From Stephan Huber, "attached you'll find a proposal for handling multi-touch-events with

osgGA. My approach is to bundle all touchpoints into one custom data
structure which is attached to an GUIEventAdapter.

The current approach simulates a moving mouse for the first touch-point,
so basic manipulators do work, sort of.

I created a MultiTouchTrackballManipulator-class, one touch-point does
rotate the view, two touch-points pan and zoom the view as known from
the iphone or other similar multi-touch-devices. A double-tap (similar
to a double-click) resets the manipulator to its home-position.

The multi-touch-trackball-implementation is not the best, see it as a
first starting point. (there's a demo-video at http://vimeo.com/15017377 )"

include/osgGA/GUIEventAdapter

@@ -255,6 +255,62 @@ public:
             ERASER
         };
         
+        enum TouchPhase 
+        {
+            TOUCH_UNKNOWN,
+            TOUCH_BEGAN,
+            TOUCH_MOVED,
+            TOUCH_STATIONERY,
+            TOUCH_ENDED
+        };
+        
+        class TouchData : public osg::Referenced {
+        public:
+            struct TouchPoint {
+                unsigned int id;
+                TouchPhase phase;
+                float x, y;
+                
+                unsigned int tapCount;
+                TouchPoint() : id(0), phase(TOUCH_UNKNOWN), x(0.0f), y(0.0f), tapCount(0) {}
+                TouchPoint(unsigned int in_id, TouchPhase in_phase, float in_x, float in_y, unsigned int in_tap_count) 
+                :    id(in_id), 
+                    phase(in_phase),
+                    x(in_x), 
+                    y(in_y), 
+                    tapCount(in_tap_count) 
+                {
+                }
+            };
+                        
+            typedef std::vector<TouchPoint> TouchSet;
+            
+            typedef TouchSet::iterator iterator;
+            typedef TouchSet::const_iterator const_iterator;
+            
+            TouchData() : osg::Referenced() {}
+            
+            unsigned int getNumTouchPoints() const { return _touches.size(); }
+                        
+            iterator begin() { return _touches.begin(); }
+            const_iterator begin() const { return _touches.begin(); }
+            
+            iterator end() { return _touches.end(); }
+            const_iterator end() const { return _touches.end(); }
+            
+            const TouchPoint get(unsigned int i) const { return _touches[i]; }
+                    
+        protected:
+            
+            void addTouchPoint(unsigned int id, TouchPhase phase, float x, float y, unsigned int tap_count) {
+                _touches.push_back(TouchPoint(id, phase, x, y, tap_count));
+            }
+            
+            TouchSet _touches;
+            
+        friend class GUIEventAdapter;    
+        };
+        
     public:
 
         GUIEventAdapter();
@@ -443,7 +499,11 @@ public:
         /// set the orientation from a tablet input device as a matrix.
         const osg::Matrix getPenOrientation() const;
 
-
+        void addTouchPoint(unsigned int id, TouchPhase phase, float x, float y, unsigned int tapCount = 0);
+        
+        TouchData* getTouchData() const { return _touchData; }
+        bool isMultiTouchEvent() const { return (_touchData.valid()); }
+        
     protected:
 
         /** Force users to create on heap, so that multiple referencing is safe.*/
@@ -489,7 +549,8 @@ public:
             TabletPen(const TabletPen& rhs) : pressure(rhs.pressure), tiltX(rhs.tiltX), tiltY(rhs.tiltY), rotation(rhs.rotation), tabletPointerType(rhs.tabletPointerType) {}
         };
         TabletPen _tabletPen;
-
+                
+        osg::ref_ptr<TouchData> _touchData; 
 };
 
 }