Geometry/Feature parsers -truncate 'where' message in on_error handler (currently 16 chars max)

include/mapnik/json/feature_grammar.hpp

@@ -128,6 +128,7 @@ struct feature_grammar :
 
     phoenix::function<put_property> put_property_;
     phoenix::function<extract_geometry> extract_geometry_;
+    boost::phoenix::function<where_message> where_message_;
 
     geometry_grammar<Iterator> geometry_grammar_;
 };

include/mapnik/json/geometry_grammar.hpp

@@ -73,6 +73,21 @@ struct cleanup
     }
 };
 
+struct where_message
+{
+    typedef std::string result_type;
+
+    template <typename Iterator>
+    std::string operator() (Iterator first, Iterator last, std::size_t size) const
+    {
+        std::string str(first, last);
+        if (str.length() > size)
+            return str.substr(0, size) + "..." ;
+        return str;
+    }
+};
+
+
 template <typename Iterator>
 struct geometry_grammar :
         qi::grammar<Iterator,qi::locals<int>, void(boost::ptr_vector<mapnik::geometry_type>& )
@@ -107,6 +122,7 @@ struct geometry_grammar :
     boost::phoenix::function<push_vertex> push_vertex_;
     boost::phoenix::function<close_path> close_path_;
     boost::phoenix::function<cleanup> cleanup_;
+    boost::phoenix::function<where_message> where_message_;
 };
 
 }}

src/json/feature_grammar.cpp

@@ -135,15 +135,18 @@ feature_grammar<Iterator,FeatureType>::feature_grammar(mapnik::transcoder const&
 
     attribute_value %= number | string_  ;
 
+    feature.name("Feature");
+    properties.name("Properties");
+    attributes.name("Attributes");
 
     on_error<fail>
         (
             feature
             , std::clog
             << phoenix::val("Error! Expecting ")
-            << _4                               // what failed?
+            << _4 // what failed?
             << phoenix::val(" here: \"")
-            << construct<std::string>(_3, _2)   // iterators to error-pos, end
+            << where_message_(_3, _2, 16) // where? 16 is max chars to output
             << phoenix::val("\"")
             << std::endl
             );

src/json/geometry_grammar.cpp

@@ -146,15 +146,20 @@ geometry_grammar<Iterator>::geometry_grammar()
     // points
     points = lit('[')[_a = SEG_MOVETO] > -(point (_a,_r1) % lit(',')[_a = SEG_LINETO]) > lit(']');
 
+    // give some rules names
+    geometry.name("Geometry");
+    geometry_collection.name("GeometryCollection");
+    geometry_dispatch.name("Geometry dispatch");
+    coordinates.name("Coordinates");
     // error handler
     on_error<fail>
         (
             geometry
             , std::clog
             << boost::phoenix::val("Error! Expecting ")
-            << _4                               // what failed?
+            << _4  // what failed?
             << boost::phoenix::val(" here: \"")
-            << construct<std::string>(_3, _2)   // iterators to error-pos, end
+            << where_message_(_3, _2, 16) // max 16 chars
             << boost::phoenix::val("\"")
             << std::endl
             );