Fix "strategies" accounting for 0-length linestrings and degenerate polygons (#137)

* Dropping a 0-length feature doesn't count as dropping-as-needed * Add an option not to reduce tiny polygons to dust at maxzoom * Add test for prevention of tiny polygon reduction at maxzoom * Fix accounting for tiny polygons not to include degenerate geometries * Revert "Add test for prevention of tiny polygon reduction at maxzoom" This reverts commit f931bbd73e. * Revert "Add an option not to reduce tiny polygons to dust at maxzoom" This reverts commit 03f0882bb6. * Fix tests * Another test that no longer has any really tiny polygons * Oops, that broke LineString simplification * This time for sure! * Update changelog and version
2026-10-02 08:25:40 +02:00 · 2023-08-29 10:54:39 -07:00
parent 6778aeac52
commit 2ec6180003
42 changed files with 56 additions and 49 deletions
@@ -1,3 +1,7 @@
+# 2.30.1
+
+* Fix spurious reports of tiny polygons and 0-length LineStrings in "strategies"
+
 # 2.30.0

 * Add --extend-zooms-if-still-dropping-maximum option
@@ -186,14 +186,15 @@ void check_polygon(drawvec &geom) {
 	}
 }

-drawvec reduce_tiny_poly(drawvec &geom, int z, int detail, bool *reduced, double *accum_area, serial_feature *this_feature, serial_feature *tiny_feature) {
+drawvec reduce_tiny_poly(drawvec &geom, int z, int detail, bool *still_needs_simplification, bool *reduced_away, double *accum_area, serial_feature *this_feature, serial_feature *tiny_feature) {
 	drawvec out;
 	const double pixel = (1LL << (32 - detail - z)) * (double) tiny_polygon_size;
 	bool includes_real = false;
 	bool includes_dust = false;

-	*reduced = true;
 	bool included_last_outer = false;
+	*still_needs_simplification = false;
+	*reduced_away = false;

 	for (size_t i = 0; i < geom.size(); i++) {
 		if (geom[i].op == VT_MOVETO) {
@@ -223,9 +224,9 @@ drawvec reduce_tiny_poly(drawvec &geom, int z, int detail, bool *reduced, double
 				// cut out of, so we are just subtracting its area from the tiny polygon
 				// rather than trying to deal with it geometrically
 				if ((area > 0 && area <= pixel * pixel) || (area < 0 && !included_last_outer)) {
-					// printf("area is only %f vs %lld so using square\n", area, pixel * pixel);
-
 					*accum_area += area;
+					*reduced_away = true;
+
 					if (area > 0 && *accum_area > pixel * pixel) {
 						// XXX use centroid;

@@ -248,21 +249,23 @@ drawvec reduce_tiny_poly(drawvec &geom, int z, int detail, bool *reduced, double
 				// as a real geometry because otherwise we can accumulate enough tiny holes
 				// that we will drop the next several outer rings getting back up to 0.
 				else {
-					// printf("area is %f so keeping instead of %lld\n", area, pixel * pixel);
-
 					for (size_t k = i; k < j && k < geom.size(); k++) {
 						out.push_back(geom[k]);
 					}

 					// which means that the overall polygon has a real geometry,
 					// which means that it gets to be simplified.
-					*reduced = false;
+					*still_needs_simplification = true;
 					includes_real = true;

 					if (area > 0) {
 						included_last_outer = true;
 					}
 				}
+			} else {
+				// area is 0: doesn't count as either having been reduced away,
+				// since it was probably just degenerate from having been clipped,
+				// or as needing simplification, since it produces no output.
 			}

 			i = j - 1;
@@ -68,7 +68,7 @@ drawvec clip_point(drawvec &geom, int z, long long buffer);
 drawvec clean_or_clip_poly(drawvec &geom, int z, int buffer, bool clip);
 drawvec simple_clip_poly(drawvec &geom, int z, int buffer);
 drawvec close_poly(drawvec &geom);
-drawvec reduce_tiny_poly(drawvec &geom, int z, int detail, bool *reduced, double *accum_area, serial_feature *this_feature, serial_feature *tiny_feature);
+drawvec reduce_tiny_poly(drawvec &geom, int z, int detail, bool *still_needs_simplification, bool *reduced_away, double *accum_area, serial_feature *this_feature, serial_feature *tiny_feature);
 int clip(double *x0, double *y0, double *x1, double *y1, double xmin, double ymin, double xmax, double ymax);
 drawvec clip_lines(drawvec &geom, int z, long long buffer);
 drawvec stairstep(drawvec &geom, int z, int detail);
@@ -8,7 +8,6 @@
 "maxzoom": "9",
 "minzoom": "8",
 "name": "tests/allow-existing/both.mbtiles",
-"strategies": "[{},{},{},{},{},{},{},{},{\"tiny_polygons\":1},{}]",
 "type": "overlay",
 "version": "2"
 }, "features": [
@@ -9,6 +9,7 @@
 "maxzoom": "1",
 "minzoom": "0",
 "name": "tests/border/out/-z1_--detect-shared-borders.json.check.mbtiles",
+"strategies": "[{\"tiny_polygons\":1},{\"tiny_polygons\":1}]",
 "type": "overlay",
 "version": "2"
 }, "features": [
@@ -9,7 +9,6 @@
 "maxzoom": "1",
 "minzoom": "0",
 "name": "tests/coalesce-id/out/-z1_--coalesce_--reorder.json.check.mbtiles",
-"strategies": "[{},{\"tiny_polygons\":2}]",
 "type": "overlay",
 "version": "2"
 }, "features": [
@@ -9,7 +9,6 @@
 "maxzoom": "11",
 "minzoom": "11",
 "name": "tests/coalesce-tract/out/-P_--coalesce_--reorder_-z11_-Z11_-y_STATEFP10_-y_COUNTYFP10_-l_merged.json.check.mbtiles",
-"strategies": "[{},{},{},{},{},{},{},{},{},{},{},{\"tiny_polygons\":5}]",
 "type": "overlay",
 "version": "2"
 }, "features": [
@@ -9,7 +9,6 @@
 "maxzoom": "2",
 "minzoom": "0",
 "name": "tests/curve/out/-z2.json.check.mbtiles",
-"strategies": "[{},{\"tiny_polygons\":1},{\"tiny_polygons\":4}]",
 "type": "overlay",
 "version": "2"
 }, "features": [
@@ -9,7 +9,6 @@
 "maxzoom": "2",
 "minzoom": "0",
 "name": "tests/curve/out/-z2_--no-clipping.json.check.mbtiles",
-"strategies": "[{},{\"tiny_polygons\":1},{\"tiny_polygons\":10}]",
 "type": "overlay",
 "version": "2"
 }, "features": [
@@ -9,7 +9,6 @@
 "maxzoom": "2",
 "minzoom": "0",
 "name": "tests/curve/out/-z2_--no-duplication.json.check.mbtiles",
-"strategies": "[{},{\"tiny_polygons\":6},{\"tiny_polygons\":6}]",
 "type": "overlay",
 "version": "2"
 }, "features": [
@@ -9,7 +9,6 @@
 "maxzoom": "5",
 "minzoom": "0",
 "name": "tests/dateline/out/-z5.json.check.mbtiles",
-"strategies": "[{},{},{},{\"tiny_polygons\":1},{},{\"tiny_polygons\":1}]",
 "type": "overlay",
 "version": "2"
 }, "features": [
@@ -9,7 +9,6 @@
 "maxzoom": "5",
 "minzoom": "0",
 "name": "tests/dateline/out/-z5_-b0.json.check.mbtiles",
-"strategies": "[{},{},{},{\"tiny_polygons\":1},{},{}]",
 "type": "overlay",
 "version": "2"
 }, "features": [
@@ -9,6 +9,7 @@
 "maxzoom": "0",
 "minzoom": "0",
 "name": "tests/named/out/-z0_-Lalgeria%3atests%2fnamed%2falg_-Lalbania%3atests%2fnamed%2falb.json.check.mbtiles",
+"strategies": "[{\"tiny_polygons\":1}]",
 "type": "overlay",
 "version": "2"
 }, "features": [
@@ -9,6 +9,7 @@
 "maxzoom": "0",
 "minzoom": "0",
 "name": "tests/named/out/-z0_-Lalgeria%3atests%2fnamed%2falg_-Lalbania%3atests%2fnamed%2falb_-lunified.json.check.mbtiles",
+"strategies": "[{\"tiny_polygons\":1}]",
 "type": "overlay",
 "version": "2"
 }, "features": [
@@ -9,7 +9,6 @@
 "maxzoom": "5",
 "minzoom": "5",
 "name": "tests/ne_110m_admin_0_countries/out/-R5%2f17%2f11.json.check.mbtiles",
-"strategies": "[{},{},{},{},{},{\"tiny_polygons\":1}]",
 "type": "overlay",
 "version": "2"
 }, "features": [
@@ -9,7 +9,7 @@
 "maxzoom": "5",
 "minzoom": "0",
 "name": "tests/ne_110m_admin_0_countries/out/-ae_-zg_-M5000_--drop-densest-as-needed.json.check.mbtiles",
-"strategies": "[{\"dropped_as_needed\":171,\"tile_size_desired\":39209},{\"dropped_as_needed\":189,\"tiny_polygons\":1,\"tile_size_desired\":25164},{\"dropped_as_needed\":161,\"tiny_polygons\":2,\"tile_size_desired\":21198},{\"dropped_as_needed\":134,\"tiny_polygons\":12,\"tile_size_desired\":10761},{\"dropped_as_needed\":62,\"tiny_polygons\":20,\"tile_size_desired\":6604},{\"tiny_polygons\":47}]",
+"strategies": "[{\"dropped_as_needed\":171,\"tile_size_desired\":39209},{\"dropped_as_needed\":189,\"tile_size_desired\":25164},{\"dropped_as_needed\":161,\"tile_size_desired\":21198},{\"dropped_as_needed\":134,\"tile_size_desired\":10761},{\"dropped_as_needed\":62,\"tile_size_desired\":6604},{\"tiny_polygons\":2}]",
 "type": "overlay",
 "version": "2"
 }, "features": [
@@ -9,7 +9,7 @@
 "maxzoom": "5",
 "minzoom": "0",
 "name": "tests/ne_110m_admin_0_countries/out/-ae_-zg_-M5000_--drop-fraction-as-needed.json.check.mbtiles",
-"strategies": "[{\"dropped_as_needed\":160,\"tile_size_desired\":39209},{\"dropped_as_needed\":188,\"tile_size_desired\":25164},{\"dropped_as_needed\":190,\"tiny_polygons\":2,\"tile_size_desired\":21198},{\"dropped_as_needed\":180,\"tiny_polygons\":9,\"tile_size_desired\":10761},{\"dropped_as_needed\":145,\"tiny_polygons\":17,\"tile_size_desired\":6604},{\"tiny_polygons\":47}]",
+"strategies": "[{\"dropped_as_needed\":160,\"tile_size_desired\":39209},{\"dropped_as_needed\":188,\"tile_size_desired\":25164},{\"dropped_as_needed\":190,\"tile_size_desired\":21198},{\"dropped_as_needed\":180,\"tile_size_desired\":10761},{\"dropped_as_needed\":145,\"tile_size_desired\":6604},{\"tiny_polygons\":2}]",
 "type": "overlay",
 "version": "2"
 }, "features": [
@@ -9,7 +9,7 @@
 "maxzoom": "5",
 "minzoom": "0",
 "name": "tests/ne_110m_admin_0_countries/out/-ae_-zg_-M5000_--drop-smallest-as-needed.json.check.mbtiles",
-"strategies": "[{\"dropped_as_needed\":174,\"tile_size_desired\":39209},{\"dropped_as_needed\":202,\"tile_size_desired\":25164},{\"dropped_as_needed\":190,\"tiny_polygons\":2,\"tile_size_desired\":21198},{\"dropped_as_needed\":156,\"tiny_polygons\":12,\"tile_size_desired\":10761},{\"dropped_as_needed\":80,\"tiny_polygons\":20,\"tile_size_desired\":6604},{\"tiny_polygons\":47}]",
+"strategies": "[{\"dropped_as_needed\":174,\"tile_size_desired\":39209},{\"dropped_as_needed\":202,\"tile_size_desired\":25164},{\"dropped_as_needed\":190,\"tile_size_desired\":21198},{\"dropped_as_needed\":156,\"tile_size_desired\":10761},{\"dropped_as_needed\":80,\"tile_size_desired\":6604},{\"tiny_polygons\":2}]",
 "type": "overlay",
 "version": "2"
 }, "features": [
@@ -9,7 +9,7 @@
 "maxzoom": "5",
 "minzoom": "0",
 "name": "tests/ne_110m_admin_0_countries/out/-ae_-zg_-M5000_--force-feature-limit.json.check.mbtiles",
-"strategies": "[{\"dropped_as_needed\":316,\"tile_size_desired\":39209},{\"dropped_as_needed\":287,\"tiny_polygons\":4,\"tile_size_desired\":25164},{\"dropped_as_needed\":223,\"tiny_polygons\":4,\"tile_size_desired\":21198},{\"dropped_as_needed\":93,\"tiny_polygons\":14,\"tile_size_desired\":10761},{\"dropped_as_needed\":9,\"tiny_polygons\":21,\"tile_size_desired\":6604},{\"tiny_polygons\":47}]",
+"strategies": "[{\"dropped_as_needed\":316,\"tile_size_desired\":39209},{\"dropped_as_needed\":287,\"tiny_polygons\":3,\"tile_size_desired\":25164},{\"dropped_as_needed\":223,\"tiny_polygons\":2,\"tile_size_desired\":21198},{\"dropped_as_needed\":93,\"tile_size_desired\":10761},{\"dropped_as_needed\":9,\"tile_size_desired\":6604},{\"tiny_polygons\":2}]",
 "type": "overlay",
 "version": "2"
 }, "features": [
@@ -9,7 +9,7 @@
 "maxzoom": "0",
 "minzoom": "0",
 "name": "tests/ne_110m_admin_0_countries/out/-z0_--tiny-polygon-size_100.json.check.mbtiles",
-"strategies": "[{\"tiny_polygons\":138}]",
+"strategies": "[{\"tiny_polygons\":150}]",
 "type": "overlay",
 "version": "2"
 }, "features": [
@@ -9,7 +9,7 @@
 "maxzoom": "0",
 "minzoom": "0",
 "name": "tests/ne_110m_admin_0_countries/out/-z0_--tiny-polygon-size_50_--order-largest-first.json.check.mbtiles",
-"strategies": "[{\"tiny_polygons\":90}]",
+"strategies": "[{\"tiny_polygons\":109}]",
 "type": "overlay",
 "version": "2"
 }, "features": [
@@ -9,7 +9,7 @@
 "maxzoom": "0",
 "minzoom": "0",
 "name": "tests/ne_110m_admin_0_countries/out/-z0_--tiny-polygon-size_50_--simplification_50.json.check.mbtiles",
-"strategies": "[{\"tiny_polygons\":90}]",
+"strategies": "[{\"tiny_polygons\":109}]",
 "type": "overlay",
 "version": "2"
 }, "features": [
@@ -9,7 +9,7 @@
 "maxzoom": "2",
 "minzoom": "0",
 "name": "tests/ne_110m_admin_0_countries/out/-z2_--convert-polygons-to-label-points.json.check.mbtiles",
-"strategies": "[{},{\"tiny_polygons\":2},{\"tiny_polygons\":3}]",
+"strategies": "[{},{},{\"tiny_polygons\":1}]",
 "type": "overlay",
 "version": "2"
 }, "features": [
@@ -9,7 +9,7 @@
 "maxzoom": "3",
 "minzoom": "0",
 "name": "tests/ne_110m_admin_0_countries/out/-z3_-ai.json.check.mbtiles",
-"strategies": "[{},{\"tiny_polygons\":2},{\"tiny_polygons\":3},{\"tiny_polygons\":12}]",
+"strategies": "[{},{},{\"tiny_polygons\":1},{}]",
 "type": "overlay",
 "version": "2"
 }, "features": [
@@ -9,7 +9,7 @@
 "maxzoom": "4",
 "minzoom": "0",
 "name": "tests/ne_110m_admin_0_countries/out/-z4_-yname.json.check.mbtiles",
-"strategies": "[{},{\"tiny_polygons\":2},{\"tiny_polygons\":3},{\"tiny_polygons\":12},{\"tiny_polygons\":20}]",
+"strategies": "[{},{\"tiny_polygons\":1},{\"tiny_polygons\":1},{},{}]",
 "type": "overlay",
 "version": "2"
 }, "features": [
@@ -9,7 +9,7 @@
 "maxzoom": "4",
 "minzoom": "0",
 "name": "tests/ne_110m_admin_0_countries/out/-z4_-yname_--drop-polygons.json.check.mbtiles",
-"strategies": "[{\"dropped_by_rate\":172},{\"dropped_by_rate\":205,\"tiny_polygons\":1},{\"dropped_by_rate\":189},{\"dropped_by_rate\":166,\"tiny_polygons\":7},{\"tiny_polygons\":20}]",
+"strategies": "[{\"dropped_by_rate\":172},{\"dropped_by_rate\":205},{\"dropped_by_rate\":189},{\"dropped_by_rate\":166},{}]",
 "type": "overlay",
 "version": "2"
 }, "features": [
@@ -9,7 +9,7 @@
 "maxzoom": "4",
 "minzoom": "0",
 "name": "tests/ne_110m_admin_0_countries/out/-z4_-yname_-S4.json.check.mbtiles",
-"strategies": "[{},{\"tiny_polygons\":2},{\"tiny_polygons\":3},{\"tiny_polygons\":12},{\"tiny_polygons\":20}]",
+"strategies": "[{},{\"tiny_polygons\":1},{\"tiny_polygons\":1},{},{}]",
 "type": "overlay",
 "version": "2"
 }, "features": [
@@ -9,7 +9,7 @@
 "maxzoom": "4",
 "minzoom": "0",
 "name": "tests/ne_110m_admin_0_countries/out/-z4_-yname_-S4_--simplification-at-maximum-zoom_2.json.check.mbtiles",
-"strategies": "[{},{\"tiny_polygons\":2},{\"tiny_polygons\":3},{\"tiny_polygons\":12},{\"tiny_polygons\":20}]",
+"strategies": "[{},{\"tiny_polygons\":1},{\"tiny_polygons\":1},{},{}]",
 "type": "overlay",
 "version": "2"
 }, "features": [
@@ -9,7 +9,7 @@
 "maxzoom": "4",
 "minzoom": "0",
 "name": "tests/ne_110m_admin_0_countries/out/-z4_-yname_-S4_--visvalingam.json.check.mbtiles",
-"strategies": "[{},{\"tiny_polygons\":2},{\"tiny_polygons\":3},{\"tiny_polygons\":12},{\"tiny_polygons\":20}]",
+"strategies": "[{},{\"tiny_polygons\":1},{\"tiny_polygons\":1},{},{}]",
 "type": "overlay",
 "version": "2"
 }, "features": [
@@ -9,7 +9,6 @@
 "maxzoom": "4",
 "minzoom": "0",
 "name": "tests/ne_110m_admin_0_countries/out/-z4_-yname_-pD.json.check.mbtiles",
-"strategies": "[{},{\"tiny_polygons\":45},{\"tiny_polygons\":29},{\"tiny_polygons\":70},{\"tiny_polygons\":120}]",
 "type": "overlay",
 "version": "2"
 }, "features": [
@@ -9,7 +9,6 @@
 "maxzoom": "4",
 "minzoom": "0",
 "name": "tests/ne_110m_admin_0_countries/out/-z4_-yname_-pc.json.check.mbtiles",
-"strategies": "[{},{\"tiny_polygons\":1},{\"tiny_polygons\":8},{\"tiny_polygons\":32},{\"tiny_polygons\":63}]",
 "type": "overlay",
 "version": "2"
 }, "features": [
@@ -9,7 +9,7 @@
 "maxzoom": "5",
 "minzoom": "0",
 "name": "tests/ne_110m_admin_0_countries/out/-z5_-M5000_--coalesce-densest-as-needed.json.check.mbtiles",
-"strategies": "[{\"coalesced_as_needed\":528,\"detail_reduced\":2,\"tile_size_desired\":39204},{\"coalesced_as_needed\":212,\"tile_size_desired\":25156},{\"coalesced_as_needed\":192,\"tiny_polygons\":3,\"tile_size_desired\":21207},{\"coalesced_as_needed\":156,\"tiny_polygons\":11,\"tile_size_desired\":10753},{\"coalesced_as_needed\":65,\"tiny_polygons\":20,\"tile_size_desired\":6588},{\"tiny_polygons\":46}]",
+"strategies": "[{\"coalesced_as_needed\":528,\"detail_reduced\":2,\"tiny_polygons\":2,\"tile_size_desired\":39204},{\"coalesced_as_needed\":212,\"tile_size_desired\":25156},{\"coalesced_as_needed\":192,\"tiny_polygons\":1,\"tile_size_desired\":21207},{\"coalesced_as_needed\":156,\"tile_size_desired\":10753},{\"coalesced_as_needed\":65,\"tile_size_desired\":6588},{\"tiny_polygons\":1}]",
 "type": "overlay",
 "version": "2"
 }, "features": [
@@ -9,7 +9,7 @@
 "maxzoom": "5",
 "minzoom": "0",
 "name": "tests/ne_110m_admin_0_countries/out/-z5_-M5000_--coalesce-fraction-as-needed.json.check.mbtiles",
-"strategies": "[{\"coalesced_as_needed\":528,\"detail_reduced\":2,\"tile_size_desired\":39204},{\"coalesced_as_needed\":217,\"tile_size_desired\":25156},{\"coalesced_as_needed\":218,\"tiny_polygons\":2,\"tile_size_desired\":21207},{\"coalesced_as_needed\":227,\"tiny_polygons\":4,\"tile_size_desired\":10753},{\"coalesced_as_needed\":192,\"tiny_polygons\":13,\"tile_size_desired\":6588},{\"tiny_polygons\":46}]",
+"strategies": "[{\"coalesced_as_needed\":528,\"detail_reduced\":2,\"tiny_polygons\":2,\"tile_size_desired\":39204},{\"coalesced_as_needed\":217,\"tile_size_desired\":25156},{\"coalesced_as_needed\":218,\"tile_size_desired\":21207},{\"coalesced_as_needed\":227,\"tile_size_desired\":10753},{\"coalesced_as_needed\":192,\"tile_size_desired\":6588},{\"tiny_polygons\":1}]",
 "type": "overlay",
 "version": "2"
 }, "features": [
@@ -9,7 +9,7 @@
 "maxzoom": "5",
 "minzoom": "0",
 "name": "tests/ne_110m_admin_0_countries/out/-z5_-M5000_--coalesce-smallest-as-needed.json.check.mbtiles",
-"strategies": "[{\"coalesced_as_needed\":1272,\"tile_size_desired\":39204},{\"coalesced_as_needed\":1191,\"tiny_polygons\":1,\"tile_size_desired\":25156},{\"coalesced_as_needed\":731,\"tiny_polygons\":3,\"tile_size_desired\":21207},{\"coalesced_as_needed\":178,\"tiny_polygons\":8,\"tile_size_desired\":10753},{\"coalesced_as_needed\":74,\"tiny_polygons\":20,\"tile_size_desired\":6588},{\"tiny_polygons\":46}]",
+"strategies": "[{\"coalesced_as_needed\":1272,\"tiny_polygons\":5,\"tile_size_desired\":39204},{\"coalesced_as_needed\":1191,\"tile_size_desired\":25156},{\"coalesced_as_needed\":731,\"tiny_polygons\":1,\"tile_size_desired\":21207},{\"coalesced_as_needed\":178,\"tile_size_desired\":10753},{\"coalesced_as_needed\":74,\"tile_size_desired\":6588},{\"tiny_polygons\":1}]",
 "type": "overlay",
 "version": "2"
 }, "features": [
@@ -9,7 +9,7 @@
 "maxzoom": "5",
 "minzoom": "0",
 "name": "tests/ne_110m_admin_0_countries/out/-z5_-M5000_--drop-smallest-as-needed.json.check.mbtiles",
-"strategies": "[{\"dropped_as_needed\":174,\"tile_size_desired\":39204},{\"dropped_as_needed\":202,\"tile_size_desired\":25156},{\"dropped_as_needed\":190,\"tiny_polygons\":2,\"tile_size_desired\":21207},{\"dropped_as_needed\":156,\"tiny_polygons\":12,\"tile_size_desired\":10753},{\"dropped_as_needed\":78,\"tiny_polygons\":20,\"tile_size_desired\":6588},{\"tiny_polygons\":46}]",
+"strategies": "[{\"dropped_as_needed\":174,\"tile_size_desired\":39204},{\"dropped_as_needed\":202,\"tile_size_desired\":25156},{\"dropped_as_needed\":190,\"tile_size_desired\":21207},{\"dropped_as_needed\":156,\"tile_size_desired\":10753},{\"dropped_as_needed\":78,\"tile_size_desired\":6588},{\"tiny_polygons\":1}]",
 "type": "overlay",
 "version": "2"
 }, "features": [
@@ -9,7 +9,7 @@
 "maxzoom": "4",
 "minzoom": "0",
 "name": "tests/ne_110m_ocean/join/ocean.mbtiles + tests/ne_110m_ocean/join/countries.mbtiles",
-"strategies": "[{},{\"tiny_polygons\":2},{\"tiny_polygons\":3},{\"tiny_polygons\":12},{\"tiny_polygons\":23}]",
+"strategies": "[{},{},{},{},{\"tiny_polygons\":4}]",
 "type": "overlay",
 "version": "2"
 }, "features": [
@@ -9,7 +9,7 @@
 "maxzoom": "4",
 "minzoom": "0",
 "name": "tests/nullisland/out/-b0_-z4.json.check.mbtiles",
-"strategies": "[{\"dropped_by_rate\":4},{\"dropped_by_rate\":8,\"tiny_polygons\":12},{\"dropped_by_rate\":8},{\"dropped_by_rate\":3},{}]",
+"strategies": "[{\"dropped_by_rate\":4},{\"dropped_by_rate\":8},{\"dropped_by_rate\":8},{\"dropped_by_rate\":3},{}]",
 "type": "overlay",
 "version": "2"
 }, "features": [
@@ -10,7 +10,7 @@
 "maxzoom": "4",
 "minzoom": "0",
 "name": "tests/nullisland/out/-b0_-z4_-ANullIsland.json.check.mbtiles",
-"strategies": "[{\"dropped_by_rate\":4},{\"dropped_by_rate\":8,\"tiny_polygons\":12},{\"dropped_by_rate\":8},{\"dropped_by_rate\":3},{}]",
+"strategies": "[{\"dropped_by_rate\":4},{\"dropped_by_rate\":8},{\"dropped_by_rate\":8},{\"dropped_by_rate\":3},{}]",
 "type": "overlay",
 "version": "2"
 }, "features": [
@@ -9,7 +9,7 @@
 "maxzoom": "4",
 "minzoom": "0",
 "name": "tests/nullisland/out/-b0_-z4_-NNullIsland.json.check.mbtiles",
-"strategies": "[{\"dropped_by_rate\":4},{\"dropped_by_rate\":8,\"tiny_polygons\":12},{\"dropped_by_rate\":8},{\"dropped_by_rate\":3},{}]",
+"strategies": "[{\"dropped_by_rate\":4},{\"dropped_by_rate\":8},{\"dropped_by_rate\":8},{\"dropped_by_rate\":3},{}]",
 "type": "overlay",
 "version": "2"
 }, "features": [
@@ -9,6 +9,7 @@
 "maxzoom": "0",
 "minzoom": "0",
 "name": "tests/polygon-winding/out/-z0_--reverse-source-polygon-winding.json.check.mbtiles",
+"strategies": "[{\"tiny_polygons\":1}]",
 "type": "overlay",
 "version": "2"
 }, "features": [
@@ -2138,14 +2138,14 @@ long long write_tile(decompressor *geoms, std::atomic<long long> *geompos_in, ch
 				add_sample_to(extents, sf.extent, extents_increment, seq);
 				// search here is for LLONG_MAX, not minextent, because we are dropping features, not coalescing them,
 				// so we shouldn't expect to find anything small that we can related this feature to.
-				if (sf.extent + coalesced_area <= minextent && find_partial(partials, sf, which_partial, layer_unmaps, LLONG_MAX)) {
+				if (minextent != 0 && sf.extent + coalesced_area <= minextent && find_partial(partials, sf, which_partial, layer_unmaps, LLONG_MAX)) {
 					preserve_attributes(arg->attribute_accum, sf, stringpool, pool_off, partials[which_partial]);
 					strategy->dropped_as_needed++;
 					continue;
 				}
 			} else if (additional[A_COALESCE_SMALLEST_AS_NEEDED]) {
 				add_sample_to(extents, sf.extent, extents_increment, seq);
-				if (sf.extent + coalesced_area <= minextent && find_partial(partials, sf, which_partial, layer_unmaps, minextent)) {
+				if (minextent != 0 && sf.extent + coalesced_area <= minextent && find_partial(partials, sf, which_partial, layer_unmaps, minextent)) {
 					partials[which_partial].geoms.push_back(sf.geometry);
 					partials[which_partial].coalesced = true;
 					coalesced_area += sf.extent;
@@ -2182,18 +2182,25 @@ long long write_tile(decompressor *geoms, std::atomic<long long> *geompos_in, ch
 			}
 			fraction_accum -= 1;

-			bool reduced = false;
-			if (sf.t == VT_POLYGON) {
+			bool still_need_simplification_after_reduction = false;
+			if (sf.t == VT_POLYGON && sf.geometry.size() > 0) {
+				bool simplified_away_by_reduction = false;
+
 				if (!prevent[P_TINY_POLYGON_REDUCTION] && !additional[A_GRID_LOW_ZOOMS]) {
-					sf.geometry = reduce_tiny_poly(sf.geometry, z, line_detail, &reduced, &accum_area, &sf, &tiny_feature);
-					if (reduced) {
+					sf.geometry = reduce_tiny_poly(sf.geometry, z, line_detail, &still_need_simplification_after_reduction, &simplified_away_by_reduction, &accum_area, &sf, &tiny_feature);
+					if (simplified_away_by_reduction) {
 						strategy->tiny_polygons++;
 					}
 					if (sf.geometry.size() == 0) {
 						continue;
 					}
+				} else {
+					still_need_simplification_after_reduction = true;  // reduction skipped, so always simplify
 				}
+			} else {
+				still_need_simplification_after_reduction = true;  // not a polygon, so simplify
 			}
+
 			if (sf.t == VT_POLYGON || sf.t == VT_LINE) {
 				if (line_is_too_small(sf.geometry, z, line_detail)) {
 					continue;
@@ -2220,7 +2227,7 @@ long long write_tile(decompressor *geoms, std::atomic<long long> *geompos_in, ch
 					p.t = sf.t;
 					p.segment = sf.segment;
 					p.original_seq = sf.seq;
-					p.reduced = reduced;
+					p.reduced = !still_need_simplification_after_reduction;
 					p.coalesced = false;
 					p.z = z;
 					p.tx = tx;
@@ -1,6 +1,6 @@
 #ifndef VERSION_HPP
 #define VERSION_HPP

-#define VERSION "v2.30.0"
+#define VERSION "v2.30.1"

 #endif