third_party/WebKit/LayoutTests/fast/js/resources/image-preload-helper.js

   1 // This is used by several tests to help get images reliably preloaded.
   2
   3 // Given a node, loads all urls specified in style declarations
   4 // attached to the node or it's decendants.
   5 // imageCount specifies the number of images we expect to find (to try to add some
   6 // protection against brittleness due to imperfect url parsing, since other missing a preload
   7 // will typically result in a test that fails only occasionally).
   8 // If failPattern is specified, then any url that matches the regex
   9 // will be expected to fail to load.
  10 function preloadImagesFromStyle(rootNode, imageCount, onComplete, failPattern) {
  11     var basePath = location.href.substring(0, location.href.lastIndexOf('/') + 1);
  12     var nodes = rootNode.querySelectorAll('[style]');
  13     var imagesToLoad = [];
  14     var seenUrls = {};
  15     for (var i = 0; i < nodes.length; i++) {
  16         var urls = nodes[i].style.cssText.split(/url\w*\(([^)]*)\)/);
  17         for (var j = 1; j < urls.length; j += 2) {
  18             // Attempt to convert URL to a relative path in order to have deterministic error messages.
  19             var url = urls[j];
  20             if (url.indexOf(basePath) == 0)
  21                 url = url.substring(basePath.length);
  22
  23             var error = false;
  24             if (failPattern && failPattern.test(url))
  25                 error = true;
  26             if (url in seenUrls)
  27                 continue;
  28             seenUrls[url] = true;
  29             imagesToLoad.push({url: url, error: error});
  30         }
  31     }
  32
  33     if (imageCount != imagesToLoad.length) {
  34         var msg = 'Found the following ' + imagesToLoad.length + ' images, when expecting ' + imageCount + ': ';
  35         for (var i = 0; i < imagesToLoad.length; i++) {
  36             msg += '\n' + imagesToLoad[i].url;
  37         }
  38         testFailed(msg);
  39     }
  40
  41     loadImages(imagesToLoad, onComplete);
  42 }
  43
  44 // For each object in the given array, attempt to load the image specified by the
  45 // url property.  If the error property is specified and true, then the load is
  46 // expected to fail.  Once all loads have completed or failed, onComplete is invoked.
  47 function loadImages(imagesToLoad, onComplete) {
  48
  49     var imagesLeftToLoad = imagesToLoad.length;
  50
  51     function onImageLoad(url, success, e) {
  52         // This debug output order is non-deterministic - only show when not running in DRT
  53         if (!window.testRunner)
  54             debug( 'Event "' + e.type + '": ' + url);
  55
  56         if (!success)
  57             testFailed('Got unexpected \'' + e.type + '\' event for image: ' + url);
  58
  59         imagesLeftToLoad--;
  60         if (imagesLeftToLoad == 0) {
  61             onComplete();
  62         }
  63         if (imagesLeftToLoad < 0)
  64             testFailed('Got more load/error callbacks than expected.');
  65     }
  66
  67     for (var i = 0; i < imagesToLoad.length; i++) {
  68         var img = new Image();
  69         var expectError = imagesToLoad[i].error;
  70         img.addEventListener('load', onImageLoad.bind(undefined, imagesToLoad[i].url, !expectError));
  71         img.addEventListener('error', onImageLoad.bind(undefined, imagesToLoad[i].url, !!expectError));
  72         img.src = imagesToLoad[i].url;
  73     }
  74 }