Update qt conversion to use runtime polymorphic conversionupstream/runtime-polymorphic-conversion-node

6 files changed, 327 insertions, 290 deletions

diff --git a/platform/qt/qt.cmake b/platform/qt/qt.cmake
index 489ae5ed08..95bd2425c9 100644
--- a/platform/qt/qt.cmake
+++ b/platform/qt/qt.cmake
@@ -64,6 +64,10 @@ include_directories(
 add_library(qmapboxgl SHARED
     platform/qt/include/qmapbox.hpp
     platform/qt/include/qmapboxgl.hpp
+    platform/qt/src/qt_conversion.cpp
+    platform/qt/src/qt_conversion.hpp
+    platform/qt/src/qt_geojson.cpp
+    platform/qt/src/qt_geojson.hpp
     platform/qt/src/qmapbox.cpp
     platform/qt/src/qmapboxgl.cpp
     platform/qt/src/qmapboxgl_p.hpp
diff --git a/platform/qt/src/qmapboxgl.cpp b/platform/qt/src/qmapboxgl.cpp
index c7c4cf1e4a..5309142fa3 100644
--- a/platform/qt/src/qmapboxgl.cpp
+++ b/platform/qt/src/qmapboxgl.cpp
@@ -14,7 +14,17 @@
 #include <mbgl/style/conversion.hpp>
 #include <mbgl/style/conversion/layer.hpp>
 #include <mbgl/style/conversion/source.hpp>
+#include <mbgl/style/conversion/filter.hpp>
+#include <mbgl/style/conversion/geojson.hpp>
+#include <mbgl/style/filter.hpp>
 #include <mbgl/style/layers/custom_layer.hpp>
+#include <mbgl/style/layers/background_layer.hpp>
+#include <mbgl/style/layers/circle_layer.hpp>
+#include <mbgl/style/layers/fill_layer.hpp>
+#include <mbgl/style/layers/fill_extrusion_layer.hpp>
+#include <mbgl/style/layers/line_layer.hpp>
+#include <mbgl/style/layers/raster_layer.hpp>
+#include <mbgl/style/layers/symbol_layer.hpp>
 #include <mbgl/style/sources/geojson_source.hpp>
 #include <mbgl/style/transition_options.hpp>
 #include <mbgl/style/image.hpp>
diff --git a/platform/qt/src/qt_conversion.cpp b/platform/qt/src/qt_conversion.cpp
new file mode 100644
index 0000000000..35a6ef4fc9
--- /dev/null
+++ b/platform/qt/src/qt_conversion.cpp
@@ -0,0 +1,133 @@
+#include <mbgl/util/feature.hpp>
+#include <mbgl/style/conversion/geojson.hpp>
+#include <QColor>
+#include <QMapbox>
+#include "qt_geojson.hpp"
+
+namespace mbgl {
+namespace style {
+namespace conversion {
+
+template<> bool ValueTraits<QVariant>::isUndefined(const QVariant& value) {
+    return value.isNull() || !value.isValid();
+}
+
+template<> bool ValueTraits<QVariant>::isArray(const QVariant& value) {
+    return value.canConvert(QVariant::List);
+}
+
+template<> std::size_t ValueTraits<QVariant>::arrayLength(const QVariant& value) {
+    return value.toList().size();
+}
+
+template<> QVariant ValueTraits<QVariant>::arrayMember(const QVariant& value, std::size_t i) {
+    return value.toList()[i];
+}
+
+template<> bool ValueTraits<QVariant>::isObject(const QVariant& value) {
+    return value.canConvert(QVariant::Map)
+        || value.type() == QVariant::ByteArray
+#if QT_VERSION >= 0x050000
+        || QString(value.typeName()) == QStringLiteral("QMapbox::Feature");
+#else
+        || QString(value.typeName()) == QString("QMapbox::Feature");
+#endif
+}
+
+template<> optional<QVariant> ValueTraits<QVariant>::objectMember(const QVariant& value, const char* key) {
+    auto map = value.toMap();
+    auto iter = map.constFind(key);
+
+    if (iter != map.constEnd()) {
+        return iter.value();
+    } else {
+        return {};
+    }
+}
+
+using EachMemberFn = std::function<optional<Error>(const std::string&, const QVariant&)>;
+
+template<> optional<Error> ValueTraits<QVariant>::eachMember(const QVariant& value, const EachMemberFn& fn) {
+    auto map = value.toMap();
+    auto iter = map.constBegin();
+
+    while (iter != map.constEnd()) {
+        optional<Error> result = fn(iter.key().toStdString(), iter.value());
+        if (result) {
+            return result;
+        }
+
+        ++iter;
+    }
+
+    return {};
+}
+
+template<> optional<bool> ValueTraits<QVariant>::toBool(const QVariant& value) {
+    if (value.type() == QVariant::Bool) {
+        return value.toBool();
+    } else {
+        return {};
+    }
+}
+
+template<> optional<float> ValueTraits<QVariant>::toNumber(const QVariant& value) {
+    if (value.type() == QVariant::Int || value.type() == QVariant::Double) {
+        return value.toFloat();
+    } else {
+        return {};
+    }
+}
+template<> optional<double> ValueTraits<QVariant>::toDouble(const QVariant& value) {
+    if (value.type() == QVariant::Int || value.type() == QVariant::Double) {
+        return value.toDouble();
+    } else {
+        return {};
+    }
+}
+
+template<> optional<std::string> ValueTraits<QVariant>::toString(const QVariant& value) {
+    if (value.type() == QVariant::String) {
+        return value.toString().toStdString();
+    } else if (value.type() == QVariant::Color) {
+        return value.value<QColor>().name().toStdString();
+    } else {
+        return {};
+    }
+}
+
+template<> optional<mbgl::Value> ValueTraits<QVariant>::toValue(const QVariant& value) {
+    if (value.type() == QVariant::Bool) {
+        return { value.toBool() };
+    } else if (value.type() == QVariant::String) {
+        return { value.toString().toStdString() };
+    } else if (value.type() == QVariant::Color) {
+        return { value.value<QColor>().name().toStdString() };
+    } else if (value.type() == QVariant::Int) {
+        return { int64_t(value.toInt()) };
+    } else if (value.canConvert(QVariant::Double)) {
+        return { value.toDouble() };
+    } else {
+        return {};
+    }
+}
+
+template <> optional<GeoJSON> ValueTraits<QVariant>::toGeoJSON(const QVariant& value, Error& error) {
+#if QT_VERSION >= 0x050000
+    if (value.typeName() == QStringLiteral("QMapbox::Feature")) {
+#else
+    if (value.typeName() == QString("QMapbox::Feature")) {
+#endif
+        return GeoJSON { asMapboxGLFeature(value.value<QMapbox::Feature>()) };
+    } else if (value.type() != QVariant::ByteArray) {
+        error = { "JSON data must be in QByteArray" };
+        return {};
+    }
+
+    QByteArray data = value.toByteArray();
+    return parseGeoJSON(std::string(data.constData(), data.size()), error);
+}
+
+} // namespace conversion
+} // namespace style
+} // namespace mbgl
diff --git a/platform/qt/src/qt_conversion.hpp b/platform/qt/src/qt_conversion.hpp
index 40d7e5b928..bd830f8432 100644
--- a/platform/qt/src/qt_conversion.hpp
+++ b/platform/qt/src/qt_conversion.hpp
@@ -1,120 +1,16 @@
 #pragma once
 
 #include <mbgl/style/conversion.hpp>
-#include <mbgl/util/feature.hpp>
 #include <mbgl/util/optional.hpp>
-
-#include <QMapbox>
-
-#include <QColor>
 #include <QVariant>
 
 namespace mbgl {
 namespace style {
 namespace conversion {
 
-inline bool isUndefined(const QVariant& value) {
-    return value.isNull() || !value.isValid();
-}
-
-inline bool isArray(const QVariant& value) {
-    return value.canConvert(QVariant::List);
-}
-
-inline std::size_t arrayLength(const QVariant& value) {
-    return value.toList().size();
-}
-
-inline QVariant arrayMember(const QVariant& value, std::size_t i) {
-    return value.toList()[i];
-}
-
-inline bool isObject(const QVariant& value) {
-    return value.canConvert(QVariant::Map)
-        || value.type() == QVariant::ByteArray
-#if QT_VERSION >= 0x050000
-        || QString(value.typeName()) == QStringLiteral("QMapbox::Feature");
-#else
-        || QString(value.typeName()) == QString("QMapbox::Feature");
-#endif
-}
-
-inline optional<QVariant> objectMember(const QVariant& value, const char* key) {
-    auto map = value.toMap();
-    auto iter = map.constFind(key);
-
-    if (iter != map.constEnd()) {
-        return iter.value();
-    } else {
-        return {};
-    }
-}
-
-using EachMemberFn = std::function<optional<Error>(const std::string&, const QVariant&)>;
-
-optional<Error> eachMember(const QVariant& value, EachMemberFn&& fn) {
-    auto map = value.toMap();
-    auto iter = map.constBegin();
-
-    while (iter != map.constEnd()) {
-        optional<Error> result = fn(iter.key().toStdString(), iter.value());
-        if (result) {
-            return result;
-        }
-
-        ++iter;
-    }
-
-    return {};
-}
-
-inline optional<bool> toBool(const QVariant& value) {
-    if (value.type() == QVariant::Bool) {
-        return value.toBool();
-    } else {
-        return {};
-    }
-}
-
-inline optional<float> toNumber(const QVariant& value) {
-    if (value.type() == QVariant::Int || value.type() == QVariant::Double) {
-        return value.toFloat();
-    } else {
-        return {};
-    }
-}
-inline optional<double> toDouble(const QVariant& value) {
-    if (value.type() == QVariant::Int || value.type() == QVariant::Double) {
-        return value.toDouble();
-    } else {
-        return {};
-    }
-}
-
-inline optional<std::string> toString(const QVariant& value) {
-    if (value.type() == QVariant::String) {
-        return value.toString().toStdString();
-    } else if (value.type() == QVariant::Color) {
-        return value.value<QColor>().name().toStdString();
-    } else {
-        return {};
-    }
-}
-
-inline optional<Value> toValue(const QVariant& value) {
-    if (value.type() == QVariant::Bool) {
-        return { value.toBool() };
-    } else if (value.type() == QVariant::String) {
-        return { value.toString().toStdString() };
-    } else if (value.type() == QVariant::Color) {
-        return { value.value<QColor>().name().toStdString() };
-    } else if (value.type() == QVariant::Int) {
-        return { int64_t(value.toInt()) };
-    } else if (value.canConvert(QVariant::Double)) {
-        return { value.toDouble() };
-    } else {
-        return {};
-    }
+template <class T, class...Args>
+optional<T> convert(const QVariant& value, Error& error, Args&&...args) {
+    return convert<T>(Value(value), error, std::forward<Args>(args)...);
 }
 
 } // namespace conversion
diff --git a/platform/qt/src/qt_geojson.cpp b/platform/qt/src/qt_geojson.cpp
new file mode 100644
index 0000000000..80377de64d
--- /dev/null
+++ b/platform/qt/src/qt_geojson.cpp
@@ -0,0 +1,166 @@
+#include "qt_geojson.hpp"
+#include <mapbox/geojson.hpp>
+#include <mbgl/util/geometry.hpp>
+#include <mbgl/util/feature.hpp>
+
+namespace QMapbox {
+
+mbgl::Point<double> asMapboxGLPoint(const QMapbox::Coordinate &coordinate) {
+    return mbgl::Point<double> { coordinate.second, coordinate.first };
+}
+
+mbgl::MultiPoint<double> asMapboxGLMultiPoint(const QMapbox::Coordinates &multiPoint) {
+    mbgl::MultiPoint<double> mbglMultiPoint;
+    mbglMultiPoint.reserve(multiPoint.size());
+    for (const auto &point: multiPoint) {
+        mbglMultiPoint.emplace_back(asMapboxGLPoint(point));
+    }
+    return mbglMultiPoint;
+};
+
+mbgl::LineString<double> asMapboxGLLineString(const QMapbox::Coordinates &lineString) {
+    mbgl::LineString<double> mbglLineString;
+    mbglLineString.reserve(lineString.size());
+    for (const auto &coordinate : lineString) {
+        mbglLineString.emplace_back(asMapboxGLPoint(coordinate));
+    }
+    return mbglLineString;
+};
+
+mbgl::MultiLineString<double> asMapboxGLMultiLineString(const QMapbox::CoordinatesCollection &multiLineString) {
+    mbgl::MultiLineString<double> mbglMultiLineString;
+    mbglMultiLineString.reserve(multiLineString.size());
+    for (const auto &lineString : multiLineString) {
+        mbglMultiLineString.emplace_back(std::forward<mbgl::LineString<double>>(asMapboxGLLineString(lineString)));
+    }
+    return mbglMultiLineString;
+};
+
+mbgl::Polygon<double> asMapboxGLPolygon(const QMapbox::CoordinatesCollection &polygon) {
+    mbgl::Polygon<double> mbglPolygon;
+    mbglPolygon.reserve(polygon.size());
+    for (const auto &linearRing : polygon) {
+        mbgl::LinearRing<double> mbglLinearRing;
+        mbglLinearRing.reserve(linearRing.size());
+        for (const auto &coordinate: linearRing) {
+            mbglLinearRing.emplace_back(asMapboxGLPoint(coordinate));
+        }
+        mbglPolygon.emplace_back(std::move(mbglLinearRing));
+    }
+    return mbglPolygon;
+};
+
+mbgl::MultiPolygon<double> asMapboxGLMultiPolygon(const QMapbox::CoordinatesCollections &multiPolygon) {
+    mbgl::MultiPolygon<double> mbglMultiPolygon;
+    mbglMultiPolygon.reserve(multiPolygon.size());
+    for (const auto &polygon : multiPolygon) {
+        mbglMultiPolygon.emplace_back(std::forward<mbgl::Polygon<double>>(asMapboxGLPolygon(polygon)));
+    }
+    return mbglMultiPolygon;
+};
+
+mbgl::Value asMapboxGLPropertyValue(const QVariant &value) {
+    auto valueList = [](const QVariantList &list) {
+        std::vector<mbgl::Value> mbglList;
+        mbglList.reserve(list.size());
+        for (const auto& listValue : list) {
+            mbglList.emplace_back(asMapboxGLPropertyValue(listValue));
+        }
+        return mbglList;
+    };
+
+    auto valueMap = [](const QVariantMap &map) {
+        std::unordered_map<std::string, mbgl::Value> mbglMap;
+        mbglMap.reserve(map.size());
+        auto it = map.constBegin();
+        while (it != map.constEnd()) {
+            mbglMap.emplace(std::make_pair(it.key().toStdString(), asMapboxGLPropertyValue(it.value())));
+            ++it;
+        }
+        return mbglMap;
+    };
+
+    switch (value.type()) {
+#if QT_VERSION >= 0x050000
+    case QMetaType::UnknownType:
+#else
+    case QVariant::Invalid:
+#endif
+        return mbgl::NullValue {};
+    case QMetaType::Bool:
+        return { value.toBool() };
+    case QMetaType::ULongLong:
+        return { uint64_t(value.toULongLong()) };
+    case QMetaType::LongLong:
+        return { int64_t(value.toLongLong()) };
+    case QMetaType::Double:
+        return { value.toDouble() };
+    case QMetaType::QString:
+        return { value.toString().toStdString() };
+    case QMetaType::QVariantList:
+        return valueList(value.toList());
+    case QMetaType::QVariantMap:
+        return valueMap(value.toMap());
+    default:
+        qWarning() << "Unsupported feature property value:" << value;
+        return {};
+    }
+}
+
+mbgl::FeatureIdentifier asMapboxGLFeatureIdentifier(const QVariant &id) {
+    switch (id.type()) {
+#if QT_VERSION >= 0x050000
+    case QMetaType::UnknownType:
+#else
+    case QVariant::Invalid:
+#endif
+        return {};
+    case QMetaType::ULongLong:
+        return { uint64_t(id.toULongLong()) };
+    case QMetaType::LongLong:
+        return { int64_t(id.toLongLong()) };
+    case QMetaType::Double:
+        return { id.toDouble() };
+    case QMetaType::QString:
+        return { id.toString().toStdString() };
+    default:
+        qWarning() << "Unsupported feature identifier:" << id;
+        return {};
+    }
+}
+
+mbgl::Feature asMapboxGLFeature(const QMapbox::Feature &feature) {
+    mbgl::PropertyMap properties;
+    properties.reserve(feature.properties.size());
+    auto it = feature.properties.constBegin();
+    while (it != feature.properties.constEnd()) {
+        properties.emplace(std::make_pair(it.key().toStdString(), asMapboxGLPropertyValue(it.value())));
+    }
+
+    mbgl::FeatureIdentifier id = asMapboxGLFeatureIdentifier(feature.id);
+
+    if (feature.type == QMapbox::Feature::PointType) {
+        const QMapbox::Coordinates &points = feature.geometry.first().first();
+        if (points.size() == 1) {
+            return { asMapboxGLPoint(points.first()), std::move(properties), std::move(id) };
+        } else {
+            return { asMapboxGLMultiPoint(points), std::move(properties), std::move(id) };
+        }
+    } else if (feature.type == QMapbox::Feature::LineStringType) {
+        const QMapbox::CoordinatesCollection &lineStrings = feature.geometry.first();
+        if (lineStrings.size() == 1) {
+            return { asMapboxGLLineString(lineStrings.first()), std::move(properties), std::move(id) };
+        } else {
+            return { asMapboxGLMultiLineString(lineStrings), std::move(properties), std::move(id) };
+        }
+    } else { // PolygonType
+        const QMapbox::CoordinatesCollections &polygons = feature.geometry;
+        if (polygons.size() == 1) {
+            return { asMapboxGLPolygon(polygons.first()), std::move(properties), std::move(id) };
+        } else {
+            return { asMapboxGLMultiPolygon(polygons), std::move(properties), std::move(id) };
+        }
+    }
+};
+
+} // namespace QMapbox
diff --git a/platform/qt/src/qt_geojson.hpp b/platform/qt/src/qt_geojson.hpp
index a6958b7edc..a9c10272ab 100644
--- a/platform/qt/src/qt_geojson.hpp
+++ b/platform/qt/src/qt_geojson.hpp
@@ -1,7 +1,8 @@
 #pragma once
 
 #include <mapbox/geojson.hpp>
-#include <mbgl/style/conversion/geojson.hpp>
+#include <mbgl/util/geometry.hpp>
+#include <mbgl/util/feature.hpp>
 
 #include <QMapbox>
 
@@ -13,187 +14,14 @@
 
 namespace QMapbox {
 
-mbgl::Point<double> asMapboxGLPoint(const QMapbox::Coordinate &coordinate) {
-    return mbgl::Point<double> { coordinate.second, coordinate.first };
-}
-
-mbgl::MultiPoint<double> asMapboxGLMultiPoint(const QMapbox::Coordinates &multiPoint) {
-    mbgl::MultiPoint<double> mbglMultiPoint;
-    mbglMultiPoint.reserve(multiPoint.size());
-    for (const auto &point: multiPoint) {
-        mbglMultiPoint.emplace_back(asMapboxGLPoint(point));
-    }
-    return mbglMultiPoint;
-};
-
-mbgl::LineString<double> asMapboxGLLineString(const QMapbox::Coordinates &lineString) {
-    mbgl::LineString<double> mbglLineString;
-    mbglLineString.reserve(lineString.size());
-    for (const auto &coordinate : lineString) {
-        mbglLineString.emplace_back(asMapboxGLPoint(coordinate));
-    }
-    return mbglLineString;
-};
-
-mbgl::MultiLineString<double> asMapboxGLMultiLineString(const QMapbox::CoordinatesCollection &multiLineString) {
-    mbgl::MultiLineString<double> mbglMultiLineString;
-    mbglMultiLineString.reserve(multiLineString.size());
-    for (const auto &lineString : multiLineString) {
-        mbglMultiLineString.emplace_back(std::forward<mbgl::LineString<double>>(asMapboxGLLineString(lineString)));
-    }
-    return mbglMultiLineString;
-};
-
-mbgl::Polygon<double> asMapboxGLPolygon(const QMapbox::CoordinatesCollection &polygon) {
-    mbgl::Polygon<double> mbglPolygon;
-    mbglPolygon.reserve(polygon.size());
-    for (const auto &linearRing : polygon) {
-        mbgl::LinearRing<double> mbglLinearRing;
-        mbglLinearRing.reserve(linearRing.size());
-        for (const auto &coordinate: linearRing) {
-            mbglLinearRing.emplace_back(asMapboxGLPoint(coordinate));
-        }
-        mbglPolygon.emplace_back(std::move(mbglLinearRing));
-    }
-    return mbglPolygon;
-};
-
-mbgl::MultiPolygon<double> asMapboxGLMultiPolygon(const QMapbox::CoordinatesCollections &multiPolygon) {
-    mbgl::MultiPolygon<double> mbglMultiPolygon;
-    mbglMultiPolygon.reserve(multiPolygon.size());
-    for (const auto &polygon : multiPolygon) {
-        mbglMultiPolygon.emplace_back(std::forward<mbgl::Polygon<double>>(asMapboxGLPolygon(polygon)));
-    }
-    return mbglMultiPolygon;
-};
-
-mbgl::Value asMapboxGLPropertyValue(const QVariant &value) {
-    auto valueList = [](const QVariantList &list) {
-        std::vector<mbgl::Value> mbglList;
-        mbglList.reserve(list.size());
-        for (const auto& listValue : list) {
-            mbglList.emplace_back(asMapboxGLPropertyValue(listValue));
-        }
-        return mbglList;
-    };
-
-    auto valueMap = [](const QVariantMap &map) {
-        std::unordered_map<std::string, mbgl::Value> mbglMap;
-        mbglMap.reserve(map.size());
-        auto it = map.constBegin();
-        while (it != map.constEnd()) {
-            mbglMap.emplace(std::make_pair(it.key().toStdString(), asMapboxGLPropertyValue(it.value())));
-            ++it;
-        }
-        return mbglMap;
-    };
-
-    switch (value.type()) {
-#if QT_VERSION >= 0x050000
-    case QMetaType::UnknownType:
-#else
-    case QVariant::Invalid:
-#endif
-        return mbgl::NullValue {};
-    case QMetaType::Bool:
-        return { value.toBool() };
-    case QMetaType::ULongLong:
-        return { uint64_t(value.toULongLong()) };
-    case QMetaType::LongLong:
-        return { int64_t(value.toLongLong()) };
-    case QMetaType::Double:
-        return { value.toDouble() };
-    case QMetaType::QString:
-        return { value.toString().toStdString() };
-    case QMetaType::QVariantList:
-        return valueList(value.toList());
-    case QMetaType::QVariantMap:
-        return valueMap(value.toMap());
-    default:
-        qWarning() << "Unsupported feature property value:" << value;
-        return {};
-    }
-}
-
-mbgl::FeatureIdentifier asMapboxGLFeatureIdentifier(const QVariant &id) {
-    switch (id.type()) {
-#if QT_VERSION >= 0x050000
-    case QMetaType::UnknownType:
-#else
-    case QVariant::Invalid:
-#endif
-        return {};
-    case QMetaType::ULongLong:
-        return { uint64_t(id.toULongLong()) };
-    case QMetaType::LongLong:
-        return { int64_t(id.toLongLong()) };
-    case QMetaType::Double:
-        return { id.toDouble() };
-    case QMetaType::QString:
-        return { id.toString().toStdString() };
-    default:
-        qWarning() << "Unsupported feature identifier:" << id;
-        return {};
-    }
-}
-
-mbgl::Feature asMapboxGLFeature(const QMapbox::Feature &feature) {
-    mbgl::PropertyMap properties;
-    properties.reserve(feature.properties.size());
-    auto it = feature.properties.constBegin();
-    while (it != feature.properties.constEnd()) {
-        properties.emplace(std::make_pair(it.key().toStdString(), asMapboxGLPropertyValue(it.value())));
-    }
-
-    mbgl::FeatureIdentifier id = asMapboxGLFeatureIdentifier(feature.id);
-
-    if (feature.type == QMapbox::Feature::PointType) {
-        const QMapbox::Coordinates &points = feature.geometry.first().first();
-        if (points.size() == 1) {
-            return { asMapboxGLPoint(points.first()), std::move(properties), std::move(id) };
-        } else {
-            return { asMapboxGLMultiPoint(points), std::move(properties), std::move(id) };
-        }
-    } else if (feature.type == QMapbox::Feature::LineStringType) {
-        const QMapbox::CoordinatesCollection &lineStrings = feature.geometry.first();
-        if (lineStrings.size() == 1) {
-            return { asMapboxGLLineString(lineStrings.first()), std::move(properties), std::move(id) };
-        } else {
-            return { asMapboxGLMultiLineString(lineStrings), std::move(properties), std::move(id) };
-        }
-    } else { // PolygonType
-        const QMapbox::CoordinatesCollections &polygons = feature.geometry;
-        if (polygons.size() == 1) {
-            return { asMapboxGLPolygon(polygons.first()), std::move(properties), std::move(id) };
-        } else {
-            return { asMapboxGLMultiPolygon(polygons), std::move(properties), std::move(id) };
-        }
-    }
-};
+mbgl::Point<double> asMapboxGLPoint(const QMapbox::Coordinate &coordinate);
+mbgl::MultiPoint<double> asMapboxGLMultiPoint(const QMapbox::Coordinates &multiPoint);
+mbgl::LineString<double> asMapboxGLLineString(const QMapbox::Coordinates &lineString);
+mbgl::MultiLineString<double> asMapboxGLMultiLineString(const QMapbox::CoordinatesCollection &multiLineString);
+mbgl::Polygon<double> asMapboxGLPolygon(const QMapbox::CoordinatesCollection &polygon);
+mbgl::MultiPolygon<double> asMapboxGLMultiPolygon(const QMapbox::CoordinatesCollections &multiPolygon);
+mbgl::Value asMapboxGLPropertyValue(const QVariant &value);
+mbgl::FeatureIdentifier asMapboxGLFeatureIdentifier(const QVariant &id);
+mbgl::Feature asMapboxGLFeature(const QMapbox::Feature &feature);
 
 } // namespace QMapbox
-
-namespace mbgl {
-namespace style {
-namespace conversion {
-
-template <>
-optional<GeoJSON> Converter<GeoJSON>::operator()(const QVariant& value, Error& error) const {
-#if QT_VERSION >= 0x050000
-    if (value.typeName() == QStringLiteral("QMapbox::Feature")) {
-#else
-    if (value.typeName() == QString("QMapbox::Feature")) {
-#endif
-        return GeoJSON { asMapboxGLFeature(value.value<QMapbox::Feature>()) };
-    } else if (value.type() != QVariant::ByteArray) {
-        error = { "JSON data must be in QByteArray" };
-        return {};
-    }
-
-    QByteArray data = value.toByteArray();
-    return convert<GeoJSON>(std::string(data.constData(), data.size()), error);
-}
-
-} // namespace conversion
-} // namespace style
-} // namespace mbgl