add poor man's deepcopy method :

'''
mapnik::util::deepcopy(map_in,map_out);
'''

include/mapnik/util/deepcopy.hpp

@@ -0,0 +1,37 @@
+/*****************************************************************************
+ * 
+ * This file is part of Mapnik (c++ mapping toolkit)
+ *
+ * Copyright (C) 2011 Artem Pavlenko
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ *
+ *****************************************************************************/
+
+//$Id$
+
+#ifndef MAPNIK_DEEPCOPY_HPP
+#define MAPNIK_DEEPCOPY_HPP
+
+#include <mapnik/map.hpp>
+
+namespace mapnik { namespace util {
+
+// poor man deepcopy implementation
+void deepcopy(Map const& map_in, Map & map_out);
+
+}} 
+
+#endif  // MAPNIK_DEEPSOPY_HPP

src/build.py

@@ -106,6 +106,7 @@ source = Split(
     color.cpp
     box2d.cpp
     datasource_cache.cpp
+    deepcopy.cpp
     expression_string.cpp
     filter_factory.cpp
     feature_type_style.cpp

src/deepcopy.cpp

@@ -0,0 +1,127 @@
+/*****************************************************************************
+ * 
+ * This file is part of Mapnik (c++ mapping toolkit)
+ *
+ * Copyright (C) 2011 Artem Pavlenko
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ *
+ *****************************************************************************/
+
+//$Id$
+
+#include <mapnik/map.hpp>
+#include <mapnik/feature.hpp>
+#include <mapnik/layer.hpp>
+#include <mapnik/rule.hpp>
+#include <mapnik/symbolizer.hpp>
+#include <mapnik/params.hpp>
+#include <mapnik/filter_factory.hpp>
+#include <mapnik/datasource_cache.hpp>
+#include <mapnik/util/deepcopy.hpp>
+
+// boost
+#include <boost/optional.hpp>
+#include <boost/foreach.hpp>
+
+
+namespace mapnik { namespace util {
+
+// poor man's deepcopy implementation
+
+void deepcopy(Map const& map_in, Map & map_out)
+{
+//  *   width_(rhs.width_),
+//  *   height_(rhs.height_),
+//  *   srs_(rhs.srs_),
+//  *   buffer_size_(rhs.buffer_size_),
+//  *   background_(rhs.background_),
+//  *   background_image_(rhs.background_image_),
+//  *   styles_(rhs.styles_),
+//      metawriters_(rhs.metawriters_),
+//      fontsets_(rhs.fontsets_),
+//  *   layers_(rhs.layers_),
+//      aspectFixMode_(rhs.aspectFixMode_),
+//      current_extent_(rhs.current_extent_),
+//  *   maximum_extent_(rhs.maximum_extent_),
+//  *   base_path_(rhs.base_path_),
+//      extra_attr_(rhs.extra_attr_),
+//      extra_params_(rhs.extra_params_)
+
+    // width, height
+    map_out.resize(map_in.width(), map_in.height());
+    // srs
+    map_out.set_srs(map_in.srs());
+    // buffer_size
+    map_out.set_buffer_size(map_in.buffer_size());
+    // background
+    boost::optional<color> background = map_in.background();
+    if  (background)
+    {
+        map_out.set_background(*background);
+    }
+    // background_image
+    boost::optional<std::string> background_image = map_in.background_image();
+    if (background_image)
+    {
+        map_out.set_background_image(*background_image);
+    }
+    // maximum extent
+    boost::optional<box2d<double> > max_extent = map_in.maximum_extent();
+    if (max_extent)
+    {
+        map_out.set_maximum_extent(*max_extent);   
+    }
+    // base_path
+    map_out.set_base_path(map_in.base_path());
+    
+    // fontsets     
+    typedef std::map<std::string,font_set> fontsets;
+    BOOST_FOREACH ( fontsets::value_type const& kv,map_in.fontsets())
+    {
+        map_out.insert_fontset(kv.first,kv.second);
+    }
+    
+    BOOST_FOREACH ( layer const& lyr_in, map_in.layers())
+    {
+        layer lyr_out(lyr_in);        
+        datasource_ptr ds_in = lyr_in.datasource();
+        if (ds_in)
+        {
+            parameters p(ds_in->params());
+            
+            // TODO : re-use datasource extent if already set.
+            datasource_ptr ds_out = datasource_cache::create(p);  
+            if (ds_out)
+            {
+                lyr_out.set_datasource(ds_out);
+            }
+        }        
+        map_out.addLayer(lyr_out);        
+    }
+    typedef std::map<std::string, feature_type_style> style_cont;
+    typedef style_cont::value_type value_type;
+    
+    style_cont const& styles = map_in.styles();
+    BOOST_FOREACH ( value_type const& kv, styles )
+    {       
+        feature_type_style const& style_in = kv.second;
+        feature_type_style style_out(style_in,true); // deep copy
+        map_out.insert_style(kv.first, style_out);
+    }
+    
+}
+
+}}