gecko-dev/toolkit/actors/UAWidgetsChild.jsm

/* vim: set ts=2 sw=2 sts=2 et tw=80: */
/* 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";

var EXPORTED_SYMBOLS = ["UAWidgetsChild"];

const { Services } = ChromeUtils.import("resource://gre/modules/Services.jsm");

class UAWidgetsChild extends JSWindowActorChild {
  constructor() {
    super();

    this.widgets = new WeakMap();
    this.prefsCache = new Map();
    this.observedPrefs = [];

    // Bug 1570744 - JSWindowActorChild's cannot be used as nsIObserver's
    // directly, so we create a new function here instead to act as our
    // nsIObserver, which forwards the notification to the observe method.
    this.observerFunction = (subject, topic, data) => {
      this.observe(subject, topic, data);
    };
  }

  didDestroy() {
    for (let pref in this.observedPrefs) {
      Services.prefs.removeObserver(pref, this.observerFunction);
    }
  }

  unwrap(obj) {
    return Cu.isXrayWrapper(obj) ? obj.wrappedJSObject : obj;
  }

  handleEvent(aEvent) {
    switch (aEvent.type) {
      case "UAWidgetSetupOrChange":
        this.setupOrNotifyWidget(aEvent.target);
        break;
      case "UAWidgetTeardown":
        this.teardownWidget(aEvent.target);
        break;
    }
  }

  setupOrNotifyWidget(aElement) {
    if (!this.widgets.has(aElement)) {
      this.setupWidget(aElement);
      return;
    }

    let { widget } = this.widgets.get(aElement);

    if (typeof widget.onchange == "function") {
      if (
        this.unwrap(aElement.openOrClosedShadowRoot) !=
        this.unwrap(widget.shadowRoot)
      ) {
        Cu.reportError(
          "Getting a UAWidgetSetupOrChange event without the ShadowRoot. " +
            "Torn down already?"
        );
        return;
      }
      try {
        widget.onchange();
      } catch (ex) {
        Cu.reportError(ex);
      }
    }
  }

  setupWidget(aElement) {
    let uri;
    let widgetName;
    // Use prefKeys to optionally send a list of preferences to forward to
    // the UAWidget. The UAWidget will receive those preferences as key-value
    // pairs as the second argument to its constructor. Updates to those prefs
    // can be observed by implementing an optional onPrefChange method for the
    // UAWidget that receives the changed pref name as the first argument, and
    // the updated value as the second.
    let prefKeys = [];
    switch (aElement.localName) {
      case "video":
      case "audio":
        uri = "chrome://global/content/elements/videocontrols.js";
        widgetName = "VideoControlsWidget";
        prefKeys = [
          "media.videocontrols.picture-in-picture.video-toggle.enabled",
          "media.videocontrols.picture-in-picture.video-toggle.always-show",
          "media.videocontrols.picture-in-picture.video-toggle.min-video-secs",
          "media.videocontrols.picture-in-picture.video-toggle.position",
          "media.videocontrols.picture-in-picture.video-toggle.has-used",
          "media.videocontrols.keyboard-tab-to-all-controls",
        ];
        break;
      case "input":
        uri = "chrome://global/content/elements/datetimebox.js";
        widgetName = "DateTimeBoxWidget";
        break;
      case "marquee":
        uri = "chrome://global/content/elements/marquee.js";
        widgetName = "MarqueeWidget";
        break;
    }

    if (!uri || !widgetName) {
      Cu.reportError(
        "Getting a UAWidgetSetupOrChange event on undefined element."
      );
      return;
    }

    let shadowRoot = aElement.openOrClosedShadowRoot;
    if (!shadowRoot) {
      Cu.reportError(
        "Getting a UAWidgetSetupOrChange event without the Shadow Root. " +
          "Torn down already?"
      );
      return;
    }

    let isSystemPrincipal = aElement.nodePrincipal.isSystemPrincipal;
    let sandbox = isSystemPrincipal
      ? Object.create(null)
      : Cu.getUAWidgetScope(aElement.nodePrincipal);

    if (!sandbox[widgetName]) {
      Services.scriptloader.loadSubScript(uri, sandbox);
    }

    let prefs = Cu.cloneInto(
      this.getPrefsForUAWidget(widgetName, prefKeys),
      sandbox
    );

    let widget = new sandbox[widgetName](shadowRoot, prefs);
    if (!isSystemPrincipal) {
      widget = widget.wrappedJSObject;
    }
    if (this.unwrap(widget.shadowRoot) != this.unwrap(shadowRoot)) {
      Cu.reportError("Widgets should expose their shadow root.");
    }
    this.widgets.set(aElement, { widget, widgetName });
    try {
      widget.onsetup();
    } catch (ex) {
      Cu.reportError(ex);
    }
  }

  teardownWidget(aElement) {
    if (!this.widgets.has(aElement)) {
      return;
    }
    let { widget } = this.widgets.get(aElement);
    if (typeof widget.destructor == "function") {
      try {
        widget.destructor();
      } catch (ex) {
        Cu.reportError(ex);
      }
    }
    this.widgets.delete(aElement);
  }

  getPrefsForUAWidget(aWidgetName, aPrefKeys) {
    let result = this.prefsCache.get(aWidgetName);
    if (result) {
      return result;
    }

    result = {};
    for (let key of aPrefKeys) {
      result[key] = this.getPref(key);
      this.observePref(key);
    }

    this.prefsCache.set(aWidgetName, result);
    return result;
  }

  observePref(prefKey) {
    Services.prefs.addObserver(prefKey, this.observerFunction);
    this.observedPrefs.push(prefKey);
  }

  getPref(prefKey) {
    switch (Services.prefs.getPrefType(prefKey)) {
      case Ci.nsIPrefBranch.PREF_BOOL: {
        return Services.prefs.getBoolPref(prefKey);
      }
      case Ci.nsIPrefBranch.PREF_INT: {
        return Services.prefs.getIntPref(prefKey);
      }
      case Ci.nsIPrefBranch.PREF_STRING: {
        return Services.prefs.getStringPref(prefKey);
      }
    }

    return undefined;
  }

  observe(subject, topic, data) {
    if (topic == "nsPref:changed") {
      for (let [widgetName, prefCache] of this.prefsCache) {
        if (prefCache.hasOwnProperty(data)) {
          let newValue = this.getPref(data);
          prefCache[data] = newValue;

          this.notifyWidgetsOnPrefChange(widgetName, data, newValue);
        }
      }
    }
  }

  notifyWidgetsOnPrefChange(nameOfWidgetToNotify, prefKey, newValue) {
    let elements = ChromeUtils.nondeterministicGetWeakMapKeys(this.widgets);
    for (let element of elements) {
      if (!Cu.isDeadWrapper(element) && element.isConnected) {
        let { widgetName, widget } = this.widgets.get(element);
        if (widgetName == nameOfWidgetToNotify) {
          if (typeof widget.onPrefChange == "function") {
            try {
              widget.onPrefChange(prefKey, newValue);
            } catch (ex) {
              Cu.reportError(ex);
            }
          }
        }
      }
    }
  }
}