adding generic event handling inside the object class

src/core/object.js

@@ -4,7 +4,7 @@
  */
 
 /*jslint devel: true, forin: true, newcap: true, plusplus: true*/
-/*jslint white: true, indent: 2*/
+/*jslint white: true, indent: 2, unparam: true*/
 
 /*global geo, ogs, inherit, $, HTMLCanvasElement, Image*/
 /*global vgl, document*/
@@ -23,6 +23,81 @@ geo.object = function(cfg) {
   if (!(this instanceof geo.object)) {
     return new geo.object();
   }
+
+  var m_eventHandlers = {};
+
+//////////////////////////////////////////////////////////////////////////////
+/**
+ *  Bind an event handler to this object
+ */
+//////////////////////////////////////////////////////////////////////////////
+  this.on = function (event, handler) {
+    if (Array.isArray(event)) {
+      event.forEach(function (e) {
+        this.on(e, handler);
+      });
+      return this;
+    }
+    if (!m_eventHandlers.hasOwnProperty(event)) {
+      m_eventHandlers[event] = [];
+    }
+    m_eventHandlers[event].push(handler);
+    return this;
+  };
+
+//////////////////////////////////////////////////////////////////////////////
+/**
+ *  Trigger an event (or events) on this object and call all handlers
+ */
+//////////////////////////////////////////////////////////////////////////////
+  this.trigger = function (event, args) {
+    if (Array.isArray(event)) {
+      event.forEach(function (e) {
+        this.trigger(e, args);
+      });
+      return this;
+    }
+    if (m_eventHandlers.hasOwnProperty(event)) {
+      m_eventHandlers[event].forEach(function (handler) {
+        handler(args);
+      });
+    }
+    return this;
+  };
+
+//////////////////////////////////////////////////////////////////////////////
+/**
+ *  Remove handlers from an event (or an array of events).
+ *
+ *  @param arg a function or array of functions to remove from the events
+ *             or if falsey remove all handlers from the events
+ */
+//////////////////////////////////////////////////////////////////////////////
+  this.off = function (event, arg) {
+    if (Array.isArray(event)) {
+      event.forEach(function (e) {
+        this.off(e, arg);
+      });
+      return this;
+    }
+    if (!arg) {
+      m_eventHandlers[event] = [];
+    } else if (Array.isArray(arg)) {
+      arg.forEach(function (handler) {
+        this.off(event, handler);
+      });
+      return this;
+    }
+    // What do we do if the handler is not already bound?
+    //   ignoring for now...
+    if (m_eventHandlers.hasOwnProperty(event)) {
+      m_eventHandlers[event] = m_eventHandlers[event].filter(function (f) {
+          return f !== arg;
+      });
+    }
+    return this;
+  };
+
   vgl.object.call(this);
 
   return this;