WIP: support to read the old style DD4hep hit collection.

Simulation/DetSimAna/src/ExampleAnaElemTool.cpp

 #include "ExampleAnaElemTool.h"
 
 #include "G4Event.hh"
+#include "G4THitsCollection.hh"
 
 #include "DD4hep/Detector.h"
 #include "DD4hep/Plugins.h"
 #include "DDG4/Geant4Converter.h"
 #include "DDG4/Geant4Mapping.h"
-
+#include "DDG4/Geant4HitCollection.h"
+#include "DDG4/Geant4Data.h"
+#include "DDG4/Geant4Hits.h"
 
 DECLARE_COMPONENT(ExampleAnaElemTool)
 
@@ -56,8 +59,65 @@ ExampleAnaElemTool::EndOfEventAction(const G4Event* anEvent) {
                << " #" << icol
                << " has " << nhits << " hits."
                << endmsg;
+        // There are different types (new and old)
+
+        dd4hep::sim::Geant4HitCollection* coll = dynamic_cast<dd4hep::sim::Geant4HitCollection*>(collect);
+        if (coll) {
+            info() << " cast to dd4hep::sim::Geant4HitCollection. " << endmsg;
+            for(size_t i=0; i<nhits; ++i)   {
+
+                dd4hep::sim::Geant4HitData* h = coll->hit(i);
+
+                dd4hep::sim::Geant4Tracker::Hit* trk_hit = dynamic_cast<dd4hep::sim::Geant4Tracker::Hit*>(h);
+                if ( 0 != trk_hit )   {
+                    dd4hep::sim::Geant4HitData::Contribution& t = trk_hit->truth;
+                    int trackID = t.trackID;
+                    // t.trackID = m_truth->particleID(trackID);
+                }
+                // Geant4Calorimeter::Hit* cal_hit = dynamic_cast<Geant4Calorimeter::Hit*>(h);
+                // if ( 0 != cal_hit )   {
+                //     Geant4HitData::Contributions& c = cal_hit->truth;
+                //     for(Geant4HitData::Contributions::iterator j=c.begin(); j!=c.end(); ++j)  {
+                //         Geant4HitData::Contribution& t = *j;
+                //         int trackID = t.trackID;
+                //         // t.trackID = m_truth->particleID(trackID);
+                //     }
+                // }
+            }
+            continue;
+        }
+
+        typedef G4THitsCollection<dd4hep::sim::Geant4Hit> HitCollection;
+        HitCollection* coll2 = dynamic_cast<HitCollection*>(collect);
+
+        if (coll2) {
+            info() << " cast to G4THitsCollection<dd4hep::sim::Geant4Hit>. " << endmsg;
+
+            for(size_t i=0; i<nhits; ++i)   {
+                dd4hep::sim::Geant4Hit* h = dynamic_cast<dd4hep::sim::Geant4Hit*>(coll2->GetHit(i));
+                if (!h) {
+                    warning() << "Failed to cast to dd4hep::sim::Geant4Hit. " << endmsg;
+                    continue;
+                }
 
+                dd4hep::sim::Geant4TrackerHit* trk_hit = dynamic_cast<dd4hep::sim::Geant4TrackerHit*>(h);
+                if (trk_hit) {
+                    info() << " cast to dd4hep::sim::Geant4TrackerHit. " << endmsg;
+                }
+
+                dd4hep::sim::Geant4CalorimeterHit* cal_hit = dynamic_cast<dd4hep::sim::Geant4CalorimeterHit*>(h);
+                if (cal_hit) {
+                    info() << " cast to dd4hep::sim::Geant4CalorimeterHit. " << endmsg;
+                }
+
+            }
+
+            continue;
+        }
 
+        warning() << "Failed to convert to collection "
+                  << collect->GetName()
+                  << endmsg;
         
     }
 }