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#pragma once
#include <mbgl/style/function/source_function.hpp>
#include <mbgl/style/function/composite_function.hpp>
#include <mbgl/util/interpolate.hpp>
#include <mbgl/util/variant.hpp>
namespace mbgl {
template <class T>
class PossiblyEvaluatedPropertyValue {
private:
using Value = variant<
T,
style::SourceFunction<T>,
style::CompositeFunction<T>>;
Value value;
public:
PossiblyEvaluatedPropertyValue() = default;
PossiblyEvaluatedPropertyValue(Value v, bool useIntegerZoom_ = false)
: value(std::move(v)),
useIntegerZoom(useIntegerZoom_) {}
bool isConstant() const {
return value.template is<T>();
}
optional<T> constant() const {
return value.match(
[&] (const T& t) { return optional<T>(t); },
[&] (const auto&) { return optional<T>(); });
}
T constantOr(const T& t) const {
return constant().value_or(t);
}
template <class... Ts>
auto match(Ts&&... ts) const {
return value.match(std::forward<Ts>(ts)...);
}
template <class Feature>
T evaluate(const Feature& feature, float zoom, T defaultValue) const {
return this->match(
[&] (const T& constant_) { return constant_; },
[&] (const style::SourceFunction<T>& function) {
return function.evaluate(feature, defaultValue);
},
[&] (const style::CompositeFunction<T>& function) {
if (useIntegerZoom) {
return function.evaluate(floor(zoom), feature, defaultValue);
} else {
return function.evaluate(zoom, feature, defaultValue);
}
}
);
}
bool useIntegerZoom;
};
namespace util {
template <typename T>
struct Interpolator<PossiblyEvaluatedPropertyValue<T>> {
PossiblyEvaluatedPropertyValue<T> operator()(const PossiblyEvaluatedPropertyValue<T>& a,
const PossiblyEvaluatedPropertyValue<T>& b,
const double t) const {
if (a.isConstant() && b.isConstant()) {
return { interpolate(*a.constant(), *b.constant(), t) };
} else {
return { a };
}
}
};
} // namespace util
} // namespace mbgl
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