From b7525e446d19afaf599d0a648af8c46cc6505c5e Mon Sep 17 00:00:00 2001
From: Glenn Waldron <gwaldron@gmail.com>
Date: Fri, 20 Dec 2024 16:21:53 -0500
Subject: [PATCH] GeoTransform: fix a bug: terrain callback was not reinstalled
 after the terrain observer_ptr went null and a new terrain was found

---
 src/osgEarth/GeoTransform     | 19 ++++++++-----------
 src/osgEarth/GeoTransform.cpp | 33 +++++++++++++++++++++++++--------
 2 files changed, 33 insertions(+), 19 deletions(-)

diff --git a/src/osgEarth/GeoTransform b/src/osgEarth/GeoTransform
index e2223b51c1..8fae2bc9b8 100644
--- a/src/osgEarth/GeoTransform
+++ b/src/osgEarth/GeoTransform
@@ -16,8 +16,7 @@
  * You should have received a copy of the GNU Lesser General Public License
  * along with this program.  If not, see <http://www.gnu.org/licenses/>
  */
-#ifndef OSGEARTH_GEO_TRANSFORM
-#define OSGEARTH_GEO_TRANSFORM
+#pragma once
 
 #include <osgEarth/Common>
 #include <osgEarth/Config>
@@ -123,16 +122,14 @@ namespace osgEarth
     protected:
         virtual ~GeoTransform();
 
-        GeoPoint                   _position;                 // Current position
-        osg::observer_ptr<Terrain> _terrain;                  // Terrain for relative height resolution
-        bool                       _terrainCallbackInstalled; // Whether the Terrain callback is in
-        bool                       _autoRecomputeHeights;     // Whether to resolve relative position Z's
-        bool                       _findTerrainInUpdateTraversal; // True is we need _terrain but don't have it
-        bool                       _clampInUpdateTraversal;       // Whether a terrain clamp is required
-
+        GeoPoint _position;                   // Current position
+        osg::observer_ptr<Terrain> _terrain;  // Terrain for relative height resolution
+        bool _terrainCallbackInstalled;       // Whether the Terrain callback is in
+        bool _autoRecomputeHeights;           // Whether to resolve relative position Z's
+        bool _findTerrainInUpdateTraversal;   // True is we need _terrain but don't have it
+        bool _clampInUpdateTraversal;         // Whether a terrain clamp is required
         osg::ref_ptr<ComputeMatrixCallback> _computeMatrixCallback;
+        osg::ref_ptr<TerrainCallbackAdapter<GeoTransform>> _terrainCallback; // Callback for terrain updates
     };
 
 } // namespace osgEarth
-
-#endif // OSGEARTH_GEO_TRANSFORM
diff --git a/src/osgEarth/GeoTransform.cpp b/src/osgEarth/GeoTransform.cpp
index 4696c5f11a..cff28e75b8 100644
--- a/src/osgEarth/GeoTransform.cpp
+++ b/src/osgEarth/GeoTransform.cpp
@@ -27,16 +27,16 @@
 using namespace osgEarth;
 
 GeoTransform::GeoTransform() :
-_findTerrainInUpdateTraversal(false),
-_terrainCallbackInstalled(false),
-_autoRecomputeHeights(true),
-_clampInUpdateTraversal(false)
+    _findTerrainInUpdateTraversal(false),
+    _terrainCallbackInstalled(false),
+    _autoRecomputeHeights(true),
+    _clampInUpdateTraversal(false)
 {
-   //nop
+    //nop
 }
 
 GeoTransform::GeoTransform(const GeoTransform& rhs, const osg::CopyOp& op) :
-osg::MatrixTransform(rhs, op)
+    osg::MatrixTransform(rhs, op)
 {
     _position = rhs._position;
     _terrain = rhs._terrain.get();
@@ -58,9 +58,24 @@ GeoTransform::setTerrain(Terrain* terrain)
     if (terrain)
     {
         if (_terrain.valid())
+        {
+            if (_terrainCallback.valid())
+            {
+                _terrain->removeTerrainCallback(_terrainCallback.get());
+                _terrainCallbackInstalled = false;
+            }
             _terrain->removeObserver(this);
+        }
+
         _terrain = terrain;
         _terrain->addObserver(this);
+
+        if (_terrainCallback.valid())
+        {
+            _terrain->addTerrainCallback(_terrainCallback);
+            _terrainCallbackInstalled = true;
+        }
+
         setPosition(_position);
     }
 }
@@ -152,8 +167,10 @@ GeoTransform::setPosition(const GeoPoint& position)
         !_terrainCallbackInstalled &&
         terrain.valid())
     {
-        // The Adapter template auto-destructs, so we never need to remote it manually.
-        terrain->addTerrainCallback( new TerrainCallbackAdapter<GeoTransform>(this) );
+        // The Adapter template auto-destructs, so we never need to remove it manually.
+        if (!_terrainCallback.valid())
+            _terrainCallback = new TerrainCallbackAdapter<GeoTransform>(this);
+        terrain->addTerrainCallback(_terrainCallback);
         _terrainCallbackInstalled = true;
     }