From c0bbab011219c3b6489d2dd7c4ea0b16bb1e08af Mon Sep 17 00:00:00 2001
From: Kolja <GitHub.Kolja@dfgh.net>
Date: Sat, 9 Aug 2025 15:52:52 +0000
Subject: [PATCH] Fix handling for CONST properties in CreateOpticalSurfaceN
 method

(cherry picked from commit b3c06177378fb735d7a6adce0f9fe64e8ac41090)
---
 geom/gdml/src/TGDMLWrite.cxx | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/geom/gdml/src/TGDMLWrite.cxx b/geom/gdml/src/TGDMLWrite.cxx
index 03c335441cd79..f94a1b1d6d535 100644
--- a/geom/gdml/src/TGDMLWrite.cxx
+++ b/geom/gdml/src/TGDMLWrite.cxx
@@ -1944,6 +1944,14 @@ XMLNodePointer_t TGDMLWrite::CreateOpticalSurfaceN(TGeoOpticalSurface *geoSurf)
       while ((property = (TNamed *)next()))
          fGdmlE->AddChild(mainN, CreatePropertyN(*property));
    }
+   // Write CONST properties
+   TList const &const_properties = geoSurf->GetConstProperties();
+   if (const_properties.GetSize()) {
+      TIter next(&const_properties);
+      TNamed *property;
+      while ((property = (TNamed *)next()))
+         fGdmlE->AddChild(mainN, CreatePropertyN(*property));
+   }
    return mainN;
 }