<!doctype HTML>

<style>
.contained {
  contain: style layout;
  background: lightgreen;
}
#small {
  width: 100px;
  height: 100px;
}
#large {
  width: 200px;
  height: 200px;
}
.child {
  width: 20px;
  height: 20%;
  background: cyan;
}
#spacer {
  width: 150px;
  height: 150px;
  background: green;
}
</style>

<div id="parent"><div class="contained" id="small"></div></div>
<div id="spacer"></div>

<script src="../../resources/testharness.js"></script>
<script src="../../resources/testharnessreport.js"></script>

<script>
async_test((t) => {
  function createChild(id) {
    let child = document.createElement("div");
    child.classList = "child";
    child.id = id;
    return child;
  }

  function measureForced() {
    t.step(() => {
      // Ensure children are laid out; this forces a layout.
      assert_equals(document.getElementById("0").offsetTop, 0, "0 forced");
      assert_equals(document.getElementById("1").offsetTop, 40, "1 forced");
      assert_equals(document.getElementById("2").offsetTop, 80, "2 forced");
      // Parent should be 100 height, since its child is locked.
      assert_equals(document.getElementById("parent").offsetTop, 8, "parent forced");
      assert_equals(document.getElementById("spacer").offsetTop, 108, "spacer forced");
    });
  }

  function forcedMeasureAfterCommit() {
    t.step(() => {
      // Ensure children are still laid out.
      assert_equals(document.getElementById("0").offsetTop, 0, "0 in commit");
      assert_equals(document.getElementById("1").offsetTop, 40, "1 in commit");
      assert_equals(document.getElementById("2").offsetTop, 80, "2 in commit");
      // Now the parent should encompass an unlocked container, so spacer is pushed down more.
      assert_equals(document.getElementById("parent").offsetTop, 8, "parent in commit");
      assert_equals(document.getElementById("spacer").offsetTop, 208, "spacer in commit");
    });
  }

  function construct(container) {
    container.id = "large";
    container.appendChild(createChild("0"));
    container.appendChild(createChild("1"));
    container.appendChild(createChild("2"));
  }

  async function runTest() {
    let container = document.getElementById("small");
    await container.displayLock.acquire({ timeout: Infinity });

    construct(container);
    measureForced();

    container.displayLock.commit();
    forcedMeasureAfterCommit();
    t.done();
  }

  window.onload = function() {
    requestAnimationFrame(() => requestAnimationFrame(runTest));
  };
}, "Measure Forced Layout");
</script>