Camera: convenience methods to find nested callback by type

include/osg/Callback

@@ -121,8 +121,33 @@ class OSG_EXPORT Callback : public virtual Object {
             }
         }
 
-    protected:
+        /** Convenience method to find a nested callback by type. */
+        template <typename T>
+        static T* findNestedCallback(osg::Callback* callback)
+        {
+            if (!callback)
+                return nullptr;
+
+            if (T* cb = dynamic_cast<T*>(callback))
+                return cb;
 
+            return findNestedCallback<T>(callback->getNestedCallback());
+        }
+
+        /** Convenience method to find a nested callback by type. */
+        template <typename T>
+        static const T* findNestedCallback(const osg::Callback* callback)
+        {
+            if (!callback)
+                return nullptr;
+
+            if (const T* cb = dynamic_cast<const T*>(callback))
+                return cb;
+
+            return findNestedCallback<T>(callback->getNestedCallback());
+        }
+
+    protected:
         virtual ~Callback() {}
         ref_ptr<Callback> _nestedCallback;
 };

include/osg/Camera

@@ -642,6 +642,14 @@ class OSG_EXPORT Camera : public Transform, public CullSettings
         /** Get the const initial draw callback.*/
         const DrawCallback* getInitialDrawCallback() const { return _initialDrawCallback.get(); }
 
+        /** Convenience method to find a nested initial draw callback by type. */
+        template <typename T>
+        T* findInitialDrawCallback() { return osg::Callback::findNestedCallback<T>(_initialDrawCallback.get()); }
+
+        /** Convenience method to find a nested initial draw callback by type. */
+        template <typename T>
+        const T* findInitialDrawCallback() const { return osg::Callback::findNestedCallback<T>(_initialDrawCallback.get()); }
+
         /** Convenience method that sets DrawCallback Initial callback of the node if it doesn't exist, or nest it into the existing one. */
         inline void addInitialDrawCallback(DrawCallback* nc)
         {
@@ -680,6 +688,14 @@ class OSG_EXPORT Camera : public Transform, public CullSettings
         /** Get the const pre draw callback.*/
         const DrawCallback* getPreDrawCallback() const { return _preDrawCallback.get(); }
 
+        /** Convenience method to find a nested pre draw callback by type. */
+        template <typename T>
+        T* findPreDrawCallback() { return osg::Callback::findNestedCallback<T>(_preDrawCallback.get()); }
+
+        /** Convenience method to find a nested pre draw callback by type. */
+        template <typename T>
+        const T* findPreDrawCallback() const { return osg::Callback::findNestedCallback<T>(_preDrawCallback.get()); }
+
         /** Convenience method that sets DrawCallback Initial callback of the node if it doesn't exist, or nest it into the existing one. */
         inline void addPreDrawCallback(DrawCallback* nc)
         {
@@ -718,6 +734,14 @@ class OSG_EXPORT Camera : public Transform, public CullSettings
         /** Get the const post draw callback.*/
         const DrawCallback* getPostDrawCallback() const { return _postDrawCallback.get(); }
 
+        /** Convenience method to find a nested post draw callback by type. */
+        template <typename T>
+        T* findPostDrawCallback() { return osg::Callback::findNestedCallback<T>(_postDrawCallback.get()); }
+
+        /** Convenience method to find a nested post draw callback by type. */
+        template <typename T>
+        const T* findPostDrawCallback() const { return osg::Callback::findNestedCallback<T>(_postDrawCallback.get()); }
+
         /** Convenience method that sets DrawCallback Initial callback of the node if it doesn't exist, or nest it into the existing one. */
         inline void addPostDrawCallback(DrawCallback* nc)
         {
@@ -756,6 +780,14 @@ class OSG_EXPORT Camera : public Transform, public CullSettings
         /** Get the const final draw callback.*/
         const DrawCallback* getFinalDrawCallback() const { return _finalDrawCallback.get(); }
 
+        /** Convenience method to find a nested final draw callback by type. */
+        template <typename T>
+        T* findFinalDrawCallback() { return osg::Callback::findNestedCallback<T>(_finalDrawCallback.get()); }
+
+        /** Convenience method to find a nested final draw callback by type. */
+        template <typename T>
+        const T* findFinalDrawCallback() const { return osg::Callback::findNestedCallback<T>(_finalDrawCallback.get()); }
+
         /** Convenience method that sets DrawCallback Initial callback of the node if it doesn't exist, or nest it into the existing one. */
         inline void addFinalDrawCallback(DrawCallback* nc)
         {