From 770d93b7cc1178d705a23997a087e884fc74374b Mon Sep 17 00:00:00 2001
From: Blake Thompson <flippmoke@gmail.com>
Date: Tue, 30 Jun 2015 22:23:44 -0500
Subject: [PATCH] Fix situation where offset_converter might start off with an
 SEG_END from the vertex, therefore starting invalid processing. Tests added
 to confirm fix. Ref #2937

---
 include/mapnik/offset_converter.hpp           |  5 ++
 test/unit/vertex_adapter/offset_converter.cpp | 75 ++++++++++++++++++-
 2 files changed, 77 insertions(+), 3 deletions(-)

diff --git a/include/mapnik/offset_converter.hpp b/include/mapnik/offset_converter.hpp
index b1f2476c8..2badce8b5 100644
--- a/include/mapnik/offset_converter.hpp
+++ b/include/mapnik/offset_converter.hpp
@@ -310,6 +310,11 @@ private:
         v1.cmd = v0.cmd;
         // PUSH INITIAL
         points.push_back(vertex2d(v0.x, v0.y, v0.cmd));
+        if (v0.cmd == SEG_END) // not enough vertices in source
+        {
+            return status_ = process;
+        }
+        
         while ((v0.cmd = geom_.vertex(&v0.x, &v0.y)) != SEG_END)
         {
             points.push_back(vertex2d(v0.x, v0.y, v0.cmd));
diff --git a/test/unit/vertex_adapter/offset_converter.cpp b/test/unit/vertex_adapter/offset_converter.cpp
index 38c91b5dc..b4b7d73c7 100644
--- a/test/unit/vertex_adapter/offset_converter.cpp
+++ b/test/unit/vertex_adapter/offset_converter.cpp
@@ -27,14 +27,22 @@ struct fake_path
         : fake_path(l.begin(), l.size()) {
     }
 
-    fake_path(std::vector<double> const &v)
-        : fake_path(v.begin(), v.size()) {
+    fake_path(std::vector<double> const &v, bool make_invalid = false)
+        : fake_path(v.begin(), v.size(), make_invalid) {
     }
 
     template <typename Itr>
-    fake_path(Itr itr, size_t sz) {
+    fake_path(Itr itr, size_t sz, bool make_invalid = false) {
         size_t num_coords = sz >> 1;
+        if (make_invalid)
+        {
+            num_coords++;
+        }
         vertices_.reserve(num_coords);
+        if (make_invalid)
+        {
+            vertices_.push_back(std::make_tuple(0,0,mapnik::SEG_END));
+        }
 
         for (size_t i = 0; i < num_coords; ++i) {
             double x = *itr++;
@@ -70,6 +78,32 @@ double dist(double x0, double y0, double x1, double y1)
     return std::sqrt(dx*dx + dy*dy);
 }
 
+void test_null_segment(double const &offset)
+{
+    fake_path path = {};
+    mapnik::offset_converter<fake_path> off_path_new(path);
+    off_path_new.set_offset(offset);
+    double x0 = 0;
+    double y0 = 0;
+    REQUIRE(off_path_new.vertex(&x0, &y0) == mapnik::SEG_END);
+    REQUIRE(off_path_new.vertex(&x0, &y0) == mapnik::SEG_END);
+    REQUIRE(off_path_new.vertex(&x0, &y0) == mapnik::SEG_END);
+}
+
+void test_invalid_segment(double const &offset)
+{
+    std::vector<double> v_path = {1, 1, 1, 2};
+    fake_path path(v_path, true);
+    mapnik::offset_converter<fake_path> off_path_new(path);
+    off_path_new.set_offset(offset);
+    double x0 = 0;
+    double y0 = 0;
+    REQUIRE(off_path_new.vertex(&x0, &y0) == mapnik::SEG_END);
+    REQUIRE(off_path_new.vertex(&x0, &y0) == mapnik::SEG_END);
+    REQUIRE(off_path_new.vertex(&x0, &y0) == mapnik::SEG_END);
+}
+
+
 void test_simple_segment(double const &offset)
 {
     fake_path path = {0, 0, 1, 0}, off_path = {0, offset, 1, offset};
@@ -263,6 +297,41 @@ void test_s_shaped_curve(double const &offset) {
 
 TEST_CASE("offset converter") {
 
+SECTION("null segment") {
+    try {
+
+        std::vector<double> offsets = { 1, -1 };
+        for (double offset : offsets) {
+            // test simple straight line segment - should be easy to
+            // find the correspondance here.
+            offset_test::test_null_segment(offset);
+        }
+    }
+    catch (std::exception const& ex)
+    {
+        std::cerr << ex.what() << "\n";
+        REQUIRE(false);
+    }
+}
+
+SECTION("invalid segment") {
+    try {
+
+        std::vector<double> offsets = { 1, -1 };
+        for (double offset : offsets) {
+            // test simple straight line segment - should be easy to
+            // find the correspondance here.
+            offset_test::test_invalid_segment(offset);
+        }
+    }
+    catch (std::exception const& ex)
+    {
+        std::cerr << ex.what() << "\n";
+        REQUIRE(false);
+    }
+}
+
+
 SECTION("simple segment") {
     try {