[core] Add `line-gradient` property

Porting of https://github.com/mapbox/mapbox-gl-js/pull/6303
See the link above for the description of the feature and
its limitations).

Based on patch from @lbud (Lauren Budorick).

1 files changed, 5 insertions, 0 deletions

diff --git a/src/mbgl/renderer/layers/render_line_layer.hpp b/src/mbgl/renderer/layers/render_line_layer.hpp
index 5d5d79c044..facab60645 100644
--- a/src/mbgl/renderer/layers/render_line_layer.hpp
+++ b/src/mbgl/renderer/layers/render_line_layer.hpp
@@ -4,6 +4,7 @@
 #include <mbgl/style/layers/line_layer_impl.hpp>
 #include <mbgl/style/layers/line_layer_properties.hpp>
 #include <mbgl/programs/uniforms.hpp>
+#include <mbgl/util/image.hpp>
 
 namespace mbgl {
 
@@ -33,6 +34,8 @@ public:
             const float,
             const mat4&) const override;
 
+    void updateColorRamp();
+
     std::unique_ptr<Bucket> createBucket(const BucketParameters&, const std::vector<const RenderLayer*>&) const override;
 
     // Paint properties
@@ -43,6 +46,8 @@ public:
 
 private:
     float getLineWidth(const GeometryTileFeature&, const float) const;
+    PremultipliedImage colorRamp;
+    optional<gl::Texture> colorRampTexture;
 };
 
 template <>