Initial implementation of WebUI generator (WUG) toolkit.

components/wug/resources/webui-view.js

+// Copyright (c) 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+Polymer('webui-view', (function() {
+  /** @const */ var CALLBACK_EVENT_FIRED = 'eventFired';
+  /** @const */ var CALLBACK_CONTEXT_CHANGED = 'contextChanged';
+  /** @const */ var CALLBACK_READY = 'ready';
+
+  return {
+    /**
+     * Dictionary of context observers that are methods of |this| bound to
+     * |this|.
+     */
+    contextObservers_: null,
+
+    /**
+     * Full path to the element in views hierarchy.
+     */
+    path_: null,
+
+    /**
+     * Whether DOM is ready.
+     */
+    domReady_: false,
+
+    /**
+     * Context used for sharing data with native backend.
+     */
+    context: null,
+
+    /**
+     * Internal storage of |this.context|. Short name has been choosen for

[Nikita (slow), 2015/02/24 15:22:42]

nit: You can make this comment shorter since you're already using short name for
this variable :)

[dzhioev (left Google), 2015/02/26 14:01:37]

What do you mean? this.C and this.context are different objects.

[Nikita (slow), 2015/02/26 14:18:20]

I suggested removing reasoning for using short name.

[dzhioev (left Google), 2015/03/02 11:02:30]

Done.

+     * reason: such name doesn't take much space in HTML data bindings, which
+     * are used very often.
+     * C binded to the native part of the context, that means that all the
+     * changes in the native part appear in C automticaly. Reverse is not true,

[Nikita (slow), 2015/02/26 14:18:20]

nit: automatically

[dzhioev (left Google), 2015/03/02 11:02:30]

Done.

+     * you should use:
+     *    this.context.set(...);
+     *    this.context.commitContextChanges();
+     * to send updates to the native part.
+     * TODO(dzhioev): make binding two-way.

[Nikita (slow), 2015/02/24 15:22:42]

Since this is purely an optimization I suggest removing this TODO. You can file
a bug though.

[dzhioev (left Google), 2015/02/26 14:01:37]

Done. Removed comment.

+     */
+    C: null,
+
+    ready: function() {
+      this.context = new wug.Context;
+      this.C = this.context.storage_;
+      this.contextObservers_ = {};
+    },
+
+    /**
+     * One of element's lifecycle methods.
+     */
+    domReady: function() {
+      var id = this.getAttribute('wugid');
+      if (!id)
+        console.error('"wugid" attribute is missing.');

[Nikita (slow), 2015/02/24 15:22:42]

nit: Should you return here and do not initialize domReady?

[dzhioev (left Google), 2015/02/26 14:01:37]

Done.

+      if (id == 'WUG_ROOT') {
+        this.setPath_('WUG_ROOT');
+      }
+      this.domReady_ = true;
+      if (this.path_)
+        this.init_();
+    },
+
+    setPath_: function(path) {
+      this.path_ = path;
+      if (this.domReady_)
+        this.init_();
+    },
+
+    init_: function() {
+      this.initContext_();
+      this.initChildren_();
+      window[this.path_ + '$contextChanged'] =
+          this.onContextChanged_.bind(this);
+      this.initialize();
+      this.send(CALLBACK_READY);
+    },
+
+    fireEvent: function(_, _, source) {
+      this.send(CALLBACK_EVENT_FIRED, source.getAttribute('event'));
+    },
+
+    i18n: function(args) {
+      if (!(args instanceof Array))
+        args = [args];
+      args[0] = this.getType() + '$' + args[0];
+      return loadTimeData.getStringF.apply(loadTimeData, args);
+    },
+
+    /**
+     * Sends message to Chrome, adding needed prefix to message name. All
+     * arguments after |messageName| are packed into message parameters list.
+     *
+     * @param {string} messageName Name of message without a prefix.
+     * @param {...*} varArgs parameters for message.
+     * @private
+     */
+    send: function(messageName, varArgs) {
+      if (arguments.length == 0)
+        throw Error('Message name is not provided.');
+      var fullMessageName = this.path_ + '$' + messageName;
+      var payload = Array.prototype.slice.call(arguments, 1);
+      chrome.send(fullMessageName, payload);
+    },
+
+    /**
+     * Starts observation of property with |key| of the context attached to
+     * current screen. This method differs from "login.ScreenContext" in that
+     * it automatically detects if observer is method of |this| and make
+     * all needed actions to make it work correctly. So it's no need for client
+     * to bind methods to |this| and keep resulting callback for
+     * |removeObserver| call:
+     *
+     *   this.addContextObserver('key', this.onKeyChanged_);

[Nikita (slow), 2015/02/24 15:22:42]

Not clear whether this example on how caller should look like.
.. or how it should not look like.

Please clarify comment.

[dzhioev (left Google), 2015/02/26 14:01:37]

Done.

+     *   ...
+     *   this.removeContextObserver('key', this.onKeyChanged_);
+     * @private
+     */
+    addContextObserver: function(key, observer) {
+      var realObserver = observer;
+      var propertyName = this.getPropertyNameOf_(observer);
+      if (propertyName) {
+        if (!this.contextObservers_.hasOwnProperty(propertyName))
+          this.contextObservers_[propertyName] = observer.bind(this);
+        realObserver = this.contextObservers_[propertyName];
+      }
+      this.context.addObserver(key, realObserver);
+    },
+
+    /**
+     * Removes |observer| from the list of context observers. Supports not only
+     * regular functions but also screen methods (see comment to
+     * |addContextObserver|).
+     * @private
+     */
+    removeContextObserver: function(observer) {
+      var realObserver = observer;
+      var propertyName = this.getPropertyNameOf_(observer);
+      if (propertyName) {
+        if (!this.contextObservers_.hasOwnProperty(propertyName))
+          return;
+        realObserver = this.contextObservers_[propertyName];
+        delete this.contextObservers_[propertyName];
+      }
+      this.context.removeObserver(realObserver);
+    },
+
+    /**
+     * Sends recent context changes to C++ handler.
+     * @private
+     */
+    commitContextChanges: function() {
+      if (!this.context.hasChanges())
+        return;
+      this.send(CALLBACK_CONTEXT_CHANGED, this.context.getChangesAndReset());
+    },
+
+    /**
+     * Called when context changed on C++ side.
+     */
+    onContextChanged_: function(diff) {
+      var changedKeys = this.context.applyChanges(diff);
+      this.contextChanged(changedKeys);
+    },
+
+    /**
+     * If |value| is the value of some property of |this| returns property's
+     * name. Otherwise returns empty string.
+     * @private
+     */
+    getPropertyNameOf_: function(value) {
+      for (var key in this)
+        if (this[key] === value)
+          return key;
+      return '';
+    }
+  };
+})());
+