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Add-ons
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  2. Mozilla
  3. Add-ons
  4. Add-on SDK
  5. Tutorials
  6. Annotator
  7. Storing annotations

Storing annotations

In This Article
  1. Storing New Annotations
  2. Listing Stored Annotations
    1. Annotation List Content Script
    2. Annotation List HTML and CSS
    3. Updating main.js
  3. Responding To OverQuota events
  4. Respecting Private Browsing

Add-ons using the techniques described in this document are considered a legacy technology in Firefox. Don't use these techniques to develop new add-ons. Use WebExtensions instead. If you maintain an add-on which uses the techniques described here, consider migrating it to use WebExtensions.

From Firefox 53 onwards, no new legacy add-ons will be accepted on addons.mozilla.org (AMO).

From Firefox 57 onwards, WebExtensions will be the only supported extension type, and Firefox will not load other types.

Even before Firefox 57, changes coming up in the Firefox platform will break many legacy extensions. These changes include multiprocess Firefox (e10s), sandboxing, and multiple content processes. Legacy extensions that are affected by these changes should migrate to WebExtensions if they can. See the "Compatibility Milestones" document for more.

A wiki page containing resources, migration paths, office hours, and more, is available to help developers transition to the new technologies.

Deprecated in Firefox 29 and removed in Firefox 38.

Warning: this tutorial relies on the since-removed Widget API and no longer works with Firefox.

The widget API is deprecated from Firefox 29 onwards. Please see the ui module for replacements. In particular, for a simple button, try the action button or toggle button APIs, and for a more complex widget try the toolbar or sidebar APIs.

Now we are able to create annotations, let's store them using the simple-storage module. In this chapter we will cover three topics relating to persistent storage:

  • using simple-storage to persist objects
  • handling exhaustion of the storage quota allocated to you
  • respecting Private Browsing

Storing New Annotations

In this section we are only touching the main.js file.

First, import the simple-storage module with a declaration like:

var simpleStorage = require('sdk/simple-storage');

In the module scope, initialize an array which will contain the stored annotations:

if (!simpleStorage.storage.annotations)
  simpleStorage.storage.annotations = [];

Now we'll add a function to the module scope which deals with a new annotation. The annotation is composed of the text the user entered and the "annotation anchor", which consists of the URL, element ID and element content:

function handleNewAnnotation(annotationText, anchor) {
  var newAnnotation = new Annotation(annotationText, anchor);
  simpleStorage.storage.annotations.push(newAnnotation);
}

This function calls a constructor for an Annotation object, which we also need to supply:

function Annotation(annotationText, anchor) {
  this.annotationText = annotationText;
  this.url = anchor[0];
  this.ancestorId = anchor[1];
  this.anchorText = anchor[2];
}

Now we need to link this code to the annotation editor, so that when the user presses the return key in the editor, we create and store the new annotation:

var annotationEditor = panels.Panel({
  width: 220,
  height: 220,
  contentURL: data.url('editor/annotation-editor.html'),
  contentScriptFile: data.url('editor/annotation-editor.js'),
  onMessage: function(annotationText) {
    if (annotationText)
      handleNewAnnotation(annotationText, this.annotationAnchor);
    annotationEditor.hide();
  },
  onShow: function() {
    this.postMessage('focus');
  }
});

Listing Stored Annotations

To prove that this works, let's implement the part of the add-on that displays all the previously entered annotations. This is implemented as a panel that's shown in response to the widget's right-click message.

The panel has three new files associated with it:

  • a content-script which builds the panel content
  • a simple HTML file used as a template for the panel's content
  • a simple CSS file to provide some basic styling.

These three files can all go in a new subdirectory of data which we will call list.

Annotation List Content Script

Here's the annotation list's content script:

self.on("message", function onMessage(storedAnnotations) {
  var annotationList = $('#annotation-list');
  annotationList.empty();
  storedAnnotations.forEach(
    function(storedAnnotation) {
      var annotationHtml = $('#template .annotation-details').clone();
      annotationHtml.find('.url').text(storedAnnotation.url)
                                 .attr('href', storedAnnotation.url);
      annotationHtml.find('.url').bind('click', function(event) {
        event.stopPropagation();
        event.preventDefault();
        self.postMessage(storedAnnotation.url);
      });
      annotationHtml.find('.selection-text')
                    .text(storedAnnotation.anchorText);
      annotationHtml.find('.annotation-text')
                    .text(storedAnnotation.annotationText);
      annotationList.append(annotationHtml);
    });
});

It builds the DOM for the panel from the array of annotations it is given.

The user will be able to click links in the panel, but we want to open them in the main browser window rather than the panel. So the content script binds a click handler to the links which will send the URL to the add-on.

Save this file in data/list as annotation-list.js.

Annotation List HTML and CSS

Here's the HTML for the annotation list:

<html>
<head>
  <meta http-equiv="Content-type" content="text/html; charset=utf-8" />
  <title>Saved annotations</title>
  <link rel="stylesheet" type="text/css" href="annotation-list.css" />
</head>
<body>
<div id="annotation-list">
</div>
<div id="template">
  <div class="annotation-details">
    <a class="url"></a>
    <div class="selection-text"></div>
    <div class="annotation-text"></div>
  </div>
</div>
</body>
</html>

Here's the corresponding CSS:

#annotation-list .annotation-details
  {
  padding: 10px;
  margin: 10px;
  border: solid 3px #EEE;
  background-color: white;
  }
#annotation-list .url, .selection-text, .annotation-text
  {
  padding: 5px;
  margin: 5px;
  }
#annotation-list .selection-text,#annotation-list .annotation-text
  {
  border: solid 1px #EEE;
  }
#annotation-list .annotation-text
  {
  font-style: italic;
  }
body
  {
  background-color: #F5F5F5;
  font: 100% arial, helvetica, sans-serif;
  }
h1
  {
  font-family: georgia,serif;
  font-size: 1.5em;
  text-align:center;
  }

Save these in data/list as annotation-list.html and annotation-list.css respectively.

Updating main.js

Here's the code to create the panel, which can go in the main function.

var annotationList = panels.Panel({
  width: 420,
  height: 200,
  contentURL: data.url('list/annotation-list.html'),
  contentScriptFile: [data.url('jquery-1.4.2.min.js'),
                      data.url('list/annotation-list.js')],
  contentScriptWhen: 'ready',
  onShow: function() {
    this.postMessage(simpleStorage.storage.annotations);
  },
  onMessage: function(message) {
    require('sdk/tabs').open(message);
  }
});

Since this panel's content script uses jQuery we will pass that in too: again, make sure the name of it matches the version of jQuery you downloaded.

When the panel is shown we send it the array of stored annotations. When the panel sends us a URL we use the tabs module to open it in a new tab.

Finally we need to connect this to the widget's right-click message:

var widget = widgets.Widget({
  id: 'toggle-switch',
  label: 'Annotator',
  contentURL: data.url('widget/pencil-off.png'),
  contentScriptWhen: 'ready',
  contentScriptFile: data.url('widget/widget.js')
});
widget.port.on('left-click', function() {
  console.log('activate/deactivate');
  widget.contentURL = toggleActivation() ?
            data.url('widget/pencil-on.png') :
            data.url('widget/pencil-off.png');
});
widget.port.on('right-click', function() {
    console.log('show annotation list');
    annotationList.show();
});

This time execute cfx xpi to build the XPI for the add-on, and install it in Firefox. Activate the add-on, add an annotation, and then right-click the widget. You should see something like this:

Restart Firefox, right-click the widget again, and check that the annotation is still there.

Until now we've always run cfx run rather than building an XPI and installing the add-on in Firefox. If the annotation does not reappear when you restart Firefox, double check you installed the add-on and didn't just use cfx run again.

Responding To OverQuota events

Add-ons have a limited quota of storage space. If the add-on exits while it is over quota, any data stored since the last time it was in quota will not be persisted.

So we want to listen to the OverQuota event emitted by simple-storage and respond to it. Add the following to your add-on's main function:

simpleStorage.on("OverQuota", function () {
  notifications.notify({
    title: 'Storage space exceeded',
    text: 'Removing recent annotations'});
  while (simpleStorage.quotaUsage > 1)
    simpleStorage.storage.annotations.pop();
});

Because we use a notification to alert the user, we need to import the notifications module:

var notifications = require("sdk/notifications");

(It should be obvious that this is an incredibly unhelpful way to deal with the problem. A real add-on should give the user a chance to choose which data to keep, and prevent the user from adding any more data until the add-on is back under quota.)

Respecting Private Browsing

Since annotations record the user's browsing history we should avoid recording annotations in private windows.

There's a very simple way to do this: do nothing. By omitting the "private-browsing" key from the annotator's "package.json" file, the annotator opts out of private browsing altogether.

This means that its widget will not appear on any private windows and its selector and matcher content scripts won't run, so the user won't be able to enter any annotations in private windows.

Try it: execute cfx run and open a new private window: you should no longer see the annotator's widget.

Now we can create and store annotations, the last piece is to display them when the user loads the page.

Document Tags and Contributors

Tags: 
  • Add-on SDK
 Contributors to this page: wbamberg, Canuckistani, asmacdo
 Last updated by: wbamberg, Dec 1, 2016, 10:51:16 AM
See also
  1. WebExtensions
  2. Getting started
    1. What are WebExtensions?
    2. Your first WebExtension
    3. Your second WebExtension
    4. Anatomy of a WebExtension
    5. Example WebExtensions
  3. How to
    1. Intercept HTTP requests
    2. Modify a web page
    3. Add a button to the toolbar
    4. Implement a settings page
  4. Concepts
    1. Using the JavaScript APIs
    2. User interface components
    3. Content scripts
    4. Match patterns
    5. Internationalization
    6. Content Security Policy
    7. Native messaging
  5. Porting
    1. Porting a Google Chrome extension
    2. Porting a legacy Firefox add-on
    3. Embedded WebExtensions
    4. Comparison with the Add-on SDK
    5. Comparison with XUL/XPCOM extensions
    6. Chrome incompatibilities
  6. Firefox workflow
    1. Temporary Installation in Firefox
    2. Debugging
    3. Getting started with web-ext
    4. web-ext command reference
    5. WebExtensions and the Add-on ID
    6. Publishing your WebExtension
  7. JavaScript APIs
    1. Browser support for JavaScript APIs
    2. alarms
    3. bookmarks
    4. browserAction
    5. browsingData
    6. commands
    7. contextMenus
    8. contextualIdentities
    9. cookies
    10. downloads
    11. events
    12. extension
    13. extensionTypes
    14. history
    15. i18n
    16. identity
    17. idle
    18. management
    19. notifications
    20. omnibox
    21. pageAction
    22. runtime
    23. sessions
    24. sidebarAction
    25. storage
    26. tabs
    27. topSites
    28. webNavigation
    29. webRequest
    30. windows
  8. Manifest keys
    1. applications
    2. author
    3. background
    4. browser_action
    5. chrome_url_overrides
    6. commands
    7. content_scripts
    8. content_security_policy
    9. default_locale
    10. description
    11. developer
    12. homepage_url
    13. icons
    14. manifest_version
    15. name
    16. omnibox
    17. options_ui
    18. page_action
    19. permissions
    20. short_name
    21. sidebar_action
    22. version
    23. web_accessible_resources
  9. Add-on SDK
  10. Getting started
    1. Installation
    2. Getting started
    3. Troubleshooting
  11. High-Level APIs
    1. addon-page
    2. base64
    3. clipboard
    4. context-menu
    5. hotkeys
    6. indexed-db
    7. l10n
    8. notifications
    9. page-mod
    10. page-worker
    11. panel
    12. passwords
    13. private-browsing
    14. querystring
    15. request
    16. selection
    17. self
    18. simple-prefs
    19. simple-storage
    20. system
    21. tabs
    22. timers
    23. ui
    24. url
    25. webextension
    26. widget
    27. windows
  12. Low-Level APIs
    1. /loader
    2. chrome
    3. console/plain-text
    4. console/traceback
    5. content/content
    6. content/loader
    7. content/mod
    8. content/symbiont
    9. content/worker
    10. core/heritage
    11. core/namespace
    12. core/promise
    13. dev/panel
    14. event/core
    15. event/target
    16. frame/hidden-frame
    17. frame/utils
    18. fs/path
    19. io/byte-streams
    20. io/file
    21. io/text-streams
    22. lang/functional
    23. lang/type
    24. loader/cuddlefish
    25. loader/sandbox
    26. net/url
    27. net/xhr
    28. places/bookmarks
    29. places/favicon
    30. places/history
    31. platform/xpcom
    32. preferences/event-target
    33. preferences/service
    34. remote/child
    35. remote/parent
    36. stylesheet/style
    37. stylesheet/utils
    38. system/child_process
    39. system/environment
    40. system/events
    41. system/runtime
    42. system/unload
    43. system/xul-app
    44. tabs/utils
    45. test/assert
    46. test/harness
    47. test/httpd
    48. test/runner
    49. test/utils
    50. ui/button/action
    51. ui/button/toggle
    52. ui/frame
    53. ui/id
    54. ui/sidebar
    55. ui/toolbar
    56. util/array
    57. util/collection
    58. util/deprecate
    59. util/list
    60. util/match-pattern
    61. util/object
    62. util/uuid
    63. window/utils
  13. Firefox for Android
  14. Getting started
    1. Walkthrough
    2. Debugging
    3. Code snippets
  15. APIs
    1. Accounts.jsm
    2. BrowserApp
    3. HelperApps.jsm
    4. Home.jsm
    5. HomeProvider.jsm
    6. JavaAddonManager.jsm
    7. NativeWindow
    8. Notifications.jsm
    9. PageActions.jsm
    10. Prompt.jsm
    11. RuntimePermissions.jsm
    12. Snackbars.jsm
    13. Sound.jsm
    14. Tab
  16. Legacy
  17. Restartless extensions
    1. Overview
  18. Overlay extensions
    1. Overview
  19. Themes
  20. Lightweight themes
    1. Overview
  21. Complete themes
    1. Overview
  22. Publishing add-ons
  23. Guides
    1. Signing and distribution overview
    2. Submit an add-on
    3. Review policies
    4. Developer agreement
    5. Featured add-ons
    6. Contact addons.mozilla.org
  24. Community and support
  25. Channels
    1. Add-ons blog
    2. Add-on forums
    3. Stack Overflow
    4. Development newsgroup
    5. IRC Channel