fune/browser/components/extensions/ext-url-overrides.js

/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

"use strict";

XPCOMUtils.defineLazyServiceGetter(this, "aboutNewTabService",
                                   "@mozilla.org/browser/aboutnewtab-service;1",
                                   "nsIAboutNewTabService");

// Bug 1320736 tracks creating a generic precedence manager for handling
// multiple addons modifying the same properties, and bug 1330494 has been filed
// to track utilizing this manager for chrome_url_overrides. Until those land,
// the edge cases surrounding multiple addons using chrome_url_overrides will
// be ignored and precedence will be first come, first serve.
let overrides = {
  // A queue of extensions in line to override the newtab page (sorted oldest to newest).
  newtab: [],
};

this.urlOverrides = class extends ExtensionAPI {
  onManifestEntry(entryName) {
    let {extension} = this;
    let {manifest} = extension;

    if (manifest.chrome_url_overrides.newtab) {
      let newtab = manifest.chrome_url_overrides.newtab;
      let url = extension.baseURI.resolve(newtab);

      // Only set the newtab URL if no other extension is overriding it.
      if (!overrides.newtab.length) {
        aboutNewTabService.newTabURL = url;
      }

      overrides.newtab.push({id: extension.id, url});
    }
  }

  onShutdown(reason) {
    let {extension} = this;

    let i = overrides.newtab.findIndex(o => o.id === extension.id);
    if (i !== -1) {
      overrides.newtab.splice(i, 1);

      if (overrides.newtab.length) {
        aboutNewTabService.newTabURL = overrides.newtab[0].url;
      } else {
        aboutNewTabService.resetNewTabURL();
      }
    }
  }
};