GeantFollowerMS.cxx

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/*
  Copyright (C) 2002-2026 CERN for the benefit of the ATLAS collaboration
*/

// GeantFollowerMS.cxx, (c) ATLAS Detector software
 
#include "TrkG4UserActions/GeantFollowerMS.h"
#include "TrkG4UserActions/IGeantFollowerMSHelper.h"
 
#include "G4Event.hh"
#include "G4Step.hh"
#include "G4Material.hh"
#include "G4Element.hh"
#include "G4StepPoint.hh"
#include "G4TouchableHistory.hh"
#include "G4LogicalVolume.hh"
#include "G4DynamicParticle.hh"
#include "G4Track.hh"
 
namespace G4UA
{
 
  GeantFollowerMS::GeantFollowerMS(const Config& config)
    : m_config(config)
    , m_helperPointer(nullptr)
  {}
 
  void GeantFollowerMS::BeginOfEventAction(const G4Event*)
  {
    // FIXME: thread-unsafe tool usage in thread-local action? ATLASSIM-3562.
    m_helperPointer->beginEvent();
  }
 
  void GeantFollowerMS::EndOfEventAction(const G4Event*)
  {
    // FIXME: thread-unsafe tool usage in thread-local action? ATLASSIM-3562.
    m_helperPointer->endEvent();
  }
 
  void GeantFollowerMS::BeginOfRunAction(const G4Run*)
  {
    if(m_config.helper.retrieve()!=StatusCode::SUCCESS) {
      G4ExceptionDescription description;
      description << "Cannot retrieve GeantFollowerMS helper";
      G4Exception("GeantFollowerMS", "GeantFollowerMS1", FatalException, description);
      return;
    }
    m_helperPointer = (&(*m_config.helper));
 
    if(m_config.trackingGeometrySvc.retrieve()!=StatusCode::SUCCESS) {
      G4ExceptionDescription description;
      description << "Cannot retrieve TrackingGeometrySvc in GeantFollowerMS";
      G4Exception("GeantFollowerMS", "GeantFollowerMS2", FatalException, description);
      return;
    }
 
     }
 
  void GeantFollowerMS::UserSteppingAction(const G4Step* aStep)
  {
    // kill secondaries
    if (aStep->GetTrack()->GetParentID()) {
      aStep->GetTrack()->SetTrackStatus(fStopAndKill);
      return;
    }
 
    // get the prestep point and follow this guy
    G4StepPoint * g4PreStep  = aStep->GetPreStepPoint();
    G4ThreeVector g4Momentum = g4PreStep->GetMomentum();
    const G4ThreeVector& g4Position = g4PreStep->GetPosition();
 
    G4Track* g4Track = aStep->GetTrack();
    const G4DynamicParticle* g4DynParticle = g4Track->GetDynamicParticle();
 
    // the material information
    const G4TouchableHistory* touchHist =
      static_cast<const G4TouchableHistory*>(aStep->GetPreStepPoint()->GetTouchable());
 
    if(touchHist) [[likely]] {
      // G4LogicalVolume
      const G4LogicalVolume *lv= touchHist->GetVolume()->GetLogicalVolume();
 
      if(lv) [[likely]] {
        const G4Material *mat    = lv->GetMaterial();
        // the step information
        double steplength     = aStep->GetStepLength();
        // the position information
        double X0             = mat->GetRadlen();
        // update the track follower
        m_helperPointer->trackParticle(g4Position, g4Momentum,
                                       g4DynParticle->GetPDGcode(),
                                       g4DynParticle->GetCharge(),
                                       steplength, X0);
      }
      else {
        G4ExceptionDescription description;
        description << "GeantFollowerMS::SteppingAction NULL G4LogicalVolume pointer.";
        G4Exception("GeantFollowerMS", "GeantFollowerMS3", FatalException, description);
      }
    }
    else {
      G4ExceptionDescription description;
      description << "GeantFollowerMS::SteppingAction NULL G4TouchableHistory pointer.";
      G4Exception("GeantFollowerMS", "GeantFollowerMS4", FatalException, description);
    }
     }
 
} // namespace G4UA