Fix area calculation for polygon rings in tippecanoe-decode

decode.cpp

@@ -33,11 +33,15 @@ struct lonlat {
 	int op;
 	double lon;
 	double lat;
+	int x;
+	int y;
 
-	lonlat(int nop, double nlon, double nlat) {
+	lonlat(int nop, double nlon, double nlat, int nx, int ny) {
 		this->op = nop;
 		this->lon = nlon;
 		this->lat = nlat;
+		this->x = nx;
+		this->y = ny;
 	}
 };
 
@@ -156,9 +160,9 @@ void handle(std::string message, int z, unsigned x, unsigned y, int describe) {
 					double lat, lon;
 					tile2latlon(wx, wy, 32, &lat, &lon);
 
-					ops.push_back(lonlat(op, lon, lat));
+					ops.push_back(lonlat(op, lon, lat, px, py));
 				} else {
-					ops.push_back(lonlat(op, 0, 0));
+					ops.push_back(lonlat(op, 0, 0, 0, 0));
 				}
 			}
 
@@ -223,23 +227,27 @@ void handle(std::string message, int z, unsigned x, unsigned y, int describe) {
 
 					int n = rings.size() - 1;
 					if (n >= 0) {
-						rings[n].push_back(ops[i]);
+						if (ops[i].op == VT_CLOSEPATH) {
+							rings[n].push_back(rings[n][0]);
+						} else {
+							rings[n].push_back(ops[i]);
+						}
 					}
 				}
 
 				int outer = 0;
 
 				for (size_t i = 0; i < rings.size(); i++) {
-					double area = 0;
+					long double area = 0;
 					for (size_t k = 0; k < rings[i].size(); k++) {
 						if (rings[i][k].op != VT_CLOSEPATH) {
-							area += rings[i][k].lon * rings[i][(k + 1) % rings[i].size()].lat;
-							area -= rings[i][k].lat * rings[i][(k + 1) % rings[i].size()].lon;
+							area += rings[i][k].x * rings[i][(k + 1) % rings[i].size()].y;
+							area -= rings[i][k].y * rings[i][(k + 1) % rings[i].size()].x;
 						}
 					}
 
 					areas[i] = area;
-					if (areas[i] <= 0 || i == 0) {
+					if (areas[i] >= 0 || i == 0) {
 						outer++;
 					}
 
@@ -254,7 +262,7 @@ void handle(std::string message, int z, unsigned x, unsigned y, int describe) {
 
 				int state = 0;
 				for (size_t i = 0; i < rings.size(); i++) {
-					if (areas[i] <= 0) {
+					if (areas[i] >= 0) {
 						if (state != 0) {
 							// new multipolygon
 							printf(" ] ], [ [ ");

tests/dateline/out/-z5.json

@@ -12,7 +12,7 @@
 }, "features": [
 { "type": "FeatureCollection", "properties": { "zoom": 0, "x": 0, "y": 0 }, "features": [
 { "type": "FeatureCollection", "properties": { "layer": "in" }, "features": [
-{ "type": "Feature", "properties": { "boolean": true, "otherboolean": false, "stringify": "[\"yes\",27.00000000,27,1.4e27,{\"foo\":\"bar\"}]", "escape": "foo\u0001bar,ü\"\\/\u0008\u000c\u000a\u000d\u0009→", "prêt": "ready" }, "geometry": { "type": "Polygon", "coordinates": [ [ [ -177.539062, 44.339565 ], [ -164.882812, 43.389082 ], [ -153.281250, 46.619261 ], [ -144.492188, 51.179343 ], [ -143.789062, 57.183902 ], [ -148.007812, 61.100789 ], [ -158.554688, 63.860036 ], [ -169.453125, 64.510643 ], [ -177.890625, 62.593341 ], [ -180.000000, 61.689872 ], [ -185.976562, 58.859224 ], [ -187.031250, 56.992883 ], [ -187.031250, 65.730626 ], [ -182.460938, 67.339861 ], [ -180.000000, 67.542167 ], [ -169.101562, 68.269387 ], [ -156.093750, 68.138852 ], [ -144.492188, 66.089364 ], [ -134.648438, 62.431074 ], [ -131.835938, 55.379110 ], [ -133.593750, 48.690960 ], [ -146.250000, 38.616870 ], [ -169.453125, 34.957995 ], [ -180.000000, 36.527295 ], [ -184.218750, 37.160317 ], [ -187.031250, 38.891033 ], [ -187.031250, 50.457504 ], [ -185.976562, 47.279229 ], [ -177.539062, 44.339565 ] ], [ [ 187.031250, 35.460670 ], [ 175.781250, 37.160317 ], [ 161.718750, 45.336702 ], [ 156.796875, 55.028022 ], [ 163.476562, 62.431074 ], [ 170.507812, 64.811557 ], [ 177.539062, 67.339861 ], [ 180.000000, 67.542167 ], [ 187.031250, 68.007571 ], [ 187.031250, 63.743631 ], [ 182.109375, 62.593341 ], [ 180.000000, 61.689872 ], [ 174.023438, 58.859224 ], [ 171.562500, 54.418930 ], [ 174.023438, 47.279229 ], [ 182.460938, 44.339565 ], [ 187.031250, 44.024422 ], [ 187.031250, 35.460670 ] ] ] } }
+{ "type": "Feature", "properties": { "boolean": true, "otherboolean": false, "stringify": "[\"yes\",27.00000000,27,1.4e27,{\"foo\":\"bar\"}]", "escape": "foo\u0001bar,ü\"\\/\u0008\u000c\u000a\u000d\u0009→", "prêt": "ready" }, "geometry": { "type": "MultiPolygon", "coordinates": [ [ [ [ -177.539062, 44.339565 ], [ -164.882812, 43.389082 ], [ -153.281250, 46.619261 ], [ -144.492188, 51.179343 ], [ -143.789062, 57.183902 ], [ -148.007812, 61.100789 ], [ -158.554688, 63.860036 ], [ -169.453125, 64.510643 ], [ -177.890625, 62.593341 ], [ -180.000000, 61.689872 ], [ -185.976562, 58.859224 ], [ -187.031250, 56.992883 ], [ -187.031250, 65.730626 ], [ -182.460938, 67.339861 ], [ -180.000000, 67.542167 ], [ -169.101562, 68.269387 ], [ -156.093750, 68.138852 ], [ -144.492188, 66.089364 ], [ -134.648438, 62.431074 ], [ -131.835938, 55.379110 ], [ -133.593750, 48.690960 ], [ -146.250000, 38.616870 ], [ -169.453125, 34.957995 ], [ -180.000000, 36.527295 ], [ -184.218750, 37.160317 ], [ -187.031250, 38.891033 ], [ -187.031250, 50.457504 ], [ -185.976562, 47.279229 ], [ -177.539062, 44.339565 ] ] ], [ [ [ 187.031250, 35.460670 ], [ 175.781250, 37.160317 ], [ 161.718750, 45.336702 ], [ 156.796875, 55.028022 ], [ 163.476562, 62.431074 ], [ 170.507812, 64.811557 ], [ 177.539062, 67.339861 ], [ 180.000000, 67.542167 ], [ 187.031250, 68.007571 ], [ 187.031250, 63.743631 ], [ 182.109375, 62.593341 ], [ 180.000000, 61.689872 ], [ 174.023438, 58.859224 ], [ 171.562500, 54.418930 ], [ 174.023438, 47.279229 ], [ 182.460938, 44.339565 ], [ 187.031250, 44.024422 ], [ 187.031250, 35.460670 ] ] ] ] } }
 ,
 { "type": "Feature", "properties": { "zoom": "z0-2" }, "geometry": { "type": "LineString", "coordinates": [ [ -112.851562, 55.178868 ], [ -117.773438, 44.590467 ], [ -104.414062, 51.179343 ] ] } }
 ] }