blockly/core/interfaces/i_navigation_policy.d.ts

Blockly is a library for building visual programming editors.

/**
 * @license
 * Copyright 2025 Google LLC
 * SPDX-License-Identifier: Apache-2.0
 */
import type { IFocusableNode } from './i_focusable_node.js';
/**
 * A set of rules that specify where keyboard navigation should proceed.
 */
export interface INavigationPolicy<T> {
    /**
     * Returns the first child element of the given element, if any.
     *
     * @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): IFocusableNode | null;
    /**
     * Returns the parent element of the given element, if any.
     *
     * @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): IFocusableNode | null;
    /**
     * Returns the peer element following the given element, if any.
     *
     * @param current The element which the user is navigating past.
     * @returns The next peer element of the current element, or null if there is
     *     none.
     */
    getNextSibling(current: T): IFocusableNode | null;
    /**
     * Returns the peer element preceding the given element, if any.
     *
     * @param current The element which the user is navigating past.
     * @returns The previous peer element of the current element, or null if
     *     there is none.
     */
    getPreviousSibling(current: T): IFocusableNode | null;
    /**
     * Returns an ID corresponding to the visual "row" the given element is part
     * of. All elements on the same visual row should share the same ID. For
     * example, icons share their parent block's row ID, as do inline connected
     * blocks or value inputs. Statement inputs, external inputs, or blocks
     * connected to one another's previous or next connections form distinct
     * visual rows and should have distinct row IDs.
     *
     * @param current The element to return the row ID of.
     * @returns The row ID of the given element.
     */
    getRowId(current: T): string;
    /**
     * 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;
    /**
     * 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;
}
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