[core] Improve LatLngBounds API

* Use "named constructors": empty, world, hull
* Make the two-argument constructor lenient (i.e., it is a hull operation)
* Add various accessors
* Enforce a single empty representation

2 files changed, 101 insertions, 25 deletions

diff --git a/test/map/transform.cpp b/test/map/transform.cpp
index 4a8b685564..8325e60ebf 100644
--- a/test/map/transform.cpp
+++ b/test/map/transform.cpp
@@ -142,18 +142,17 @@ TEST(Transform, PerspectiveProjection) {
 TEST(Transform, ConstrainHeightOnly) {
     MockView view;
     LatLng loc;
-    LatLngBounds bounds;
 
     Transform transform(view, ConstrainMode::HeightOnly);
     transform.resize({{ 1000, 1000 }});
     transform.setScale(1024);
 
-    transform.setLatLng(bounds.sw);
+    transform.setLatLng(LatLngBounds::world().southwest());
     loc = transform.getState().pointToLatLng({ 500, 500 });
     ASSERT_NEAR(-85.021422866378714, loc.latitude, 0.0001);
     ASSERT_NEAR(180, std::abs(loc.longitude), 0.0001);
 
-    transform.setLatLng(bounds.ne);
+    transform.setLatLng(LatLngBounds::world().northeast());
     loc = transform.getState().pointToLatLng({ 500, 500 });
     ASSERT_NEAR(85.021422866378742, loc.latitude, 0.0001);
     ASSERT_NEAR(180, std::abs(loc.longitude), 0.0001);
@@ -162,18 +161,17 @@ TEST(Transform, ConstrainHeightOnly) {
 TEST(Transform, ConstrainWidthAndHeight) {
     MockView view;
     LatLng loc;
-    LatLngBounds bounds;
 
     Transform transform(view, ConstrainMode::WidthAndHeight);
     transform.resize({{ 1000, 1000 }});
     transform.setScale(1024);
 
-    transform.setLatLng(bounds.sw);
+    transform.setLatLng(LatLngBounds::world().southwest());
     loc = transform.getState().pointToLatLng({ 500, 500 });
     ASSERT_NEAR(-85.021422866378714, loc.latitude, 0.0001);
     ASSERT_NEAR(-179.65667724609375, loc.longitude, 0.0001);
 
-    transform.setLatLng(bounds.ne);
+    transform.setLatLng(LatLngBounds::world().northeast());
     loc = transform.getState().pointToLatLng({ 500, 500 });
     ASSERT_NEAR(85.021422866378742, loc.latitude, 0.0001);
     ASSERT_NEAR(179.65667724609358, std::abs(loc.longitude), 0.0001);
diff --git a/test/util/geo.cpp b/test/util/geo.cpp
index 88f8bc496b..96335c5dba 100644
--- a/test/util/geo.cpp
+++ b/test/util/geo.cpp
@@ -5,7 +5,86 @@
 
 using namespace mbgl;
 
-TEST(Geo, LatLngFromTileID) {
+TEST(LatLngBounds, World) {
+    auto result = LatLngBounds::world();
+    ASSERT_DOUBLE_EQ(-90,  result.south());
+    ASSERT_DOUBLE_EQ( 90,  result.north());
+    ASSERT_DOUBLE_EQ(-180, result.west());
+    ASSERT_DOUBLE_EQ( 180, result.east());
+}
+
+TEST(LatLngBounds, Singleton) {
+    auto result = LatLngBounds::singleton({1, 2});
+    ASSERT_DOUBLE_EQ(1, result.south());
+    ASSERT_DOUBLE_EQ(1, result.north());
+    ASSERT_DOUBLE_EQ(2, result.west());
+    ASSERT_DOUBLE_EQ(2, result.east());
+}
+
+TEST(LatLngBounds, Hull) {
+    double s = 1, w = 2, n = 3, e = 4;
+
+    auto swne = LatLngBounds::hull({s, w}, {n, e});
+    ASSERT_DOUBLE_EQ(s, swne.south());
+    ASSERT_DOUBLE_EQ(n, swne.north());
+    ASSERT_DOUBLE_EQ(w, swne.west());
+    ASSERT_DOUBLE_EQ(e, swne.east());
+
+    auto nesw = LatLngBounds::hull({n, e}, {s, w});
+    ASSERT_DOUBLE_EQ(s, nesw.south());
+    ASSERT_DOUBLE_EQ(n, nesw.north());
+    ASSERT_DOUBLE_EQ(w, nesw.west());
+    ASSERT_DOUBLE_EQ(e, nesw.east());
+
+    auto senw = LatLngBounds::hull({s, e}, {n, w});
+    ASSERT_DOUBLE_EQ(s, senw.south());
+    ASSERT_DOUBLE_EQ(n, senw.north());
+    ASSERT_DOUBLE_EQ(w, senw.west());
+    ASSERT_DOUBLE_EQ(e, senw.east());
+
+    auto nwse = LatLngBounds::hull({n, w}, {s, e});
+    ASSERT_DOUBLE_EQ(s, nwse.south());
+    ASSERT_DOUBLE_EQ(n, nwse.north());
+    ASSERT_DOUBLE_EQ(w, nwse.west());
+    ASSERT_DOUBLE_EQ(e, nwse.east());
+}
+
+TEST(LatLngBounds, Empty) {
+    ASSERT_TRUE(LatLngBounds::empty().isEmpty());
+    ASSERT_FALSE(LatLngBounds::world().isEmpty());
+}
+
+TEST(LatLngBounds, Center) {
+    auto result = LatLngBounds::hull({1, 2}, {3, 4}).center();
+    ASSERT_DOUBLE_EQ(2, result.latitude);
+    ASSERT_DOUBLE_EQ(3, result.longitude);
+}
+
+TEST(LatLngBounds, Southwest) {
+    auto result = LatLngBounds::hull({1, 2}, {3, 4}).southwest();
+    ASSERT_DOUBLE_EQ(1, result.latitude);
+    ASSERT_DOUBLE_EQ(2, result.longitude);
+}
+
+TEST(LatLngBounds, Northeast) {
+    auto result = LatLngBounds::hull({1, 2}, {3, 4}).northeast();
+    ASSERT_DOUBLE_EQ(3, result.latitude);
+    ASSERT_DOUBLE_EQ(4, result.longitude);
+}
+
+TEST(LatLngBounds, Southeast) {
+    auto result = LatLngBounds::hull({1, 2}, {3, 4}).southeast();
+    ASSERT_DOUBLE_EQ(1, result.latitude);
+    ASSERT_DOUBLE_EQ(4, result.longitude);
+}
+
+TEST(LatLngBounds, Northwest) {
+    auto result = LatLngBounds::hull({1, 2}, {3, 4}).northwest();
+    ASSERT_DOUBLE_EQ(3, result.latitude);
+    ASSERT_DOUBLE_EQ(2, result.longitude);
+}
+
+TEST(LatLng, FromTileID) {
     for (int i = 0; i < 20; i++) {
         const LatLng ll{ TileID(i, 0, 0, 0) };
         ASSERT_DOUBLE_EQ(-180, ll.longitude);
@@ -25,37 +104,36 @@ TEST(Geo, LatLngFromTileID) {
     }
 }
 
-
-TEST(Geo, LatLngBoundsFromTileID) {
+TEST(LatLngBounds, FromTileID) {
     {
         const LatLngBounds bounds{ TileID(0, 0, 0, 0) };
-        ASSERT_DOUBLE_EQ(-180, bounds.sw.longitude);
-        ASSERT_DOUBLE_EQ(-85.051128779806604, bounds.sw.latitude);
-        ASSERT_DOUBLE_EQ(180, bounds.ne.longitude);
-        ASSERT_DOUBLE_EQ(85.051128779806604, bounds.ne.latitude);
+        ASSERT_DOUBLE_EQ(-180, bounds.west());
+        ASSERT_DOUBLE_EQ(-85.051128779806604, bounds.south());
+        ASSERT_DOUBLE_EQ(180, bounds.east());
+        ASSERT_DOUBLE_EQ(85.051128779806604, bounds.north());
     }
 
     {
         const LatLngBounds bounds{ TileID(1, 0, 1, 0) };
-        ASSERT_DOUBLE_EQ(-180, bounds.sw.longitude);
-        ASSERT_DOUBLE_EQ(-85.051128779806604, bounds.sw.latitude);
-        ASSERT_DOUBLE_EQ(0, bounds.ne.longitude);
-        ASSERT_DOUBLE_EQ(0, bounds.ne.latitude);
+        ASSERT_DOUBLE_EQ(-180, bounds.west());
+        ASSERT_DOUBLE_EQ(-85.051128779806604, bounds.south());
+        ASSERT_DOUBLE_EQ(0, bounds.east());
+        ASSERT_DOUBLE_EQ(0, bounds.north());
     }
 
     {
         const LatLngBounds bounds{ TileID(1, 1, 1, 0) };
-        ASSERT_DOUBLE_EQ(0, bounds.sw.longitude);
-        ASSERT_DOUBLE_EQ(-85.051128779806604, bounds.sw.latitude);
-        ASSERT_DOUBLE_EQ(180, bounds.ne.longitude);
-        ASSERT_DOUBLE_EQ(0, bounds.ne.latitude);
+        ASSERT_DOUBLE_EQ(0, bounds.west());
+        ASSERT_DOUBLE_EQ(-85.051128779806604, bounds.south());
+        ASSERT_DOUBLE_EQ(180, bounds.east());
+        ASSERT_DOUBLE_EQ(0, bounds.north());
     }
 
     {
         const LatLngBounds bounds{ TileID(1, 0, 0, 0) };
-        ASSERT_DOUBLE_EQ(-180, bounds.sw.longitude);
-        ASSERT_DOUBLE_EQ(0, bounds.sw.latitude);
-        ASSERT_DOUBLE_EQ(0, bounds.ne.longitude);
-        ASSERT_DOUBLE_EQ(85.051128779806604, bounds.ne.latitude);
+        ASSERT_DOUBLE_EQ(-180, bounds.west());
+        ASSERT_DOUBLE_EQ(0, bounds.south());
+        ASSERT_DOUBLE_EQ(0, bounds.east());
+        ASSERT_DOUBLE_EQ(85.051128779806604, bounds.north());
     }
 }