layout/style/test/test_img_src_causing_reflow.html


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<!doctype html>
<meta charset="utf-8">
<title>Test for bug 1787072</title>
<script src="/tests/SimpleTest/SimpleTest.js"></script>
<style>
img {
  width: 100px;
  height: 100px;
  background-color: blue;
}
</style>
<img> <!-- Initially broken -->
<script>
add_task(async function() {
  const utils = SpecialPowers.DOMWindowUtils;
  const img = document.querySelector("img");
  img.getBoundingClientRect();

  let origFramesConstructed = utils.framesConstructed;
  let origFramesReflowed = utils.framesReflowed;

  let error = new Promise(r => img.addEventListener("error", r, { once: true }));

  // Doesn't need to be an actual image.
  img.src = "/some-valid-url";

  img.getBoundingClientRect();
  is(origFramesReflowed, utils.framesReflowed, "Shouldn't have reflowed when going broken -> loading");
  is(origFramesConstructed, utils.framesConstructed, "Shouldn't have reflowed when going broken -> loading");

  await error;

  is(origFramesReflowed, utils.framesReflowed, "Shouldn't have reflowed when going loading -> broken");
  is(origFramesConstructed, utils.framesConstructed, "Shouldn't have reflowed when going loading -> broken");
});
</script>