mapnik/src/load_map.cpp

/*****************************************************************************
 *
 * This file is part of Mapnik (c++ mapping toolkit)
 *
 * Copyright (C) 2006 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
 *
 *****************************************************************************/
// mapnik
#include <mapnik/load_map.hpp>

#include <mapnik/version.hpp>
#include <mapnik/image_reader.hpp>
#include <mapnik/color.hpp>
#include <mapnik/color_factory.hpp>

#include <mapnik/layer.hpp>
#include <mapnik/datasource_cache.hpp>
#include <mapnik/font_engine_freetype.hpp>
#include <mapnik/font_set.hpp>

#include <mapnik/ptree_helpers.hpp>
#include <mapnik/libxml2_loader.hpp>

#include <mapnik/filter_factory.hpp>
#include <mapnik/path_expression_grammar.hpp>
#include <mapnik/raster_colorizer.hpp>

// boost
#include <boost/optional.hpp>
#include <boost/algorithm/string.hpp>
#include <boost/lexical_cast.hpp>
#include <boost/tokenizer.hpp>
#include <boost/property_tree/ptree.hpp>
#include <boost/property_tree/xml_parser.hpp>
#include <boost/static_assert.hpp>
#include <boost/filesystem/operations.hpp>

// stl
#include <iostream>

using boost::lexical_cast;
using boost::bad_lexical_cast;
using boost::tokenizer;
using boost::property_tree::ptree;

using std::cerr;
using std::endl;

namespace mapnik
{
   using boost::optional;

   class map_parser : boost::noncopyable {
      public:
         map_parser( bool strict, std::string const& filename = "" ) :
            strict_( strict ),
            filename_( filename ),
            relative_to_xml_(true),
            font_manager_(font_engine_) {}

         void parse_map( Map & map, ptree const & sty);
      private:
         void parse_style( Map & map, ptree const & sty);
         void parse_layer( Map & map, ptree const & lay);

         void parse_fontset(Map & map, ptree const & fset);
         void parse_font(font_set & fset, ptree const & f);

         void parse_rule( feature_type_style & style, ptree const & r);

         void parse_point_symbolizer( rule_type & rule, ptree const & sym);
         void parse_line_pattern_symbolizer( rule_type & rule, ptree const & sym);
         void parse_polygon_pattern_symbolizer( rule_type & rule, ptree const & sym);
         void parse_text_symbolizer( rule_type & rule, ptree const & sym);
         void parse_shield_symbolizer( rule_type & rule, ptree const & sym);
         void parse_line_symbolizer( rule_type & rule, ptree const & sym);
         void parse_polygon_symbolizer( rule_type & rule, ptree const & sym);
         void parse_building_symbolizer( rule_type & rule, ptree const & sym );
         void parse_raster_symbolizer( rule_type & rule, ptree const & sym );
         void parse_markers_symbolizer( rule_type & rule, ptree const & sym );
         void parse_glyph_symbolizer( rule_type & rule, ptree const & sym );

         void parse_raster_colorizer(raster_colorizer_ptr const& rc, ptree const& node );

         void ensure_font_face( const std::string & face_name );

         std::string ensure_relative_to_xml( boost::optional<std::string> opt_path );

         bool strict_;
         std::string filename_;
         bool relative_to_xml_;
         std::map<std::string,parameters> datasource_templates_;
         freetype_engine font_engine_;
         face_manager<freetype_engine> font_manager_;
         std::map<std::string,std::string> file_sources_;
         std::map<std::string,font_set> fontsets_;
    };

    void load_map(Map & map, std::string const& filename, bool strict)
    {
        ptree pt;
#ifdef HAVE_LIBXML2
        read_xml2(filename, pt);
#else
        try
        {
            read_xml(filename, pt);
        }
        catch (const boost::property_tree::xml_parser_error & ex)
        {
            throw config_error( ex.what() );
        }
#endif
        map_parser parser( strict, filename);
        parser.parse_map(map, pt);
    }

    void load_map_string(Map & map, std::string const& str, bool strict, std::string const& base_url)
    {
        ptree pt;
#ifdef HAVE_LIBXML2
        read_xml2_string(str, pt, base_url);
#else
        try
        {
           std::istringstream s(str);
           read_xml(s,pt);
        }
        catch (const boost::property_tree::xml_parser_error & ex)
        {
           throw config_error( ex.what() ) ;
        }
#endif

        map_parser parser( strict, base_url);
        parser.parse_map(map, pt);
    }

    void map_parser::parse_map( Map & map, ptree const & pt )
    {
        try
        {
            ptree const & map_node = pt.get_child("Map");

            try
            {
                optional<color> bgcolor = get_opt_attr<color>(map_node, "bgcolor");
                if (bgcolor) {
                    map.set_background( * bgcolor );
                }

                map.set_srs( get_attr(map_node, "srs", map.srs() ));

                optional<unsigned> buffer_size = get_opt_attr<unsigned>(map_node,"buffer_size");
                if (buffer_size)
                {
                   map.set_buffer_size(*buffer_size);
                }

                // Check if relative paths should be interpreted as relative to/from XML location
                // Default is true, and map_parser::ensure_relative_to_xml will be called to modify path
                optional<boolean> paths_from_xml = get_opt_attr<boolean>(map_node, "paths_from_xml");
                if (paths_from_xml)
                {
                    relative_to_xml_ = *paths_from_xml;
                }

                optional<std::string> min_version_string = get_opt_attr<std::string>(map_node, "minimum_version");
                
                if (min_version_string)
                {
                    boost::char_separator<char> sep(".");
                    boost::tokenizer<boost::char_separator<char> > tokens(*min_version_string,sep);
                    unsigned i = 0;
                    bool success = false;
                    int n[3];
                    for (boost::tokenizer<boost::char_separator<char> >::iterator beg=tokens.begin(); 
                         beg!=tokens.end();++beg)
                    {
                       try 
                       {
                          n[i] = boost::lexical_cast<int>(boost::trim_copy(*beg));
                       }
                       catch (boost::bad_lexical_cast & ex)
                       {
                          std::clog << *beg << " : " << ex.what() << "\n";
                          break;
                       }
                       if (i==2) 
                       {
                          success = true;
                          break;
                       }
                       ++i;
                    }
                    if (success)
                    {
                       int min_version = (n[0] * 100000) + (n[1] * 100) + (n[2]);
                       if (min_version > MAPNIK_VERSION)
                       {
                          throw config_error(std::string("This map uses features only present in Mapnik version ") + *min_version_string + " and newer");
                       }
                       
                    }
                
                }
            }
            catch (const config_error & ex)
            {
                ex.append_context("(in node Map)");
                throw;
            }

            ptree::const_iterator itr = map_node.begin();
            ptree::const_iterator end = map_node.end();

            for (; itr != end; ++itr)
            {
                ptree::value_type const& v = *itr;

                if (v.first == "Style")
                {
                    parse_style( map, v.second );
                }
                else if (v.first == "Layer")
                {
                    parse_layer(map, v.second );
                }
                else if (v.first == "FontSet")
                {
                    parse_fontset(map, v.second);
                }
                else if (v.first == "FileSource")
                {
                  std::string name = get_attr<string>( v.second, "name");
                  std::string value = get_value<string>( v.second, "");
                  file_sources_[name] = value;
                }
                else if (v.first == "Datasource")
                {
                    std::string name = get_attr(v.second, "name", string("Unnamed"));
                    parameters params;
                    ptree::const_iterator paramIter = v.second.begin();
                    ptree::const_iterator endParam = v.second.end();
                    for (; paramIter != endParam; ++paramIter)
                    {
                        ptree const& param = paramIter->second;

                        if (paramIter->first == "Parameter")
                        {
                            std::string name = get_attr<string>(param, "name");
                            std::string value = get_value<string>( param,
                                    "datasource parameter");
                            params[name] = value;
                        }
                        else if( paramIter->first != "<xmlattr>" &&
                            paramIter->first != "<xmlcomment>" )
                        {
                            throw config_error(std::string("Unknown child node in ") +
                                    "'Datasource'. Expected 'Parameter' but got '" +
                                    paramIter->first + "'");
                        }
                    }
                    datasource_templates_[name] = params;
                }
                else if (v.first != "<xmlcomment>" &&
                        v.first != "<xmlattr>")
                {
                    throw config_error(std::string("Unknown child node in 'Map'. ") +
                            "Expected 'Style' or 'Layer' but got '" + v.first + "'");
                }
            }
        }
        catch (const boost::property_tree::ptree_bad_path &)
        {
            throw config_error("Not a map file. Node 'Map' not found.");
        }
    }

    void map_parser::parse_style( Map & map, ptree const & sty )
    {
        string name("<missing name>");
        try
        {
            name = get_attr<string>(sty, "name");
            feature_type_style style;

            ptree::const_iterator ruleIter = sty.begin();
            ptree::const_iterator endRule = sty.end();

            for (; ruleIter!=endRule; ++ruleIter)
            {
                ptree::value_type const& rule_tag = *ruleIter;
                if (rule_tag.first == "Rule")
                {
                    parse_rule( style, rule_tag.second );
                }
                else if (rule_tag.first != "<xmlcomment>" &&
                        rule_tag.first != "<xmlattr>" )
                {
                    throw config_error(std::string("Unknown child node in 'Style'. ") +
                            "Expected 'Rule' but got '" + rule_tag.first + "'");
                }
            }

            map.insert_style(name, style);

        } catch (const config_error & ex) {
            if ( ! name.empty() ) {
                ex.append_context(string("in style '") + name + "' in map '" + filename_ + "')");
            }
            throw;
        }
    }

    void map_parser::parse_fontset( Map & map, ptree const & fset )
    {
        string name("<missing name>");
        try
        {
            name = get_attr<string>(fset, "name");
            font_set fontset(name);

            ptree::const_iterator itr = fset.begin();
            ptree::const_iterator end = fset.end();

            for (; itr != end; ++itr)
            {
                ptree::value_type const& font_tag = *itr;

                if (font_tag.first == "Font")
                {
                    parse_font(fontset, font_tag.second);
                }
                else if (font_tag.first != "<xmlcomment>" &&
                    font_tag.first != "<xmlattr>" )
                {
                    throw config_error(std::string("Unknown child node in 'FontSet'. ") +
                        "Expected 'Font' but got '" + font_tag.first + "'");
                }
            }

            map.insert_fontset(name, fontset);

            // XXX Hack because map object isn't accessible by text_symbolizer
            // when it's parsed
            fontsets_.insert(pair<std::string, font_set>(name, fontset));
        } catch (const config_error & ex) {
            if ( ! name.empty() ) {
                ex.append_context(string("in FontSet '") + name + "' in map '" + filename_ + "')");
            }
            throw;
        }
    }

    void map_parser::parse_font(font_set & fset, ptree const & f)
	{
        std::string face_name = get_attr(f, "face_name", string());

        if ( strict_ )
        {
            ensure_font_face( face_name );
        }

        fset.add_face_name(face_name);
	 }

    void map_parser::parse_layer( Map & map, ptree const & lay )
    {
        std::string name;
        try
        {
            name = get_attr(lay, "name", string("Unnamed"));

            // XXX if no projection is given inherit from map? [DS]
            std::string srs = get_attr(lay, "srs", map.srs());

            layer lyr(name, srs);

            optional<boolean> status = get_opt_attr<boolean>(lay, "status");
            if (status)
            {
                lyr.setActive( * status );
            }

            optional<std::string> title =  get_opt_attr<string>(lay, "title");
            if (title)
            {
                lyr.set_title( * title );
            }

            optional<std::string> abstract =  get_opt_attr<string>(lay, "abstract");
            if (abstract)
            {
                lyr.set_abstract( * abstract );
            }

            optional<double> minZoom = get_opt_attr<double>(lay, "minzoom");
            if (minZoom)
            {
                lyr.setMinZoom( * minZoom );
            }

            optional<double> maxZoom = get_opt_attr<double>(lay, "maxzoom");
            if (maxZoom)
            {
                lyr.setMaxZoom( * maxZoom );
            }

            optional<boolean> queryable = get_opt_attr<boolean>(lay, "queryable");
            if (queryable)
            {
                lyr.setQueryable( * queryable );
            }

            optional<boolean> clear_cache =
                get_opt_attr<boolean>(lay, "clear_label_cache");
            if (clear_cache)
            {
                lyr.set_clear_label_cache( * clear_cache );
            }


            ptree::const_iterator itr2 = lay.begin();
            ptree::const_iterator end2 = lay.end();

            for(; itr2 != end2; ++itr2)
            {
                ptree::value_type const& child = *itr2;

                if (child.first == "StyleName")
                {
                    // TODO check references [DS]
                    lyr.add_style(child.second.data());
                }
                else if (child.first == "Datasource")
                {
                    parameters params;
                    optional<std::string> base = get_opt_attr<std::string>( child.second, "base" );
                    if( base )
                    {
                       std::map<std::string,parameters>::const_iterator base_itr = datasource_templates_.find(*base);
                       if (base_itr!=datasource_templates_.end())
                          params = base_itr->second;
                    }

                    ptree::const_iterator paramIter = child.second.begin();
                    ptree::const_iterator endParam = child.second.end();
                    for (; paramIter != endParam; ++paramIter)
                    {
                        ptree const& param = paramIter->second;

                        if (paramIter->first == "Parameter")
                        {
                            std::string name = get_attr<string>(param, "name");
                            std::string value = get_value<string>( param,
                                    "datasource parameter");
                            params[name] = value;
                        }
                        else if( paramIter->first != "<xmlattr>"  &&
                            paramIter->first != "<xmlcomment>" )
                        {
                            throw config_error(std::string("Unknown child node in ") +
                                    "'Datasource'. Expected 'Parameter' but got '" +
                                    paramIter->first + "'");
                        }
                    }

                    if ( relative_to_xml_ ) {
                        boost::optional<std::string> base_param = params.get<std::string>("base");
                        boost::optional<std::string> file_param = params.get<std::string>("file");

                        if (base_param){
                            params["base"] = ensure_relative_to_xml(base_param);
                        }

                        else if (file_param){
                            params["file"] = ensure_relative_to_xml(file_param);
                        }
                    }
                    #ifdef MAPNIK_DEBUG
                    else {
                      std::clog << "\nFound relative paths in xml, leaving unchanged...\n";
                    }
                    #endif

                    //now we are ready to create datasource
                    try
                    {
                        boost::shared_ptr<datasource> ds =
                            datasource_cache::instance()->create(params);
                        lyr.set_datasource(ds);
                    }

                    // catch problem at datasource registration
                    catch (const mapnik::config_error & ex )
                    {
                        throw config_error( ex.what() );
                    }

                    // catch problem at the datasource creation
                    catch (const mapnik::datasource_exception & ex )
                    {
                        throw config_error( ex.what() );
                    }

                    catch (...)
                    {
                       //throw config_error("exception...");
                    }
                }
                else if (child.first != "<xmlattr>" &&
                        child.first != "<xmlcomment>")
                {
                    throw config_error(std::string("Unknown child node in 'Layer'. ") +
                            "Expected 'StyleName' or 'Datasource' but got '" +
                            child.first + "'");
                }
            }

            map.addLayer(lyr);

        } catch (const config_error & ex) {
            if ( ! name.empty() ) {
                ex.append_context(std::string("(encountered during parsing of layer '") + name + "' in map '" + filename_ + "')");
            }
            throw;
        }
    }

    void map_parser::parse_rule( feature_type_style & style, ptree const & r )
    {
        std::string name;
        try
        {
            name = get_attr( r, "name", string());
            std::string title = get_attr( r, "title", string());

            rule_type rule(name,title);

            optional<std::string> filter_expr =
                get_opt_child<string>( r, "Filter");
            if (filter_expr)
            {
               // TODO - can we use encoding defined for XML document for filter expressions?
               rule.set_filter(parse_expression(*filter_expr,"utf8"));
            }

            optional<std::string> else_filter =
                get_opt_child<string>(r, "ElseFilter");
            if (else_filter)
            {
                rule.set_else(true);
            }

            optional<double> min_scale =
                get_opt_child<double>(r, "MinScaleDenominator");
            if (min_scale)
            {
                rule.set_min_scale(*min_scale);
            }

            optional<double> max_scale =
                get_opt_child<double>(r, "MaxScaleDenominator");
            if (max_scale)
            {
                rule.set_max_scale(*max_scale);
            }

            ptree::const_iterator symIter = r.begin();
            ptree::const_iterator endSym = r.end();

            for( ;symIter != endSym; ++symIter)
            {
                ptree::value_type const& sym = *symIter;

                if ( sym.first == "PointSymbolizer")
                {
                    parse_point_symbolizer( rule, sym.second );
                }
                else if ( sym.first == "LinePatternSymbolizer")
                {
                    parse_line_pattern_symbolizer( rule, sym.second );
                }
                else if ( sym.first == "PolygonPatternSymbolizer")
                {
                    parse_polygon_pattern_symbolizer( rule, sym.second );
                }
                else if ( sym.first == "TextSymbolizer")
                {
                    parse_text_symbolizer( rule, sym.second );
                }
                else if ( sym.first == "ShieldSymbolizer")
                {
                    parse_shield_symbolizer( rule, sym.second );
                }
                else if ( sym.first == "LineSymbolizer")
                {
                    parse_line_symbolizer( rule, sym.second );
                }
                else if ( sym.first == "PolygonSymbolizer")
                {
                    parse_polygon_symbolizer( rule, sym.second );
                }
                else if ( sym.first == "BuildingSymbolizer")
                {
                    parse_building_symbolizer( rule, sym.second );
                }
                else if ( sym.first == "RasterSymbolizer")
                {
                    parse_raster_symbolizer( rule, sym.second );
                }
                else if ( sym.first == "MarkersSymbolizer")
                {
                    rule.append(markers_symbolizer());
                }
                else if ( sym.first == "GlyphSymbolizer")
                {
                    parse_glyph_symbolizer( rule, sym.second );
                }

                else if ( sym.first != "MinScaleDenominator" &&
                        sym.first != "MaxScaleDenominator" &&
                        sym.first != "Filter" &&
                        sym.first != "ElseFilter" &&
                        sym.first != "<xmlcomment>" &&
                        sym.first != "<xmlattr>" )
                {
                    throw config_error(std::string("Unknown symbolizer '") +
                            sym.first + "'");
                }
            }

            style.add_rule(rule);

        }
        catch (const config_error & ex)
        {
            if ( ! name.empty() )
            {
                ex.append_context(string("in rule '") + name + "' in map '" + filename_ + "')");
            }
            throw;
        }
    }

    void map_parser::parse_point_symbolizer( rule_type & rule, ptree const & sym )
    {
        try
        {
            optional<std::string> file =  get_opt_attr<string>(sym, "file");
            optional<std::string> base =  get_opt_attr<string>(sym, "base");
            optional<boolean> allow_overlap =
                get_opt_attr<boolean>(sym, "allow_overlap");
            optional<float> opacity =
                get_opt_attr<float>(sym, "opacity");
	    
            if (file)
            {
                try
                {
                   if( base )
                   {
                      std::map<std::string,std::string>::const_iterator itr = file_sources_.find(*base);
                      if (itr!=file_sources_.end())
                      {
                         *file = itr->second + "/" + *file;
                      }
                   }

                   if ( relative_to_xml_ )
                   {
                      *file = ensure_relative_to_xml(file);
                   }
                   #ifdef MAPNIK_DEBUG
                   else {
                     std::clog << "\nFound relative paths in xml, leaving unchanged...\n";
                   }
                   #endif
		   
                   point_symbolizer symbol(parse_path(*file));
		   
                   if (allow_overlap)
                   {
                      symbol.set_allow_overlap( * allow_overlap );
                   }
                   if (opacity)
                   {
                      symbol.set_opacity( * opacity );
                   }
                   rule.append(symbol);
                }
                catch (image_reader_exception const & ex )
                {
                    string msg("Failed to load image file '" + * file +
                            "': " + ex.what());
                    if (strict_)
                    {
                        throw config_error(msg);
                    }
                    else
                    {
                        clog << "### WARNING: " << msg << endl;
                    }
                }

            }
            else
            {
                rule.append(point_symbolizer());
            }
        }
        catch (const config_error & ex)
        {
            ex.append_context("in PointSymbolizer");
            throw;
        }
    }

    void map_parser::parse_line_pattern_symbolizer( rule_type & rule, ptree const & sym )
    {
        try
        {
            std::string file = get_attr<string>(sym, "file");
            optional<std::string> base = get_opt_attr<string>(sym, "base");
            
	    try
            {
               if( base )
               {
                   std::map<std::string,std::string>::const_iterator itr = file_sources_.find(*base);
                   if (itr!=file_sources_.end())
                   {
                      file = itr->second + "/" + file;
                   }
               }
               if ( relative_to_xml_ )
               {
                  file = ensure_relative_to_xml(file);
               }
               #ifdef MAPNIK_DEBUG
               else {
                 std::clog << "\nFound relative paths in xml, leaving unchanged...\n";
               }
               #endif


               line_pattern_symbolizer symbol(parse_path(file));
               rule.append(symbol);
            }
            catch (image_reader_exception const & ex )
            {
                string msg("Failed to load image file '" + file +
                        "': " + ex.what());
                if (strict_)
                {
                    throw config_error(msg);
                }
                else
                {
                    clog << "### WARNING: " << msg << endl;
                }
            }
        }
        catch (const config_error & ex)
        {
            ex.append_context("in LinePatternSymbolizer");
            throw;
        }
    }

    void map_parser::parse_polygon_pattern_symbolizer( rule_type & rule,
                ptree const & sym )
    {
        try
        {
            std::string file = get_attr<string>(sym, "file");
            optional<std::string> base = get_opt_attr<string>(sym, "base");
	    
            try
            {
                if( base )
                {
                   std::map<std::string,std::string>::iterator itr = file_sources_.find(*base);
                   if (itr!=file_sources_.end())
                   {
                      file = itr->second + "/" + file;
                   }
                }
                if ( relative_to_xml_ )
                {
                   file = ensure_relative_to_xml(file);
                }
                #ifdef MAPNIK_DEBUG
                else {
                  std::clog << "\nFound relative paths in xml, leaving unchanged...\n";
                }
                #endif
		
                polygon_pattern_symbolizer symbol(parse_path(file));
                rule.append(symbol);
            }
            catch (image_reader_exception const & ex )
            {
                string msg("Failed to load image file '" + file +
                        "': " + ex.what());
                if (strict_)
                {
                    throw config_error(msg);
                }
                else
                {
                    clog << "### WARNING: " << msg << endl;
                }
            }
        }
        catch (const config_error & ex)
        {
            ex.append_context("in PolygonPatternSymbolizer");
            throw;
        }
    }

    void map_parser::parse_text_symbolizer( rule_type & rule, ptree const & sym )
    {
        try
        {
            std::string name = get_attr<string>(sym, "name");
	    
            optional<std::string> face_name =
                 get_opt_attr<std::string>(sym, "face_name");

            optional<std::string> fontset_name =
                 get_opt_attr<std::string>(sym, "fontset_name");

            unsigned size = get_attr(sym, "size", 10U);

            color c = get_attr(sym, "fill", color(0,0,0));

            text_symbolizer text_symbol = text_symbolizer(parse_expression(name, "utf8"), size, c);
	    	    
            if (fontset_name && face_name)
            {
                throw config_error(std::string("Can't have both face_name and fontset_name"));
            }
            else if (fontset_name)
            {
                std::map<std::string,font_set>::const_iterator itr = fontsets_.find(*fontset_name);
                if (itr != fontsets_.end())
                {
                    text_symbol.set_fontset(itr->second);
                }
                else
                {
                    throw config_error("Unable to find any fontset named '" + *fontset_name + "'");
                }
            }
            else if (face_name)
            {
                if ( strict_ )
                {
                    ensure_font_face(*face_name);
                }
                text_symbol.set_face_name(*face_name);
            }
            else
            {
                throw config_error(std::string("Must have face_name or fontset_name"));
            }

            double dx = get_attr(sym, "dx", 0.0);
            double dy = get_attr(sym, "dy", 0.0);
            text_symbol.set_displacement(dx,dy);

            label_placement_e placement =
                    get_attr<label_placement_e>(sym, "placement", POINT_PLACEMENT);
            text_symbol.set_label_placement( placement );
            // vertical alignment
            
            vertical_alignment_e default_vertical_alignment = MIDDLE;
            if (dy > 0.0 )
            {
                default_vertical_alignment = BOTTOM;
            }
            else if( dy < 0.0 )
            {
                default_vertical_alignment = TOP;
            }
            
            vertical_alignment_e valign = get_attr<vertical_alignment_e>(sym, "vertical_alignment", default_vertical_alignment);
            text_symbol.set_vertical_alignment(valign);

            // halo fill and radius
            optional<color> halo_fill = get_opt_attr<color>(sym, "halo_fill");
            if (halo_fill)
            {
                text_symbol.set_halo_fill( * halo_fill );
            }
            optional<unsigned> halo_radius =
                get_opt_attr<unsigned>(sym, "halo_radius");
            if (halo_radius)
            {
                text_symbol.set_halo_radius(*halo_radius);
            }

            // text ratio and wrap width
            optional<unsigned> text_ratio =
                get_opt_attr<unsigned>(sym, "text_ratio");
            if (text_ratio)
            {
                text_symbol.set_text_ratio(*text_ratio);
            }

            optional<unsigned> wrap_width =
                get_opt_attr<unsigned>(sym, "wrap_width");
            if (wrap_width)
            {
                text_symbol.set_wrap_width(*wrap_width);
            }

            optional<boolean> wrap_before =
                get_opt_attr<boolean>(sym, "wrap_before");
            if (wrap_before)
            {
                text_symbol.set_wrap_before(*wrap_before);
            }

            // character used to break long strings
            optional<std::string> wrap_char =
                get_opt_attr<std::string>(sym, "wrap_character");
            if (wrap_char && (*wrap_char).size() > 0)
            {
                text_symbol.set_wrap_char((*wrap_char)[0]);
            }

            // text conversion before rendering
            text_convert_e tconvert =
                get_attr<text_convert_e>(sym, "text_convert", NONE);
            text_symbol.set_text_convert(tconvert);

            // spacing between text lines
            optional<unsigned> line_spacing = get_opt_attr<unsigned>(sym, "line_spacing");
            if (line_spacing)
            {
                text_symbol.set_line_spacing(*line_spacing);
            }

            // spacing between characters in text
            optional<unsigned> character_spacing = get_opt_attr<unsigned>(sym, "character_spacing");
            if (character_spacing)
            {
                text_symbol.set_character_spacing(*character_spacing);
            }

            // spacing between repeated labels on lines
            optional<unsigned> spacing = get_opt_attr<unsigned>(sym, "spacing");
            if (spacing)
            {
                text_symbol.set_label_spacing(*spacing);
            }

            // minimum distance between labels
            optional<unsigned> min_distance =
                get_opt_attr<unsigned>(sym, "min_distance");
            if (min_distance)
            {
                text_symbol.set_minimum_distance(*min_distance);
            }

            // do not render labels around edges
            optional<boolean> avoid_edges =
                get_opt_attr<boolean>(sym, "avoid_edges");
            if (avoid_edges)
            {
                text_symbol.set_avoid_edges( * avoid_edges);
            }

            // allow_overlap
            optional<boolean> allow_overlap =
                get_opt_attr<boolean>(sym, "allow_overlap");
            if (allow_overlap)
            {
                text_symbol.set_allow_overlap( * allow_overlap );
            }

            // opacity
            optional<double> opacity =
                get_opt_attr<double>(sym, "opacity");
            if (opacity)
            {
                text_symbol.set_opacity( * opacity );
            }

            // max_char_angle_delta
            optional<double> max_char_angle_delta =
		get_opt_attr<double>(sym, "max_char_angle_delta");
            if (max_char_angle_delta)
            {
               text_symbol.set_max_char_angle_delta( * max_char_angle_delta);
            }
	    
            // horizontal alignment
            horizontal_alignment_e halign = get_attr<horizontal_alignment_e>(sym, "horizontal_alignment", H_MIDDLE);
            text_symbol.set_horizontal_alignment(halign);

            // justify alignment
            justify_alignment_e jalign = get_attr<justify_alignment_e>(sym, "justify_alignment", J_MIDDLE);
            text_symbol.set_justify_alignment(jalign);

            rule.append(text_symbol);
        }
        catch (const config_error & ex)
        {
            ex.append_context("in TextSymbolizer");
            throw;
        }
    }

    void map_parser::parse_shield_symbolizer( rule_type & rule, ptree const & sym )
    {
        try
        {
            std::string name =  get_attr<string>(sym, "name");

            optional<std::string> face_name =
                 get_opt_attr<std::string>(sym, "face_name");

            optional<std::string> fontset_name =
                 get_opt_attr<std::string>(sym, "fontset_name");

            unsigned size = get_attr(sym, "size", 10U);
            color fill = get_attr(sym, "fill", color(0,0,0));

            std::string image_file = get_attr<string>(sym, "file");
            optional<std::string> base = get_opt_attr<string>(sym, "base");
	    
            try
            {
                if( base )
                {
                    std::map<std::string,std::string>::const_iterator itr = file_sources_.find(*base);
                    if (itr!=file_sources_.end())
                    {
                       image_file = itr->second + "/" + image_file;
                    }
                }

                if ( relative_to_xml_ )
                {
                   image_file = ensure_relative_to_xml(image_file);
                }
                #ifdef MAPNIK_DEBUG
                else {
                  std::clog << "\nFound relative paths in xml, leaving unchanged...\n";
                }
                #endif

                shield_symbolizer shield_symbol(parse_expression(name, "utf8"),size,fill,parse_path(image_file));
                
		if (fontset_name && face_name)
                {
                    throw config_error(std::string("Can't have both face_name and fontset_name"));
                }
                else if (fontset_name)
                {
                    std::map<std::string,font_set>::const_iterator itr = fontsets_.find(*fontset_name);
                    if (itr != fontsets_.end())
                    {
                        shield_symbol.set_fontset(itr->second);
                    }
                    else
                    {
                        throw config_error("Unable to find any fontset named '" + *fontset_name + "'");
                    }
                }
                else if (face_name)
                {
                    if ( strict_ )
                    {
                        ensure_font_face(*face_name);
                    }
                    shield_symbol.set_face_name(*face_name);
                }
                else
                {
                    throw config_error(std::string("Must have face_name or fontset_name"));
                }
                // text displacement
                double dx = get_attr(sym, "dx", 0.0);
                double dy = get_attr(sym, "dy", 0.0);
                shield_symbol.set_displacement(dx,dy);

                label_placement_e placement =
                   get_attr<label_placement_e>(sym, "placement", POINT_PLACEMENT);
                shield_symbol.set_label_placement( placement );

               // don't render shields around edges
                optional<boolean> avoid_edges =
                   get_opt_attr<boolean>(sym, "avoid_edges");
                if (avoid_edges)
                {
                   shield_symbol.set_avoid_edges( *avoid_edges);
                }

                // halo fill and radius
                optional<color> halo_fill = get_opt_attr<color>(sym, "halo_fill");
                if (halo_fill)
                {
                   shield_symbol.set_halo_fill( * halo_fill );
                }
                optional<unsigned> halo_radius =
                   get_opt_attr<unsigned>(sym, "halo_radius");
                if (halo_radius)
                {
                   shield_symbol.set_halo_radius(*halo_radius);
                }

                // minimum distance between labels
                optional<unsigned> min_distance =
                    get_opt_attr<unsigned>(sym, "min_distance");
                if (min_distance)
                {
                    shield_symbol.set_minimum_distance(*min_distance);
                }

                // spacing between repeated labels on lines
                optional<unsigned> spacing = get_opt_attr<unsigned>(sym, "spacing");
                if (spacing)
                {
                    shield_symbol.set_label_spacing(*spacing);
                }

                // allow_overlap
                optional<boolean> allow_overlap =
                    get_opt_attr<boolean>(sym, "allow_overlap");
                if (allow_overlap)
                {
                    shield_symbol.set_allow_overlap( * allow_overlap );
                }

                // vertical alignment
                vertical_alignment_e valign = get_attr<vertical_alignment_e>(sym, "vertical_alignment", MIDDLE);
                shield_symbol.set_vertical_alignment(valign);

                // horizontal alignment
                horizontal_alignment_e halign = get_attr<horizontal_alignment_e>(sym, "horizontal_alignment", H_MIDDLE);
                shield_symbol.set_horizontal_alignment(halign);

                // justify alignment
                justify_alignment_e jalign = get_attr<justify_alignment_e>(sym, "justify_alignment", J_MIDDLE);
                shield_symbol.set_justify_alignment(jalign);

                optional<unsigned> wrap_width =
                    get_opt_attr<unsigned>(sym, "wrap_width");
                if (wrap_width)
                {
                    shield_symbol.set_wrap_width(*wrap_width);
                }

                optional<boolean> wrap_before =
                    get_opt_attr<boolean>(sym, "wrap_before");
                if (wrap_before)
                {
                    shield_symbol.set_wrap_before(*wrap_before);
                }

                // character used to break long strings
                optional<std::string> wrap_char =
                    get_opt_attr<std::string>(sym, "wrap_character");
                if (wrap_char && (*wrap_char).size() > 0)
                {
                    shield_symbol.set_wrap_char((*wrap_char)[0]);
                }

                // text conversion before rendering
                text_convert_e tconvert =
                    get_attr<text_convert_e>(sym, "text_convert", NONE);
                shield_symbol.set_text_convert(tconvert);

                // spacing between text lines
                optional<unsigned> line_spacing = get_opt_attr<unsigned>(sym, "line_spacing");
                if (line_spacing)
                {
                    shield_symbol.set_line_spacing(*line_spacing);
                }

                // spacing between characters in text
                optional<unsigned> character_spacing = get_opt_attr<unsigned>(sym, "character_spacing");
                if (character_spacing)
                {
                    shield_symbol.set_character_spacing(*character_spacing);
                }

                // opacity
                optional<double> opacity =
                    get_opt_attr<double>(sym, "opacity");
                if (opacity)
                {
                    shield_symbol.set_opacity( * opacity );
                }

                // unlock_image
                optional<boolean> unlock_image =
                    get_opt_attr<boolean>(sym, "unlock_image");
                if (unlock_image)
                {
                    shield_symbol.set_unlock_image( * unlock_image );
                }

                // no text
                optional<boolean> no_text =
                    get_opt_attr<boolean>(sym, "no_text");
                if (no_text)
                {
                    shield_symbol.set_no_text( * no_text );
                }

                rule.append(shield_symbol);
            }
            catch (image_reader_exception const & ex )
            {
               string msg("Failed to load image file '" + image_file +
                            "': " + ex.what());
               if (strict_)
               {
                  throw config_error(msg);
               }
               else
               {
                  clog << "### WARNING: " << msg << endl;
               }
            }

        }
        catch (const config_error & ex)
        {
            ex.append_context("in ShieldSymbolizer");
            throw;
        }
    }

    void map_parser::parse_line_symbolizer( rule_type & rule, ptree const & sym )
    {
        try
        {
            stroke strk;
	    // stroke color
	    optional<color> c=  get_opt_attr<color>(sym, "stroke");
	    if (c) strk.set_color(*c);
	    // stroke-width
	    optional<double> width =  get_opt_attr<double>(sym, "stroke-width");
	    if (width) strk.set_width(*width);
	    // stroke-opacity
	    optional<double> opacity = get_opt_attr<double>(sym, "stroke-opacity");
	    if (opacity) strk.set_opacity(*opacity);
	    // stroke-linejoin
	    optional<line_join_e> line_join = get_opt_attr<line_join_e>(sym, "stroke-linejoin");
	    if (line_join) strk.set_line_join(*line_join);
	    // stroke-linecap
	    optional<line_cap_e> line_cap = get_opt_attr<line_cap_e>(sym, "stroke-linecap");
	    if (line_cap) strk.set_line_cap(*line_cap);
	    // stroke-dashaffset
	    optional<double> offset = get_opt_attr<double>(sym, "stroke-dashoffet");
	    if (offset) strk.set_dash_offset(*offset);
	    // stroke-dasharray
	    optional<string> str = get_opt_attr<string>(sym,"stroke-dasharray");
	    if (str) 
	    {
		tokenizer<> tok (*str);
		std::vector<double> dash_array;
		tokenizer<>::iterator itr = tok.begin();
		for (; itr != tok.end(); ++itr)
		{
		    try
		    {
			double f = boost::lexical_cast<double>(*itr);
			dash_array.push_back(f);
		    }
		    catch ( boost::bad_lexical_cast &)
		    {
			throw config_error(std::string("Failed to parse dasharray ") +
					   "'. Expected a " +
					   "list of floats but got '" + (*str) + "'");
		    }
		}
		if (dash_array.size())
		{
		    size_t size = dash_array.size();
		    if ( size % 2)
		    {
			for (size_t i=0; i < size ;++i)
			{
			    dash_array.push_back(dash_array[i]);
			}
		    }
		    std::vector<double>::const_iterator pos = dash_array.begin();
		    while (pos != dash_array.end())
		    {
			strk.add_dash(*pos,*(pos + 1));
			pos +=2;
		    }
		}
	    }
            rule.append(line_symbolizer(strk));
        }
        catch (const config_error & ex)
        {
            ex.append_context("in LineSymbolizer");
            throw;
        }
    }

    
    void map_parser::parse_polygon_symbolizer( rule_type & rule, ptree const & sym )
    {
        try
        {
            polygon_symbolizer poly_sym;

            ptree::const_iterator cssIter = sym.begin();
            ptree::const_iterator endCss = sym.end();

            for(; cssIter != endCss; ++cssIter)
            {
                ptree::value_type const& css_tag = *cssIter;
                ptree const & css = cssIter->second;

                if (css_tag.first == "CssParameter")
                {
                    std::string css_name  = get_attr<string>(css, "name");
                    if (css_name == "fill")
                    {
                        color c = get_css<color>(css, css_name);
                        poly_sym.set_fill(c);
                    }
                    else if (css_name == "fill-opacity")
                    {
                        float opacity = get_css<float>(css, css_name);
                        poly_sym.set_opacity(opacity);
                    }
                    else if (css_name == "gamma")
                    {
                        float gamma = get_css<float>(css, css_name);
                        poly_sym.set_gamma(gamma);
                    }                    
                    else
                    {
                        throw config_error(std::string("Failed to parse unknown CSS ") +
                                "parameter '" + css_name + "'");
                    }
                }
                else if (css_tag.first != "<xmlcomment>" &&
                        css_tag.first != "<xmlattr>" )
                {
                    throw config_error(std::string("Unknown child node. ") +
                            "Expected 'CssParameter' but got '" + css_tag.first + "'");
                }
            }
            rule.append(poly_sym);

        }
        catch (const config_error & ex)
        {
            ex.append_context("in PolygonSymbolizer");
            throw;
        }
    }


    void map_parser::parse_building_symbolizer( rule_type & rule, ptree const & sym )
    {
        try {
            building_symbolizer building_sym;

            ptree::const_iterator cssIter = sym.begin();
            ptree::const_iterator endCss = sym.end();

            for(; cssIter != endCss; ++cssIter)
            {
                ptree::value_type const& css_tag = *cssIter;
                ptree const & css = cssIter->second;

                if (css_tag.first == "CssParameter")
                {
                    std::string css_name  = get_attr<string>(css, "name");
                    std::string data = css.data();
                    if (css_name == "fill")
                    {
                        color c = get_css<color>(css, css_name);
                        building_sym.set_fill(c);
                    }
                    else if (css_name == "fill-opacity")
                    {
                        float opacity = get_css<float>(css, css_name);
                        building_sym.set_opacity(opacity);
                    }
                    else if (css_name == "height")
                    {
                       float height = get_css<float>(css,css_name);
                       building_sym.set_height(height);
                    }
                    else
                    {
                        throw config_error(std::string("Failed to parse unknown CSS ") +
                                "parameter '" + css_name + "'");
                    }
                }
                else if (css_tag.first != "<xmlcomment>" &&
                        css_tag.first != "<xmlattr>" )
                {
                    throw config_error(std::string("Unknown child node. ") +
                            "Expected 'CssParameter' but got '" + css_tag.first + "'");
                }
            }
            rule.append(building_sym);
        }
        catch (const config_error & ex)
        {
            ex.append_context("in BuildingSymbolizer");
            throw;
        }
    }

    void map_parser::parse_raster_symbolizer( rule_type & rule, ptree const & sym )
    {
        try
        {
            raster_symbolizer raster_sym;

            ptree::const_iterator cssIter = sym.begin();
            ptree::const_iterator endCss = sym.end();

            for(; cssIter != endCss; ++cssIter)
            {
                ptree::value_type const& css_tag = *cssIter;
                ptree const & css = cssIter->second;

                if (css_tag.first == "CssParameter")
                {
                    std::string css_name  = get_attr<string>(css, "name");
                    if (css_name == "mode")
                    {
                        raster_sym.set_mode(get_css<string>(css, css_name));
                    }
                    else if (css_name == "scaling")
                    {
                        raster_sym.set_scaling(get_css<string>(css, css_name));
                    }
                    else if (css_name == "opacity")
                    {
                        float opacity = get_css<float>(css, css_name);
                        raster_sym.set_opacity(opacity);
                    }
                    else
                    {
                        throw config_error(std::string("Failed to parse unknown CSS ") +
                                "parameter '" + css_name + "'");
                    }
                }
                else if (css_tag.first == "RasterColorizer")
                {
                   raster_colorizer_ptr colorizer(new raster_colorizer());
                   raster_sym.set_colorizer(colorizer);
                   parse_raster_colorizer(colorizer, css_tag.second);
                }
                else if (css_tag.first != "<xmlcomment>" &&
                        css_tag.first != "<xmlattr>" )
                {
                    throw config_error(std::string("Unknown child node. ") +
                            "Expected 'CssParameter' but got '" + css_tag.first + "'");
                }
            }
            rule.append(raster_sym);
        }
        catch (const config_error & ex)
        {
            ex.append_context("in RasterSymbolizer");
            throw;
        }
    }

    void map_parser::parse_glyph_symbolizer(rule_type & rule, ptree const &sym)
    {
        try
        {
            // Parse required constructor args
            std::string face_name = get_attr<std::string>(sym, "face_name");
            std::string _char = get_attr<std::string>(sym, "char");

            glyph_symbolizer glyph_sym = glyph_symbolizer(
                face_name,
                parse_expression(_char, "utf8")
                );

            //
            // parse and set optional attrs.
            //

            // angle
            optional<std::string> angle =
                 get_opt_attr<std::string>(sym, "angle");
            if (angle)
                glyph_sym.set_angle(parse_expression(*angle, "utf8"));

            angle_mode_e angle_mode =
                    get_attr<angle_mode_e>(sym, "angle_mode", TRIGONOMETRIC);
            glyph_sym.set_angle_mode(angle_mode);
	    	    
            // value
            optional<std::string> value =
                 get_opt_attr<std::string>(sym, "value");
            if (value)
                glyph_sym.set_value(parse_expression(*value, "utf8"));

            // size
            optional<std::string> size =
                 get_opt_attr<std::string>(sym, "size");
            if (size)
                glyph_sym.set_size(parse_expression(*size, "utf8"));

            // color
            optional<std::string> _color =
                 get_opt_attr<std::string>(sym, "color");
            if (_color)
                glyph_sym.set_color(parse_expression(*_color, "utf8"));

            // halo_fill
            optional<color> halo_fill = get_opt_attr<color>(sym, "halo_fill");
            if (halo_fill)
                glyph_sym.set_halo_fill(*halo_fill);

            // halo_radius
            optional<unsigned> halo_radius = get_opt_attr<unsigned>(
                sym,
                "halo_radius");
            if (halo_radius)
                glyph_sym.set_halo_radius(*halo_radius);

            // allow_overlap
            optional<boolean> allow_overlap = get_opt_attr<boolean>(
                sym,
                "allow_overlap"
                );
            if (allow_overlap)
                glyph_sym.set_allow_overlap(*allow_overlap);

            // avoid_edges
            optional<boolean> avoid_edges = get_opt_attr<boolean>(
                sym,
                "avoid_edges"
                );
            if (avoid_edges)
                glyph_sym.set_avoid_edges(*avoid_edges);

            // displacement
            optional<double> dx = get_opt_attr<double>(sym, "dx");
            optional<double> dy = get_opt_attr<double>(sym, "dy");
            if (dx && dy)
                glyph_sym.set_displacement(*dx, *dy);

            // colorizer
            ptree::const_iterator childIter = sym.begin();
            ptree::const_iterator endChild = sym.end();

            for (; childIter != endChild; ++childIter)
            {
                ptree::value_type const& tag = *childIter;

                if (tag.first == "RasterColorizer")
                {
                   raster_colorizer_ptr colorizer(new raster_colorizer());
                   glyph_sym.set_colorizer(colorizer);
                   parse_raster_colorizer(colorizer, tag.second);
                }
                else if (tag.first!="<xmlcomment>" && tag.first!="<xmlattr>" )
                {
                    throw config_error(std::string("Unknown child node. ") +
                                       "Expected 'RasterColorizer' but got '" +
                                       tag.first + "'");
                }
            }


            rule.append(glyph_sym);
        }
        catch (const config_error & ex)
        {
            ex.append_context("in GlyphSymbolizer");
            throw;
        }
    }

    void map_parser::parse_raster_colorizer(raster_colorizer_ptr const& rc,
                                            ptree const& node )
    {
        try
        {
            ptree::const_iterator cbIter = node.begin();
            ptree::const_iterator endCb = node.end();

            for(; cbIter != endCb; ++cbIter)
            {
                ptree::value_type const& cb_tag = *cbIter;
                ptree const & cb = cbIter->second;

                if (cb_tag.first == "ColorBand")
                {
                    std::string value_s  = get_attr<string>(cb, "value");
                    float value;
                    std::stringstream(value_s) >> value;
                    optional<color> c = get_opt_attr<color>(cb, "color");
                    if (!c) {
                       throw config_error("missing color");
                    }
                    unsigned midpoints = get_attr(cb, "midpoints", 0);
                    rc->append_band(value, *c, midpoints);
                }
                else if (cb_tag.first != "<xmlcomment>" &&
                         cb_tag.first != "<xmlattr>" )
                {
                    throw config_error(std::string("Unknown child node. ") +
                            "Expected 'ColorBand' but got '" + cb_tag.first + "'");
                }
            }
        }
        catch (const config_error & ex)
        {
            ex.append_context("in RasterColorizer");
            throw;
        }
    }

    void map_parser::ensure_font_face( const std::string & face_name )
    {
        if ( ! font_manager_.get_face( face_name ) )
        {
            throw config_error("Failed to find font face '" +
                    face_name + "'");
        }
    }

    std::string map_parser::ensure_relative_to_xml( boost::optional<std::string> opt_path )
    {
        boost::filesystem::path xml_path = filename_;
        boost::filesystem::path rel_path = *opt_path;
        if ( !rel_path.has_root_path() ) {
            boost::filesystem::path full = boost::filesystem::complete(xml_path.branch_path()/rel_path).normalize();
            #ifdef MAPNIK_DEBUG
              std::clog << "\nModifying relative paths to be relative to xml...\n";
              std::clog << "original base path: " << *opt_path << "\n";
              std::clog << "relative base path: " << full.string() << "\n";
            #endif
            return full.string();
        }
        return *opt_path;
    }

} // end of namespace mapnik