@needle-tools/engine/src/engine/xr/events.ts

Needle Engine is a web-based runtime for 3D apps. It runs on your machine for development with great integrations into editors like Unity or Blender - and can be deployed onto any device! It is flexible, extensible and networking and XR are built-in.

import type { NeedleXRSession } from "./NeedleXRSession.js";

export declare type XRSessionEventArgs = { session: NeedleXRSession };

const onXRSessionStartListeners: ((evt: XRSessionEventArgs) => void)[] = [];

/**
 * 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);
 * });
 * ```
 */
export function onXRSessionStart(fn: (evt: XRSessionEventArgs) => void) {
    if (onXRSessionStartListeners.indexOf(fn) === -1) {
        onXRSessionStartListeners.push(fn);
    }
}
/**
 * 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 function offXRSessionStart(fn: (evt: XRSessionEventArgs) => void) {
    const index = onXRSessionStartListeners.indexOf(fn);
    if (index !== -1) {
        onXRSessionStartListeners.splice(index, 1);
    }
}

const onXRSessionEndListeners: ((evt: XRSessionEventArgs) => 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);
 * });
 * ```
 */
export function onXRSessionEnd(fn: (evt: XRSessionEventArgs) => void) {
    if (onXRSessionEndListeners.indexOf(fn) === -1) {
        onXRSessionEndListeners.push(fn);
    }
};

/**
 * 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 function offXRSessionEnd(fn: (evt: XRSessionEventArgs) => void) {
    const index = onXRSessionEndListeners.indexOf(fn);
    if (index !== -1) {
        onXRSessionEndListeners.splice(index, 1);
    }
}


/**
 * @internal
 * Invoke the XRSessionStart event
 * @param evt The XRSession event arguments
 */
export function invokeXRSessionStart(evt: XRSessionEventArgs) {
    globalThis.dispatchEvent(new CustomEvent("needle-xrsession-start", { detail: evt }));
    for (let i = 0; i < onXRSessionStartListeners.length; i++) {
        onXRSessionStartListeners[i](evt);
    }
}

/**
 * @internal
 * Invoke the XRSessionEnd event
 * @param evt The XRSession event arguments
 */
export function invokeXRSessionEnd(evt: XRSessionEventArgs) {
    globalThis.dispatchEvent(new CustomEvent("needle-xrsession-end", { detail: evt }));
    for (let i = 0; i < onXRSessionEndListeners.length; i++) {
        onXRSessionEndListeners[i](evt);
    }
}