Copy antimeridian-crossing geometries to the other side too

read_json.cpp

@@ -290,17 +290,45 @@ std::vector<mvt_layer> parse_layers(FILE *fp, int z, unsigned x, unsigned y, int
 		// so move it to the other side.
 
 		if (fix_longitudes) {
+			const long long quarter_world = 1LL << 30;
+			const long long world = 1LL << 32;
+
+			bool copy_to_left = false;
+			bool copy_to_right = false;
+
 			for (size_t i = 0; i < dv.size(); i++) {
+				// is this vertex on a different side of the world
+				// than the first vertex? then shift this one to match
 				if (i > 0) {
-					if ((dv[0].x < (1LL << 30)) &&
-					    (dv[i].x > 3 * (1LL << 30))) {
-						dv[i].x -= 1LL << 32;
+					if ((dv[0].x < quarter_world) && (dv[i].x > 3 * quarter_world)) {
+						dv[i].x -= world;
 					}
-					if ((dv[0].x > 3 * (1LL << 30)) &&
-					    (dv[i].x < (1LL << 30))) {
-						dv[i].x += 1LL << 32;
+					if ((dv[0].x > 3 * quarter_world) && (dv[i].x < quarter_world)) {
+						dv[i].x += world;
 					}
 				}
+
+				// does it stick off the edge of the world?
+				// then we need another copy on the other side of the world
+				if (dv[i].x < 0) {
+					copy_to_right = true;
+				}
+				if (dv[i].x > world) {
+					copy_to_left = true;
+				}
+			}
+
+			if (copy_to_left) {
+				size_t n = dv.size();
+				for (size_t i = 0; i < n; i++) {
+					dv.emplace_back(dv[i].op, dv[i].x - world, (long long) dv[i].y);
+				}
+			}
+			if (copy_to_right) {
+				size_t n = dv.size();
+				for (size_t i = 0; i < n; i++) {
+					dv.emplace_back(dv[i].op, dv[i].x + world, (long long) dv[i].y);
+				}
 			}
 		}
 
@@ -319,8 +347,9 @@ std::vector<mvt_layer> parse_layers(FILE *fp, int z, unsigned x, unsigned y, int
 		}
 
 		if (mb_geometry[t] == VT_POLYGON) {
-			// we can try scaling up because these are tile coordinates
-			dv = clean_or_clip_poly(dv, 0, 0, false, true);
+			// don't try scaling up because we may have coordinates
+			// on the other side of the world
+			dv = clean_or_clip_poly(dv, z, 256, true, false);
 			if (dv.size() < 3) {
 				dv.clear();
 			}