declare namespace viewer {
    /**
     * Utility class providing simplified access to the clients fullscreen API. The toggle can be used to toggle
     * fullscreen for a HTML element while managing the execution of custom toggle code.
     *
     * ```
     * canvas.element.addEventListener('click', function() { gloperate.viewer.Fullscreen.toggle(canvas.element); });
     * ```
     *
     * Use `:fullscreen` (or `:-moz-full-screen`, `:-webkit-full-screen`, and `:-ms-full-screen`) selectors in order to
     * configure fullscreen specific style. Alternatively, an additional class, e.g., `fullscreen`, could be toggled
     * via callaback.
     */
    class Fullscreen {
        /**
         * Cached fullscreenchange event function of the clients specific fullscreen API.
         */
        protected static _event: string;
        /**
         * Callback that is to be triggered within the remove event listener.
         */
        protected static _callback: (() => void) | undefined;
        /**
         * Backup of the element's initial width and height.
         */
        protected static _size: [string, string];
        /**
         * Cached exit call of the clients specific fullscreen API.
         */
        protected static _exit: () => void;
        /**
         * Cached request call of the clients specific fullscreen API.
         */
        protected static _request: (element: HTMLElement) => void;
        /**
         * Cached element call returning the fullscreen element specific to the clients fullscreen API.
         */
        protected static _element: () => HTMLElement;
        /**
         * Event listener used to add the remove event listener using on indirection, that is, the first fullscreen
         * event triggered after a request is ignored. This is important for triggering the fullscreen callback before
         * the request is completed. The listener adds the removeListener and removes itself as listener.
         */
        protected static addEventListener: EventListener;
        /**
         * Event listener that is used to account for implicit fullscreen exit events, e.g., user explicitly uses a GUI
         * element for entering fullscreen, but uses ESC to exit fullscreen. The listener triggers the callback provided
         * on toggle and removes itself as listener.
         */
        protected static removeEventListener: EventListener;
        /**
         * Query and cache the client specific fullscreen API.
         */
        protected static queryAndCacheAPI(): void;
        /**
         * Returns whether or not a fullscreen element exists, indicating if fullscreen is active or not.
         */
        static active(): boolean;
        /**
         * Requests or exits fullscreen mode for a given element. If the element is already in fullscreen, fullscreen
         * mode is exited. Else, fullscreen mode is requested. The function considers various platform specific
         * fullscreen interfaces, i.e., native, ms, moz, and webkit.
         * @param element - Element to toggle fullscreen state of.
         */
        static toggle(element: HTMLElement, callback?: () => void): void;
    }
}
export = viewer;