native_client_sdk/src/build_tools/screenshot_extension/injected.js

   1 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 // Only inject once.
   6 if (!document.body.getAttribute('screenshot_extension_injected')) {
   7   document.body.setAttribute('screenshot_extension_injected', true);
   8   (function() {
   9
  10     // Bounce message from webpage to background page.
  11     //
  12     // Expecting a message called with:
  13     // window.postMessage({
  14     //    id: <a value that is passed back unchanged to the response for
  15     //         identification>,
  16     //    target: 'background'
  17     // }, '*');
  18     //
  19     // When the screenshot is captured, a message will be posted to the window.
  20     // Listen for it like this:
  21     //
  22     // window.addEventListener('message', function(event) {
  23     //   if (event.source !== window)
  24     //     return;
  25     //
  26     //   if (event.data.target !== 'page')
  27     //     return;
  28     //
  29     //   // event.data is an object:
  30     //   // {
  31     //   //   id: <the id passed to the request>,
  32     //   //   target: 'page',
  33     //   //   data: <a data URI of MIMEtype image/png with the tab screenshot>
  34     //   // }
  35     //   //
  36     //   // or if there is an error:
  37     //   //
  38     //   // {
  39     //   //   id: <the id passed to the request>,
  40     //   //   target: 'page',
  41     //   //   error: <an error string>
  42     //   // }
  43     // }, false);
  44     //
  45     window.addEventListener('message', function(event) {
  46       if (event.source !== window)
  47         return;
  48
  49       // Ignore messages not destined for the background page.
  50       if (event.data.target !== 'background')
  51         return;
  52
  53       var id = event.data.id;
  54       console.log('sending message: id=' + id);
  55
  56       chrome.runtime.sendMessage(null, {},
  57           function(responseData) {
  58             // Bounce response from background page back to webpage.
  59             var lastError = chrome.runtime.lastError;
  60             if (lastError) {
  61               console.log('lastError: ' + lastError);
  62
  63               window.postMessage({id: id, target: 'page', error: lastError},
  64                                  '*');
  65               return;
  66             }
  67
  68             console.log('received response: id=' + id);
  69
  70             window.postMessage({id: id, target: 'page', data: responseData},
  71                                '*');
  72       });
  73     }, false);
  74   })();
  75 }