more generic expressions in enum

support expressions in halo-comp-op symbolizer property

include/mapnik/symbolizer.hpp

@@ -51,8 +51,6 @@
 // boost
 #include <boost/variant/variant_fwd.hpp>
 #include <boost/concept_check.hpp>
-// agg
-#include "agg_pixfmt_rgba.h"
 
 namespace agg { struct trans_affine; }
 
@@ -132,7 +130,8 @@ enum class property_types : std::uint8_t
     target_dash_array,
     target_colorizer,
     target_repeat_key,
-    target_group_symbolizer_properties
+    target_group_symbolizer_properties,
+    target_halo_comp_op
 };
 
 inline bool operator==(symbolizer_base const& lhs, symbolizer_base const& rhs)
@@ -174,7 +173,9 @@ struct expression_result
     typedef T result_type;
     static result_type convert(value_type const& val)
     {
-        return static_cast<T>(val.convert<value_integer>());
+        auto result = comp_op_from_string(val.to_string());
+        if (result) return static_cast<result_type>(*result);
+        return result_type(0);
     }
 };
 
@@ -188,18 +189,6 @@ struct expression_result<T,false>
     }
 };
 
-template <>
-struct expression_result<agg::comp_op_e,true>
-{
-    typedef agg::comp_op_e result_type;
-    static result_type convert(value_type const& val)
-    {
-        auto result = comp_op_from_string(val.to_string());
-        if (result) return static_cast<result_type>(*result);
-        return agg::comp_op_src_over;
-    }
-};
-
 
 // enum
 template <typename T, bool is_enum = true>

src/load_map.cpp

@@ -862,7 +862,7 @@ struct set_symbolizer_property_impl
         }
         catch (config_error const&)
         {
-            // try parser as an expression
+            // try parsing as an expression
             optional<expression_ptr> val = node.get_opt_attr<expression_ptr>(name);
             if (val) put(sym, key, *val);
         }
@@ -878,13 +878,14 @@ struct set_symbolizer_property_impl<Symbolizer, composite_mode_e>
         std::string const& name = std::get<0>(get_meta(key));
         try
         {
-            optional<std::string> comp_op_name = node.get_opt_attr<std::string>("comp-op");
+            optional<std::string> comp_op_name = node.get_opt_attr<std::string>(name);
+
             if (comp_op_name)
             {
                 optional<composite_mode_e> comp_op = comp_op_from_string(*comp_op_name);
                 if (comp_op)
                 {
-                    put(sym, keys::comp_op, *comp_op);
+                    put(sym, key, *comp_op);
                 }
                 else
                 {
@@ -1203,19 +1204,7 @@ void map_parser::parse_text_symbolizer(rule & rule, xml_node const& node)
         text_symbolizer text_symbol;
         parse_symbolizer_base(text_symbol, node);
         // halo-comp-op
-        optional<std::string> comp_op_name = node.get_opt_attr<std::string>("halo-comp-op");
+        set_symbolizer_property<symbolizer_base,composite_mode_e>(text_symbol, keys::halo_comp_op, node);
-        if (comp_op_name)
-        {
-            optional<composite_mode_e> halo_comp_op = comp_op_from_string(*comp_op_name);
-            if (halo_comp_op)
-            {
-                put(text_symbol, keys::halo_comp_op, *halo_comp_op);
-            }
-            else
-            {
-                throw config_error("failed to parse halo-comp-op: '" + *comp_op_name + "'");
-            }
-        }
 
         put<text_placements_ptr>(text_symbol, keys::text_placements_, placement_finder);
         optional<halo_rasterizer_e> halo_rasterizer_ = node.get_opt_attr<halo_rasterizer_e>("halo-rasterizer");

src/symbolizer_keys.cpp

@@ -98,7 +98,7 @@ static const property_meta_type key_meta[to_integral(keys::MAX_SYMBOLIZER_KEY)]
     property_meta_type{ "largest-box-only", false, nullptr, property_types::target_bool },
     property_meta_type{ "minimum-path-length", false, nullptr, property_types::target_double },
     property_meta_type{ "halo-comp-op", enumeration_wrapper(src_over),
-                        [](enumeration_wrapper e) { return *comp_op_to_string(composite_mode_e(e.value)); }, property_types::target_comp_op},
+                        [](enumeration_wrapper e) { return *comp_op_to_string(composite_mode_e(e.value)); }, property_types::target_halo_comp_op},
 };
 
 property_meta_type const& get_meta(mapnik::keys key)