From a6dfa6079ce201b63af93fa85271770cec250328 Mon Sep 17 00:00:00 2001
From: Jan Kieseler <jan.kieseler@kit.edu>
Date: Wed, 20 Sep 2023 20:29:25 +0000
Subject: [PATCH] attempt to make re-init possible

---
 src/G4System.cc | 31 +++++++++++++++++++++++++------
 1 file changed, 25 insertions(+), 6 deletions(-)

diff --git a/src/G4System.cc b/src/G4System.cc
index fbb83cc..9d05e19 100644
--- a/src/G4System.cc
+++ b/src/G4System.cc
@@ -5,11 +5,25 @@ void G4System::init(ConstructionWrapper &CW, bool gui){
 
   char* argv[]={(char*)"dummy"};
 
-  // Construct the default run manager
-  //
-  runManager =
-    G4RunManagerFactory::CreateRunManager(G4RunManagerType::Default);
-  runManager->SetNumberOfThreads(20);//more doesn't make sense
+  bool first_init=true;
+
+  if(runManager == nullptr){
+    // Construct the default run manager
+    //
+    runManager =
+      G4RunManagerFactory::CreateRunManager(G4RunManagerType::Default);
+    runManager->SetNumberOfThreads(20);//more doesn't make sense
+  }
+  else{
+     // Abort the current run
+     runManager->AbortRun(true);
+
+     // Clear any pending events
+     runManager->Clear();
+     first_init = false;
+
+  }
+
 
   G4String session;
   ui = nullptr;
@@ -29,7 +43,12 @@ void G4System::init(ConstructionWrapper &CW, bool gui){
   actionInitialization = new B4a::ActionInitialization(detConstruction);
   runManager->SetUserInitialization(actionInitialization);
 
-  //actionInitialization->setGeneratorProperties(100, 10000, "e-");
+  if(! first_init){
+    runManager->GeometryHasBeenModified();
+    runManager->ReinitializeGeometry();
+    runManager->PhysicsHasBeenModified();
+    runManager->ReinitializePhysics();
+  }
 
   // Initialize visualization
   //