Custom about: URLs

This page describes how to register a new about: URL for your extension.

Setup for Firefox 4+

This is a simple example of a custom about page for bootstrapped addons. This example creates an about page with url about:myaboutpage which takes a user to a page that writes some text out.

Make sure to generate a unique aboutPage_id, see this page to learn more about generating UUID's: UUID.

It is imported to QueryInterface the Components.manager otherwise this will not work.

This example can be easily modified, just modify the global const at in the // globals section.

const {classes: Cc, interfaces: Ci, manager: Cm, results: Cr, utils: Cu, Constructor: CC} = Components;
Cm.QueryInterface(Ci.nsIComponentRegistrar);
Components.utils.import("resource://gre/modules/Services.jsm");
// globals
const ABOUTPAGE_DESCRIPTION = 'This is my custom about page';
const ABOUTPAGE_ID = 'aa132730-2278-11e5-867f-0800200c9a66'; // make sure you generate a unique id from https://www.famkruithof.net/uuid/uuidgen
const ABOUTPAGE_WORD = 'myaboutpage'
const ABOUTPAGE_URI = 'data:text/html,hi this is the page that is shown when navigate to about:myaboutpage';
// const ABOUTPAGE_URI = 'chrome://myaboutaddon/content/index.html';
class AboutPage {
  static get classID() { return Components.ID(`{${ABOUTPAGE_ID}}`); }
  static get classDescription() { return ABOUTPAGE_DESCRIPTION; }
  static get contractID() { return `@mozilla.org/network/protocol/about;1?what=${ABOUTPAGE_WORD}`; }
  static get QueryInterface() { return XPCOMUtils.generateQI([Ci.nsIAboutModule]); }
  constructor() {
    Object.freeze(this);
  }
  getURIFlags(aURI) {
    return Ci.nsIAboutModule.ALLOW_SCRIPT;
  }
  newChannel(aURI, aSecurity_or_aLoadInfo) {
    let channel;
    if (Services.vc.compare(Services.appinfo.version, '47.*') > 0) {
        const uri = Services.io.newURI(ABOUTPAGE_URI, null, null);
        // greater than or equal to firefox48 so aSecurity_or_aLoadInfo is aLoadInfo
        channel = Services.io.newChannelFromURIWithLoadInfo(uri, aSecurity_or_aLoadInfo);
    } else {
        channel = Services.io.newChannel(ABOUTPAGE_URI, null, null);
    }
    channel.originalURI = aURI;
    return channel;
  }
}
class Factory {
  constructor(component) {
    this.component = component;
    this.register();
    Object.freeze(this);
  }
  createInstance(outer, iid) {
    if (outer) {
      throw Cr.NS_ERROR_NO_AGGREGATION;
    }
    return new this.component();
  }
  register() {
    Cm.registerFactory(this.component.classID,
                       this.component.classDescription,
                       this.component.contractID,
                       this);
  }
  unregister() {
    Cm.unregisterFactory(this.component.prototype.classID, this);
  }
}

Instantiation Firefox 4+

Now in the startup procedure of your bootstrapped addon make sure to do register the factory, for example:

let factory;
function startup(aData, aReason) {
    // ...
    factory = new Factory(AboutCustom);
    // ...
}

And then on shutdown of your bootstrapped addon make sure to destroy the factory:

function shutdown(aData, aReason) {
    if (aReason == APP_SHUTDOWN) { return }
    // ...
    factory.unregister();
    // ....
}

And there you have it, your own custom about page.

See Also

• Which URIs load where - Note on how to use about: pages in e10s, can force them to load per tab