Introduce new osgGA::Event and osgGA::EventHandler base classes that the old GUIEventAdapter and GUIEventHandler now subclass from.

The new osgGA::Event is written to support more generic events than the original GUIEventAdapter which are written for keyboard and mouse events.

include/osgGA/Event

@@ -0,0 +1,52 @@
+/* -*-c++-*- OpenSceneGraph - Copyright (C) 1998-2013 Robert Osfield
+ *
+ * This library is open source and may be redistributed and/or modified under
+ * the terms of the OpenSceneGraph Public License (OSGPL) version 0.0 or
+ * (at your option) any later version.  The full license is in LICENSE file
+ * included with this distribution, and on the openscenegraph.org website.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * OpenSceneGraph Public License for more details.
+*/
+
+#ifndef OSGGA_EVENT
+#define OSGGA_EVENT 1
+
+#include <osgGA/Export>
+#include <osg/Object>
+
+namespace osgGA {
+
+// forward declare
+class GUIEventAdapter;
+
+/** Base Event class.*/
+class OSGGA_EXPORT Event : public osg::Object
+{
+public:
+    Event();
+
+    Event(const Event& rhs, const osg::CopyOp& copyop=osg::CopyOp::SHALLOW_COPY);
+
+    META_Object(osgGA, Event);
+
+    virtual GUIEventAdapter* asGUIEventAdapter() { return 0; }
+    virtual const GUIEventAdapter* asGUIEventAdapter() const { return 0; }
+
+    /** set time in seconds of event. */
+    void setTime(double time) { _time = time; }
+
+    /** get time in seconds of event. */
+    double getTime() const { return _time; }
+
+protected:
+    virtual ~Event() {}
+
+    double _time;
+};
+
+}
+
+#endif