For EZ property sets, added a setter that performs an "atomic" test-and-set:

it's atomic in the sense that a single server event will test the variable, 
and only set it if the previous value was null (i.e. didn't exist). 
This allows for a level of elementary synchronization between the clients.

The new function on EZGameControl is:
  _gameCtrl.testAndSet (propertyName, newValue[, index])

I hoped to generalize this to test against arbitrary values, but that's 
significantly harder, since properties accept numerous types as values,
and those can have different representations on the client and the server.
So it remains a check against null until we need to generalize it. :)





git-svn-id: svn+ssh://src.earth.threerings.net/vilya/trunk@193 c613c5cb-e716-0410-b11b-feb51c14d237

src/as/com/threerings/ezgame/data/PropertySetEvent.as

@@ -35,7 +35,7 @@ public class PropertySetEvent extends NamedEvent
     override public function applyToObject (target :DObject) :Boolean
     {
         _oldValue =
-            EZGameObject(target).applyPropertySet(_name, _data, _index);
+            EZGameObject(target).applyPropertySet(_name, _data, _index, _testAndSet);
         return true;
     }
 
@@ -69,6 +69,7 @@ public class PropertySetEvent extends NamedEvent
         super.readObject(ins);
         _index = ins.readInt();
         _data = EZObjectMarshaller.decode(ins.readObject());
+        _testAndSet = ins.readBoolean();
     }
 
     // from interface Streamable
@@ -77,6 +78,7 @@ public class PropertySetEvent extends NamedEvent
         super.writeObject(out);
         out.writeInt(_index);
         out.writeObject(_data);
+        out.writeBoolean(_testAndSet);
     }
 
     override protected function notifyListener (listener :Object) :void
@@ -99,6 +101,9 @@ public class PropertySetEvent extends NamedEvent
     /** The client-side data that is assigned to this property. */
     protected var _data :Object;
 
+    /** When true, the property will only be set if its previous value was null. */
+    protected var _testAndSet :Boolean;
+
     /** The old value. */
     protected var _oldValue :Object;
 }