[core] Force getGeometries() return const ref

6 files changed, 24 insertions, 18 deletions

diff --git a/src/mbgl/tile/geojson_tile_data.hpp b/src/mbgl/tile/geojson_tile_data.hpp
index 3605af9690..21a65144d9 100644
--- a/src/mbgl/tile/geojson_tile_data.hpp
+++ b/src/mbgl/tile/geojson_tile_data.hpp
@@ -25,15 +25,17 @@ public:
         return feature.id;
     }
 
-    GeometryCollection getGeometries() const override {
-        GeometryCollection geometry = apply_visitor(ToGeometryCollection(), feature.geometry);
-
-        // https://github.com/mapbox/geojson-vt-cpp/issues/44
-        if (getType() == FeatureType::Polygon) {
-            geometry = fixupPolygons(geometry);
+    const GeometryCollection& getGeometries() const override {
+        if (!geometry) {
+            geometry = apply_visitor(ToGeometryCollection(), feature.geometry);
+
+            // https://github.com/mapbox/geojson-vt-cpp/issues/44
+            if (getType() == FeatureType::Polygon) {
+                geometry = fixupPolygons(*geometry);
+            }
         }
 
-        return geometry;
+        return *geometry;
     }
 
     optional<Value> getValue(const std::string& key) const override {
@@ -43,6 +45,8 @@ public:
         }
         return optional<Value>();
     }
+
+    mutable optional<GeometryCollection> geometry;
 };
 
 class GeoJSONTileLayer : public GeometryTileLayer {
diff --git a/src/mbgl/tile/geometry_tile.cpp b/src/mbgl/tile/geometry_tile.cpp
index 7f1bed49f4..a431ae423e 100644
--- a/src/mbgl/tile/geometry_tile.cpp
+++ b/src/mbgl/tile/geometry_tile.cpp
@@ -360,7 +360,7 @@ void GeometryTile::querySourceFeatures(
                     continue;
                 }
 
-                result.push_back(convertFeature(*feature, id.canonical));
+                result.emplace_back(convertFeature(*feature, id.canonical));
             }
         }
     }
diff --git a/src/mbgl/tile/geometry_tile_data.cpp b/src/mbgl/tile/geometry_tile_data.cpp
index 680f8d1497..2dda9ecae4 100644
--- a/src/mbgl/tile/geometry_tile_data.cpp
+++ b/src/mbgl/tile/geometry_tile_data.cpp
@@ -112,7 +112,7 @@ static Feature::geometry_type convertGeometry(const GeometryTileFeature& geometr
         );
     };
 
-    GeometryCollection geometries = geometryTileFeature.getGeometries();
+    const GeometryCollection& geometries = geometryTileFeature.getGeometries();
 
     switch (geometryTileFeature.getType()) {
         case FeatureType::Unknown: {
diff --git a/src/mbgl/tile/geometry_tile_data.hpp b/src/mbgl/tile/geometry_tile_data.hpp
index 6ce67a532e..db3378a019 100644
--- a/src/mbgl/tile/geometry_tile_data.hpp
+++ b/src/mbgl/tile/geometry_tile_data.hpp
@@ -44,7 +44,7 @@ public:
     virtual optional<Value> getValue(const std::string& key) const = 0;
     virtual PropertyMap getProperties() const { return PropertyMap(); }
     virtual FeatureIdentifier getID() const { return NullValue {}; }
-    virtual GeometryCollection getGeometries() const = 0;
+    virtual const GeometryCollection& getGeometries() const = 0;
 };
 
 class GeometryTileLayer {
diff --git a/src/mbgl/tile/vector_tile_data.cpp b/src/mbgl/tile/vector_tile_data.cpp
index 2d47515e0f..926e596080 100644
--- a/src/mbgl/tile/vector_tile_data.cpp
+++ b/src/mbgl/tile/vector_tile_data.cpp
@@ -34,14 +34,15 @@ FeatureIdentifier VectorTileFeature::getID() const {
     return feature.getID();
 }
 
-GeometryCollection VectorTileFeature::getGeometries() const {
-    const float scale = float(util::EXTENT) / feature.getExtent();
-    auto lines = feature.getGeometries<GeometryCollection>(scale);
-    if (feature.getVersion() >= 2 || feature.getType() != mapbox::vector_tile::GeomType::POLYGON) {
-        return lines;
-    } else {
-        return fixupPolygons(lines);
+const GeometryCollection& VectorTileFeature::getGeometries() const {
+    if (!lines) {
+        const float scale = float(util::EXTENT) / feature.getExtent();
+        lines = feature.getGeometries<GeometryCollection>(scale);
+        if (feature.getVersion() < 2 && feature.getType() == mapbox::vector_tile::GeomType::POLYGON) {
+            lines = fixupPolygons(*lines);
+        }
     }
+    return *lines;
 }
 
 VectorTileLayer::VectorTileLayer(std::shared_ptr<const std::string> data_,
diff --git a/src/mbgl/tile/vector_tile_data.hpp b/src/mbgl/tile/vector_tile_data.hpp
index 7c95121a37..525c7935e4 100644
--- a/src/mbgl/tile/vector_tile_data.hpp
+++ b/src/mbgl/tile/vector_tile_data.hpp
@@ -17,10 +17,11 @@ public:
     optional<Value> getValue(const std::string& key) const override;
     std::unordered_map<std::string, Value> getProperties() const override;
     FeatureIdentifier getID() const override;
-    GeometryCollection getGeometries() const override;
+    const GeometryCollection& getGeometries() const override;
 
 private:
     mapbox::vector_tile::feature feature;
+    mutable optional<GeometryCollection> lines;
 };
 
 class VectorTileLayer : public GeometryTileLayer {