From 11ff758c38b7ed8ee0d7d794d30d710d56255802 Mon Sep 17 00:00:00 2001
From: Artem Pavlenko <artem@mapnik.org>
Date: Tue, 2 Mar 2021 17:07:13 +0000
Subject: [PATCH] Add proj_transform::definition() method

---
 include/mapnik/proj_transform.hpp |  1 +
 src/proj_transform.cpp            | 23 ++++++++++++++++++++++-
 2 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/include/mapnik/proj_transform.hpp b/include/mapnik/proj_transform.hpp
index daf84b52c..2287ef74f 100644
--- a/include/mapnik/proj_transform.hpp
+++ b/include/mapnik/proj_transform.hpp
@@ -54,6 +54,7 @@ public:
     bool backward (box2d<double> & box) const;
     bool forward (box2d<double> & box, std::size_t points) const;
     bool backward (box2d<double> & box, std::size_t points) const;
+    std::string definition() const;
 private:
     PJ_CONTEXT* ctx_ = nullptr;
     PJ* transform_ = nullptr;
diff --git a/src/proj_transform.cpp b/src/proj_transform.cpp
index 380b55b3a..5f391bb0d 100644
--- a/src/proj_transform.cpp
+++ b/src/proj_transform.cpp
@@ -28,7 +28,7 @@
 #include <mapnik/proj_transform.hpp>
 #include <mapnik/coord.hpp>
 #include <mapnik/util/is_clockwise.hpp>
-
+#include <mapnik/util/trim.hpp>
 // boost
 #include <boost/geometry/algorithms/envelope.hpp>
 
@@ -451,4 +451,25 @@ bool proj_transform::forward(box2d<double>& env, std::size_t points) const
     return true;
 }
 
+std::string proj_transform::definition() const
+{
+#ifdef MAPNIK_USE_PROJ
+    if (transform_)
+    {
+        PJ_PROJ_INFO info = proj_pj_info(transform_);
+        return mapnik::util::trim_copy(info.definition);
+    }
+    else
+#endif
+        if (wgs84_to_merc_)
+        {
+            return "wgs84 => merc";
+        }
+        else if (merc_to_wgs84_)
+        {
+            return "merc => wgs84";
+        }
+    return "unknown";
+ }
+
 }