Fix line properties on Metal

include/mbgl/renderer/layer_tweaker.hpp

@@ -41,32 +41,33 @@ using StringIdentity = std::size_t;
 class LayerTweaker {
 protected:
     LayerTweaker(std::string id, Immutable<style::LayerProperties> properties);
-
+    
 public:
     LayerTweaker() = delete;
     virtual ~LayerTweaker() = default;
-
+    
     const std::string& getID() const { return id; }
-
+    
 #if MLN_RENDER_BACKEND_METAL
     /// Build the common expression inupts UBO
     static shaders::ExpressionInputsUBO buildExpressionUBO(double zoom, uint64_t frameCount);
-
+    
     /// @brief Check whether a property name exists within the previously set collection.
     bool hasPropertyAsUniform(StringIdentity) const;
     shaders::AttributeSource getAttributeSource(StringIdentity) const;
-
+    
     template <shaders::BuiltIn ShaderType>
     shaders::AttributeSource getAttributeSource(size_t index) {
         using ShaderClass = shaders::ShaderSource<ShaderType, gfx::Backend::Type::Metal>;
         return getAttributeSource(ShaderClass::attributes[index].nameID);
     }
 #endif // MLN_RENDER_BACKEND_METAL
-
+    
     /// @brief Set the collection of attribute names which will be provided at uniform values rather than per-vertex
     /// attributes.
     /// @details These values should not have "a_" prefixes, as produced by `readDataDrivenPaintProperties`.
     void setPropertiesAsUniforms(const std::unordered_set<StringIdentity>&);
+    const std::unordered_set<StringIdentity>& getPropertiesAsUniforms() const;
 
     void enableOverdrawInspector(bool);
 

src/mbgl/renderer/layer_tweaker.cpp

@@ -85,6 +85,20 @@ void LayerTweaker::setPropertiesAsUniforms([[maybe_unused]] const std::unordered
 #endif
 }
 
+#if !MLN_RENDER_BACKEND_METAL
+namespace {
+const std::unordered_set<StringIdentity> emptyIDSet;
+}
+#endif
+
+const std::unordered_set<StringIdentity>& LayerTweaker::getPropertiesAsUniforms() const {
+#if MLN_RENDER_BACKEND_METAL
+    return propertiesAsUniforms;
+#else
+    return emptyIDSet;
+#endif
+}
+
 void LayerTweaker::enableOverdrawInspector(bool value) {
     if (overdrawInspector != value) {
         overdrawInspector = value;

src/mbgl/renderer/layers/render_line_layer.cpp

@@ -83,6 +83,12 @@ void RenderLineLayer::evaluate(const PropertyEvaluationParameters& parameters) {
 #if MLN_DRAWABLE_RENDERER
     if (layerGroup) {
         auto newTweaker = std::make_shared<LineLayerTweaker>(getID(), evaluatedProperties);
+
+        // propertiesAsUniforms isn't recalculated every update, so carry it over
+        if (layerTweaker) {
+            newTweaker->setPropertiesAsUniforms(layerTweaker->getPropertiesAsUniforms());
+        }
+
         replaceTweaker(layerTweaker, std::move(newTweaker), {layerGroup});
     }
 #endif
@@ -566,6 +572,8 @@ void RenderLineLayer::update(gfx::ShaderRegistry& shaders,
             else if (shaderUniforms.get(idLineSDFInterpolationUBOName)) {
                 drawableUniforms.createOrUpdate(idLineSDFInterpolationUBOName, &lineSDFInterpolationUBO, context);
             }
+
+            // TODO: vertex attributes or `propertiesAsUniforms` updated, is that needed?
         });
 
         if (tileLayerGroup->getDrawableCount(renderPass, tileID) > 0) {