picture-aspect-ratio.html

<!doctype html>

<title>Image width and height attributes are used to infer aspect-ratio</title>

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

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

<style>

  img:not([nowidth]) {

    width: 100%;

    max-width: 100px;

    height: auto;

</style>

<picture>

  <source srcset="/images/green-100x50.png"></source>

  <img>

</picture>

<picture>

  <source srcset="/images/green-100x50.png" width="100" height="100"></source>

  <img>

</picture>

<picture>

  <source srcset="/images/green-100x50.png" width="100" height="100"></source>

  <img width="50" height="100">

</picture>

<picture>

  <source srcset="/images/green-100x50.png" width="100" height="100" id="twosource-s1"></source>

  <source srcset="/images/green-100x50.png" width="300" height="150"></source>

  <img id="twosource-img">

</picture>

<div style="width: 100px;">

  <picture>

    <source srcset="/images/green-100x50.png" width="100%" height="50%" id="percent-src"></source>

    <img style="contain:size;" id="percent-img" nowidth="true">

  </picture>

</div>

<picture>

  <source srcset="/images/green-100x50.png" width="100abc" height="50abc" id="trailing-src"></source>

  <img style="contain:size;" id="trailing-img" nowidth="true">

</picture>

<script>

let guard = async_test("source width and height attributes are used to infer aspect-ratio in <picture>");

function assert_ratio(img, expected, description) {

  let epsilon = 0.001;

  assert_approx_equals(parseFloat(getComputedStyle(img).width, 10) / parseFloat(getComputedStyle(img).height, 10),

                       expected, epsilon, description);

function createPicture(width, height) {

  var picture = document.createElement("picture");

  var source = document.createElement("source");

  if (width !== undefined)

    source.setAttribute("width", width);

  if (height !== undefined)

    source.setAttribute("height", height);

  source.setAttribute("srcset", "/images/green.png");

  picture.appendChild(source);

  var img = document.createElement("img");

  picture.appendChild(img);

  document.body.appendChild(picture);

  return img;

function assert_cs(img, val) {

  assert_equals(getComputedStyle(img).aspectRatio, val);

// Create and append a new image and immediately check the ratio.

// This is not racy because the spec requires the user agent to queue a task:

// https://html.spec.whatwg.org/multipage/images.html#updating-the-image-data

test(function() {

  var img = createPicture(100, 100);

  assert_ratio(img, 1.0);

  assert_cs(img, "auto 100 / 100");

  img.style.display = "none";

  img.setAttribute("nowidth", "true");

  assert_equals(getComputedStyle(img).width, "100px");

  assert_equals(getComputedStyle(img).height, "100px");

  var source = img.previousSibling;

  assert_equals(getComputedStyle(source).width, "auto");

  assert_equals(getComputedStyle(source).height, "auto");

}, "Computed style for width/height/aspect-ratio");

test(function() {

  img = createPicture(200, 100);

  img.setAttribute("width", 250);

  img.setAttribute("height", 50);

  assert_ratio(img, 2.0);

  assert_cs(img, "auto 200 / 100");

  img.style.display = "none";

  img.setAttribute("nowidth", "true");

  assert_equals(getComputedStyle(img).width, "200px");

  assert_equals(getComputedStyle(img).height, "100px");

  source = img.previousSibling;

  assert_equals(getComputedStyle(source).width, "auto");

  assert_equals(getComputedStyle(source).height, "auto");

}, "Source width/height should take precedence over img attributes.");

test(function() {

  img.parentNode.removeChild(img.previousSibling);

  assert_cs(img, "auto 250 / 50");

  img.src = "/images/green.png";

  assert_ratio(img, 5.0);

  img.style.display = "none";

  img.setAttribute("nowidth", "true");

  assert_equals(getComputedStyle(img).width, "250px");

  assert_equals(getComputedStyle(img).height, "50px");

}, "Make sure style gets invalidated correctly when the source gets removed.");

test(function() {

  img = createPicture(100, undefined);

  img.setAttribute("width", 200);

  img.setAttribute("height", 100);

  assert_cs(img, "auto");

  img.style.display = "none";

  img.setAttribute("nowidth", "true");

  assert_equals(getComputedStyle(img).width, "100px");

  assert_equals(getComputedStyle(img).height, "auto");

}, "If the <source> has only one of width/height, we don't get an aspect ratio, even if the <img> has both.");

test(function() {

  img = createPicture(undefined, undefined);

  img.setAttribute("width", 200);

  img.setAttribute("height", 100);

  assert_cs(img, "auto 200 / 100");

}, "If we don't have width/height on the source, we fall back to width/height on the <img>.");

test(function() {

  img = createPicture(100, undefined);

  img.parentNode.style.display = "none";

  img.setAttribute("width", "200");

  img.setAttribute("height", "300");

  img.setAttribute("nowidth", "true");

  assert_cs(img, "auto");

  assert_equals(getComputedStyle(img).width, "100px");

  assert_equals(getComputedStyle(img).height, "auto");

}, "If we only have one width attribute, we should get width mapped but no aspect ratio, even if <img> has attributes.");

test(function() {

  img = createPicture(undefined, 100);

  img.parentNode.style.display = "none";

  img.setAttribute("width", "200");

  img.setAttribute("height", "300");

  img.setAttribute("nowidth", "true");

  assert_cs(img, "auto");

  assert_equals(getComputedStyle(img).width, "auto");

  assert_equals(getComputedStyle(img).height, "100px");

}, "If we only have height attribute, we should get height mapped but no aspect ratio, even if <img> has attributes.");

test(function() {

  img = createPicture(100, 100);

  assert_cs(img, "auto 100 / 100");

  img.previousSibling.setAttribute("height", "300");

  assert_cs(img, "auto 100 / 300");

  img.previousSibling.setAttribute("width", "10");

  assert_cs(img, "auto 10 / 300");

  img.style.display = "none";

  img.setAttribute("nowidth", "true");

  assert_equals(getComputedStyle(img).width, "10px");

  assert_equals(getComputedStyle(img).height, "300px");

}, "Dynamically changing width/height should change computed style");

test(function() {

  img = document.getElementById("twosource-img");

  assert_cs(img, "auto 100 / 100");

  source = document.getElementById("twosource-s1");

  source.setAttribute("type", "x-foo/x-bar");

  // We should now match the second source

  assert_cs(img, "auto 300 / 150");

  img.style.display = "none";

  img.setAttribute("nowidth", "true");

  assert_equals(getComputedStyle(img).width, "300px");

  assert_equals(getComputedStyle(img).height, "150px");

}, "Changing which <source> matches should change computed style");

test(function() {

  img = document.getElementById("percent-img");

  assert_equals(img.offsetWidth, 100);

  assert_equals(img.offsetHeight, 0);

  assert_cs(img, "auto");

  source = document.getElementById("percent-src");

  assert_equals(source.width, 100);

  assert_equals(source.height, 50);

  img.style.display = "none";

  img.setAttribute("nowidth", "true");

  assert_equals(getComputedStyle(img).width, "100%");

  assert_equals(getComputedStyle(img).height, "50%");

}, "Percentages on source should be ignored for aspect-ratio but used for width/height.");

test(function() {

  img = document.getElementById("trailing-img");

  assert_equals(img.offsetWidth, 100);

  assert_equals(img.offsetHeight, 50);

  assert_cs(img, "auto 100 / 50");

  source = document.getElementById("trailing-src");

  assert_equals(source.width, 100);

  assert_equals(source.height, 50);

  img.style.display = "none";

  img.setAttribute("nowidth", "true");

  assert_equals(getComputedStyle(img).width, "100px");

  assert_equals(getComputedStyle(img).height, "50px");

}, "Trailing garbage should be ignored but not make the attribute invalid");

onload = function() {

  let images = document.querySelectorAll("img");

  test(function() {

    var img = images[0];

    assert_ratio(img, 2.0, "2.0 is the original aspect ratio of green-100x50.png");

    assert_cs(img, "auto");

    img.style.display = "none";

    img.setAttribute("nowidth", "true");

    assert_equals(getComputedStyle(img).width, "auto");

    assert_equals(getComputedStyle(img).height, "auto");

  }, "Loaded picture test: Both <source> and <img> are without width and height attributes");

  test(function () {

    img = images[1];

    assert_ratio(img, 2.0, "Loaded image's aspect ratio, at least by default, overrides width / height ratio.");

    assert_cs(img, "auto 100 / 100");

    img.style.display = "none";

    img.setAttribute("nowidth", "true");

    assert_equals(getComputedStyle(img).width, "100px");

    assert_equals(getComputedStyle(img).height, "100px");

  }, "Loaded picture test: <source> with width and height attributes, <img> without width and height attributes");

  test(function () {

    img = images[2];

    assert_ratio(img, 2.0, "Loaded image's aspect ratio, at least by default, overrides width / height ratio (2).");

    assert_cs(img, "auto 100 / 100");

    img.style.display = "none";

    img.setAttribute("nowidth", "true");

    assert_equals(getComputedStyle(img).width, "100px");

    assert_equals(getComputedStyle(img).height, "100px");

  }, "Loaded picture test: Both <source> and <img> are with width and height attributes");

  guard.done();

};

</script>

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