From 3c23faf65ade59b62d41b68891bfac238acfc9ea Mon Sep 17 00:00:00 2001
From: John Firebaugh <john.firebaugh@gmail.com>
Date: Thu, 20 Apr 2017 15:28:28 -0700
Subject: [PATCH] [core] More complete fix for composite function interpolation
 edge case

b5b4549 / #8613 handled the edge case for layout properties, but not paint properties. Move the check for a degenerate range to interpolationFactor in order to handle both correctly.
---
 include/mbgl/style/function/composite_function.hpp | 3 ---
 mapbox-gl-js                                       | 2 +-
 src/mbgl/util/interpolate.cpp                      | 4 +++-
 3 files changed, 4 insertions(+), 5 deletions(-)

diff --git a/include/mbgl/style/function/composite_function.hpp b/include/mbgl/style/function/composite_function.hpp
index 2b4ae504c..9275ccdf8 100644
--- a/include/mbgl/style/function/composite_function.hpp
+++ b/include/mbgl/style/function/composite_function.hpp
@@ -100,9 +100,6 @@ public:
     T evaluate(float zoom, const GeometryTileFeature& feature, T finalDefaultValue) const {
         std::tuple<Range<float>, Range<InnerStops>> ranges = coveringRanges(zoom);
         Range<T> resultRange = evaluate(std::get<1>(ranges), feature, finalDefaultValue);
-        // If the covering stop range is constant, just return the output value directly.
-        if (resultRange.min == resultRange.max) return resultRange.min;
-        // Otherwise, interpolate between the two stops.
         return util::interpolate(
             resultRange.min,
             resultRange.max,
diff --git a/mapbox-gl-js b/mapbox-gl-js
index fbea85652..dff6bf91e 160000
--- a/mapbox-gl-js
+++ b/mapbox-gl-js
@@ -1 +1 @@
-Subproject commit fbea8565244ad254eb9678798b4a21c88916dd85
+Subproject commit dff6bf91eca37071bb25356295f53f7e2aa4230d
diff --git a/src/mbgl/util/interpolate.cpp b/src/mbgl/util/interpolate.cpp
index 306a5c663..066fa9c46 100644
--- a/src/mbgl/util/interpolate.cpp
+++ b/src/mbgl/util/interpolate.cpp
@@ -8,7 +8,9 @@ namespace util {
 float interpolationFactor(float base, Range<float> range, float z) {
     const float zoomDiff = range.max - range.min;
     const float zoomProgress = z - range.min;
-    if (base == 1.0f) {
+    if (zoomDiff == 0) {
+        return 0;
+    } else if (base == 1.0f) {
         return zoomProgress / zoomDiff;
     } else {
         return (std::pow(base, zoomProgress) - 1) / (std::pow(base, zoomDiff) - 1);