[core] Fix LatLngBounds default coordinates

LatLngBounds southwest and northeast coordinate points were inverted, so
they could be extended via LatLngBounds::extend(). However, this looks
confusing and error-prone.

A static LatLngBounds::getExtendable() is added to address cases when we
want to extend LatLngBounds.

include/mbgl/util/geo.hpp

@@ -41,12 +41,19 @@ struct ProjectedMeters {
 };
 
 struct LatLngBounds {
-    LatLng sw = {90, 180};
-    LatLng ne = {-90, -180};
+    LatLng sw = {-90, -180};
+    LatLng ne = {90, 180};
 
-    inline LatLngBounds(const LatLng& sw_ = {90, 180}, const LatLng& ne_ = {-90, -180})
+    inline LatLngBounds() {}
+
+    inline LatLngBounds(const LatLng& sw_, const LatLng& ne_)
         : sw(sw_), ne(ne_) {}
 
+    static inline LatLngBounds getExtendable() {
+        LatLngBounds bounds;
+        return { bounds.ne, bounds.sw };
+    }
+
     inline operator bool() const {
         return sw && ne;
     }

platform/android/jni.cpp

@@ -1186,9 +1186,7 @@ jlongArray JNICALL nativeGetAnnotationsInBounds(JNIEnv *env, jobject obj, jlong
         return nullptr;
     }
 
-    mbgl::LatLngBounds bounds;
-    bounds.sw = { swLat, swLon };
-    bounds.ne = { neLat, neLon };
+    mbgl::LatLngBounds bounds({ swLat, swLon }, { neLat, neLon });
 
     // assume only points for now
     std::vector<uint32_t> annotations = nativeMapView->getMap().getPointAnnotationsInBounds(bounds);

platform/ios/MGLMapView.mm

@@ -1099,7 +1099,7 @@ std::chrono::steady_clock::duration durationInSeconds(float duration)
 
         // figure out what that means in coordinate space
         CLLocationCoordinate2D coordinate;
-        mbgl::LatLngBounds tapBounds;
+        mbgl::LatLngBounds tapBounds = mbgl::LatLngBounds::getExtendable();
 
         coordinate = [self convertPoint:tapRectLowerLeft  toCoordinateFromView:self];
         tapBounds.extend(MGLLatLngFromLocationCoordinate2D(coordinate));
@@ -1997,7 +1997,7 @@ CLLocationCoordinate2D MGLLocationCoordinate2DFromLatLng(mbgl::LatLng latLng)
 
 - (mbgl::LatLngBounds)viewportBounds
 {
-    mbgl::LatLngBounds bounds;
+    mbgl::LatLngBounds bounds = mbgl::LatLngBounds::getExtendable();
 
     bounds.extend(MGLLatLngFromLocationCoordinate2D(
         [self convertPoint:CGPointMake(0, 0) toCoordinateFromView:self]));
@@ -2517,7 +2517,7 @@ CLLocationCoordinate2D MGLLocationCoordinate2DFromLatLng(mbgl::LatLng latLng)
 {
     if ( ! annotations || ! annotations.count) return;
 
-    mbgl::LatLngBounds bounds;
+    mbgl::LatLngBounds bounds = mbgl::LatLngBounds::getExtendable();
 
     for (id <MGLAnnotation> annotation in annotations)
     {

platform/ios/MGLMultiPoint.mm

@@ -19,6 +19,7 @@
     {
         _count = count;
         _coords = (CLLocationCoordinate2D *)malloc(_count * sizeof(CLLocationCoordinate2D));
+        _bounds = mbgl::LatLngBounds::getExtendable();
 
         for (NSUInteger i = 0; i < _count; i++)
         {

src/mbgl/annotation/annotation_manager.cpp

@@ -68,7 +68,7 @@ AnnotationIDs AnnotationManager::getPointAnnotationsInBounds(const LatLngBounds&
 }
 
 LatLngBounds AnnotationManager::getBoundsForAnnotations(const AnnotationIDs& ids) const {
-    LatLngBounds result;
+    LatLngBounds result = LatLngBounds::getExtendable();
 
     for (const auto& id : ids) {
         if (pointAnnotations.find(id) != pointAnnotations.end()) {

test/ios/MapViewTests.m

@@ -317,12 +317,14 @@ const NSTimeInterval MGLAnimationDurationOverDefault = MGLAnimationDurationDefau
 
     tester.mapView.centerCoordinate = newCenterCoordinate;
 
-    XCTAssertEqual(tester.mapView.centerCoordinate.latitude,
+    XCTAssertEqualWithAccuracy(tester.mapView.centerCoordinate.latitude,
                    newCenterCoordinate.latitude,
+                   0.001,
                    @"setting center should change latitude");
 
-    XCTAssertEqual(tester.mapView.centerCoordinate.longitude,
+    XCTAssertEqualWithAccuracy(tester.mapView.centerCoordinate.longitude,
                    newCenterCoordinate.longitude,
+                   0.001,
                    @"setting center should change longitude");
 }