@tldraw/utils/dist-cjs/lib/throttle.js

A tiny little drawing app (private utilities).

"use strict";
var __defProp = Object.defineProperty;
var __getOwnPropDesc = Object.getOwnPropertyDescriptor;
var __getOwnPropNames = Object.getOwnPropertyNames;
var __hasOwnProp = Object.prototype.hasOwnProperty;
var __export = (target, all) => {
  for (var name in all)
    __defProp(target, name, { get: all[name], enumerable: true });
};
var __copyProps = (to, from, except, desc) => {
  if (from && typeof from === "object" || typeof from === "function") {
    for (let key of __getOwnPropNames(from))
      if (!__hasOwnProp.call(to, key) && key !== except)
        __defProp(to, key, { get: () => from[key], enumerable: !(desc = __getOwnPropDesc(from, key)) || desc.enumerable });
  }
  return to;
};
var __toCommonJS = (mod) => __copyProps(__defProp({}, "__esModule", { value: true }), mod);
var throttle_exports = {};
__export(throttle_exports, {
  fpsThrottle: () => fpsThrottle,
  throttleToNextFrame: () => throttleToNextFrame
});
module.exports = __toCommonJS(throttle_exports);
const isTest = () => typeof process !== "undefined" && process.env.NODE_ENV === "test" && // @ts-expect-error
!globalThis.__FORCE_RAF_IN_TESTS__;
const fpsQueue = [];
const targetFps = 60;
const targetTimePerFrame = Math.ceil(1e3 / targetFps);
let frame;
let time = 0;
let last = 0;
const flush = () => {
  const queue = fpsQueue.splice(0, fpsQueue.length);
  for (const fn of queue) {
    fn();
  }
};
function tick() {
  if (frame) {
    return;
  }
  const now = Date.now();
  const elapsed = now - last;
  if (time + elapsed < targetTimePerFrame) {
    frame = requestAnimationFrame(() => {
      frame = void 0;
      tick();
    });
    return;
  }
  frame = requestAnimationFrame(() => {
    frame = void 0;
    last = now;
    time = Math.min(time + elapsed - targetTimePerFrame, targetTimePerFrame * 10);
    flush();
  });
}
let started = false;
function fpsThrottle(fn) {
  if (isTest()) {
    fn.cancel = () => frame && cancelAnimationFrame(frame);
    return fn;
  }
  const throttledFn = () => {
    if (fpsQueue.includes(fn)) {
      return;
    }
    fpsQueue.push(fn);
    if (!started) {
      started = true;
      last = Date.now() - targetTimePerFrame - 1;
    }
    tick();
  };
  throttledFn.cancel = () => {
    const index = fpsQueue.indexOf(fn);
    if (index > -1) {
      fpsQueue.splice(index, 1);
    }
  };
  return throttledFn;
}
function throttleToNextFrame(fn) {
  if (isTest()) {
    fn();
    return () => {
    };
  }
  if (!fpsQueue.includes(fn)) {
    fpsQueue.push(fn);
    if (!started) {
      started = true;
      last = Date.now() - targetTimePerFrame - 1;
    }
    tick();
  }
  return () => {
    const index = fpsQueue.indexOf(fn);
    if (index > -1) {
      fpsQueue.splice(index, 1);
    }
  };
}
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