From ecc5acbdb953e172fcc652b55ed19b8b581e2146 Mon Sep 17 00:00:00 2001
From: artemp <artem@mapnik.org>
Date: Mon, 24 Feb 2014 15:20:06 +0000
Subject: [PATCH] attempt to handle multi-polygons in shape.input

---
 include/mapnik/geom_util.hpp     | 41 ++++++++++++++++++++++++++++++++
 plugins/input/shape/shape_io.cpp | 14 +++++++----
 2 files changed, 51 insertions(+), 4 deletions(-)

diff --git a/include/mapnik/geom_util.hpp b/include/mapnik/geom_util.hpp
index 81d5f16c6..405e191e4 100644
--- a/include/mapnik/geom_util.hpp
+++ b/include/mapnik/geom_util.hpp
@@ -247,6 +247,47 @@ double path_length(PathType & path)
     return length;
 }
 
+template <typename PathType>
+bool hit_test_first(PathType & path, double x, double y, double tol)
+{
+    bool inside=false;
+    double x0 = 0;
+    double y0 = 0;
+    double x1 = 0;
+    double y1 = 0;
+    path.rewind(0);
+    unsigned command = path.vertex(&x0, &y0);
+    if (command == SEG_END)
+    {
+        return false;
+    }
+    unsigned count = 0;
+    mapnik::geometry_type::types geom_type = static_cast<mapnik::geometry_type::types>(path.type());
+    while (SEG_END != (command = path.vertex(&x1, &y1)))
+    {
+        if (command == SEG_CLOSE)
+        {
+            break;
+        }
+        ++count;
+        if (command == SEG_MOVETO)
+        {
+            x0 = x1;
+            y0 = y1;
+            continue;
+        }
+
+        if ((((y1 <= y) && (y < y0)) ||
+             ((y0 <= y) && (y < y1))) &&
+            (x < (x0 - x1) * (y - y1)/ (y0 - y1) + x1))
+            inside=!inside;
+
+        x0 = x1;
+        y0 = y1;
+    }
+    return inside;
+}
+
 namespace label {
 
 template <typename PathType>
diff --git a/plugins/input/shape/shape_io.cpp b/plugins/input/shape/shape_io.cpp
index 85e3f966e..a0587dd4e 100644
--- a/plugins/input/shape/shape_io.cpp
+++ b/plugins/input/shape/shape_io.cpp
@@ -25,12 +25,13 @@
 // mapnik
 #include <mapnik/debug.hpp>
 #include <mapnik/datasource.hpp>
+#include <mapnik/geom_util.hpp>
 
 // boost
 
 using mapnik::datasource_exception;
 using mapnik::geometry_type;
-
+using mapnik::hit_test_first;
 const std::string shape_io::SHP = ".shp";
 const std::string shape_io::DBF = ".dbf";
 const std::string shape_io::INDEX = ".index";
@@ -156,9 +157,9 @@ void shape_io::read_polygon(shape_file::record_type & record, mapnik::geometry_c
         parts[i] = record.read_ndr_integer();
     }
 
+    std::unique_ptr<geometry_type> poly(new geometry_type(mapnik::geometry_type::types::Polygon));
     for (int k = 0; k < num_parts; ++k)
     {
-        std::unique_ptr<geometry_type> poly(new geometry_type(mapnik::geometry_type::types::Polygon));
         int start = parts[k];
         int end;
         if (k == num_parts - 1)
@@ -172,14 +173,19 @@ void shape_io::read_polygon(shape_file::record_type & record, mapnik::geometry_c
 
         double x = record.read_double();
         double y = record.read_double();
+        if (k > 0 && !hit_test_first(*poly, x, y, 0))
+        {
+            geom.push_back(poly.release());
+            poly.reset(new geometry_type(mapnik::geometry_type::types::Polygon));
+        }
         poly->move_to(x, y);
-        for (int j=start+1;j<end;j++)
+        for (int j = start + 1; j < end; ++j)
         {
             x = record.read_double();
             y = record.read_double();
             poly->line_to(x, y);
         }
         poly->close_path();
-        geom.push_back(poly.release());
     }
+    geom.push_back(poly.release());
 }