[core] create GeoJSON tiles from inline GeoJSON in sources

1 files changed, 134 insertions, 0 deletions

diff --git a/src/mbgl/tile/geojson_tile.cpp b/src/mbgl/tile/geojson_tile.cpp
new file mode 100644
index 0000000000..9f14780ca4
--- /dev/null
+++ b/src/mbgl/tile/geojson_tile.cpp
@@ -0,0 +1,134 @@
+#include <mbgl/tile/geojson_tile.hpp>
+#include <mbgl/storage/file_source.hpp>
+#include <mapbox/geojsonvt.hpp>
+
+namespace mbgl {
+
+GeoJSONTileFeature::GeoJSONTileFeature(FeatureType type_,
+                                       GeometryCollection&& geometries_,
+                                       GeoJSONTileFeature::Tags&& tags_)
+    : type(type_), geometries(std::move(geometries_)), tags(std::move(tags_)) {
+}
+
+FeatureType GeoJSONTileFeature::getType() const {
+    return type;
+}
+
+mapbox::util::optional<Value> GeoJSONTileFeature::getValue(const std::string& key) const {
+    auto it = tags.find(key);
+    if (it != tags.end()) {
+        return mapbox::util::optional<Value>(it->second);
+    }
+    return mapbox::util::optional<Value>();
+}
+
+GeometryCollection GeoJSONTileFeature::getGeometries() const {
+    return geometries;
+}
+
+GeoJSONTileLayer::GeoJSONTileLayer(Features&& features_) : features(std::move(features_)) {
+}
+
+std::size_t GeoJSONTileLayer::featureCount() const {
+    return features.size();
+}
+
+util::ptr<const GeometryTileFeature> GeoJSONTileLayer::getFeature(std::size_t i) const {
+    return features[i];
+}
+
+GeoJSONTile::GeoJSONTile(std::shared_ptr<GeoJSONTileLayer> layer_) : layer(std::move(layer_)) {
+}
+
+util::ptr<GeometryTileLayer> GeoJSONTile::getLayer(const std::string&) const {
+    // We're ignoring the layer name because GeoJSON tiles only have one layer.
+    return layer;
+}
+
+// Converts the geojsonvt::Tile to a a GeoJSONTile. They have a differing internal structure.
+std::unique_ptr<GeoJSONTile> convertTile(const mapbox::geojsonvt::Tile& tile) {
+    std::shared_ptr<GeoJSONTileLayer> layer;
+
+    if (tile) {
+        std::vector<std::shared_ptr<const GeoJSONTileFeature>> features;
+        std::vector<Coordinate> line;
+
+        for (auto& feature : tile.features) {
+            const FeatureType featureType =
+                (feature.type == mapbox::geojsonvt::TileFeatureType::Point
+                     ? FeatureType::Point
+                     : (feature.type == mapbox::geojsonvt::TileFeatureType::LineString
+                            ? FeatureType::LineString
+                            : (feature.type == mapbox::geojsonvt::TileFeatureType::Polygon
+                                   ? FeatureType::Polygon
+                                   : FeatureType::Unknown)));
+            if (featureType == FeatureType::Unknown) {
+                continue;
+            }
+
+            GeometryCollection geometry;
+
+            // Flatten the geometry; GeoJSONVT distinguishes between a Points array and Rings array
+            // (Points = GeoJSON types Point, MultiPoint, LineString)
+            // (Rings = GeoJSON types MultiLineString, Polygon, MultiPolygon)
+            // However, in Mapbox GL, we use one structure for both types, and just have one outer
+            // element for Points.
+            if (feature.tileGeometry.is<mapbox::geojsonvt::TilePoints>()) {
+                line.clear();
+                for (auto& point : feature.tileGeometry.get<mapbox::geojsonvt::TilePoints>()) {
+                    line.emplace_back(point.x, point.y);
+                }
+                geometry.emplace_back(std::move(line));
+            } else if (feature.tileGeometry.is<mapbox::geojsonvt::TileRings>()) {
+                for (auto& ring : feature.tileGeometry.get<mapbox::geojsonvt::TileRings>()) {
+                    line.clear();
+                    for (auto& point : ring) {
+                        line.emplace_back(point.x, point.y);
+                    }
+                    geometry.emplace_back(std::move(line));
+                }
+            }
+
+            GeoJSONTileFeature::Tags tags{ feature.tags.begin(), feature.tags.end() };
+
+            features.emplace_back(std::make_shared<GeoJSONTileFeature>(
+                featureType, std::move(geometry), std::move(tags)));
+        }
+
+        layer = std::make_unique<GeoJSONTileLayer>(std::move(features));
+    }
+
+    return std::make_unique<GeoJSONTile>(layer);
+}
+
+GeoJSONTileMonitor::GeoJSONTileMonitor(mapbox::geojsonvt::GeoJSONVT* geojsonvt_, const TileID& id)
+    : tileID(id), geojsonvt(geojsonvt_) {
+}
+
+GeoJSONTileMonitor::~GeoJSONTileMonitor() = default;
+
+// A monitor can have its GeoJSONVT object swapped out (e.g. when loading a new GeoJSON file).
+// In that case, we're sending new notifications to all observers.
+void GeoJSONTileMonitor::setGeoJSONVT(mapbox::geojsonvt::GeoJSONVT* vt) {
+    // Don't duplicate notifications in case of nil changes.
+    if (geojsonvt != vt) {
+        geojsonvt = vt;
+        update();
+    }
+}
+
+void GeoJSONTileMonitor::update() {
+    if (geojsonvt) {
+        auto tile = convertTile(geojsonvt->getTile(tileID.z, tileID.x, tileID.y));
+        callback(nullptr, std::move(tile), Seconds::zero(), Seconds::zero());
+    }
+}
+
+std::unique_ptr<FileRequest>
+GeoJSONTileMonitor::monitorTile(const GeometryTileMonitor::Callback& cb) {
+    callback = cb;
+    update();
+    return nullptr;
+}
+
+} // namespace mbgl