test_restyling_xhr_doc.html

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'use strict';

// This test supplements the web-platform-tests in:

//

//   web-animations/interfaces/Animatable/animate-no-browsing-context.html

//

// Specifically, it covers the case where we have a running animation

// targetting an element in a document without a browsing context.

//

// Currently the behavior in this case is not well-defined. For example,

// if we were to simply take an element from such a document, and do:

//

//  const xdoc = xhr.responseXML;

//  const div = xdoc.getElementById('test');

//  div.style.opacity = '0';

//  alert(getComputedStyle(div).opacity);

//

// We'd get '0' in Firefox and Edge, but an empty string in Chrome.

//

// However, if instead of using the style attribute, we set style in a <style>

// element in *either* the document we're calling from *or* the XHR doc and

// do the same we get '1' in Firefox and Edge, but an empty string in Chrome.

//

// That is, no browser appears to apply styles to elements in a document without

// a browsing context unless the styles are defined using the style attribute,

// and even then Chrome does not.

//

// There is some prose in CSSOM which says,

//

//    Note: This means that even if obj is in a different document (e.g. one

//    fetched via XMLHttpRequest) it will still use the style rules associated

//    with the document that is associated with the global object on which

//    getComputedStyle() was invoked to compute the CSS declaration block.[1]

//

// However, this text has been around since at least 2013 and does not appear

// to be implemented.

//

// As a result, it's not really possible to write a cross-browser test for the

// behavior for animations in this context since it's not clear what the result

// should be. That said, we still want to exercise this particular code path so

// we make this case a Mozilla-specific test. The other similar tests cases for

// which the behavior is well-defined are covered by web-platform-tests.

//

// [1] https://drafts.csswg.org/cssom/#extensions-to-the-window-interface

function getXHRDoc(t) {

  return new Promise(resolve => {

    const xhr = new XMLHttpRequest();

    xhr.open('GET', 'xhr_doc.html');

    xhr.responseType = 'document';

    xhr.onload = t.step_func(() => {

      assert_equals(xhr.readyState, xhr.DONE,

                    'Request should complete successfully');

      assert_equals(xhr.status, 200,

                    'Response should be OK');

      resolve(xhr.responseXML);

});

    xhr.send();

});

promise_test(t => {

  let anim;

  return getXHRDoc(t).then(xhrdoc => {

    const div = xhrdoc.getElementById('test');

    anim = div.animate({ opacity: [ 0, 1 ] }, 1000);

    // Give the animation an active timeline and kick-start it.

    anim.timeline = document.timeline;

    anim.startTime = document.timeline.currentTime;

    assert_equals(anim.playState, 'running',

                  'The animation should be running');

    // Gecko currently skips applying animation styles to elements in documents

    // without browsing contexts.

    assert_not_equals(getComputedStyle(div).opacity, '0',

                      'Style should NOT be updated');

});

}, 'Forcing an animation targetting an element in a document without a'

    + ' browsing context to play does not cause style to update');

promise_test(t => {

  let anim;

  return getXHRDoc(t).then(xhrdoc => {

    const div = addDiv(t);

    anim = div.animate({ opacity: [ 0, 1 ] }, 1000);

    assert_equals(getComputedStyle(div).opacity, '0',

                  'Style should be updated');

    // Trigger an animation restyle to be queued

    anim.currentTime = 0.1;

    // Adopt node into XHR doc

    xhrdoc.body.appendChild(div);

    // We should skip applying animation styles to elements in documents

    // without a pres shell.

    assert_equals(getComputedStyle(div).opacity, '1',

                  'Style should NOT be updated');

});

}, 'Moving an element with a pending animation restyle to a document without'

   + ' a browsing context resets animation style');

</script>