Bindings layer for declarative events API

chrome/renderer/resources/extensions/event.js

 // Copyright (c) 2012 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.
 
 var chrome = chrome || {};
 (function () {
   native function GetChromeHidden();
   native function AttachEvent(eventName);
   native function DetachEvent(eventName);
   native function Print();
@@ skipping 40 matching lines @@
 
   // Event object.  If opt_eventName is provided, this object represents
   // the unique instance of that named event, and dispatching an event
   // with that name will route through this object's listeners.
   //
   // Example:
   //   chrome.tabs.onChanged = new chrome.Event("tab-changed");
   //   chrome.tabs.onChanged.addListener(function(data) { alert(data); });
   //   chromeHidden.Event.dispatch("tab-changed", "hi");
   // will result in an alert dialog that says 'hi'.
-  chrome.Event = function(opt_eventName, opt_argSchemas) {
+  //
+  // If opt_eventOptions exists, it is a dictionary that contains the boolean
+  // entries "supportsListeners" and "supportsRules".
+  chrome.Event = function(opt_eventName, opt_argSchemas, opt_eventOptions) {
     this.eventName_ = opt_eventName;
     this.listeners_ = [];
+    this.eventOptions_ = opt_eventOptions ||
+        {"supportsListeners": true, "supportsRules": false};
 
     // Validate event parameters if we are in debug.
     if (opt_argSchemas &&
         chromeHidden.validateCallbacks &&
         chromeHidden.validate) {
 
       this.validate_ = function(args) {
         try {
           chromeHidden.validate(args, opt_argSchemas);
         } catch (exception) {
           return "Event validation error during " + opt_eventName + " -- " +
                  exception;
         }
       };
+    } else {
+      this.validate_ = function() {}
     }
   };
 
   // A map of event names to the event object that is registered to that name.
   var attachedNamedEvents = {};
 
   // An array of all attached event objects, used for detaching on unload.
   var allAttachedEvents = [];
 
   // A map of functions that massage event arguments before they are dispatched.
@@ skipping 32 matching lines @@
   };
 
   // Test if a named event has any listeners.
   chromeHidden.Event.hasListener = function(name) {
     return (attachedNamedEvents[name] &&
             attachedNamedEvents[name].listeners_.length > 0);
   };
 
   // Registers a callback to be called when this event is dispatched.
   chrome.Event.prototype.addListener = function(cb) {
+    if (!this.eventOptions_.supportsListeners)
+      throw new Error("This event does not support listeners.");
     if (this.listeners_.length == 0) {
       this.attach_();
     }
     this.listeners_.push(cb);
   };
 
   // Unregisters a callback.
   chrome.Event.prototype.removeListener = function(cb) {
+    if (!this.eventOptions_.supportsListeners)
+      throw new Error("This event does not support listeners.");
     var idx = this.findListener_(cb);
     if (idx == -1) {
       return;
     }
 
     this.listeners_.splice(idx, 1);
     if (this.listeners_.length == 0) {
       this.detach_();
     }
   };
 
   // Test if the given callback is registered for this event.
   chrome.Event.prototype.hasListener = function(cb) {
+    if (!this.eventOptions_.supportsListeners)
+      throw new Error("This event does not support listeners.");
     return this.findListener_(cb) > -1;
   };
 
   // Test if any callbacks are registered for this event.
-  chrome.Event.prototype.hasListeners = function(cb) {
+  chrome.Event.prototype.hasListeners = function() {
+    if (!this.eventOptions_.supportsListeners)
+      throw new Error("This event does not support listeners.");
     return this.listeners_.length > 0;
   };
 
   // Returns the index of the given callback if registered, or -1 if not
   // found.
   chrome.Event.prototype.findListener_ = function(cb) {
     for (var i = 0; i < this.listeners_.length; i++) {
       if (this.listeners_[i] == cb) {
         return i;
       }
     }
 
     return -1;
   };
 
   // Dispatches this event object to all listeners, passing all supplied
   // arguments to this function each listener.
   chrome.Event.prototype.dispatch = function(varargs) {
+    if (!this.eventOptions_.supportsListeners)
+      throw new Error("This event does not support listeners.");
     var args = Array.prototype.slice.call(arguments);
-    if (this.validate_) {
-      var validationErrors = this.validate_(args);
-      if (validationErrors) {
-        return validationErrors;
-      }
+    var validationErrors = this.validate_(args);
+    if (validationErrors) {
+      return validationErrors;
     }
     for (var i = 0; i < this.listeners_.length; i++) {
       try {
         this.listeners_[i].apply(null, args);
       } catch (e) {
         console.error("Error in event handler for '" + this.eventName_ +
                       "': " + e.stack);
       }
     }
   };
@@ skipping 30 matching lines @@
 
     delete attachedNamedEvents[this.eventName_];
   };
 
   chrome.Event.prototype.destroy_ = function() {
     this.listeners_ = [];
     this.validate_ = [];
     this.detach_();
   };
 
+  chrome.Event.prototype.addRules = function(rules, opt_cb) {
+    if (!this.eventOptions_.supportsRules)
+      throw new Error("This event does not support rules.");
+    chrome.experimental.declarative.addRules(this.eventName_, rules, opt_cb);

[not at google - send to devlin, 2012/02/01 23:07:23]

You'll still need to check that the experimental.declarative API exists.

This might be most easily done in the constructor, like

if (this.eventOptions_.supportsRules &&
    (!chrome.experimental || !chrome.experimental.declarative)) {
  throw new Error("You must have access to the experimental.declarative " +
                  "API to support rules in events");
}

Possibly when this API gets taken out of experimental the presence of events
with rules will imply permission to use the API? Or possibly not? Not a decision
that needs to be made right now though, extensions will definitely need the
experimental permission to use this.

[battre, 2012/02/02 13:49:59]

Anticipating that experimental.declarative will become "declarative" and that
you don't need to request permission for "declarative" I have split this into
two if statements.

Done.

+  }
+
+  chrome.Event.prototype.removeRules = function(ruleIdentifiers, opt_cb) {
+    if (!this.eventOptions_.supportsRules)
+      throw new Error("This event does not support rules.");
+    chrome.experimental.declarative.removeRules(
+        this.eventName_, ruleIdentifiers, opt_cb);
+  }
+
+  chrome.Event.prototype.getRules = function(ruleIdentifiers, cb) {
+    if (!this.eventOptions_.supportsRules)
+      throw new Error("This event does not support rules.");
+    chrome.experimental.declarative.getRules(
+        this.eventName_, ruleIdentifiers, cb);
+  }
+
   // Special load events: we don't use the DOM unload because that slows
   // down tab shutdown.  On the other hand, onUnload might not always fire,
   // since Chrome will terminate renderers on shutdown (SuddenTermination).
   chromeHidden.onLoad = new chrome.Event();
   chromeHidden.onUnload = new chrome.Event();
 
   chromeHidden.dispatchOnLoad =
       chromeHidden.onLoad.dispatch.bind(chromeHidden.onLoad);
 
   chromeHidden.dispatchOnUnload = function() {
     chromeHidden.onUnload.dispatch();
     for (var i = 0; i < allAttachedEvents.length; ++i) {
       var event = allAttachedEvents[i];
       if (event)
         event.detach_();
     }
   };
 
   chromeHidden.dispatchError = function(msg) {
     console.error(msg);
   };
 })();