Gui: add convenient smart pointer CoinPtr to manager coin node

src/Gui/ViewProvider.h

@@ -30,6 +30,7 @@
 #include <bitset>
 #include <QIcon>
 #include <boost/signals2.hpp>
+#include <boost/intrusive_ptr.hpp>
 
 #include <App/TransactionalObject.h>
 #include <Base/Vector3D.h>
@@ -77,6 +78,26 @@ enum ViewStatus {
 };
 
 
+/** Convenience smart pointer to wrap coin node. 
+ *
+ * It is basically boost::intrusive plus implicit pointer conversion to save the
+ * trouble of typing get() all the time.
+ */
+template<class T>
+class CoinPtr: public boost::intrusive_ptr<T> {
+public:
+    // Too bad, VC2013 does not support constructor inheritance
+    //using boost::intrusive_ptr<T>::intrusive_ptr;
+    typedef boost::intrusive_ptr<T> inherited;
+    CoinPtr() {}
+    CoinPtr(T *p, bool add_ref=true):inherited(p,add_ref){}
+    template<class Y> CoinPtr(CoinPtr<Y> const &r):inherited(r){}
+
+    operator T *() const {
+        return this->get();
+    }
+};
+
 
 /** General interface for all visual stuff in FreeCAD
   * This class is used to generate and handle all around