port mapnik/mapnik@66160e9

mapbox · Apr 18, 2016 · 69aab12 · 69aab12 · artemp · Apr 20, 2016
1 parent 59a0868
commit 69aab12
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Showing 2 changed files with 12 additions and 3 deletions.
diff --git a/src/vector_tile_geometry_decoder.hpp b/src/vector_tile_geometry_decoder.hpp
@@ -10,7 +10,6 @@
 //mapnik
 #include <mapnik/box2d.hpp>
 #include <mapnik/geometry.hpp>
-#include <mapnik/util/is_clockwise.hpp>
 #if defined(DEBUG)
 #include <mapnik/debug.hpp>
 #endif

diff --git a/src/vector_tile_geometry_decoder.ipp b/src/vector_tile_geometry_decoder.ipp
@@ -25,13 +25,23 @@ namespace detail
 template <typename T>
 bool ring_is_clockwise(T const& ring)
 {
-    long double area = 0.0;
     std::size_t num_points = ring.size();
+    if (num_points < 3)
+    {
+        return false;
+    }
+    double area = 0.0;
+    double orig_x = ring[0].x;
+    double orig_y = ring[0].y;
     for (std::size_t i = 0; i < num_points; ++i)
     {
         auto const& p0 = ring[i];
         auto const& p1 = ring[(i + 1) % num_points];
-        area += static_cast<long double>(p0.x) * static_cast<long double>(p1.y) - static_cast<long double>(p0.y) * static_cast<long double>(p1.x);
+        double x0 = p0.x - orig_x;
+        double y0 = p0.y - orig_y;
+        double x1 = p1.x - orig_x;
+        double y1 = p1.y - orig_y;
+        area += x0 * y1 - x1 * y0;
     }
     return (area < 0.0) ? true : false;
 }