import type { Context } from "../engine_context.js";
import { NeedleXRSession } from "./NeedleXRSession.js";
export declare type XRSessionEventArgs = {
    session: NeedleXRSession;
};
/**
 * Add a listener for when an XR session starts
 * This event is triggered when the XR session is started, either by the user or by the application before all other XR start events
 * @param fn The function to call when the XR session starts
 * @example
 * ```js
 * onXRSessionStart((evt) => {
 *   console.log("XR session started", evt);
 * });
 * ```
 * @returns A function to remove the listener
 */
export declare function onXRSessionStart(fn: (evt: XRSessionEventArgs) => void): () => void;
/**
 * Remove a listener for when an XR session starts
 * @param fn The function to remove from the listeners
 * @example
 * ```js
 * const myFunction = (evt) => {
 *  console.log("XR session started", evt);
 * };
 * onXRSessionStart(myFunction);
 * offXRSessionStart(myFunction);
 * ```
 */
export declare function offXRSessionStart(fn: (evt: XRSessionEventArgs) => void): void;
/**
 * Add a listener for when an XR session ends
 * This event is triggered when the XR session is ended, either by the user or by the application before all other XR end events
 * @param fn The function to call when the XR session ends
 * @example
 * ```js
 * onXRSessionEnd((evt) => {
 *    console.log("XR session ended", evt);
 * });
 * ```
 * @returns A function to remove the listener
 */
export declare function onXRSessionEnd(fn: (evt: XRSessionEventArgs) => void): () => void;
/**
 * Remove a listener for when an XR session ends
 * @param fn The function to remove from the listeners
 * @example
 * ```js
 * const myFunction = (evt) => {
 *  console.log("XR session ended", evt);
 * };
 * onXRSessionEnd(myFunction);
 * offXRSessionEnd(myFunction);
 * ```
 */
export declare function offXRSessionEnd(fn: (evt: XRSessionEventArgs) => void): void;
export declare type XRSessionRequestEventArgs = {
    readonly mode: XRSessionMode;
    readonly init: XRSessionInit;
    readonly context: Context;
};
/**
 * Add a listener that fires before an XR session is requested.
 * Use this to modify the session init options, e.g. to add optional features like `camera-access`.
 * @param fn The function to call before the XR session is requested
 * @example
 * ```js
 * onBeforeXRSession((args) => {
 *   args.init.optionalFeatures ??= [];
 *   args.init.optionalFeatures.push("camera-access");
 * });
 * ```
 * @return A function to remove the listener
 */
export declare function onBeforeXRSession(fn: (args: XRSessionRequestEventArgs) => void): () => void;
/**
 * Remove a listener for before an XR session is requested
 * @param fn The function to remove from the listeners
 */
export declare function offBeforeXRSession(fn: (args: XRSessionRequestEventArgs) => void): void;
/**
 * @internal
 * Invoke the XRSessionStart event
 * @param evt The XRSession event arguments
 */
export declare function invokeXRSessionStart(evt: XRSessionEventArgs): void;
/**
 * @internal
 * Invoke the XRSessionEnd event
 * @param evt The XRSession event arguments
 */
export declare function invokeXRSessionEnd(evt: XRSessionEventArgs): void;