test_drawDiscardedImage.html

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<!DOCTYPE HTML>

<html>

<!--

https://bugzilla.mozilla.org/show_bug.cgi?id=731419

-->

<head>

  <title>Test for Bug 731419 - Draw an ostensibly discarded image to a canvas</title>

  <script src="/tests/SimpleTest/SimpleTest.js"></script>

  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>

</head>

<body>

<!--

  Load an image in an iframe, then draw that image to a canvas.  Then set the

  iframe to display:none (after bug 731419, this causes the image's decoded

  data to be discarded) and draw the image to a canvas again.  We should draw

  the same image data both times.

-->

<script>

SimpleTest.waitForExplicitFinish();

var data1;

function drawImage()

  var canvas = document.getElementById('canvas');

  var ctx = canvas.getContext('2d');

  var iframeDoc = document.getElementById('iframe').contentDocument;

  ctx.clearRect(0, 0, canvas.height, canvas.width);

  ctx.drawImage(iframeDoc.getElementById('image'), 0, 0);

  return canvas.toDataURL();

function iframeLoad()

  data1 = drawImage();

  document.getElementById('iframe').style.display = 'none';

  // Spin the event loop a few times to give the image in the display:none

  // iframe a chance to be discarded.

  SimpleTest.executeSoon(function() {

    SimpleTest.executeSoon(function() {

      SimpleTest.executeSoon(function() {

        step2();

});

});

});

function step2()

  is(drawImage(), data1, "Same image before and after iframe display:none");

  SimpleTest.finish();

</script>

<canvas id='canvas'></canvas>

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</body>

</html>