blockly
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Blockly is a library for building visual programming editors.
63 lines • 2.52 kB
TypeScript
/**
* @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 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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