[core] Move layer specific color ramp updates behind common update() method

src/mbgl/renderer/layers/render_heatmap_layer.cpp

@@ -185,6 +185,10 @@ void RenderHeatmapLayer::render(PaintParameters& parameters, RenderSource*) {
     }
 }
 
+void RenderHeatmapLayer::update() {
+    updateColorRamp();
+}
+
 void RenderHeatmapLayer::updateColorRamp() {
     auto colorValue = unevaluated.get<HeatmapColor>().getValue();
     if (colorValue.isUndefined()) {

src/mbgl/renderer/layers/render_heatmap_layer.hpp

@@ -18,6 +18,7 @@ public:
     bool hasTransition() const override;
     bool hasCrossfade() const override;
     void render(PaintParameters&, RenderSource*) override;
+    void update() final;
 
     bool queryIntersectsFeature(
             const GeometryCoordinates&,
@@ -27,8 +28,6 @@ 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
@@ -40,6 +39,9 @@ public:
     PremultipliedImage colorRamp;
     optional<OffscreenTexture> renderTexture;
     optional<gl::Texture> colorRampTexture;
+
+private:
+    void updateColorRamp();
 };
 
 template <>

src/mbgl/renderer/layers/render_line_layer.cpp

@@ -294,4 +294,8 @@ float RenderLineLayer::getLineWidth(const GeometryTileFeature& feature, const fl
 }
 
 
+void RenderLineLayer::update() {
+    updateColorRamp();
+}
+
 } // namespace mbgl

src/mbgl/renderer/layers/render_line_layer.hpp

@@ -32,6 +32,7 @@ public:
     bool hasTransition() const override;
     bool hasCrossfade() const override;
     void render(PaintParameters&, RenderSource*) override;
+    void update() final;
 
     RenderLinePaintProperties::PossiblyEvaluated paintProperties() const;
 
@@ -43,7 +44,6 @@ public:
             const float,
             const mat4&) const override;
 
-    void updateColorRamp();
 
     std::unique_ptr<Bucket> createBucket(const BucketParameters&, const std::vector<const RenderLayer*>&) const override;
     std::unique_ptr<Layout> createLayout(const BucketParameters&,
@@ -59,6 +59,7 @@ public:
 
 private:
     float getLineWidth(const GeometryTileFeature&, const float) const;
+    void updateColorRamp();
     CrossfadeParameters crossfade;
     PremultipliedImage colorRamp;
     optional<gl::Texture> colorRampTexture;

src/mbgl/renderer/render_layer.cpp

@@ -86,6 +86,10 @@ void RenderLayer::sortRenderTiles(const TransformState&) {
     std::sort(renderTiles.begin(), renderTiles.end(), [](const auto& a, const auto& b) { return a.get().id < b.get().id; });
 }
 
+void RenderLayer::update() {
+    // no-op
+}
+
 RenderLayer::RenderTiles RenderLayer::filterRenderTiles(RenderTiles tiles, FilterFunctionPtr filterFn) const {
     assert(filterFn != nullptr);
     RenderTiles filtered;

src/mbgl/renderer/render_layer.hpp

@@ -95,7 +95,14 @@ public:
     void setImpl(Immutable<style::Layer::Impl>);
 
     virtual void markContextDestroyed();
+
+    // TODO: Figure out how to remove this or whether layers other than
+    // RenderHeatmapLayer and RenderLineLayer need paint property updates,
+    // similar to color ramp. Temporarily moved to the base.
+    virtual void update();
+
     friend std::string layoutKey(const RenderLayer&);
+
 protected:
     // Checks whether the current hardware can render this layer. If it can't, we'll show a warning
     // in the console to inform the developer.

src/mbgl/renderer/renderer_impl.cpp

@@ -15,7 +15,6 @@
 #include <mbgl/renderer/layers/render_custom_layer.hpp>
 #include <mbgl/renderer/layers/render_fill_extrusion_layer.hpp>
 #include <mbgl/renderer/layers/render_fill_layer.hpp>
-#include <mbgl/renderer/layers/render_heatmap_layer.hpp>
 #include <mbgl/renderer/layers/render_hillshade_layer.hpp>
 #include <mbgl/renderer/style_diff.hpp>
 #include <mbgl/renderer/query.hpp>
@@ -186,14 +185,7 @@ void Renderer::Impl::render(const UpdateParameters& updateParameters) {
 
         if (layerAdded || layerChanged) {
             layer.transition(transitionParameters);
-
-            if (layer.is<RenderHeatmapLayer>()) {
-                layer.as<RenderHeatmapLayer>()->updateColorRamp();
-            }
-
-            if (layer.is<RenderLineLayer>()) {
-                layer.as<RenderLineLayer>()->updateColorRamp();
-            }
+            layer.update();
         }
 
         if (layerAdded || layerChanged || zoomChanged || layer.hasTransition() || layer.hasCrossfade()) {