More helper methods for Canvas and PropertyBasedElement.

simgear/props/PropertyBasedElement.hxx

@@ -55,6 +55,17 @@ namespace simgear
         setValue(_node->getNode(name, true), val);
       }
 
+      template<class T>
+      T get( const std::string& name,
+             typename boost::call_traits<T>::param_type def = T() )
+      {
+        SGPropertyNode const* child = _node->getNode(name);
+        if( !child )
+          return def;
+
+        return getValue<T>(child);
+      }
+
       virtual void setSelf(const PropertyBasedElementPtr& self);
 
     protected:

simgear/props/props.hxx

@@ -1796,6 +1796,12 @@ inline const char * getValue<const char*>(const SGPropertyNode* node)
     return node->getStringValue ();
 }
 
+template<>
+inline std::string getValue<std::string>(const SGPropertyNode* node)
+{
+    return node->getStringValue();
+}
+
 inline bool setValue(SGPropertyNode* node, bool value)
 {
     return node->setBoolValue(value);