Highly improved Chrome extension

Full list feature changes in this commit:
- Support for iframes
- Switched to content-type (MIME) detection instead of hard-coding a
  case-sensitive check for the .PDF extension
- The PDF's original URL is visible in the omnibox
- Support for incognito mode

Note: PDF viewer is disabled for the file:// + incognito
combination, because it's currently impossible to get the combination
to work.

See mozilla#3017 (comment)

extensions/chrome/hide-xhtml-error.css

@@ -0,0 +1,3 @@
+parsererror {
+   display: none;
+}

extensions/chrome/insertviewer.js

@@ -0,0 +1,128 @@
+/* -*- Mode: Java; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set shiftwidth=2 tabstop=2 autoindent cindent expandtab: */
+/*
+Copyright 2012 Mozilla Foundation
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+/* globals chrome */
+
+'use strict';
+
+var VIEWER_URL = chrome.extension.getURL('content/web/viewer.html');
+var BASE_URL = VIEWER_URL.replace(/[^\/]+$/, '');
+
+function getViewerURL(pdf_url) {
+  return VIEWER_URL + '?file=' + encodeURIComponent(pdf_url);
+}
+
+function showViewer(url) {
+  // Cancel page load and empty document.
+  window.stop();
+  document.body.textContent = '';
+
+  replaceDocumentWithViewer(url);
+}
+function makeLinksAbsolute(doc) {
+  normalize('href', 'link[href]');
+  normalize('src', 'style[src],script[src]');
+
+  function normalize(attribute, selector) {
+    var nodes = doc.querySelectorAll(selector);
+    for (var i=0; i<nodes.length; ++i) {
+      var node = nodes[i];
+      var newAttribute = makeAbsolute(node.getAttribute(attribute));
+      node.setAttribute(attribute, newAttribute);
+    }
+  }
+  function makeAbsolute(url) {
+    if (url.indexOf('://') !== -1) return url;
+    return BASE_URL + url;
+  }
+}
+function replaceDocumentWithViewer(url) {
+  var x = new XMLHttpRequest();
+  x.open('GET', VIEWER_URL);
+  x.responseType = 'document';
+  x.onload = function() {
+    // Resolve all relative URLs
+    makeLinksAbsolute(x.response);
+
+    // Remove all <script> elements (added back later).
+    // I assumed that no inline script tags exist.
+    var scripts = [];
+    while (x.response.scripts.length) {
+      var script = x.response.scripts[0];
+      var newScript = document.createElement('script');
+      newScript.onload = loadNextScript;
+      newScript.src = script.src;
+      script.parentNode.removeChild(script);
+      scripts.push(newScript);
+    }
+
+    // Replace document with viewer
+    var docEl = document.adoptNode(x.response.documentElement);
+    document.replaceChild(docEl, document.documentElement);
+    // Force Chrome to render content
+    // (without this line, the layout is broken and querySelector
+    //  fails to find elements, even when they appear in the doc)
+    document.body.innerHTML += '';
+
+    // Load all scripts
+    loadNextScript();
+
+    function loadNextScript() {
+      if (scripts.length > 0)
+        document.head.appendChild(scripts.shift());
+      else
+        renderPDF(url);
+    }
+  };
+  x.send();
+}
+function renderPDF(url) {
+  var args = {
+    BASE_URL: BASE_URL,
+    pdf_url: url
+  };
+  // The following technique is explained at
+  // http://stackoverflow.com/a/9517879/938089
+  var script = document.createElement('script');
+  script.textContent =
+  '(function(args) {' +
+  '  PDFJS.workerSrc = args.BASE_URL + PDFJS.workerSrc;' +
+  '  window.DEFAULT_URL = args.pdf_url;' +
+  '  window.IMAGE_DIR = args.BASE_URL + window.IMAGE_DIR;' +
+  '})(' + JSON.stringify(args) + ');';
+  document.head.appendChild(script);
+
+  // Trigger domready
+  if (document.readyState === 'complete') {
+    var event = document.createEvent('Event');
+    event.initEvent('DOMContentLoaded', true, true);
+    document.dispatchEvent(event);
+  }
+}
+
+
+// Activate the content script only once per frame (until reload)
+if (!window.hasRun) {
+  window.hasRun = true;
+  chrome.extension.onMessage.addListener(function listener(message) {
+    if (message && message.type === 'showPDFViewer' &&
+        message.url === location.href) {
+          chrome.extension.onMessage.removeListener(listener);
+          showViewer(message.url);
+        }
+  });
+}

extensions/chrome/manifest.json

@@ -10,14 +10,20 @@
   },
   "permissions": [
     "webRequest", "webRequestBlocking",
-    "http://*/*.pdf",
-    "https://*/*.pdf",
-    "file:///*/*.pdf",
-    "http://*/*.PDF",
-    "https://*/*.PDF",
-    "file://*/*.PDF"
+    "<all_urls>",
+    "tabs"
   ],
+  "content_scripts": [{
+      "matches": [
+          "*://*/*.pdf*",
+          "*://*/*.PDF*"
+       ],
+       "css": ["hide-xhtml-error.css"]
+  }],
   "background": {
     "page": "pdfHandler.html"
-  }
+  },
+  "web_accessible_resources": [
+    "content/*"
+  ]
 }

extensions/chrome/pdfHandler-local.js

@@ -0,0 +1,69 @@
+/* -*- Mode: Java; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set shiftwidth=2 tabstop=2 autoindent cindent expandtab: */
+/*
+Copyright 2012 Mozilla Foundation
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+/* globals chrome, isPdfDownloadable */
+
+'use strict';
+
+// The onHeadersReceived event is not generated for local resources.
+// Fortunately, local PDF files will have the .pdf extension, so there's
+// no need to detect the Content-Type
+// Unfortunately, the omnibox won't show the URL.
+// Unfortunately, this method will not work for pages in incognito mode,
+//  unless "incognito":"split" is used AND http:/crbug.com/224094 is fixed.
+
+// Keeping track of incognito tab IDs will become obsolete when
+// "incognito":"split" can be used.
+var incognitoTabIds = [];
+chrome.windows.getAll({ populate: true }, function(windows) {
+  windows.forEach(function(win) {
+    if (win.incognito) {
+      win.tabs.forEach(function(tab) {
+        incognitoTabIds.push(tab.id);
+      });
+    }
+  });
+});
+chrome.tabs.onCreated.addListener(function(tab) {
+  if (tab.incognito) incognitoTabIds.push(tab.id);
+});
+chrome.tabs.onRemoved.addListener(function(tabId) {
+  var index = incognitoTabIds.indexOf(tabId);
+  if (index !== -1) incognitoTabIds.splice(index, 1);
+});
+
+chrome.webRequest.onBeforeRequest.addListener(
+  function(details) {
+    if (isPdfDownloadable(details)) // Defined in pdfHandler.js
+      return;
+
+    if (incognitoTabIds.indexOf(details.tabId) !== -1)
+      return; // Doesn't work in incognito mode, so don't redirect.
+
+    var viewerPage = 'content/web/viewer.html';
+    var url = chrome.extension.getURL(viewerPage) +
+      '?file=' + encodeURIComponent(details.url);
+    return { redirectUrl: url };
+  },
+  {
+    urls: [
+      'file://*/*.pdf',
+      'file://*/*.PDF'
+    ],
+    types: ['main_frame', 'sub_frame']
+  },
+  ['blocking']);

extensions/chrome/pdfHandler.html

@@ -15,3 +15,4 @@
 limitations under the License.
 -->
 <script src="pdfHandler.js"></script>
+<script src="pdfHandler-local.js"></script>

extensions/chrome/pdfHandler.js

@@ -23,25 +23,94 @@ function isPdfDownloadable(details) {
   return details.url.indexOf('pdfjs.action=download') >= 0;
 }
 
-chrome.webRequest.onBeforeRequest.addListener(
+function insertPDFJSForTab(tabId, url) {
+  chrome.tabs.executeScript(tabId, {
+    file: 'insertviewer.js',
+    allFrames: true,
+    runAt: 'document_start'
+  }, function() {
+    chrome.tabs.sendMessage(tabId, {
+      type: 'showPDFViewer',
+      url: url
+    });
+  });
+}
+function activatePDFJSForTab(tabId, url) {
+  chrome.tabs.onUpdated.addListener(function listener(_tabId) {
+    if (tabId === _tabId) {
+      insertPDFJSForTab(tabId, url);
+      chrome.tabs.onUpdated.removeListener(listener);
+    }
+  });
+}
+
+chrome.webRequest.onHeadersReceived.addListener(
   function(details) {
-    if (isPdfDownloadable(details))
+    // Check if the response is a PDF file
+    var isPDF = false;
+    var headers = details.responseHeaders;
+    var header, i;
+    var cdHeader;
+    if (!headers)
+      return;
+    for (i=0; i<headers.length; ++i) {
+      header = headers[i];
+      if (header.name.toLowerCase() == 'content-type') {
+        var headerValue = header.value.toLowerCase().split(';',1)[0].trim();
+        isPDF = headerValue === 'application/pdf' ||
+                headerValue === 'application/octet-stream' &&
+                details.url.toLowerCase().indexOf('.pdf') > 0;
+        break;
+      }
+    }
+    if (!isPDF)
       return;
 
-    var viewerPage = 'content/web/viewer.html';
-    var url = chrome.extension.getURL(viewerPage) +
-      '?file=' + encodeURIComponent(details.url);
-    return { redirectUrl: url };
+    if (isPdfDownloadable(details)) {
+      // Force download by ensuring that Content-Disposition: attachment is set
+      if (!cdHeader) {
+        for (; i<headers.length; ++i) {
+          header = headers[i];
+          if (header.name.toLowerCase() == 'content-disposition') {
+            cdHeader = header;
+            break;
+          }
+        }
+      }
+      if (!cdHeader) {
+        cdHeader = {name: 'Content-Disposition', value: ''};
+        headers.push(cdHeader);
+      }
+      if (cdHeader.value.toLowerCase().indexOf('attachment') === -1) {
+        cdHeader.value = 'attachment' + cdHeader.value.replace(/^[^;]+/i, '');
+        return {
+          responseHeaders: headers
+        };
+      }
+      return;
+    }
+
+    // Replace frame's content with the PDF viewer
+    // This approach maintains the friendly URL in the 
+    // location bar
+    activatePDFJSForTab(details.tabId, details.url);
+
+    return {
+      responseHeaders: [
+        // Set Cache-Control header to avoid downloading a file twice
+        {name:'Cache-Control',value:'max-age=600'},
+        // Temporary render response as XHTML.
+        // Since PDFs are never valid XHTML, the garbage is not going to be
+        // rendered. insertviewer.js will quickly replace the document with
+        // the PDF.js viewer.
+        {name:'Content-Type',value:'application/xhtml+xml; charset=US-ASCII'},
+      ]
+    };
   },
   {
     urls: [
-      'http://*/*.pdf',
-      'https://*/*.pdf',
-      'file://*/*.pdf',
-      'http://*/*.PDF',
-      'https://*/*.PDF',
-      'file://*/*.PDF'
+      '<all_urls>'
     ],
-    types: ['main_frame']
+    types: ['main_frame', 'sub_frame']
   },
-  ['blocking']);
+  ['blocking','responseHeaders']);

make.js

@@ -591,6 +591,7 @@ target.chrome = function() {
       [['extensions/chrome/*.json',
         'extensions/chrome/*.html',
         'extensions/chrome/*.js',
+        'extensions/chrome/*.css',
         'extensions/chrome/icon*.png',],
        CHROME_BUILD_DIR],
       ['external/webL10n/l10n.js', CHROME_BUILD_CONTENT_DIR + '/web'],
@@ -607,6 +608,22 @@ target.chrome = function() {
   sed('-i', /PDFJSSCRIPT_VERSION/, EXTENSION_VERSION,
       CHROME_BUILD_DIR + '/manifest.json');
 
+  // Allow PDF.js resources to be loaded by adding the files to
+  // the "web_accessible_resources" section.
+  var file_list = ls('-RA', CHROME_BUILD_CONTENT_DIR);
+  var public_chrome_files = file_list.reduce(function(war, file) {
+    // Exclude directories (naive: Exclude paths without dot)
+    if (file.indexOf('.') !== -1) {
+        // Only add a comma after the first file
+        if (war)
+          war += ',\n';
+        war += JSON.stringify('content/' + file);
+    }
+    return war;
+  }, '');
+  sed('-i', /"content\/\*"/, public_chrome_files,
+      CHROME_BUILD_DIR + '/manifest.json');
+
   // Bundle the files to a Chrome extension file .crx if path to key is set
   var pem = env['PDFJS_CHROME_KEY'];
   if (!pem) {