Hiding subtraction volumes from Geant4 visualization (#43)

Added code to check if any solids are subtraction solids. Hide these
volumes from visualization (NOT deleting anything)

This is needed as QT and OGL fails to plot these properly.

---------

Co-authored-by: Dmitri Smirnov <dmixsmi@gmail.com>

src/g4app.h

@@ -1,12 +1,15 @@
 #include <filesystem>
 
+#include "G4BooleanSolid.hh"
 #include "G4Event.hh"
 #include "G4GDMLParser.hh"
+#include "G4LogicalVolumeStore.hh"
 #include "G4OpBoundaryProcess.hh"
 #include "G4OpticalPhoton.hh"
 #include "G4PhysicalConstants.hh"
 #include "G4PrimaryParticle.hh"
 #include "G4PrimaryVertex.hh"
+#include "G4SubtractionSolid.hh"
 #include "G4SystemOfUnits.hh"
 #include "G4ThreeVector.hh"
 #include "G4Track.hh"
@@ -30,6 +33,31 @@
 #include "U4/U4Touchable.h"
 #include "U4/U4Track.h"
 
+bool IsSubtractionSolid(G4VSolid *solid)
+{
+    if (!solid)
+        return false;
+
+    // Check if the solid is directly a G4SubtractionSolid
+    if (dynamic_cast<G4SubtractionSolid *>(solid))
+        return true;
+
+    // If the solid is a Boolean solid, check its constituent solids
+    G4BooleanSolid *booleanSolid = dynamic_cast<G4BooleanSolid *>(solid);
+    if (booleanSolid)
+    {
+        G4VSolid *solidA = booleanSolid->GetConstituentSolid(0);
+        G4VSolid *solidB = booleanSolid->GetConstituentSolid(1);
+
+        // Recursively check the constituent solids
+        if (IsSubtractionSolid(solidA) || IsSubtractionSolid(solidB))
+            return true;
+    }
+
+    // For other solid types, return false
+    return false;
+}
+
 struct DetectorConstruction : G4VUserDetectorConstruction
 {
 
@@ -46,6 +74,30 @@ struct DetectorConstruction : G4VUserDetectorConstruction
 
         G4CXOpticks::SetGeometry(world);
 
+        G4LogicalVolumeStore *lvStore = G4LogicalVolumeStore::GetInstance();
+
+        static G4VisAttributes invisibleVisAttr(false);
+
+        // Check if the store is not empty
+        if (lvStore && !lvStore->empty())
+        {
+            // Iterate over all logical volumes in the store
+            for (auto &logicalVolume : *lvStore)
+            {
+                G4VSolid *solid = logicalVolume->GetSolid();
+
+                // Check if the solid uses subtraction
+                if (IsSubtractionSolid(solid))
+                {
+                    // Assign the invisible visual attributes to the logical volume
+                    logicalVolume->SetVisAttributes(&invisibleVisAttr);
+
+                    // Optionally, print out the name of the logical volume
+                    G4cout << "Hiding logical volume: " << logicalVolume->GetName() << G4endl;
+                }
+            }
+        }
+
         return world;
     }