/*!
{
  "name": "sizes attribute",
  "async": true,
  "property": "sizes",
  "tags": ["image"],
  "authors": ["Mat Marquis"],
  "notes": [{
    "name": "WHATWG Spec",
    "href": "https://html.spec.whatwg.org/multipage/embedded-content.html#the-img-element"
  }, {
    "name": "Srcset and sizes",
    "href": "https://ericportis.com/posts/2014/srcset-sizes/"
  }]
}
!*/
/* DOC
Test for the `sizes` attribute on images
*/
define(['Modernizr', 'createElement', 'addTest'], function(Modernizr, createElement, addTest) {
  Modernizr.addAsyncTest(function() {
    var width1, width2, test;
    var image = createElement('img');
    // in a perfect world this would be the test...
    var isSizes = 'sizes' in image;

    // ... but we need to deal with Safari 9...
    if (!isSizes && ('srcset' in image)) {
      width2 = 'data:image/gif;base64,R0lGODlhAgABAPAAAP///wAAACH5BAAAAAAALAAAAAACAAEAAAICBAoAOw==';
      width1 = 'data:image/gif;base64,R0lGODlhAQABAAAAACH5BAEKAAEALAAAAAABAAEAAAICTAEAOw==';

      test = function() {
        addTest('sizes', image.width === 2);
      };

      image.onload = test;
      image.onerror = test;
      image.setAttribute('sizes', '9px');

      image.srcset = width1 + ' 1w,' + width2 + ' 8w';
      image.src = width1;
    } else {
      addTest('sizes', isSizes);
    }
  });
});