Consolidate definitions of earth circumference etc.

src/expire-tiles.cpp

@@ -28,11 +28,9 @@
 #include "options.hpp"
 #include "reprojection.hpp"
 #include "table.hpp"
+#include "tile.hpp"
 #include "wkb.hpp"
 
-#define EARTH_CIRCUMFERENCE 40075016.68
-#define HALF_EARTH_CIRCUMFERENCE (EARTH_CIRCUMFERENCE / 2)
-
 // How many tiles worth of space to leave either side of a changed feature
 static constexpr double const tile_expiry_leeway = 0.1;
 
@@ -98,8 +96,8 @@ geom::point_t expire_tiles::coords_to_tile(geom::point_t const &point)
 {
     auto const c = m_projection->target_to_tile(point);
 
-    return {m_map_width * (0.5 + c.x() / EARTH_CIRCUMFERENCE),
-            m_map_width * (0.5 - c.y() / EARTH_CIRCUMFERENCE)};
+    return {m_map_width * (0.5 + c.x() / tile_t::earth_circumference),
+            m_map_width * (0.5 - c.y() / tile_t::earth_circumference)};
 }
 
 void expire_tiles::from_point_list(geom::point_list_t const &list)
@@ -220,12 +218,13 @@ int expire_tiles::from_bbox(geom::box_t const &box)
 
     double const width = box.width();
     double const height = box.height();
-    if (width > HALF_EARTH_CIRCUMFERENCE + 1) {
+    if (width > tile_t::half_earth_circumference + 1) {
         /* Over half the planet's width within the bounding box - assume the
            box crosses the international date line and split it into two boxes */
-        int ret =
-            from_bbox({-HALF_EARTH_CIRCUMFERENCE, box.min_y(), box.min_x(), box.max_y()});
-        ret += from_bbox({box.max_x(), box.min_y(), HALF_EARTH_CIRCUMFERENCE, box.max_y()});
+        int ret = from_bbox({-tile_t::half_earth_circumference, box.min_y(),
+                             box.min_x(), box.max_y()});
+        ret += from_bbox({box.max_x(), box.min_y(),
+                          tile_t::half_earth_circumference, box.max_y()});
         return ret;
     }
 

src/tile.hpp

@@ -21,6 +21,10 @@
 class tile_t
 {
 public:
+    static constexpr double const earth_circumference = 40075016.68;
+    static constexpr double const half_earth_circumference =
+        earth_circumference / 2;
+
     /// Construct an invalid tile.
     tile_t() noexcept = default;
 
@@ -62,20 +66,32 @@ public:
     /// The width/height of the tile in web mercator (EPSG:3857) coordinates.
     double extent() const noexcept
     {
-        return (2 * extent_max) / static_cast<double>(1UL << m_zoom);
+        return earth_circumference / static_cast<double>(1UL << m_zoom);
     }
 
     /// Minimum X coordinate of this tile in web mercator (EPSG:3857) units.
-    double xmin() const noexcept { return -extent_max + m_x * extent(); }
+    double xmin() const noexcept
+    {
+        return -half_earth_circumference + m_x * extent();
+    }
 
     /// Maximum X coordinate of this tile in web mercator (EPSG:3857) units.
-    double xmax() const noexcept { return -extent_max + (m_x + 1) * extent(); }
+    double xmax() const noexcept
+    {
+        return -half_earth_circumference + (m_x + 1) * extent();
+    }
 
     /// Minimum Y coordinate of this tile in web mercator (EPSG:3857) units.
-    double ymin() const noexcept { return extent_max - (m_y + 1) * extent(); }
+    double ymin() const noexcept
+    {
+        return half_earth_circumference - (m_y + 1) * extent();
+    }
 
     /// Maximum Y coordinate of this tile in web mercator (EPSG:3857) units.
-    double ymax() const noexcept { return extent_max - m_y * extent(); }
+    double ymax() const noexcept
+    {
+        return half_earth_circumference - m_y * extent();
+    }
 
     /**
      * Convert a point from web mercator (EPSG:3857) coordinates to
@@ -140,7 +156,6 @@ public:
     static tile_t from_quadkey(uint64_t quadkey, uint32_t zoom) noexcept;
 
 private:
-    static constexpr double const extent_max = 20037508.342789244;
     static constexpr uint32_t const invalid_zoom =
         std::numeric_limits<uint32_t>::max();
     static constexpr uint32_t const max_zoom = 32;

tests/test-tile.cpp

@@ -11,8 +11,6 @@
 
 #include "tile.hpp"
 
-static constexpr double const world = 20037508.342789244;
-
 TEST_CASE("invalid tile", "[NoDB]")
 {
     tile_t const tile;
@@ -57,16 +55,16 @@ TEST_CASE("tile_t coordinates zoom=0", "[NoDB]")
 {
     tile_t const tile{0, 0, 0};
 
-    REQUIRE(tile.xmin() == Approx(-world));
-    REQUIRE(tile.ymin() == Approx(-world));
-    REQUIRE(tile.xmax() == Approx(world));
-    REQUIRE(tile.ymax() == Approx(world));
+    REQUIRE(tile.xmin() == Approx(-tile_t::half_earth_circumference));
+    REQUIRE(tile.ymin() == Approx(-tile_t::half_earth_circumference));
+    REQUIRE(tile.xmax() == Approx(tile_t::half_earth_circumference));
+    REQUIRE(tile.ymax() == Approx(tile_t::half_earth_circumference));
 
     REQUIRE(tile.center().x() == Approx(0.0));
     REQUIRE(tile.center().y() == Approx(0.0));
     REQUIRE(tile.center() == geom::point_t{0.0, 0.0});
 
-    REQUIRE(tile.extent() == Approx(world * 2));
+    REQUIRE(tile.extent() == Approx(tile_t::earth_circumference));
 
     geom::point_t const p{12345.6, 7891.0};
     auto const tp = tile.to_tile_coords(p, 256);
@@ -81,17 +79,18 @@ TEST_CASE("tile_t coordinates zoom=2", "[NoDB]")
 {
     tile_t const tile{2, 1, 2};
 
-    REQUIRE(tile.xmin() == Approx(-world / 2));
-    REQUIRE(tile.ymin() == Approx(-world / 2));
+    REQUIRE(tile.xmin() == Approx(-tile_t::half_earth_circumference / 2));
+    REQUIRE(tile.ymin() == Approx(-tile_t::half_earth_circumference / 2));
     REQUIRE(tile.xmax() == Approx(0.0));
     REQUIRE(tile.ymax() == Approx(0.0));
 
-    REQUIRE(tile.center().x() == Approx(-world / 4));
-    REQUIRE(tile.center().y() == Approx(-world / 4));
+    REQUIRE(tile.center().x() == Approx(-tile_t::half_earth_circumference / 4));
+    REQUIRE(tile.center().y() == Approx(-tile_t::half_earth_circumference / 4));
 
-    REQUIRE(tile.extent() == Approx(world / 2));
+    REQUIRE(tile.extent() == Approx(tile_t::half_earth_circumference / 2));
 
-    geom::point_t const p{-world / 4, -world / 8};
+    geom::point_t const p{-tile_t::half_earth_circumference / 4,
+                          -tile_t::half_earth_circumference / 8};
     auto const tp = tile.to_tile_coords(p, 4096);
     REQUIRE(tp.x() == Approx(2048));
     REQUIRE(tp.y() == Approx(2048 + 1024));