Filtered events.

chrome/renderer/resources/extensions/event.js

Index: chrome/renderer/resources/extensions/event.js
diff --git a/chrome/renderer/resources/extensions/event.js b/chrome/renderer/resources/extensions/event.js
index a6d636342eea978f3568208f7345f8b763559306..30c4c2d2450228928c35761c79a29a41470d896d 100644
--- a/chrome/renderer/resources/extensions/event.js
+++ b/chrome/renderer/resources/extensions/event.js
@@ -5,6 +5,9 @@
   var eventBindingsNatives = requireNative('event_bindings');
   var AttachEvent = eventBindingsNatives.AttachEvent;
   var DetachEvent = eventBindingsNatives.DetachEvent;
+  var AttachFilteredEvent = eventBindingsNatives.AttachFilteredEvent;
+  var DetachFilteredEvent = eventBindingsNatives.DetachFilteredEvent;
+  var MatchAgainstEventFilter = eventBindingsNatives.MatchAgainstEventFilter;
   var sendRequest = require('sendRequest').sendRequest;
   var utils = require('utils');
   var validate = require('schemaUtils').validate;
@@ -75,6 +78,78 @@
     };
   })();
 
+  // Handles adding/removing/dispatching listeners for unfiltered events.
+  var UnfilteredAttachmentStrategy = function(event) {
+    this.event_ = event;
+  };
+
+  UnfilteredAttachmentStrategy.prototype.onAddedListener =
+      function(listener) {
+    // Only attach / detach on the first / last listener removed.
+    if (this.event_.listeners_.length == 0)
+      AttachEvent(this.event_.eventName_);
+  };
+
+  UnfilteredAttachmentStrategy.prototype.onRemovedListener =
+      function(listener) {
+    if (this.event_.listeners_.length == 0)
+      this.detach(true);
+  };
+
+  UnfilteredAttachmentStrategy.prototype.detach = function(manual) {
+    var i = allAttachedEvents.indexOf(this.event_);

[battre, 2012/06/20 09:50:46]

where is this declared?

[koz (OOO until 15th September), 2012/06/21 02:23:11]

It was declared lower down, but I've moved above these classes so that its
declaration appears before its use.

+    if (i >= 0)
+      delete allAttachedEvents[i];
+    DetachEvent(this.event_.eventName_, manual);
+  };
+
+  UnfilteredAttachmentStrategy.prototype.getListenersByIDs = function(ids) {
+    return this.event_.listeners_;
+  };
+
+  var FilteredAttachmentStrategy = function(event) {
+    this.event_ = event;
+    this.listenerMap_ = {};
+  };
+
+  FilteredAttachmentStrategy.idToEventMap = {};
+
+  FilteredAttachmentStrategy.prototype.onAddedListener = function(listener) {
+    var id = AttachFilteredEvent(this.event_.eventName_,
+        listener.filters || {});
+    if (id == -1)
+      throw new Error("Can't add listener");
+    listener.id = id;
+    this.listenerMap_[id] = listener;
+    FilteredAttachmentStrategy.idToEventMap[id] = this.event_;
+  };
+
+  FilteredAttachmentStrategy.prototype.onRemovedListener = function(listener) {
+    this.detachListener(listener, true);
+  };
+
+  FilteredAttachmentStrategy.prototype.detachListener =
+      function(listener, manual) {
+    if (listener.id == undefined)
+      throw new Error("listener.id undefined - '" + listener + "'");
+    var id = listener.id;
+    delete this.listenerMap_[id];
+    delete FilteredAttachmentStrategy.idToEventMap[id];
+    DetachFilteredEvent(id, manual);
+  };
+
+  FilteredAttachmentStrategy.prototype.detach = function(manual) {
+    for (var i in this.listenerMap_)
+      this.detachListener(this.listenerMap_[i], manual);
+  };
+
+  FilteredAttachmentStrategy.prototype.getListenersByIDs = function(ids) {
+    var result = [];
+    for (var i = 0; i < ids.length; i++)
+      result.push(this.listenerMap_[ids[i]]);
+    return result;
+  };
+
   // 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. Note that
@@ -92,11 +167,20 @@
     this.eventName_ = opt_eventName;
     this.listeners_ = [];
     this.eventOptions_ = opt_eventOptions ||
-        {"supportsListeners": true, "supportsRules": false};
+        {supportsFilters: false,
+         supportsListeners: true,
+         supportsRules: false,
+        };
 
     if (this.eventOptions_.supportsRules && !opt_eventName)
       throw new Error("Events that support rules require an event name.");
 
+    if (this.eventOptions_.supportsFilters) {
+      this.attachmentStrategy_ = new FilteredAttachmentStrategy(this);
+    } else {
+      this.attachmentStrategy_ = new UnfilteredAttachmentStrategy(this);
+    }
+
     // Validate event arguments (the data that is passed to the callbacks)
     // if we are in debug.
     if (opt_argSchemas &&
@@ -136,7 +220,12 @@
   // Dispatches a named event with the given JSON array, which is deserialized
   // before dispatch. The JSON array is the list of arguments that will be
   // sent with the event callback.
-  chromeHidden.Event.dispatchJSON = function(name, args) {
+  chromeHidden.Event.dispatchJSON = function(name, args, filteringInfo) {
+    var listenerIDs;
+
+    if (filteringInfo) {
+      listenerIDs = MatchAgainstEventFilter(name, filteringInfo);

[battre, 2012/06/20 09:50:46]

would it make sense to change this logic such that C++ does the (name,
filteringInfo) -> listenerIDs mapping before calling dispatchJSON and pass the
listenerIDs instead of filteringInfo? Would this save one round trip?

[koz (OOO until 15th September), 2012/06/21 02:23:11]

Yes, that would work, but it wouldn't save a round trip to the browser, just to
C++, which is quite cheap as I understand it. This dispatch code is likely to
change a bit if we deprecate unfiltered events and handle them as filtered
events with an empty filter, so it might make sense to leave any changes like
this until then?

[battre, 2012/06/21 05:35:16]

SGTM

+    }
     if (attachedNamedEvents[name]) {
       if (args) {
         // TODO(asargent): This is an antiquity. Until all callers of
@@ -148,8 +237,7 @@
         if (eventArgumentMassagers[name])
           eventArgumentMassagers[name](args);
       }
-      var result = attachedNamedEvents[name].dispatch.apply(
-          attachedNamedEvents[name], args);
+      var result = attachedNamedEvents[name].dispatch_(args, listenerIDs);
       if (result && result.validationErrors)
         return result.validationErrors;
     }
@@ -170,13 +258,34 @@
   };
 
   // Registers a callback to be called when this event is dispatched.
-  chrome.Event.prototype.addListener = function(cb) {
+  chrome.Event.prototype.addListener = function(cb, filters) {
     if (!this.eventOptions_.supportsListeners)
       throw new Error("This event does not support listeners.");
+    if (filters) {
+      if (!this.eventOptions_.supportsFilters)
+        throw new Error("This event does not support filters.");
+      if (filters.url && !(filters.url instanceof Array))
+        throw new Error("filters.url should be an array");
+    }
+    var listener = {callback: cb, filters: filters};
+    this.attach_(listener);
+    this.listeners_.push(listener);
+  };
+
+  chrome.Event.prototype.attach_ = function(listener) {
+    this.attachmentStrategy_.onAddedListener(listener);
     if (this.listeners_.length == 0) {
-      this.attach_();
+      allAttachedEvents[allAttachedEvents.length] = this;

[battre, 2012/06/20 09:50:46]

Is my understanding correct, that this adds the Event to allAttachedEvents
regardless whether this is a filtered or unfiltered event? My reason for asking
is that only UnfilteredAttachmentStrategy.prototype.detach removes the Event
from the array. Maybe for symmetry reasons, adding and removing elements to/from
allAttachedEvents should happen in the same class.

[koz (OOO until 15th September), 2012/06/21 02:23:11]

Nice spot, this code is really hairy. Done.

+      if (!this.eventName_)
+        return;
+
+      if (attachedNamedEvents[this.eventName_]) {
+        throw new Error("chrome.Event '" + this.eventName_ +
+                        "' is already attached.");
+      }
+
+      attachedNamedEvents[this.eventName_] = this;
     }
-    this.listeners_.push(cb);
   };
 
   // Unregisters a callback.
@@ -188,9 +297,19 @@
       return;
     }
 
-    this.listeners_.splice(idx, 1);
+    var removedListener = this.listeners_.splice(idx, 1)[0];
+    this.attachmentStrategy_.onRemovedListener(removedListener);
+
     if (this.listeners_.length == 0) {
-      this.detach_(true);
+      if (!this.eventName_)
+        return;
+
+      if (!attachedNamedEvents[this.eventName_]) {
+        throw new Error("chrome.Event '" + this.eventName_ +
+                        "' is not attached.");
+      }
+
+      delete attachedNamedEvents[this.eventName_];
     }
   };
 
@@ -212,7 +331,7 @@
   // found.
   chrome.Event.prototype.findListener_ = function(cb) {
     for (var i = 0; i < this.listeners_.length; i++) {
-      if (this.listeners_[i] == cb) {
+      if (this.listeners_[i].callback == cb) {
         return i;
       }
     }
@@ -220,21 +339,21 @@
     return -1;
   };
 
-  // Dispatches this event object to all listeners, passing all supplied
-  // arguments to this function each listener.
-  chrome.Event.prototype.dispatch = function(varargs) {
+  chrome.Event.prototype.dispatch_ = function(args, listenerIDs) {
     if (!this.eventOptions_.supportsListeners)
       throw new Error("This event does not support listeners.");
-    var args = Array.prototype.slice.call(arguments);
     var validationErrors = this.validateEventArgs_(args);
     if (validationErrors) {
       console.error(validationErrors);
       return {validationErrors: validationErrors};
     }
+
+    var listeners = this.attachmentStrategy_.getListenersByIDs(listenerIDs);
+
     var results = [];
-    for (var i = 0; i < this.listeners_.length; i++) {
+    for (var i = 0; i < listeners.length; i++) {
       try {
-        var result = this.listeners_[i].apply(null, args);
+        var result = listeners[i].callback.apply(null, args);
         if (result !== undefined)
           results.push(result);
       } catch (e) {
@@ -244,39 +363,17 @@
     }
     if (results.length)
       return {results: results};
-  };
-
-  // Attaches this event object to its name.  Only one object can have a given
-  // name.
-  chrome.Event.prototype.attach_ = function() {
-    AttachEvent(this.eventName_);
-    allAttachedEvents[allAttachedEvents.length] = this;
-    if (!this.eventName_)
-      return;
-
-    if (attachedNamedEvents[this.eventName_]) {
-      throw new Error("chrome.Event '" + this.eventName_ +
-                      "' is already attached.");
-    }
+  }
 
-    attachedNamedEvents[this.eventName_] = this;
+  // Dispatches this event object to all listeners, passing all supplied
+  // arguments to this function each listener.
+  chrome.Event.prototype.dispatch = function(varargs) {
+    return this.dispatch_(Array.prototype.slice.call(arguments), undefined);
   };
 
   // Detaches this event object from its name.
-  chrome.Event.prototype.detach_ = function(manual) {
-    var i = allAttachedEvents.indexOf(this);
-    if (i >= 0)
-      delete allAttachedEvents[i];
-    DetachEvent(this.eventName_, manual);
-    if (!this.eventName_)
-      return;
-
-    if (!attachedNamedEvents[this.eventName_]) {
-      throw new Error("chrome.Event '" + this.eventName_ +
-                      "' is not attached.");
-    }
-
-    delete attachedNamedEvents[this.eventName_];
+  chrome.Event.prototype.detach_ = function() {
+    this.attachmentStrategy_.detach(false);
   };
 
   chrome.Event.prototype.destroy_ = function() {
@@ -363,7 +460,7 @@
     for (var i = 0; i < allAttachedEvents.length; ++i) {
       var event = allAttachedEvents[i];
       if (event)
-        event.detach_(false);
+        event.detach_();
     }
   };