/**
* Provides a robust, stoppable animation loop based on requestAnimationFrame.
* Ensures that only one loop instance is running at any given time.
* Can run on requestAnimationFrame (default) or at a custom interval.
* Supports an optional frame limit for one-shot animations.
* @exports module:lib/util/Looper
* @author Frank Kudermann - alphanull
* @version 1.0.0
* @license MIT
*/
export default class Looper {
/**
* The user-defined render function to be called on each frame/tick.
* @type {Function}
*/
#renderFn;
/**
* Current timer ID (RAF or interval), or null if stopped.
* @type {number|null}
*/
#timerId = null;
/**
* The update interval in milliseconds. If null, uses requestAnimationFrame.
* @type {number|null}
*/
#interval = null;
/**
* The maximum number of frames/ticks to run, or null for unlimited.
* @type {number|null}
*/
#tickLimit = null;
/**
* Current tick/frame count for a limited run.
* @type {number}
*/
#tickCount = 0;
/**
* Number of frames/ticks since the last FPS calculation.
* @type {number}
*/
#frameCount = 0;
/**
* Timestamp of the last FPS calculation.
* @type {number}
*/
#lastFpsUpdate = 0;
/**
* Most recent calculated FPS value.
* @type {number}
*/
#currentFps = 0;
/**
* Creates a new RAFLoop instance.
* @param {Function} renderFn The function to execute on each frame/tick. Must not be null.
* @param {number} [interval] Optional: update interval in milliseconds. If omitted or falsy, uses requestAnimationFrame.
* @throws {TypeError} If renderFn is not a function.
*/
constructor(renderFn, interval) {
if (typeof renderFn !== 'function') throw new TypeError('RAFLoop: renderFn must be a function.');
this.#renderFn = renderFn;
this.#interval = typeof interval === 'number' && interval > 0 ? interval : null;
}
/**
* Starts the loop if not already running.
* Optionally limits the number of ticks/frames.
* If called again while running, changes the tick limit or makes the loop unlimited.
* @param {number} [limit] Optional maximum number of ticks; unlimited if omitted or invalid.
*/
start(limit) {
const isFiniteLimit = typeof limit === 'number' && Number.isFinite(limit) && limit > 0;
if (this.#timerId !== null) {
// Already running: update limit if needed.
if (isFiniteLimit) {
this.#tickLimit = limit;
} else {
this.#tickLimit = null;
}
return;
}
this.#tickLimit = isFiniteLimit ? limit : null;
this.#tickCount = 0;
this.#lastFpsUpdate = performance.now();
this.#frameCount = 0;
if (this.#interval === null) {
this.#tickRAF(); // RAF mode
} else {
this.#timerId = setInterval(() => { this.#handleTick(); }, this.#interval); // Interval mode
}
}
/**
* Stops the loop if running.
*/
stop() {
if (this.#timerId !== null) {
if (this.#interval === null) {
cancelAnimationFrame(this.#timerId); // RAF mode
} else {
clearInterval(this.#timerId); // Interval mode
}
this.#timerId = null;
}
this.#tickLimit = null;
this.#tickCount = 0;
}
/**
* Returns whether the loop is currently running.
* @returns {boolean} True if the loop is active, false otherwise.
*/
isRunning() {
return this.#timerId !== null;
}
/**
* Returns the currently measured frames/ticks per second (FPS/TPS).
* @returns {number} The most recent FPS/TPS value, updated once per second.
*/
getFPS() {
return this.#currentFps;
}
/**
* Internal tick method for RAF mode.
* @private
*/
#tickRAF = () => {
this.#timerId = requestAnimationFrame(this.#tickRAF);
this.#handleTick();
};
/**
* Internal tick logic shared by RAF and interval.
* Increments tick counter, handles limit and FPS calculation.
* @private
*/
#handleTick() {
// FPS Calculation
const now = performance.now();
this.#frameCount += 1;
if (now - this.#lastFpsUpdate >= 1000) {
this.#currentFps = Math.round(this.#frameCount * 1000 / (now - this.#lastFpsUpdate));
this.#frameCount = 0;
this.#lastFpsUpdate = now;
}
// Limited run: tick counting
if (this.#tickLimit !== null) {
this.#tickCount += 1;
if (this.#tickCount > this.#tickLimit) {
this.stop();
return;
}
}
this.#renderFn();
}
/**
* Performs full cleanup by stopping the loop and clearing the render function.
* Should be called when the instance is no longer needed.
*/
destroy() {
this.stop();
this.#renderFn = null;
}
}
