From 3fc219a8249b054cc64938079b4fb9b989bfcb23 Mon Sep 17 00:00:00 2001
From: Roy-043 <70520633+Roy-043@users.noreply.github.com>
Date: Sun, 1 Jun 2025 11:52:28 +0200
Subject: [PATCH] BIM: Terrain should not also be in Group of Site

Addresses one of the issues mentioned in #21667.

* If the Terrain is dropped on the Site it is added to the Group (as before) but the Terrain property is then also set to None.
* If one of the objects in Group is selected as the Terrain it is removed from the Group.
---
 src/Mod/BIM/ArchSite.py | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/src/Mod/BIM/ArchSite.py b/src/Mod/BIM/ArchSite.py
index 2fdf971929..b1ff111b0a 100644
--- a/src/Mod/BIM/ArchSite.py
+++ b/src/Mod/BIM/ArchSite.py
@@ -659,8 +659,15 @@ class _Site(ArchIFC.IfcProduct):
 
     def onChanged(self, obj, prop):
         ArchComponent.Component.onChanged(self, obj, prop)
-        if prop == "Terrain" and obj.Terrain and FreeCAD.GuiUp:
-            obj.Terrain.ViewObject.hide()
+        if prop == "Terrain" and obj.Terrain:
+            if obj.Terrain in getattr(obj,"Group",[]):
+                grp = obj.Group
+                grp.remove(obj.Terrain)
+                obj.Group = grp
+            if FreeCAD.GuiUp:
+                obj.Terrain.ViewObject.hide()
+        if prop == "Group" and getattr(obj,"Terrain",None) in obj.Group:
+            obj.Terrain = None
 
     def getMovableChildren(self, obj):
         return obj.Additions + obj.Subtractions