From 3e928f41c854f5895656eb718643d9280e63bc69 Mon Sep 17 00:00:00 2001
From: Ansis Brammanis <brammanis@gmail.com>
Date: Tue, 28 Apr 2015 18:14:34 -0700
Subject: [PATCH] fix line tessellation

-js: https://github.com/mapbox/mapbox-gl-js/commit/7cf7ef763df7257ee45eb0b060e6043781bf5e4a
---
 src/mbgl/renderer/line_bucket.cpp | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/mbgl/renderer/line_bucket.cpp b/src/mbgl/renderer/line_bucket.cpp
index 78da158f1..302f55cbd 100644
--- a/src/mbgl/renderer/line_bucket.cpp
+++ b/src/mbgl/renderer/line_bucket.cpp
@@ -183,8 +183,9 @@ void LineBucket::addGeometry(const std::vector<Coordinate>& vertices) {
                 // Almost parallel lines
                 joinNormal = nextNormal;
             } else {
+                const float direction = prevNormal.x * nextNormal.y - prevNormal.y * nextNormal.x > 0 ? -1 : 1;
                 const float bevelLength = miterLength * util::mag(prevNormal + nextNormal) /
-                                          util::mag(prevNormal - nextNormal);
+                                          util::mag(prevNormal - nextNormal * direction);
                 joinNormal = util::perp(joinNormal) * bevelLength;
             }