1 files changed, 268 insertions, 0 deletions
diff --git a/src/mbgl/style/properties.hpp b/src/mbgl/style/properties.hpp
new file mode 100644
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--- /dev/null
+++ b/src/mbgl/style/properties.hpp
@@ -0,0 +1,268 @@
+#pragma once
+
+#include <mbgl/style/transition_options.hpp>
+#include <mbgl/style/conversion/stringify.hpp>
+#include <mbgl/renderer/cascade_parameters.hpp>
+#include <mbgl/renderer/paint_property_binder.hpp>
+#include <mbgl/renderer/property_evaluation_parameters.hpp>
+#include <mbgl/renderer/cascade_parameters.hpp>
+#include <mbgl/util/indexed_tuple.hpp>
+#include <mbgl/util/ignore.hpp>
+
+namespace mbgl {
+
+class GeometryTileFeature;
+
+namespace style {
+
+template <class Value>
+class Transitioning {
+public:
+    Transitioning() = default;
+
+    Transitioning(Value value_,
+                  Transitioning<Value> prior_,
+                  TransitionOptions transition,
+                  TimePoint now)
+        : begin(now + transition.delay.value_or(Duration::zero())),
+          end(begin + transition.duration.value_or(Duration::zero())),
+          value(std::move(value_)) {
+        if (transition.isDefined()) {
+            prior = { std::move(prior_) };
+        }
+    }
+
+    template <class Evaluator>
+    auto evaluate(const Evaluator& evaluator, TimePoint now) const {
+        auto finalValue = value.evaluate(evaluator);
+        if (!prior) {
+            // No prior value.
+            return finalValue;
+        } else if (now >= end) {
+            // Transition from prior value is now complete.
+            prior = {};
+            return finalValue;
+        } else if (value.isDataDriven()) {
+            // Transitions to data-driven properties are not supported.
+            // We snap immediately to the data-driven value so that, when we perform layout,
+            // we see the data-driven function and can use it to populate vertex buffers.
+            prior = {};
+            return finalValue;
+        } else if (now < begin) {
+            // Transition hasn't started yet.
+            return prior->get().evaluate(evaluator, now);
+        } else {
+            // Interpolate between recursively-calculated prior value and final.
+            float t = std::chrono::duration<float>(now - begin) / (end - begin);
+            return util::interpolate(prior->get().evaluate(evaluator, now), finalValue,
+                                     util::DEFAULT_TRANSITION_EASE.solve(t, 0.001));
+        }
+    }
+
+    bool hasTransition() const {
+        return bool(prior);
+    }
+
+    bool isUndefined() const {
+        return value.isUndefined();
+    }
+
+    const Value& getValue() const {
+        return value;
+    }
+
+private:
+    mutable optional<mapbox::util::recursive_wrapper<Transitioning<Value>>> prior;
+    TimePoint begin;
+    TimePoint end;
+    Value value;
+};
+
+template <class Value>
+class Transitionable {
+public:
+    Value value;
+    TransitionOptions transition;
+
+    Transitioning<Value> cascade(const CascadeParameters& params, Transitioning<Value> prior) const {
+        return Transitioning<Value>(value,
+                                    std::move(prior),
+                                    transition.reverseMerge(params.transition),
+                                    params.now);
+    }
+};
+template <class Value>
+class Cascading {
+public:
+    bool isUndefined() const {
+        return values.find(ClassID::Default) == values.end();
+    }
+
+    const Value& get(const optional<std::string>& klass) const {
+        static const Value staticValue{};
+        const auto it = values.find(klass ? ClassDictionary::Get().lookup(*klass) : ClassID::Default);
+        return it == values.end() ? staticValue : it->second;
+    }
+
+    void set(const Value& value_, const optional<std::string>& klass) {
+        values[klass ? ClassDictionary::Get().lookup(*klass) : ClassID::Default] = value_;
+    }
+
+    const TransitionOptions& getTransition(const optional<std::string>& klass) const {
+        static const TransitionOptions staticValue{};
+        const auto it = transitions.find(klass ? ClassDictionary::Get().lookup(*klass) : ClassID::Default);
+        return it == transitions.end() ? staticValue : it->second;
+    }
+
+    void setTransition(const TransitionOptions& transition, const optional<std::string>& klass) {
+        transitions[klass ? ClassDictionary::Get().lookup(*klass) : ClassID::Default] = transition;
+    }
+
+    Transitioning<Value> cascade(const CascadeParameters& params, Transitioning<Value> prior) const {
+        TransitionOptions transition;
+        Value value;
+
+        for (const auto classID : params.classes) {
+            if (values.find(classID) != values.end()) {
+                value = values.at(classID);
+                break;
+            }
+        }
+
+        for (const auto classID : params.classes) {
+            if (transitions.find(classID) != transitions.end()) {
+                transition = transitions.at(classID).reverseMerge(transition);
+                break;
+            }
+        }
+
+        return Transitioning<Value>(std::move(value),
+                                    std::move(prior),
+                                    transition.reverseMerge(params.transition),
+                                    params.now);
+    }
+
+private:
+    std::map<ClassID, Value> values;
+    std::map<ClassID, TransitionOptions> transitions;
+};
+
+
+template <class P>
+struct IsDataDriven : std::integral_constant<bool, P::IsDataDriven> {};
+
+template <class... Ps>
+class Properties {
+public:
+    /*
+        For style properties we implement a two step evaluation process: if you have a zoom level,
+        you can evaluate a set of unevaluated property values, producing a set of possibly evaluated
+        values, where undefined, constant, or camera function values have been fully evaluated, and
+        source or composite function values have not.
+
+        Once you also have a particular feature, you can evaluate that set of possibly evaluated values
+        fully, producing a set of fully evaluated values.
+
+        This is in theory maximally efficient in terms of avoiding repeated evaluation of camera
+        functions, though it's more of a historical accident than a purposeful optimization.
+    */
+
+    using          PropertyTypes = TypeList<Ps...>;
+    using         CascadingTypes = TypeList<typename Ps::CascadingType...>;
+    using       UnevaluatedTypes = TypeList<typename Ps::UnevaluatedType...>;
+    using PossiblyEvaluatedTypes = TypeList<typename Ps::PossiblyEvaluatedType...>;
+    using         EvaluatedTypes = TypeList<typename Ps::Type...>;
+
+    using DataDrivenProperties = FilteredTypeList<PropertyTypes, IsDataDriven>;
+    using Binders = PaintPropertyBinders<DataDrivenProperties>;
+
+    template <class TypeList>
+    using Tuple = IndexedTuple<PropertyTypes, TypeList>;
+
+    class Evaluated : public Tuple<EvaluatedTypes> {
+    public:
+        using Tuple<EvaluatedTypes>::Tuple;
+    };
+
+    class PossiblyEvaluated : public Tuple<PossiblyEvaluatedTypes> {
+    public:
+        using Tuple<PossiblyEvaluatedTypes>::Tuple;
+
+        template <class T>
+        static T evaluate(float, const GeometryTileFeature&, const T& t, const T&) {
+            return t;
+        }
+
+        template <class T>
+        static T evaluate(float z, const GeometryTileFeature& feature,
+                          const PossiblyEvaluatedPropertyValue<T>& v, const T& defaultValue) {
+            return v.match(
+                [&] (const T& t) {
+                    return t;
+                },
+                [&] (const SourceFunction<T>& t) {
+                    return t.evaluate(feature, defaultValue);
+                },
+                [&] (const CompositeFunction<T>& t) {
+                    return t.evaluate(z, feature, defaultValue);
+                });
+        }
+
+        template <class P>
+        auto evaluate(float z, const GeometryTileFeature& feature) const {
+            return evaluate(z, feature, this->template get<P>(), P::defaultValue());
+        }
+
+        Evaluated evaluate(float z, const GeometryTileFeature& feature) const {
+            return Evaluated {
+                evaluate<Ps>(z, feature)...
+            };
+        }
+    };
+
+    class Unevaluated : public Tuple<UnevaluatedTypes> {
+    public:
+        using Tuple<UnevaluatedTypes>::Tuple;
+
+        bool hasTransition() const {
+            bool result = false;
+            util::ignore({ result |= this->template get<Ps>().hasTransition()... });
+            return result;
+        }
+
+        template <class P>
+        auto evaluate(const PropertyEvaluationParameters& parameters) const {
+            using Evaluator = typename P::EvaluatorType;
+            return this->template get<P>()
+                .evaluate(Evaluator(parameters, P::defaultValue()), parameters.now);
+        }
+
+        PossiblyEvaluated evaluate(const PropertyEvaluationParameters& parameters) const {
+            return PossiblyEvaluated {
+                evaluate<Ps>(parameters)...
+            };
+        }
+
+        template <class Writer>
+        void stringify(Writer& writer) const {
+            writer.StartObject();
+            util::ignore({ (conversion::stringify<Ps>(writer, this->template get<Ps>()), 0)... });
+            writer.EndObject();
+        }
+    };
+
+    class Cascading : public Tuple<CascadingTypes> {
+    public:
+        using Tuple<CascadingTypes>::Tuple;
+
+        Unevaluated cascade(const CascadeParameters& parameters, Unevaluated&& prior) const {
+            return Unevaluated {
+                this->template get<Ps>()
+                    .cascade(parameters, std::move(prior.template get<Ps>()))...
+            };
+        }
+    };
+};
+
+} // namespace style
+} // namespace mbgl