Geant4HepEmTrackingPhysics.cpp

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//==========================================================================
//  AIDA Detector description implementation
//--------------------------------------------------------------------------
// Copyright (C) Organisation europeenne pour la Recherche nucleaire (CERN)
// All rights reserved.
//
// For the licensing terms see $DD4hepINSTALL/LICENSE.
// For the list of contributors see $DD4hepINSTALL/doc/CREDITS.
//
//==========================================================================
 
#ifndef DDG4_GEANT4HEPEMTRACKINGPHYSICS_H
#define DDG4_GEANT4HEPEMTRACKINGPHYSICS_H 1
 
#include <DDG4/Geant4PhysicsList.h>
 
#include <G4Electron.hh>
#include <G4Gamma.hh>
#include <G4Positron.hh>
#include <G4VUserPhysicsList.hh>
 
#include <G4HepEmConfig.hh>
#include <G4HepEmTrackingManager.hh>
 
#include <string>
#include <vector>
 
namespace dd4hep {
 
  namespace sim {
 
 
    class Geant4HepEmTrackingPhysics : public Geant4PhysicsList {
    protected:
      DDG4_DEFINE_ACTION_CONSTRUCTORS(Geant4HepEmTrackingPhysics);
 
      std::vector<std::string> m_woodcockRegions;
 
    public:
      Geant4HepEmTrackingPhysics(Geant4Context* context, const std::string& nam)
        : Geant4PhysicsList(context, nam) {
        declareProperty("WoodcockRegions", m_woodcockRegions);
      }
 
      virtual ~Geant4HepEmTrackingPhysics() = default;
 
 
      virtual void constructProcesses(G4VUserPhysicsList* /* physics_list */) override {
        // Allocate one tracking manager for this thread.  G4HepEmTrackingManager
        // handles e-/e+/gamma internally by dispatching on particle type, so one
        // shared instance per thread suffices.  Ownership lies with Geant4.
        auto* tm = new G4HepEmTrackingManager();
 
        for (const auto& region : m_woodcockRegions) {
          info("+++ Enabling Woodcock photon tracking in G4Region: %s", region.c_str());
          tm->GetConfig()->SetWoodcockTrackingRegion(region);
        }
 
        // Warn if another custom tracking manager is already installed —
        // SetTrackingManager() is exclusive and will silently replace it.
        auto warnIfConflict = [&](G4ParticleDefinition* particle) {
          if (particle->GetTrackingManager() != nullptr) {
            warning("+++ Replacing existing tracking manager for %s with G4HepEmTrackingManager",
                    particle->GetParticleName().c_str());
          }
        };
        warnIfConflict(G4Electron::Definition());
        warnIfConflict(G4Positron::Definition());
        warnIfConflict(G4Gamma::Definition());
 
        G4Electron::Definition()->SetTrackingManager(tm);
        G4Positron::Definition()->SetTrackingManager(tm);
        G4Gamma::Definition()   ->SetTrackingManager(tm);
 
        info("+++ Installed G4HepEmTrackingManager for e-/e+/gamma");
      }
    };
  }  // namespace sim
}  // namespace dd4hep
 
#endif  // DDG4_GEANT4HEPEMTRACKINGPHYSICS_H
 
#include <DDG4/Factories.h>
using namespace dd4hep::sim;
DECLARE_GEANT4ACTION(Geant4HepEmTrackingPhysics)