<!DOCTYPE html>
<script src="../resources/js-test.js"></script>
<script src="helper-functions.js"></script>
<div style="width:100%; height:700px;"></div>
<div id="target" style="background-color: green; width:0px; height:0px"></div>
<div style="width:100%; height:700px;"></div>

<script>
description("Intersection observer test with zero-size target element.");
var target = document.getElementById("target");
var entries = [];
var observer = new IntersectionObserver(changes => { entries = entries.concat(changes) }, {});

onload = function() {
  observer.observe(target);
  entries.push(...observer.takeRecords());
  shouldBeEqualToNumber("entries.length", 0);
  document.scrollingElement.scrollTop = 300;
  // See README for explanation of double RAF.
  requestAnimationFrame(() => { requestAnimationFrame(step1) });
};

function step1() {
  entries.push(...observer.takeRecords());
  shouldBeEqualToNumber("entries.length", 1);
  if (entries.length > 0) {
    shouldBeEqualToNumber("entries[0].boundingClientRect.left", 8);
    shouldBeEqualToNumber("entries[0].boundingClientRect.right", 8);
    shouldBeEqualToNumber("entries[0].boundingClientRect.top", 408);
    shouldBeEqualToNumber("entries[0].boundingClientRect.bottom", 408);
    shouldBeEqualToNumber("entries[0].intersectionRect.left", 8);
    shouldBeEqualToNumber("entries[0].intersectionRect.right", 8);
    shouldBeEqualToNumber("entries[0].intersectionRect.top", 408);
    shouldBeEqualToNumber("entries[0].intersectionRect.bottom", 408);
    shouldBeEqualToNumber("entries[0].rootBounds.left", 0);
    shouldBeEqualToNumber("entries[0].rootBounds.right", 785);
    shouldBeEqualToNumber("entries[0].rootBounds.top", 0);
    shouldBeEqualToNumber("entries[0].rootBounds.bottom", 600);
    shouldEvaluateToSameObject("entries[0].target", target);

    // ClientRect members of IntersectionObserverEntry should be stable.
    shouldEvaluateToSameObject("entries[0].boundingClientRect", entries[0].boundingClientRect);
    shouldEvaluateToSameObject("entries[0].intersectionRect", entries[0].intersectionRect);
    shouldEvaluateToSameObject("entries[0].rootBounds", entries[0].rootBounds);
  }
  document.scrollingElement.scrollTop = 100;
  requestAnimationFrame(step2);
}

function step2() {
  entries.push(...observer.takeRecords());
  shouldBeEqualToNumber("entries.length", 2);
  if (entries.length > 1) {
    shouldBeEqualToNumber("entries[1].boundingClientRect.left", 8);
    shouldBeEqualToNumber("entries[1].boundingClientRect.right", 8);
    shouldBeEqualToNumber("entries[1].boundingClientRect.top", 608);
    shouldBeEqualToNumber("entries[1].boundingClientRect.bottom", 608);
    shouldBeEqualToNumber("entries[1].intersectionRect.left", 0);
    shouldBeEqualToNumber("entries[1].intersectionRect.right", 0);
    shouldBeEqualToNumber("entries[1].intersectionRect.top", 0);
    shouldBeEqualToNumber("entries[1].intersectionRect.bottom", 0);
    shouldBeEqualToNumber("entries[1].rootBounds.left", 0);
    shouldBeEqualToNumber("entries[1].rootBounds.right", 785);
    shouldBeEqualToNumber("entries[1].rootBounds.top", 0);
    shouldBeEqualToNumber("entries[1].rootBounds.bottom", 600);
    shouldEvaluateToSameObject("entries[1].target", target);
  }
  finishJSTest();
  document.scrollingElement.scrollTop = 0;
}
</script>