From 0161b8ab46495a99bebaea62e229f66edd88d547 Mon Sep 17 00:00:00 2001
From: Gleb Mazovetskiy <glex.spb@gmail.com>
Date: Thu, 14 Jan 2021 00:19:02 +0000
Subject: [PATCH] include/osg/Callback: nullptr -> NULL

Fixes travis, which explictly requires c++98
---
 include/osg/Callback | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/include/osg/Callback b/include/osg/Callback
index 35480a39c..02a517168 100644
--- a/include/osg/Callback
+++ b/include/osg/Callback
@@ -121,6 +121,32 @@ class OSG_EXPORT Callback : public virtual Object {
             }
         }
 
+        /** Convenience method to find a nested callback by type. */
+        template <typename T>
+        static T* findNestedCallback(osg::Callback* callback)
+        {
+            if (!callback)
+                return NULL;
+
+            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 NULL;
+
+            if (const T* cb = dynamic_cast<const T*>(callback))
+                return cb;
+
+            return findNestedCallback<T>(callback->getNestedCallback());
+        }
+
     protected:
 
         virtual ~Callback() {}