Making sense of touch events on iframes in iOS 4.1

gistfile1.js

function translateTouchEvent(element, target, evt, edata) {
  // IN 4.1 ONLY, if we have a touch start on the layer, and it's been
  // almost no time since we had a touch end on the layer, discard the start.
  // (This is the most broken thing about 4.1.)
  if (
    p.brokenModel_4_1 &&
    !edata.frame &&
    !p.touching &&
    edata.start &&
    p.edataPrev &&
    p.edataPrev.end &&
    (edata.time - p.edataPrev.time) < 30
  ) {
    evt.preventDefault();
    return;
  }

  // If we don't have a touch and we see a start or a move on anything, start
  // a touch.
  if (!p.touching && !edata.end) {
    return fireStart(evt, target, edata);
  }

  // If this is a move event and we already have a touch, continue the move.
  if (edata.move && p.touching) {
    return fireMove(evt, edata);
  }

  if (p.brokenModel_4_1) {
    // IN 4.1 ONLY, if we have a touch in progress, and we see a start, end
    // or cancel event (moves are covered in previous rule), and the event
    // is not on the iframe, end the touch.
    // (This is because 4.1 bizarrely sends a random event to the layer
    // above the iframe, rather than an end event to the iframe itself.)
    if (p.touching && !edata.frame) {
      // However, a touch start will fire on the layer when moving out of
      // the overlap with the frame. This would trigger the end of the touch.
      // And the immediately subsequent move starts a new touch.
      //
      // To get around this, we only provisionally end the touch - if we get
      // a touchmove momentarily, we'll cancel this touchend.
      return fireProvisionalEnd(evt, edata);
    }
  } else {
    // In older versions of MobileSafari, if the touch ends when we're
    // touching something, just fire it.
    if (edata.end && p.touching) {
      return fireProvisionalEnd(evt, edata);
    }
  }

  // IN 4.1 ONLY, a touch that has started outside an iframe should not be
  // endable by the iframe.
  if (
    p.brokenModel_4_1 &&
    p.originator != element &&
    edata.frame &&
    edata.end
  ) {
    evt.preventDefault();
    return;
  }

  // If we see a touch end on the frame, end the touch.
  if (edata.frame && edata.end && p.touching) {
    return fireProvisionalEnd(evt, edata);
  }
}