add Projection.expanded() function to ask proj4 what its internal, normalized definition looks like (useful only for debugging)

bindings/python/mapnik_projection.cpp

@@ -104,6 +104,8 @@ void export_projection ()
         .def ("params", make_function(&projection::params,
                                       return_value_policy<copy_const_reference>()),
               "Returns the PROJ.4 string for this projection.\n")
+        .def ("expanded",&projection::expanded,
+              "normalize PROJ.4 definition by expanding +init= syntax\n")
         .add_property ("geographic", &projection::is_geographic,
                        "This property is True if the projection is a geographic projection\n"
                        "(i.e. it uses lon/lat coordinates)\n")

include/mapnik/projection.hpp

@@ -68,6 +68,8 @@ public:
       
     void forward(double & x, double &y ) const;
     void inverse(double & x,double & y) const;
+
+    std::string expanded() const;
         
 private:
     void init(); 

src/projection.cpp

@@ -25,6 +25,10 @@
 // mapnik
 #include <mapnik/projection.hpp>
 #include <mapnik/utils.hpp>
+
+// boost
+#include <boost/algorithm/string.hpp>
+
 // proj4
 #include <proj_api.h>
 
@@ -139,6 +143,16 @@ void projection::init()
     if (!proj_) throw proj_init_error(params_);
     is_geographic_ = pj_is_latlong(proj_) ? true : false;
 }
+
+std::string projection::expanded() const
+{
+    if (proj_) {
+        std::string def(pj_get_def( proj_, 0 ));
+        //boost::algorithm::ireplace_first(def,params_,"");
+        return boost::trim_copy(def);
+    }
+    return std::string("");
+}
     
 void projection::swap (projection& rhs)
 {

tests/python_tests/projection_test.py

@@ -6,6 +6,12 @@ import mapnik2, pickle
 
 # Tests that exercise map projections.
 
+def test_normalizing_definition():
+    p = mapnik2.Projection('+init=epsg:4326')
+    expanded = p.expanded()
+    eq_('+proj=longlat' in expanded,True)
+
+
 # Trac Ticket #128
 def test_wgs84_inverse_forward():
     p = mapnik2.Projection('+init=epsg:4326')