optimized <object_ref> handling for the common case of simple reference with no overwrites

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@60494 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/xrc/xmlres.cpp

@@ -844,6 +844,22 @@ wxObject *wxXmlResource::CreateResFromNode(wxXmlNode *node, wxObject *parent,
             return NULL;
         }
 
+        if ( !node->GetChildren() )
+        {
+            // In the typical, simple case, <object_ref> is used to link
+            // to another node and doesn't have any content of its own that
+            // would overwrite linked object's properties. In this case,
+            // we can simply create the resource from linked node.
+
+            return CreateResFromNode(refNode, parent, instance);
+        }
+        else
+        {
+            // In the more complicated (but rare) case, <object_ref> has
+            // subnodes that partially overwrite content of the referenced
+            // object. In this case, we need to merge both XML trees and
+            // load the resource from result of the merge.
+
             wxXmlNode copy(*refNode);
             MergeNodesOver(copy, *node, GetFileNameFromNode(node, Data()));
 
@@ -853,6 +869,7 @@ wxObject *wxXmlResource::CreateResFromNode(wxXmlNode *node, wxObject *parent,
 
             return CreateResFromNode(&copy, parent, instance);
         }
+    }
 
     if (handlerToUse)
     {