From a9aa1c69b8eaff0ba87aad57b1d3d0bc3984f1c8 Mon Sep 17 00:00:00 2001
From: artemp <artem@mapnik.org>
Date: Thu, 16 Mar 2017 12:39:12 +0000
Subject: [PATCH] save_map - support nested layers + serialize layer
 compositing mode

---
 src/save_map.cpp | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/src/save_map.cpp b/src/save_map.cpp
index 008658849..f5825ce73 100644
--- a/src/save_map.cpp
+++ b/src/save_map.cpp
@@ -514,6 +514,17 @@ void serialize_layer( ptree & map_node, layer const& lyr, bool explicit_defaults
         set_attr( layer_node, "name", lyr.name() );
     }
 
+    auto const comp_op = lyr.comp_op();
+
+    if (comp_op)
+    {
+        set_attr(layer_node, "comp-op", *comp_op_to_string(*comp_op));
+    }
+    else if (explicit_defaults)
+    {
+        set_attr(layer_node, "comp-op", "src-over");
+    }
+
     if ( lyr.srs() != "" )
     {
         set_attr( layer_node, "srs", lyr.srs() );
@@ -583,6 +594,12 @@ void serialize_layer( ptree & map_node, layer const& lyr, bool explicit_defaults
     {
         serialize_datasource( layer_node, datasource );
     }
+
+    // serialize nested layers
+    for (auto const& child : lyr.layers())
+    {
+        serialize_layer(layer_node, child, explicit_defaults );
+    }
 }
 
 void serialize_map(ptree & pt, Map const& map, bool explicit_defaults)