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  6. Annotator
  7. Displaying annotations

Displaying annotations

In This Article
  1. Matcher page-mod
    1. Matcher Content Script
    2. Updating main.js
  2. Annotation panel
    1. Annotation panel HTML
    2. Annotation panel Content Script
    3. Updating main.js

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.

In this chapter we'll use a page-mod to locate elements of web pages that have annotations associated with them, and a panel to display the annotations.

Matcher page-mod

Matcher Content Script

The content script for the matcher page-mod is initialized with a list of all the annotations that the user has created.

When a page is loaded the matcher searches the DOM for elements that match annotations. If it finds any it binds functions to that element's mouseenter and mouseleave events to send messages to the main module, asking it to show or hide the annotation.

Like the selector, the matcher also listens for the window's unload event and on unload sends a detach message to the main module, so the add-on can clean it up.

The complete content script is here:

self.on('message', function onMessage(annotations) {
  annotations.forEach(
    function(annotation) {
      if(annotation.url == document.location.toString()) {
        createAnchor(annotation);
      }
  });
  $('.annotated').css('border', 'solid 3px yellow');
  $('.annotated').bind('mouseenter', function(event) {
    self.port.emit('show', $(this).attr('annotation'));
    event.stopPropagation();
    event.preventDefault();
  });
  $('.annotated').bind('mouseleave', function() {
    self.port.emit('hide');
  });
});
function createAnchor(annotation) {
  annotationAnchorAncestor = $('#' + annotation.ancestorId);
  annotationAnchor = $(annotationAnchorAncestor).parent().find(
                     ':contains(' + annotation.anchorText + ')').last();
  $(annotationAnchor).addClass('annotated');
  $(annotationAnchor).attr('annotation', annotation.annotationText);
}

Save this in data as matcher.js.

Updating main.js

First, initialize an array to hold workers associated with the matcher's content scripts:

var matchers = [];

In the main function, add the code to create the matcher:

var matcher = pageMod.PageMod({
  include: ['*'],
  contentScriptWhen: 'ready',
  contentScriptFile: [data.url('jquery-1.4.2.min.js'),
                      data.url('matcher.js')],
  onAttach: function(worker) {
    if(simpleStorage.storage.annotations) {
      worker.postMessage(simpleStorage.storage.annotations);
    }
    worker.port.on('show', function(data) {
      annotation.content = data;
      annotation.show();
    });
    worker.port.on('hide', function() {
      annotation.content = null;
      annotation.hide();
    });
    worker.on('detach', function () {
      detachWorker(this, matchers);
    });
    matchers.push(worker);
  }
});

When a new page is loaded the function assigned to onAttach is called. This function:

  • initializes the content script instance with the current set of annotations
  • provides a handler for messages from that content script, handling the three messages - show, hide and detach - that the content script might send
  • adds the worker to an array, so we it can send messages back later.

Then in the module's scope implement a function to update the matcher's workers, and edit handleNewAnnotation to call this new function when the user enters a new annotation:

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

Annotation panel

The annotation panel just shows the content of an annotation.

There are two files associated with the annotation panel:

  • a simple HTML file to use as a template
  • a simple content script to build the panel's content

These files will live in a new subdirectory of data which we'll call annotation.

Annotation panel HTML

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en">
<head>
    <title>Annotation</title>
    <style media="all" type="text/css">
body {
        font: 100% arial, helvetica, sans-serif;
        background-color: #F5F5F5;
    }
div {
        text-align:left;
    }
</style>
</head>
<body>
<div id="annotation">
</div>
</body>
</html>

Save this in data/annotation as annotation.html.

Annotation panel Content Script

The annotation panel has a minimal content script that sets the text:

self.on('message', function(message) {
  $('#annotation').text(message);
});

Save this in data/annotation as annotation.js.

Updating main.js

Finally, update main.js with the code to construct the annotation panel:

var annotation = panels.Panel({
  width: 200,
  height: 180,
  contentURL: data.url('annotation/annotation.html'),
  contentScriptFile: [data.url('jquery-1.4.2.min.js'),
                      data.url('annotation/annotation.js')],
  onShow: function() {
    this.postMessage(this.content);
  }
});

Execute cfx run one last time. Activate the annotator and enter an annotation. You should see a yellow border around the item you annotated:

When you move your mouse over the item, the annotation should appear:

Obviously this add-on isn't complete yet. It could do with more beautiful styling, it certainly needs a way to delete annotations, it should deal with OverQuota more reliably, and the matcher could be made to match more reliably.

But we hope this gives you an idea of the things that are possible with the modules in the SDK.

Document Tags and Contributors

Tags: 
  • Add-on SDK
 Contributors to this page: wbamberg, Canuckistani, asmacdo
 Last updated by: wbamberg, Dec 1, 2016, 10:50:39 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