[core] Coordinate wrapping fixes

- Make returning LatLngs unwrapped by default.
- PointAnnotation and ShapeAnnotation are always wrapped so they can be
  selected via intersection from the visible tile boundaries.
- Fixes LatLng::wrap() calculation.
- Fixes LatLng::unwrapForShortestPath() calculation.

The new unwrapForShortestPath algorithm unwraps the start coordinate
either forwards or backwards depending on the end coordinate value, so
we can always cross the antimeridian when needed and still obtain a
wrapped end coordinate in the end.

Fixes #4214.

3 files changed, 28 insertions, 18 deletions

diff --git a/include/mbgl/annotation/point_annotation.hpp b/include/mbgl/annotation/point_annotation.hpp
index e226673997..3dea9a3e3e 100644
--- a/include/mbgl/annotation/point_annotation.hpp
+++ b/include/mbgl/annotation/point_annotation.hpp
@@ -9,9 +9,8 @@ namespace mbgl {
 
 class PointAnnotation {
 public:
-    inline PointAnnotation(const LatLng& position_, const std::string& icon_ = "")
-        : position(position_), icon(icon_) {
-    }
+    PointAnnotation(const LatLng& position_, const std::string& icon_ = "")
+        : position(position_.wrapped()), icon(icon_) {}
 
     const LatLng position;
     const std::string icon;
diff --git a/include/mbgl/annotation/shape_annotation.hpp b/include/mbgl/annotation/shape_annotation.hpp
index fffa7dab6e..121cb7f1d7 100644
--- a/include/mbgl/annotation/shape_annotation.hpp
+++ b/include/mbgl/annotation/shape_annotation.hpp
@@ -33,11 +33,24 @@ public:
         std::string>; // creates an annotation whose type and properties are sourced from a style layer
 
     ShapeAnnotation(const AnnotationSegments& segments_, const Properties& properties_)
-        : segments(segments_), properties(properties_) {
-    }
+        : segments(wrapCoordinates(segments_)), properties(properties_) {}
 
     const AnnotationSegments segments;
     const Properties properties;
+
+private:
+    AnnotationSegments wrapCoordinates(const AnnotationSegments& segments_) {
+        AnnotationSegments wrappedSegments;
+        // Wrap all segments coordinates.
+        for (const auto& segment_ : segments_) {
+            AnnotationSegment wrappedSegment;
+            for (const auto& latLng_ : segment_) {
+                wrappedSegment.push_back(latLng_.wrapped());
+            }
+            wrappedSegments.push_back(wrappedSegment);
+        }
+        return wrappedSegments;
+    }
 };
 
 } // namespace mbgl
diff --git a/include/mbgl/util/geo.hpp b/include/mbgl/util/geo.hpp
index 56d575ceaa..9e2d7a2bb1 100644
--- a/include/mbgl/util/geo.hpp
+++ b/include/mbgl/util/geo.hpp
@@ -25,19 +25,17 @@ public:
     LatLng wrapped() const { return { latitude, longitude, Wrapped }; }
 
     void wrap() {
-        if (longitude < -util::LONGITUDE_MAX) longitude = std::fmod(longitude, util::LONGITUDE_MAX * 2);
-        if (longitude > util::LONGITUDE_MAX) longitude = -util::LONGITUDE_MAX + std::fmod(longitude, util::LONGITUDE_MAX);
-    }
-
-    /** If a path crossing the antemeridian would be shorter, extend the final
-      coordinate so that interpolating between the two endpoints will cross it. */
-    void unwrapForShortestPath(const LatLng& start) {
-        if (std::abs(start.longitude) + std::abs(longitude) > util::LONGITUDE_MAX) {
-            if (start.longitude > 0 && longitude < 0) {
-                longitude += util::DEGREES_MAX;
-            } else if (start.longitude < 0 && longitude > 0) {
-                longitude -= util::DEGREES_MAX;
-            }
+        if (longitude < -util::LONGITUDE_MAX) longitude = util::LONGITUDE_MAX + std::fmod(longitude + util::LONGITUDE_MAX, util::DEGREES_MAX);
+        if (longitude > util::LONGITUDE_MAX) longitude = -util::LONGITUDE_MAX + std::fmod(longitude + util::LONGITUDE_MAX, util::DEGREES_MAX);
+    }
+
+    // If we pass through the antimeridian, we update the start coordinate to make sure
+    // the end coordinate is always wrapped.
+    void unwrapForShortestPath(const LatLng& end) {
+        if (end.longitude < -util::LONGITUDE_MAX) {
+            longitude += util::DEGREES_MAX;
+        } else if (end.longitude > util::LONGITUDE_MAX) {
+            longitude -= util::DEGREES_MAX;
         }
     }