Tighten MLT wording

.gitignore

@@ -43,7 +43,6 @@ tests/**/*.mbtiles
 tests/**/*.check
 tests/**/*.geobuf
 
-# MLT build directory
 mlt-build/
 
 # Vim

.gitmodules

@@ -1,4 +1,3 @@
 [submodule "maplibre-tile-spec"]
 	path = maplibre-tile-spec
 	url = https://github.com/maplibre/maplibre-tile-spec.git
-	branch = main

Makefile

@@ -606,20 +606,15 @@ layer-json-test: tippecanoe tippecanoe-decode
 	rm -f tests/layer-json/out.mbtiles.json.check tests/layer-json/out.mbtiles
 
 mlt-test: tippecanoe
-	# Points: MLT output, verify tile count matches MVT
 	./tippecanoe -q --output-format=mlt -z5 -f -o tests/mlt/points.mbtiles tests/mlt/points.geojson
 	./tippecanoe -q -z5 -f -o tests/mlt/points-mvt.mbtiles tests/mlt/points.geojson
 	@test $$(sqlite3 tests/mlt/points.mbtiles "SELECT COUNT(*) FROM tiles") -eq $$(sqlite3 tests/mlt/points-mvt.mbtiles "SELECT COUNT(*) FROM tiles") || (echo "FAIL: MLT and MVT tile counts differ" && exit 1)
-	# Verify format metadata
 	@test "$$(sqlite3 tests/mlt/points.mbtiles "SELECT value FROM metadata WHERE name='format'")" = "mlt" || (echo "FAIL: format metadata is not 'mlt'" && exit 1)
-	# Verify tiles are gzip compressed
 	@sqlite3 tests/mlt/points.mbtiles "SELECT hex(substr(tile_data, 1, 2)) FROM tiles LIMIT 1" | grep -q "1F8B" || (echo "FAIL: MLT tiles not gzip compressed" && exit 1)
-	# Directory output with .mlt extension
 	rm -rf tests/mlt/dir-out
 	./tippecanoe -q --output-format=mlt -z2 -f -e tests/mlt/dir-out tests/mlt/points.geojson
 	@test $$(find tests/mlt/dir-out -name '*.mlt' | wc -l) -gt 0 || (echo "FAIL: No .mlt files in directory output" && exit 1)
 	@test $$(find tests/mlt/dir-out -name '*.pbf' | wc -l) -eq 0 || (echo "FAIL: .pbf files in MLT directory output" && exit 1)
-	# Pretessellate flag
 	./tippecanoe -q --output-format=mlt --pretessellate -z5 -f -o tests/mlt/points-tess.mbtiles tests/mlt/points.geojson
 	@test $$(sqlite3 tests/mlt/points-tess.mbtiles "SELECT COUNT(*) FROM tiles") -gt 0 || (echo "FAIL: No tiles with pretessellate" && exit 1)
 	rm -f tests/mlt/points.mbtiles tests/mlt/points-mvt.mbtiles tests/mlt/points-tess.mbtiles

README.md

@@ -553,9 +553,9 @@ the same layer, enclose them in an `all` expression so they will all be evaluate
  * `-pf` or `--no-feature-limit`: Don't limit tiles to 200,000 features
  * `-pk` or `--no-tile-size-limit`: Don't limit tiles to 500K bytes
  * `-pC` or `--no-tile-compression`: Don't compress the vector tile data. If you are getting "Unimplemented type 3" error messages from a renderer, it is probably because it expects uncompressed tiles using this option rather than the normal gzip-compressed tiles.
- * `--output-format=`*format*: Set the tile encoding format. Supported values: `mvt` (default, Mapbox Vector Tiles) or `mlt` ([MapLibre Tiles](https://github.com/maplibre/maplibre-tile-spec)). MLT is a columnar format that typically produces smaller tiles than MVT.
+ * `--output-format=`*format*: Set the tile encoding format. Supported values: `mvt` (default, Mapbox Vector Tiles) or `mlt` ([MapLibre Tiles](https://github.com/maplibre/maplibre-tile-spec)).
- * `--pretessellate`: When using `--output-format=mlt`, pre-triangulate polygon geometries for faster rendering. Only applies to layers where all features are polygons.
+ * `--pretessellate`: When using `--output-format=mlt`, pre-triangulate polygon geometries. Only applies to layers where all features are polygons.
- * `--no-mlt-feature-sort`: When using `--output-format=mlt`, disable within-tile spatial sorting of features by Hilbert curve index. Sorting is on by default and improves compression.
+ * `--no-mlt-feature-sort`: When using `--output-format=mlt`, disable within-tile spatial sorting of features by Hilbert curve index. Sorting is on by default.
  * `-pg` or `--no-tile-stats`: Don't generate the `tilestats` row in the tileset metadata. Uploads without [tilestats](https://github.com/mapbox/mapbox-geostats) will take longer to process.
  * `--tile-stats-attributes-limit=`*count*: Include `tilestats` information about at most *count* attributes instead of the default 1000.
  * `--tile-stats-sample-values-limit=`*count*: Calculate `tilestats` attribute statistics based on *count* values instead of the default 1000.

mlt.cpp

@@ -11,8 +11,7 @@
 
 using Vertex = mlt::Encoder::Vertex;
 
-// Try to parse a JSON object string into MLT STRUCT (flat string children only)
+static bool parse_json_object_property(const std::string &s, mlt::Encoder::StructValue &out) {
-static bool try_parse_json_object(const std::string &s, mlt::Encoder::StructValue &out) {
 	if (s.empty() || s[0] != '{') {
 		return false;
 	}
@@ -60,7 +59,6 @@ static bool try_parse_json_object(const std::string &s, mlt::Encoder::StructValu
 			child_val = "null";
 			break;
 		default:
-			// Nested object/array - stringify back
 			char *nested = json_stringify(val);
 			child_val = nested;
 			free(nested);
@@ -101,7 +99,7 @@ static mlt::Encoder::PropertyValue convert_value(const mvt_value &val) {
 	case mvt_string: {
 		std::string s = val.get_string_value();
 		mlt::Encoder::StructValue struct_val;
-		if (try_parse_json_object(s, struct_val)) {
+		if (parse_json_object_property(s, struct_val)) {
 			return struct_val;
 		}
 		return s;
@@ -111,8 +109,6 @@ static mlt::Encoder::PropertyValue convert_value(const mvt_value &val) {
 	}
 }
 
-// Split MVT command stream into coordinate rings (sequences between moveto commands).
-// Each ring is a vector of vertices. For polygons, closepath is implicit (MLT strips closing points).
 static std::vector<std::vector<Vertex>> extract_rings(const mvt_feature &feature) {
 	std::vector<std::vector<Vertex>> rings;
 
@@ -124,7 +120,6 @@ static std::vector<std::vector<Vertex>> extract_rings(const mvt_feature &feature
 		} else if (g.op == mvt_lineto) {
 			rings.back().push_back({static_cast<int32_t>(g.x), static_cast<int32_t>(g.y)});
 		}
-		// mvt_closepath: polygon ring close — MLT stores without closing point
 	}
 	return rings;
 }
@@ -160,12 +155,9 @@ static mlt::Encoder::Geometry convert_geometry(const mvt_feature &feature) {
 		break;
 
 	case mvt_polygon: {
-		// Outer rings are clockwise (positive area), holes are counter-clockwise.
-		// Group into polygons: each outer ring starts a new polygon.
 		std::vector<std::vector<std::vector<Vertex>>> polygons;
 
 		for (auto &ring : rings) {
-			// Signed area to detect winding: positive = clockwise = outer ring (in MVT screen coords)
 			long long area2 = 0;
 			for (size_t i = 0; i < ring.size(); i++) {
 				size_t j = (i + 1) % ring.size();
@@ -173,7 +165,6 @@ static mlt::Encoder::Geometry convert_geometry(const mvt_feature &feature) {
 			}
 
 			if (area2 >= 0) {
-				// Outer ring — start new polygon
 				polygons.emplace_back();
 			}
 			if (!polygons.empty()) {