if any.
    */
-  getPreviousSibling<T extends INavigable<T>>(
+  getPreviousSibling(current: IFocusableNode): IFocusableNode | null {
-    current: T,
-  ): INavigable<any> | null {
     const result = this.get(current)?.getPreviousSibling(current);
     if (!result) return null;
     if (!this.get(result)?.isNavigable(result)) {

core/rendered_connection.ts

@@ -24,7 +24,6 @@ import {IContextMenu} from './interfaces/i_contextmenu.js';
 import type {IFocusableNode} from './interfaces/i_focusable_node.js';
 import type {IFocusableTree} from './interfaces/i_focusable_tree.js';
 import {hasBubble} from './interfaces/i_has_bubble.js';
-import type {INavigable} from './interfaces/i_navigable.js';
 import * as internalConstants from './internal_constants.js';
 import {Coordinate} from './utils/coordinate.js';
 import * as svgMath from './utils/svg_math.js';
@@ -38,7 +37,7 @@ const BUMP_RANDOMNESS = 10;
  */
 export class RenderedConnection
   extends Connection
-  implements IContextMenu, IFocusableNode, INavigable<RenderedConnection>
+  implements IContextMenu, IFocusableNode
 {
   // TODO(b/109816955): remove '!', see go/strict-prop-init-fix.
   sourceBlock_!: BlockSvg;
@@ -664,15 +663,6 @@ export class RenderedConnection
       | unknown
       | null as SVGElement | null;
   }
-
-  /**
-   * Returns this connection's class for keyboard navigation.
-   *
-   * @returns RenderedConnection.
-   */
-  getClass() {
-    return RenderedConnection;
-  }
 }
 
 export namespace RenderedConnection {

core/workspace_svg.ts

@@ -53,7 +53,6 @@ import {
 import type {IFocusableTree} from './interfaces/i_focusable_tree.js';
 import {hasBubble} from './interfaces/i_has_bubble.js';
 import type {IMetricsManager} from './interfaces/i_metrics_manager.js';
-import type {INavigable} from './interfaces/i_navigable.js';
 import type {IToolbox} from './interfaces/i_toolbox.js';
 import type {LineCursor} from './keyboard_nav/line_cursor.js';
 import type {Marker} from './keyboard_nav/marker.js';
@@ -100,11 +99,7 @@ const ZOOM_TO_FIT_MARGIN = 20;
  */
 export class WorkspaceSvg
   extends Workspace
-  implements
+  implements IContextMenu, IFocusableNode, IFocusableTree
-    IContextMenu,
-    IFocusableNode,
-    IFocusableTree,
-    INavigable<WorkspaceSvg>
 {
   /**
    * A wrapper function called when a resize event occurs.
@@ -2823,15 +2818,6 @@ export class WorkspaceSvg
     }
   }
 
-  /**
-   * Returns the class of this workspace.
-   *
-   * @returns WorkspaceSvg.
-   */
-  getClass() {
-    return WorkspaceSvg;
-  }
-
   /**
    * Returns an object responsible for coordinating movement of focus between
    * items on this workspace in response to keyboard navigation commands.
@@ -2841,6 +2827,16 @@ export class WorkspaceSvg
   getNavigator(): Navigator {
     return this.navigator;
   }
+
+  /**
+   * Sets the Navigator instance used by this workspace.
+   *
+   * @param newNavigator A Navigator object to coordinate movement between
+   *     elements on the workspace.
+   */
+  setNavigator(newNavigator: Navigator) {
+    this.navigator = newNavigator;
+  }
 }
 
 /**

tests/typescript/src/field/different_user_input.ts

@@ -61,10 +61,6 @@ class FieldMitosis extends Field<CellGroup> {
     });
     this.value_ = {cells};
   }
-
-  getClass() {
-    return FieldMitosis;
-  }
 }
 
 fieldRegistry.register('field_mitosis', FieldMitosis);