buuh/packages/core/lib/raf.js

// Ported from nanoraf 3.1.0 (MIT) — https://github.com/choojs/nanoraf
// Only call requestAnimationFrame when needed.

import { ok, equal } from './assert.js'

export default function nanoraf (render, raf) {
  equal(typeof render, 'function', 'nanoraf: render should be a function')
  ok(typeof raf === 'function' || typeof raf === 'undefined', 'nanoraf: raf should be a function or undefined')

  // Wrap rather than alias: calling an extracted requestAnimationFrame
  // with no receiver throws 'Illegal invocation' in strict-mode ESM
  // (the CJS original survived only thanks to sloppy-mode this-patching).
  if (!raf) raf = (cb) => globalThis.requestAnimationFrame(cb)
  let redrawScheduled = false
  let args = null

  return function frame (...frameArgs) {
    if (args === null && !redrawScheduled) {
      redrawScheduled = true

      raf(function redraw () {
        redrawScheduled = false
        const _args = args
        args = null
        render(..._args)
      })
    }

    args = frameArgs
  }
}