From Stephan Huber,

"attached you'll find some modifications to Producer, osgGA and
osgProducer to enable Mac OS X support for

+ scrollwheels,
+ mightymouse-srollballs
+ new tracking-pads with scroll feature
+ tablet-support (pressure, proximity and pointertype) (Wacom only tested)

I think there was a bug in the windows-implementation of scroll-wheel
support (wrong order of ScrollingMotion-enum, casting problem) which is
fixed now.

The scrollwheel-code is a bit klunky across platforms, some devices on
OS X can report an absolute delta in pixel-coordinates not only the
direction, so for now there is scrollingMotion (which describes the
direction) and scrolldeltax and scrolldeltay. I decided to leave the
scrollingmotion-stuff to not break old code relying on this."

src/osgGA/EventQueue.cpp

@@ -87,6 +87,24 @@ void EventQueue::windowResize(float Xmin, float Ymin, float Xmax, float Ymax)
     addEvent(event);
 }
 
+void EventQueue::penPressure(float pressure)
+{
+    GUIEventAdapter* event = new GUIEventAdapter(*_accumulateEventState);
+    event->setEventType(GUIEventAdapter::PEN_PRESSURE);
+    event->setPenPressure(pressure);
+    
+    addEvent(event);
+}
+
+void EventQueue::penProximity(GUIEventAdapter::TabletPointerType pt, bool isEntering)
+{
+    GUIEventAdapter* event = new GUIEventAdapter(*_accumulateEventState);
+    event->setEventType( (isEntering) ? GUIEventAdapter::PEN_PROXIMITY_ENTER : GUIEventAdapter::PEN_PROXIMITY_LEAVE);
+    event->setTabletPointerType(pt);
+    
+    addEvent(event);
+}
+
 void EventQueue::mouseScroll(GUIEventAdapter::ScrollingMotion sm)
 {
     GUIEventAdapter* event = new GUIEventAdapter(*_accumulateEventState);
@@ -96,6 +114,16 @@ void EventQueue::mouseScroll(GUIEventAdapter::ScrollingMotion sm)
     addEvent(event);
 }
 
+void EventQueue::mouseScroll2D(float x, float y)
+{
+    GUIEventAdapter* event = new GUIEventAdapter(*_accumulateEventState);
+    event->setEventType(GUIEventAdapter::SCROLL);
+    event->setScrollingMotionDelta(x,y);
+    
+    addEvent(event);
+}
+
+
 void EventQueue::mouseWarp(float x, float y)
 {
     _accumulateEventState->setX(x);