From d0d33a3ee735d2297edac0d837559193fced315d Mon Sep 17 00:00:00 2001
From: Ansis Brammanis <brammanis@gmail.com>
Date: Fri, 23 Jan 2015 17:12:41 -0500
Subject: [PATCH] don't permanently crossfade line patterns

js: a2e8527b4023d19fa0c58130a105aaf283f4b152
---
 src/mbgl/renderer/painter_line.cpp | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/src/mbgl/renderer/painter_line.cpp b/src/mbgl/renderer/painter_line.cpp
index 2d57bb26e..8b080908b 100644
--- a/src/mbgl/renderer/painter_line.cpp
+++ b/src/mbgl/renderer/painter_line.cpp
@@ -70,6 +70,10 @@ void Painter::renderLine(LineBucket& bucket, util::ptr<StyleLayer> layer_desc, c
         bucket.drawPoints(*linejoinShader);
     }
 
+    float duration = 300 * 1_millisecond;
+    const float fraction = std::fmod(float(state.getZoom()), 1.0f);
+    float t = std::min((util::now() - lastIntegerZoomTime) / duration, 1.0f);
+
     if (properties.dash_array.size()) {
 
         useProgram(linesdfShader->program);
@@ -99,7 +103,15 @@ void Painter::renderLine(LineBucket& bucket, util::ptr<StyleLayer> layer_desc, c
         SpriteAtlasPosition imagePos = spriteAtlas.getPosition(properties.image, true);
 
         float factor = 8.0 / std::pow(2, state.getIntegerZoom() - id.z);
-        float fade = std::fmod(state.getZoom(), 1.0);
+        float fade;
+        if (state.getZoom() > lastIntegerZoom) {
+            // zooming in
+            fade = fraction + (1.0f - fraction) * t;
+            factor *= 2.0;
+        } else {
+            // zooming out
+            fade = fraction - fraction * t;
+        }
 
         useProgram(linepatternShader->program);