<object> / <embed> support in Chromium extension

extensions/chromium/contentscript.js

@@ -25,15 +25,108 @@ function getViewerURL(pdf_url) {
   return VIEWER_URL + '?file=' + encodeURIComponent(pdf_url);
 }
 
-document.addEventListener('beforeload', function(event) {
-  var elem = event.target;
-  if (elem.nodeName.toUpperCase() !== 'EMBED') {
+// (un)prefixed property names
+var createShadowRoot, shadowRoot;
+if (typeof Element.prototype.createShadowRoot !== 'undefined') {
+  // Chrome 35+
+  createShadowRoot = 'createShadowRoot';
+  shadowRoot = 'shadowRoot';
+} else if (typeof Element.prototype.webkitCreateShadowRoot !== 'undefined') {
+  // Chrome 25 - 34
+  createShadowRoot = 'webkitCreateShadowRoot';
+  shadowRoot = 'webkitShadowRoot';
+  try {
+    document.createElement('embed').webkitCreateShadowRoot();
+  } catch (e) {
+    // Only supported since Chrome 33.
+    createShadowRoot = shadowRoot = '';
+  }
+}
+
+// Only observe the document if we can make use of Shadow DOM.
+if (createShadowRoot) {
+  if ('animation' in document.documentElement.style) {
+    document.addEventListener('animationstart', onAnimationStart, true);
+  } else {
+    document.addEventListener('webkitAnimationStart', onAnimationStart, true);
+  }
+}
+
+function onAnimationStart(event) {
+  if (event.animationName === 'pdfjs-detected-object-or-embed') {
+    watchObjectOrEmbed(event.target);
+  }
+}
+
+// Called for every <object> or <embed> element in the page.
+// It does not trigger any Mutation observers, but it may modify the
+// shadow DOM rooted under the given element.
+// Calling this function multiple times for the same element is safe, i.e.
+// it has no side effects.
+function watchObjectOrEmbed(elem) {
+  var mimeType = elem.type;
+  if (mimeType && 'application/pdf' !== mimeType.toLowerCase()) {
     return;
   }
-  if (!/^application\/pdf$/i.test(elem.type)) {
+  // <embed src> <object data>
+  var srcAttribute = 'src' in elem ? 'src' : 'data';
+  var path = elem[srcAttribute];
+  if (!mimeType && !/\.pdf($|[?#])/i.test(path)) {
     return;
   }
-  event.preventDefault();
-  elem.type = 'text/html';
-  elem.src = getViewerURL(elem.src);
-}, true);
+
+  if (elem[shadowRoot]) {
+    // If the element already has a shadow root, assume that we've already
+    // seen this element.
+    return;
+  }
+  elem[createShadowRoot]();
+
+  function updateViewerFrame() {
+    var path = elem[srcAttribute];
+    if (!path) {
+      elem[shadowRoot].textContent = '';
+    } else {
+      elem[shadowRoot].innerHTML =
+        // Set display: inline-block; to the host element (<embed>/<object>) to
+        // ensure that the dimensions defined on the host element are applied to
+        // the iframe (http://crbug.com/358648).
+        // The styles are declared in the shadow DOM to allow page authors to
+        // override these styles (e.g. .style.display = 'none';).
+        '<style>\n' +
+        // Chrome 35+
+        ':host { display: inline-block; }\n' +
+        // Chrome 33 and 34 (not 35+ because of http://crbug.com/351248)
+        '*:not(style):not(iframe) { display: inline-block; }\n' +
+        'iframe { width: 100%; height: 100%; border: 0; }\n' +
+        '</style>' +
+        '<iframe allowfullscreen></iframe>';
+      elem[shadowRoot].lastChild.src = getEmbeddedViewerURL(path);
+    }
+  }
+
+  updateViewerFrame();
+
+  // Watch for page-initiated changes of the src/data attribute.
+  var srcObserver = new MutationObserver(updateViewerFrame);
+  srcObserver.observe(elem, {
+    attributes: true,
+    childList: false,
+    characterData: false,
+    attributeFilter: [srcAttribute]
+  });
+}
+
+// Get the viewer URL, provided that the path is a valid URL.
+function getEmbeddedViewerURL(path) {
+  var fragment = /^([^#]*)(#.*)?$/.exec(path);
+  path = fragment[1];
+  fragment = fragment[2] || '';
+
+  // Resolve relative path to document.
+  var a = document.createElement('a');
+  a.href = document.baseURI;
+  a.href = path;
+  path = a.href;
+  return getViewerURL(path) + fragment;
+}