path: root/src/mbgl/renderer/paint_property_binder.hpp

#pragma once

#include <mbgl/gfx/context.hpp>
#include <mbgl/gfx/uniform.hpp>
#include <mbgl/gfx/attribute.hpp>
#include <mbgl/gfx/upload_pass.hpp>
#include <mbgl/programs/attributes.hpp>
#include <mbgl/util/literal.hpp>
#include <mbgl/util/type_list.hpp>
#include <mbgl/renderer/possibly_evaluated_property_value.hpp>
#include <mbgl/renderer/paint_property_statistics.hpp>
#include <mbgl/renderer/cross_faded_property_evaluator.hpp>
#include <mbgl/util/variant.hpp>
#include <mbgl/renderer/image_atlas.hpp>
#include <mbgl/util/indexed_tuple.hpp>
#include <mbgl/layout/pattern_layout.hpp>

#include <bitset>

namespace mbgl {

/*
   ZoomInterpolatedAttribute<Attr> is a 'compound' attribute, representing two values of the
   the base attribute Attr.  These two values are provided to the shader to allow interpolation
   between zoom levels, without the need to repopulate vertex buffers each frame as the map is
   being zoomed.
*/
template <class AttributeType>
using ZoomInterpolatedAttributeType = gfx::AttributeType<typename AttributeType::ElementType, AttributeType::Dimensions * 2>;

inline std::array<float, 1> attributeValue(float v) {
    return {{ v }};
}

/*
 * Pack a pair of values, interpreted as uint8's, into a single float.
 * Used to conserve vertex attributes. Values are unpacked in the vertex
 * shader using the `unpack_float()` function, defined in _prelude.vertex.glsl.
 */
template <typename T>
inline uint16_t packUint8Pair(T a, T b) {
    return static_cast<uint16_t>(a) * 256 + static_cast<uint16_t>(b);
}

/*
    Encode a four-component color value into a pair of floats.  Since csscolorparser
    uses 8-bit precision for each color component, for each float we use the upper 8
    bits for one component (e.g. (color.r * 255) * 256), and the lower 8 for another.
    
    Also note that colors come in as floats 0..1, so we scale by 255.
*/
inline std::array<float, 2> attributeValue(const Color& color) {
    return {{
        static_cast<float>(packUint8Pair(255 * color.r, 255 * color.g)),
        static_cast<float>(packUint8Pair(255 * color.b, 255 * color.a))
    }};
}

template <size_t N>
std::array<float, N*2> zoomInterpolatedAttributeValue(const std::array<float, N>& min, const std::array<float, N>& max) {
    std::array<float, N*2> result;
    for (size_t i = 0; i < N; i++) {
        result[i]   = min[i];
        result[i+N] = max[i];
    }
    return result;
}

/*
   PaintPropertyBinder is an abstract class serving as the interface definition for
   the strategy used for constructing, uploading, and binding paint property data as
   GLSL attributes.

   It has three concrete subclasses, one for each of the three strategies we use:

   * For _constant_ properties -- those whose value is a constant, or the constant
     result of evaluating a camera function at a particular camera position -- we
     don't need a vertex buffer, and instead use a uniform.
   * For source functions, we use a vertex buffer with a single attribute value,
     the evaluated result of the source function for the given feature.
   * For composite functions, we use a vertex buffer with two attributes: min and
     max values covering the range of zooms at which we expect the tile to be
     displayed. These values are calculated by evaluating the composite function for
     the given feature at strategically chosen zoom levels. In addition to this
     attribute data, we also use a uniform value which the shader uses to interpolate
     between the min and max value at the final displayed zoom level. The use of a
     uniform allows us to cheaply update the value on every frame.

   Note that the shader source varies depending on whether we're using a uniform or
   attribute. Like GL JS, we dynamically compile shaders at runtime to accomodate this.
*/

template <class T, class UniformValueType, class PossiblyEvaluatedType, class... As>
class PaintPropertyBinder {
public:

    virtual ~PaintPropertyBinder() = default;

    virtual void populateVertexVector(const GeometryTileFeature& feature,
                                      std::size_t length, const ImagePositions&,
                                      const optional<PatternDependency>&,
                                      const style::expression::Value&) = 0;
    virtual void upload(gfx::UploadPass&) = 0;
    virtual void setPatternParameters(const optional<ImagePosition>&, const optional<ImagePosition>&, const CrossfadeParameters&) = 0;
    virtual std::tuple<ExpandToType<As, optional<gfx::AttributeBinding>>...> attributeBinding(const PossiblyEvaluatedType& currentValue) const = 0;
    virtual std::tuple<ExpandToType<As, float>...> interpolationFactor(float currentZoom) const = 0;
    virtual std::tuple<ExpandToType<As, UniformValueType>...> uniformValue(const PossiblyEvaluatedType& currentValue) const = 0;

    static std::unique_ptr<PaintPropertyBinder> create(const PossiblyEvaluatedType& value, float zoom, T defaultValue);

    PaintPropertyStatistics<T> statistics;
};

template <class T, class A>
class ConstantPaintPropertyBinder : public PaintPropertyBinder<T, T, PossiblyEvaluatedPropertyValue<T>, A> {
public:
    ConstantPaintPropertyBinder(T constant_)
        : constant(std::move(constant_)) {
    }

    void populateVertexVector(const GeometryTileFeature&, std::size_t, const ImagePositions&, const optional<PatternDependency>&, const style::expression::Value&) override {}
    void upload(gfx::UploadPass&) override {}
    void setPatternParameters(const optional<ImagePosition>&, const optional<ImagePosition>&, const CrossfadeParameters&) override {};

    std::tuple<optional<gfx::AttributeBinding>> attributeBinding(const PossiblyEvaluatedPropertyValue<T>&) const override {
        return {};
    }

    std::tuple<float> interpolationFactor(float) const override {
        return std::tuple<float> { 0.0f };
    }

    std::tuple<T> uniformValue(const PossiblyEvaluatedPropertyValue<T>& currentValue) const override {
        return std::tuple<T> { currentValue.constantOr(constant) };
    }

private:
    T constant;
};

template <class T, class... As>
class ConstantCrossFadedPaintPropertyBinder final : public PaintPropertyBinder<T, std::array<uint16_t, 4>,PossiblyEvaluatedPropertyValue<Faded<T>>, As...> {
public:
    ConstantCrossFadedPaintPropertyBinder(Faded<T> constant_)
        : constant(std::move(constant_)), constantPatternPositions({}) {
    }

    void populateVertexVector(const GeometryTileFeature&, std::size_t, const ImagePositions&, const optional<PatternDependency>&, const style::expression::Value&) override {}
    void upload(gfx::UploadPass&) override {}

    void setPatternParameters(const optional<ImagePosition>& posA, const optional<ImagePosition>& posB, const CrossfadeParameters&) override {
        if (!posA || !posB) {
            return;
        } else {
            constantPatternPositions = std::tuple<std::array<uint16_t, 4>, std::array<uint16_t, 4>> { posB->tlbr(), posA->tlbr() };
        }
    }

    std::tuple<optional<gfx::AttributeBinding>, optional<gfx::AttributeBinding>>
    attributeBinding(const PossiblyEvaluatedPropertyValue<Faded<T>>&) const override {
        return {};
    }

    std::tuple<float, float> interpolationFactor(float) const override {
        return std::tuple<float, float> { 0.0f, 0.0f };
    }

    std::tuple<std::array<uint16_t, 4>, std::array<uint16_t, 4>> uniformValue(const PossiblyEvaluatedPropertyValue<Faded<T>>&) const override {
        return constantPatternPositions;
    }

private:
    Faded<T> constant;
    std::tuple<std::array<uint16_t, 4>, std::array<uint16_t, 4>> constantPatternPositions;
};

template <class T, class A>
class SourceFunctionPaintPropertyBinder final : public PaintPropertyBinder<T, T, PossiblyEvaluatedPropertyValue<T>, A> {
public:
    using BaseAttributeType = A;
    using BaseVertex = gfx::VertexType<BaseAttributeType>;

    using AttributeType = ZoomInterpolatedAttributeType<A>;

    SourceFunctionPaintPropertyBinder(style::PropertyExpression<T> expression_, T defaultValue_)
        : expression(std::move(expression_)),
          defaultValue(std::move(defaultValue_)) {
    }
    void setPatternParameters(const optional<ImagePosition>&, const optional<ImagePosition>&, const CrossfadeParameters&) override {};
    void populateVertexVector(const GeometryTileFeature& feature, std::size_t length, const ImagePositions&, const optional<PatternDependency>&, const style::expression::Value& formattedSection) override {
        using style::expression::EvaluationContext;
        auto evaluated = expression.evaluate(EvaluationContext(&feature).withFormattedSection(&formattedSection), defaultValue);
        this->statistics.add(evaluated);
        auto value = attributeValue(evaluated);
        for (std::size_t i = vertexVector.elements(); i < length; ++i) {
            vertexVector.emplace_back(BaseVertex { value });
        }
    }

    void upload(gfx::UploadPass& uploadPass) override {
        vertexBuffer = uploadPass.createVertexBuffer(std::move(vertexVector));
    }

    std::tuple<optional<gfx::AttributeBinding>> attributeBinding(const PossiblyEvaluatedPropertyValue<T>& currentValue) const override {
        if (currentValue.isConstant()) {
            return {};
        } else {
            return std::tuple<optional<gfx::AttributeBinding>>{
                gfx::attributeBinding(*vertexBuffer)
            };
        }
    }

    std::tuple<float> interpolationFactor(float) const override {
        return std::tuple<float> { 0.0f };
    }

    std::tuple<T> uniformValue(const PossiblyEvaluatedPropertyValue<T>& currentValue) const override {
        if (currentValue.isConstant()) {
            return std::tuple<T>{ *currentValue.constant() };
        } else {
            // Uniform values for vertex attribute arrays are unused.
            return {};
        }
    }

private:
    style::PropertyExpression<T> expression;
    T defaultValue;
    gfx::VertexVector<BaseVertex> vertexVector;
    optional<gfx::VertexBuffer<BaseVertex>> vertexBuffer;
};

template <class T, class A>
class CompositeFunctionPaintPropertyBinder final : public PaintPropertyBinder<T, T, PossiblyEvaluatedPropertyValue<T>, A> {
public:

    using AttributeType = ZoomInterpolatedAttributeType<A>;
    using AttributeValue = typename AttributeType::Value;
    using Vertex = gfx::VertexType<AttributeType>;

    CompositeFunctionPaintPropertyBinder(style::PropertyExpression<T> expression_, float zoom, T defaultValue_)
        : expression(std::move(expression_)),
          defaultValue(std::move(defaultValue_)),
          zoomRange({zoom, zoom + 1}) {
    }
    void setPatternParameters(const optional<ImagePosition>&, const optional<ImagePosition>&, const CrossfadeParameters&) override {};
    void populateVertexVector(const GeometryTileFeature& feature, std::size_t length, const ImagePositions&, const optional<PatternDependency>&, const style::expression::Value& formattedSection) override {
        using style::expression::EvaluationContext;
        Range<T> range = {
                expression.evaluate(EvaluationContext(zoomRange.min, &feature).withFormattedSection(&formattedSection), defaultValue),
                expression.evaluate(EvaluationContext(zoomRange.max, &feature).withFormattedSection(&formattedSection), defaultValue),
        };
        this->statistics.add(range.min);
        this->statistics.add(range.max);
        AttributeValue value = zoomInterpolatedAttributeValue(
            attributeValue(range.min),
            attributeValue(range.max));
        for (std::size_t i = vertexVector.elements(); i < length; ++i) {
            vertexVector.emplace_back(Vertex { value });
        }
    }

    void upload(gfx::UploadPass& uploadPass) override {
        vertexBuffer = uploadPass.createVertexBuffer(std::move(vertexVector));
    }

    std::tuple<optional<gfx::AttributeBinding>> attributeBinding(const PossiblyEvaluatedPropertyValue<T>& currentValue) const override {
        if (currentValue.isConstant()) {
            return {};
        } else {
            return std::tuple<optional<gfx::AttributeBinding>>{
                gfx::attributeBinding(*vertexBuffer)
            };
        }
    }

    std::tuple<float> interpolationFactor(float currentZoom) const override {
        if (expression.useIntegerZoom) {
            return std::tuple<float> { expression.interpolationFactor(zoomRange, std::floor(currentZoom)) };
        } else {
            return std::tuple<float> { expression.interpolationFactor(zoomRange, currentZoom) };
        }
    }

    std::tuple<T> uniformValue(const PossiblyEvaluatedPropertyValue<T>& currentValue) const override {
        if (currentValue.isConstant()) {
            return std::tuple<T> { *currentValue.constant() };
        } else {
            // Uniform values for vertex attribute arrays are unused.
            return {};
        }
    }

private:
    style::PropertyExpression<T> expression;
    T defaultValue;
    Range<float> zoomRange;
    gfx::VertexVector<Vertex> vertexVector;
    optional<gfx::VertexBuffer<Vertex>> vertexBuffer;
};

template <class T, class A1, class A2>
class CompositeCrossFadedPaintPropertyBinder final : public PaintPropertyBinder<T, std::array<uint16_t, 4>, PossiblyEvaluatedPropertyValue<Faded<T>>, A1, A2> {
public:
    using AttributeType = ZoomInterpolatedAttributeType<A1>;
    using AttributeType2 = ZoomInterpolatedAttributeType<A2>;

    using BaseAttributeType = A1;
    using BaseAttributeType2 = A2;

    using Vertex = gfx::VertexType<BaseAttributeType>;
    using Vertex2 = gfx::VertexType<BaseAttributeType2>;

    CompositeCrossFadedPaintPropertyBinder(style::PropertyExpression<T> expression_, float zoom, T defaultValue_)
        : expression(std::move(expression_)),
          defaultValue(std::move(defaultValue_)),
          zoomRange({zoom, zoom + 1}) {
    }

    void setPatternParameters(const optional<ImagePosition>&, const optional<ImagePosition>&, const CrossfadeParameters& crossfade_) override {
        crossfade = crossfade_;
    };

    void populateVertexVector(const GeometryTileFeature&, std::size_t length, const ImagePositions& patternPositions, const optional<PatternDependency>& patternDependencies, const style::expression::Value&) override {
    
        if (patternDependencies->mid.empty())  {
            // Unlike other propperties with expressions that evaluate to null, the default value for `*-pattern` properties is an empty
            // string and will not have a valid entry in patternPositions. We still need to populate the attribute buffers to avoid crashes
            // when we try to draw the layer because we don't know at draw time if all features were evaluated to valid pattern dependencies.
            for (std::size_t i = zoomInVertexVector.elements(); i < length; ++i) {
                patternToVertexVector.emplace_back(Vertex { std::array<uint16_t, 4>{{0, 0, 0, 0}} });
                zoomInVertexVector.emplace_back(Vertex2 { std::array<uint16_t, 4>{{0, 0, 0, 0}} } );
                zoomOutVertexVector.emplace_back(Vertex2 { std::array<uint16_t, 4>{{0, 0, 0, 0}} });
            }
        } else if (!patternPositions.empty()) {
            const auto min = patternPositions.find(patternDependencies->min);
            const auto mid = patternPositions.find(patternDependencies->mid);
            const auto max = patternPositions.find(patternDependencies->max);

            const auto end = patternPositions.end();
            if (min == end || mid == end || max == end) return;

            const ImagePosition imageMin = min->second;
            const ImagePosition imageMid = mid->second;
            const ImagePosition imageMax = max->second;

            for (std::size_t i = zoomInVertexVector.elements(); i < length; ++i) {
                patternToVertexVector.emplace_back(Vertex { imageMid.tlbr() });
                zoomInVertexVector.emplace_back(Vertex2 { imageMin.tlbr() });
                zoomOutVertexVector.emplace_back(Vertex2 { imageMax.tlbr() });
            }
        }
    }

    void upload(gfx::UploadPass& uploadPass) override {
        patternToVertexBuffer = uploadPass.createVertexBuffer(std::move(patternToVertexVector));
        zoomInVertexBuffer = uploadPass.createVertexBuffer(std::move(zoomInVertexVector));
        zoomOutVertexBuffer = uploadPass.createVertexBuffer(std::move(zoomOutVertexVector));
    }

    std::tuple<optional<gfx::AttributeBinding>, optional<gfx::AttributeBinding>> attributeBinding(const PossiblyEvaluatedPropertyValue<Faded<T>>& currentValue) const override {
        if (currentValue.isConstant()) {
            return {};
        } else {
            return std::tuple<optional<gfx::AttributeBinding>, optional<gfx::AttributeBinding>>{
                gfx::attributeBinding(*patternToVertexBuffer),
                gfx::attributeBinding(crossfade.fromScale == 2 ? *zoomInVertexBuffer : *zoomOutVertexBuffer)
            };
        }
    }

    std::tuple<float, float> interpolationFactor(float) const override {
        return std::tuple<float, float> { 0.0f, 0.0f };
    }

    std::tuple<std::array<uint16_t, 4>, std::array<uint16_t, 4>>  uniformValue(const PossiblyEvaluatedPropertyValue<Faded<T>>& ) const override {
        // Uniform values for vertex attribute arrays are unused.
        return {};
    }

private:
    style::PropertyExpression<T> expression;
    T defaultValue;
    Range<float> zoomRange;
    gfx::VertexVector<Vertex> patternToVertexVector;
    gfx::VertexVector<Vertex2> zoomInVertexVector;
    gfx::VertexVector<Vertex2> zoomOutVertexVector;
    optional<gfx::VertexBuffer<Vertex>> patternToVertexBuffer;
    optional<gfx::VertexBuffer<Vertex2>> zoomInVertexBuffer;
    optional<gfx::VertexBuffer<Vertex2>> zoomOutVertexBuffer;
    CrossfadeParameters crossfade;
};

template <class T, class PossiblyEvaluatedType>
struct CreateBinder {
    template <class A>
    static std::unique_ptr<PaintPropertyBinder<T, T, PossiblyEvaluatedType, A>> create(const PossiblyEvaluatedType& value, float zoom, T defaultValue) {
        return value.match(
            [&] (const T& constant) -> std::unique_ptr<PaintPropertyBinder<T, T, PossiblyEvaluatedType, A>> {
                return std::make_unique<ConstantPaintPropertyBinder<T, A>>(constant);
            },
            [&] (const style::PropertyExpression<T>& expression) -> std::unique_ptr<PaintPropertyBinder<T, T, PossiblyEvaluatedType, A>>  {
                if (expression.isZoomConstant()) {
                    return std::make_unique<SourceFunctionPaintPropertyBinder<T, A>>(expression, defaultValue);
                } else {
                    return std::make_unique<CompositeFunctionPaintPropertyBinder<T, A>>(expression, zoom, defaultValue);
                }
            }
        );
    }
};

template <class T>
struct CreateBinder<T, PossiblyEvaluatedPropertyValue<Faded<T>>> {
    template <class A1, class A2>
    static std::unique_ptr<PaintPropertyBinder<T, std::array<uint16_t, 4>, PossiblyEvaluatedPropertyValue<Faded<T>>, A1, A2>> create(const PossiblyEvaluatedPropertyValue<Faded<T>>& value, float zoom, T defaultValue) {
        return value.match(
            [&] (const Faded<T>& constant) -> std::unique_ptr<PaintPropertyBinder<T, std::array<uint16_t, 4>, PossiblyEvaluatedPropertyValue<Faded<T>>, A1, A2>> {
                return std::make_unique<ConstantCrossFadedPaintPropertyBinder<T, A1, A2>>(constant);
            },
            [&] (const style::PropertyExpression<T>& expression) -> std::unique_ptr<PaintPropertyBinder<T, std::array<uint16_t, 4>, PossiblyEvaluatedPropertyValue<Faded<T>>, A1, A2>>  {
                return std::make_unique<CompositeCrossFadedPaintPropertyBinder<T, A1, A2>>(expression, zoom, defaultValue);
            }
        );
    }
};

template <class T, class UniformValueType, class PossiblyEvaluatedType, class... As>
std::unique_ptr<PaintPropertyBinder<T, UniformValueType, PossiblyEvaluatedType, As... >>
PaintPropertyBinder<T, UniformValueType, PossiblyEvaluatedType, As...>::create(const PossiblyEvaluatedType& value, float zoom, T defaultValue) {
    return CreateBinder<T, PossiblyEvaluatedType>::template create<As...>(value, zoom, defaultValue);
}

template <class Attr>
struct ZoomInterpolatedAttribute : public Attr {
    using Type = ZoomInterpolatedAttributeType<typename Attr::Type>;
};

template <class Attr>
struct InterpolationUniform {
    using Value = float;
    static constexpr auto name() {
        return concat_literals<&Attr::name, &string_literal<'_', 't'>::value>::value();
    }
};

template <class Ps>
class PaintPropertyBinders;

template <class... Ps>
class PaintPropertyBinders<TypeList<Ps...>> {
private:
    template <class T, class PossiblyEvaluatedType, class... As>
    struct Detail;

    template <class T, class UniformValueType, class PossiblyEvaluatedType, class... As>
    struct Detail<T, UniformValueType, PossiblyEvaluatedType, TypeList<As...>> {
        using Binder = PaintPropertyBinder<T, UniformValueType, PossiblyEvaluatedType, typename As::Type...>;
        using ZoomInterpolatedAttributeList = TypeList<ZoomInterpolatedAttribute<As>...>;
        using InterpolationUniformList = TypeList<InterpolationUniform<As>...>;
    };

    template <class P>
    using Property = Detail<typename P::Type, typename P::Uniform::Value, typename P::PossiblyEvaluatedType, typename P::AttributeList>;

public:
    template <class P>
    using Binder = typename Property<P>::Binder;

    using Binders = IndexedTuple<
        TypeList<Ps...>,
        TypeList<std::unique_ptr<Binder<Ps>>...>>;

    template <class EvaluatedProperties>
    PaintPropertyBinders(const EvaluatedProperties& properties, float z)
        : binders(Binder<Ps>::create(properties.template get<Ps>(), z, Ps::defaultValue())...) {
        (void)z; // Workaround for https://gcc.gnu.org/bugzilla/show_bug.cgi?id=56958
    }

    PaintPropertyBinders(PaintPropertyBinders&&) = default;
    PaintPropertyBinders(const PaintPropertyBinders&) = delete;

    void populateVertexVectors(const GeometryTileFeature& feature, std::size_t length, const ImagePositions& patternPositions, const optional<PatternDependency>& patternDependencies, const style::expression::Value& formattedSection = {}) {
        util::ignore({
            (binders.template get<Ps>()->populateVertexVector(feature, length, patternPositions, patternDependencies, formattedSection), 0)...
        });
    }

    void setPatternParameters(const optional<ImagePosition>& posA, const optional<ImagePosition>& posB, const CrossfadeParameters& crossfade) const {
        util::ignore({
            (binders.template get<Ps>()->setPatternParameters(posA, posB, crossfade), 0)...
        });
    }

    void upload(gfx::UploadPass& uploadPass) {
        util::ignore({
            (binders.template get<Ps>()->upload(uploadPass), 0)...
        });
    }

    template <class P>
    using ZoomInterpolatedAttributeList = typename Property<P>::ZoomInterpolatedAttributeList;
    template <class P>
    using InterpolationUniformList = typename Property<P>::InterpolationUniformList;

    using AttributeList = TypeListConcat<ZoomInterpolatedAttributeList<Ps>...>;
    using AttributeBindings = gfx::AttributeBindings<AttributeList>;

    template <class EvaluatedProperties>
    AttributeBindings attributeBindings(const EvaluatedProperties& currentProperties) const {
        return AttributeBindings { std::tuple_cat(
           binders.template get<Ps>()->attributeBinding(currentProperties.template get<Ps>())...
        ) };
    }

    using UniformList = TypeListConcat<InterpolationUniformList<Ps>..., typename Ps::UniformList...>;
    using UniformValues = gfx::UniformValues<UniformList>;

    template <class EvaluatedProperties>
    UniformValues uniformValues(float currentZoom, EvaluatedProperties& currentProperties) const {
        (void)currentZoom; // Workaround for https://gcc.gnu.org/bugzilla/show_bug.cgi?id=56958
        return UniformValues (
            std::tuple_cat(
                // interpolation uniform values
                binders.template get<Ps>()->interpolationFactor(currentZoom)...,
                // uniform values
                binders.template get<Ps>()->uniformValue(currentProperties.template get<Ps>())...)
        );
    }

    template <class P>
    const auto& statistics() const {
        return binders.template get<P>()->statistics;
    }

    using Bitset = std::bitset<sizeof...(Ps)>;

    template <class EvaluatedProperties>
    static Bitset constants(const EvaluatedProperties& currentProperties) {
        Bitset result;
        util::ignore({
            result.set(TypeIndex<Ps, Ps...>::value,
                       currentProperties.template get<Ps>().isConstant())...
        });
        return result;
    }

private:
    Binders binders;
};

} // namespace mbgl