/**
 * @license
 * Copyright 2020 Google Inc.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
/**
 * Utility to trap focus in a given root element, e.g. for modal components such
 * as dialogs. The root should have at least one focusable child element,
 * for setting initial focus when trapping focus.
 * Also tracks the previously focused element, and restores focus to that
 * element when releasing focus.
 */
export declare class FocusTrap {
    private readonly root;
    private readonly options;
    private elFocusedBeforeTrapFocus;
    constructor(root: HTMLElement, options?: FocusOptions);
    /**
     * Traps focus in `root`. Also focuses on either `initialFocusEl` if set;
     * otherwises sets initial focus to the first focusable child element.
     */
    trapFocus(): void;
    /**
     * Releases focus from `root`. Also restores focus to the previously focused
     * element.
     */
    releaseFocus(): void;
    /**
     * Wraps tab focus within `el` by adding two hidden sentinel divs which are
     * used to mark the beginning and the end of the tabbable region. When
     * focused, these sentinel elements redirect focus to the first/last
     * children elements of the tabbable region, ensuring that focus is trapped
     * within that region.
     */
    private wrapTabFocus;
    /**
     * Focuses on `initialFocusEl` if defined and a child of the root element.
     * Otherwise, focuses on the first focusable child element of the root.
     */
    private focusInitialElement;
    private getFocusableElements;
    private createSentinel;
}
/** Customization options. */
export interface FocusOptions {
    initialFocusEl?: HTMLElement;
    skipInitialFocus?: boolean;
    skipRestoreFocus?: boolean;
}