utils.js

/* ***** BEGIN LICENSE BLOCK *****
 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 * http://www.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is Home Dash Utility.
 *
 * The Initial Developer of the Original Code is The Mozilla Foundation.
 * Portions created by the Initial Developer are Copyright (C) 2011
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *   Edward Lee <edilee@mozilla.com>
 *   Erik Vold <erikvvold@gmail.com>
 *
 * Alternatively, the contents of this file may be used under the terms of
 * either the GNU General Public License Version 2 or later (the "GPL"), or
 * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
 * in which case the provisions of the GPL or the LGPL are applicable instead
 * of those above. If you wish to allow use of your version of this file only
 * under the terms of either the GPL or the LGPL, and not to allow others to
 * use your version of this file under the terms of the MPL, indicate your
 * decision by deleting the provisions above and replace them with the notice
 * and other provisions required by the GPL or the LGPL. If you do not delete
 * the provisions above, a recipient may use your version of this file under
 * the terms of any one of the MPL, the GPL or the LGPL.
 *
 * ***** END LICENSE BLOCK ***** */

"use strict";

/**
 * Helper that adds event listeners and remembers to remove on unload
 */
function listen(window, node, event, func, capture) {
  // Default to use capture
  if (capture == null)
    capture = true;

  node.addEventListener(event, func, capture);
  function undoListen() {
    node.removeEventListener(event, func, capture);
  }

  // Undo the listener on unload and provide a way to undo everything
  let undoUnload = unload(undoListen, window);
  return function() {
    undoListen();
    undoUnload();
  };
}

/**
 * Load various packaged styles for the add-on and undo on unload
 *
 * @usage loadStyles(addon, styles): Load specified styles
 * @param [object] addon: Add-on object from AddonManager
 * @param [array of strings] styles: Style files to load
 */
function loadStyles(addon, styles) {
  let sss = Cc["@mozilla.org/content/style-sheet-service;1"].
            getService(Ci.nsIStyleSheetService);
  styles.forEach(function(fileName) {
    let fileURI = addon.getResourceURI("styles/" + fileName + ".css");
    sss.loadAndRegisterSheet(fileURI, sss.USER_SHEET);
    unload(function() sss.unregisterSheet(fileURI, sss.USER_SHEET));
  });
}

/**
 * Save callbacks to run when unloading. Optionally scope the callback to a
 * container, e.g., window. Provide a way to run all the callbacks.
 *
 * @usage unload(): Run all callbacks and release them.
 *
 * @usage unload(callback): Add a callback to run on unload.
 * @param [function] callback: 0-parameter function to call on unload.
 * @return [function]: A 0-parameter function that undoes adding the callback.
 *
 * @usage unload(callback, container) Add a scoped callback to run on unload.
 * @param [function] callback: 0-parameter function to call on unload.
 * @param [node] container: Remove the callback when this container unloads.
 * @return [function]: A 0-parameter function that undoes adding the callback.
 */
function unload(callback, container) {
  // Initialize the array of unloaders on the first usage
  let unloaders = unload.unloaders;
  if (unloaders == null)
    unloaders = unload.unloaders = [];

  // Calling with no arguments runs all the unloader callbacks
  if (callback == null) {
    unloaders.slice().forEach(function(unloader) unloader());
    unloaders.length = 0;
    return;
  }

  // The callback is bound to the lifetime of the container if we have one
  if (container != null) {
    // Remove the unloader when the container unloads
    container.addEventListener("unload", removeUnloader, false);

    // Wrap the callback to additionally remove the unload listener
    let origCallback = callback;
    callback = function() {
      container.removeEventListener("unload", removeUnloader, false);
      origCallback();
    }
  }

  // Wrap the callback in a function that ignores failures
  function unloader() {
    try {
      callback();
    }
    catch(ex) {}
  }
  unloaders.push(unloader);

  // Provide a way to remove the unloader
  function removeUnloader() {
    let index = unloaders.indexOf(unloader);
    if (index != -1)
      unloaders.splice(index, 1);
  }
  return removeUnloader;
}

/**
 * Apply a callback to each open and new browser windows.
 *
 * @usage watchWindows(callback): Apply a callback to each browser window.
 * @param [function] callback: 1-parameter function that gets a browser window.
 */
function watchWindows(callback) {
  // Wrap the callback in a function that ignores failures
  function watcher(window) {
    try {
      // Now that the window has loaded, only handle browser windows
      let {documentElement} = window.document;
      if (documentElement.getAttribute("windowtype") == "navigator:browser")
        callback(window);
    }
    catch(ex) {}
  }

  // Wait for the window to finish loading before running the callback
  function runOnLoad(window) {
    // Listen for one load event before checking the window type
    window.addEventListener("load", function runOnce() {
      window.removeEventListener("load", runOnce, false);
      watcher(window);
    }, false);
  }

  // Add functionality to existing windows
  let windows = Services.wm.getEnumerator(null);
  while (windows.hasMoreElements()) {
    // Only run the watcher immediately if the window is completely loaded
    let window = windows.getNext();
    if (window.document.readyState == "complete")
      watcher(window);
    // Wait for the window to load before continuing
    else
      runOnLoad(window);
  }

  // Watch for new browser windows opening then wait for it to load
  function windowWatcher(subject, topic) {
    if (topic == "domwindowopened")
      runOnLoad(subject);
  }
  Services.ww.registerNotification(windowWatcher);

  // Make sure to stop watching for windows if we're unloading
  unload(function() Services.ww.unregisterNotification(windowWatcher));
}