/**
 * Marks the page as scrolled.
 *
 * A header can carry a second set of colours for the scrolled page - transparent over the hero,
 * solid once the reader has moved on, the way the Flatsome transparent header works. The
 * stylesheet holds both states; this only says which one applies. Without the script the header
 * keeps its normal colours, which is a readable page, not a broken one.
 */
export function initScrolled(doc = document) {
  const view = doc.defaultView;
  let queued = false;
  const sync = () => { queued = false; doc.documentElement.classList.toggle('is-scrolled', view.scrollY > 40); };
  const onScroll = () => { if (!queued) { queued = true; view.requestAnimationFrame(sync); } };
  view.addEventListener('scroll', onScroll, { passive: true });
  sync();
  return () => { view.removeEventListener('scroll', onScroll); doc.documentElement.classList.remove('is-scrolled'); };
}

if (!document.querySelector('#editor')) initScrolled();