/**
 * Allow the scheduler to be modified, e.g. when switching to an immersive XRSession.
 *
 * TODO: we may want to only do this for a subset of animations, like just those subject to
 *  an XRSession, while letting others use the default. This global hook won't work for that.
 *
 * @param {{requestAnimationFrame, cancelAnimationFrame}} scheduler - an object holding
 *        the two scheduling functions.
 */
export function setAnimationScheduler(scheduler: {
    requestAnimationFrame: any;
    cancelAnimationFrame: any;
}): void;
export default Runner;
/**
 * @class Runner
 * A container for {@link Tween} instances that handles invoking them on each animation frame.
 */
declare class Runner {
    tweens: any[];
    destructor(): void;
    /**
     * Add a tween to the runner. It will be invoked on the next frame, not immediately.
     * @param {Tween} tween
     */
    start(tween: Tween): void;
    /**
     * Remove a tween from the runner.
     * @param tween
     */
    stop(tween: any): void;
    /**
     * Pause a tween; call `runner.start(tween)` to unpause it
     * @param tween
     */
    pause(tween: any): void;
    _tick(now: any): void;
    /**
     * Stop all running tweens.
     */
    stopAll(): void;
    /**
     * Override to specify a function that will be called at the end of every frame, after all
     * tweens have been updated.
     */
    onTick(): void;
    /**
     * Override to specify a function that will be called after all running tweens have completed.
     */
    onDone(): void;
}