Add --order-smallest-first and --order-largest-first options

CHANGELOG.md

@@ -1,6 +1,7 @@
 ## 2.9.0
 
 * Add an option to generate label points in place of polygons
+* Add --order-smallest-first and --order-largest-first options
 
 ## 2.8.1
 

README.md

@@ -506,6 +506,8 @@ the same layer, enclose them in an `all` expression so they will all be evaluate
  * `-ah` or `--hilbert`: Put features in Hilbert Curve order instead of the usual Z-Order. This improves the odds that spatially adjacent features will be sequentially adjacent, and should improve density calculations and spatial coalescing. It should be the default eventually.
  * `--order-by=`_attribute_: Order features by the specified _attribute_, in alphabetical or numerical order. Multiple `--order-by` and `--order-descending-by` options may be specified, the first being the primary sort key.
  * `--order-descending-by=`_attribute_: Order features by the specified _attribute_, in reverse alphabetical or numerical order. Multiple `--order-by` and `--order-descending-by` options may be specified, the first being the primary sort key.
+ * `--order-smallest-first`: Order features so the smallest geometry comes first in each tile. Multiple `--order-by` and `--order-descending-by` options may be specified, the first being the primary sort key.
+ * `--order-largest-first`: Order features so the largest geometry comes first in each tile. Multiple `--order-by` and `--order-descending-by` options may be specified, the first being the primary sort key.
 
 ### Adding calculated attributes
 

main.cpp

@@ -86,6 +86,7 @@ std::string attribute_for_id = "";
 
 std::vector<order_field> order_by;
 bool order_reverse;
+bool order_by_size = false;
 
 int prevent[256];
 int additional[256];
@@ -2751,6 +2752,8 @@ int main(int argc, char **argv) {
 		{"hilbert", no_argument, &additional[A_HILBERT], 1},
 		{"order-by", required_argument, 0, '~'},
 		{"order-descending-by", required_argument, 0, '~'},
+		{"order-smallest-first", no_argument, 0, '~'},
+		{"order-largest-first", no_argument, 0, '~'},
 
 		{"Adding calculated attributes", 0, 0, 0},
 		{"calculate-feature-density", no_argument, &additional[A_CALCULATE_FEATURE_DENSITY], 1},
@@ -2887,6 +2890,12 @@ int main(int argc, char **argv) {
 				order_by.push_back(order_field(optarg, false));
 			} else if (strcmp(opt, "order-descending-by") == 0) {
 				order_by.push_back(order_field(optarg, true));
+			} else if (strcmp(opt, "order-smallest-first") == 0) {
+				order_by.push_back(order_field(ORDER_BY_SIZE, false));
+				order_by_size = true;
+			} else if (strcmp(opt, "order-largest-first") == 0) {
+				order_by.push_back(order_field(ORDER_BY_SIZE, true));
+				order_by_size = true;
 			} else if (strcmp(opt, "simplification-at-maximum-zoom") == 0) {
 				maxzoom_simplification = atof_require(optarg, "Mazoom simplification");
 				if (maxzoom_simplification <= 0) {

main.hpp

@@ -66,6 +66,10 @@ struct order_field {
 
 extern std::vector<order_field> order_by;
 
+// not legal UTF-8, so can't appear as a real attribute name
+#define ORDER_BY_SIZE "\200size"
+extern bool order_by_size;
+
 int mkstemp_cloexec(char *name);
 FILE *fopen_oflag(const char *name, const char *mode, int oflag);
 bool progress_time();

man/tippecanoe.1

@@ -653,6 +653,10 @@ the line or polygon within one tile unit of its proper location. You can probabl
 \fB\fC\-\-order\-by=\fR\fIattribute\fP: Order features by the specified \fIattribute\fP, in alphabetical or numerical order. Multiple \fB\fC\-\-order\-by\fR and \fB\fC\-\-order\-descending\-by\fR options may be specified, the first being the primary sort key.
 .IP \(bu 2
 \fB\fC\-\-order\-descending\-by=\fR\fIattribute\fP: Order features by the specified \fIattribute\fP, in reverse alphabetical or numerical order. Multiple \fB\fC\-\-order\-by\fR and \fB\fC\-\-order\-descending\-by\fR options may be specified, the first being the primary sort key.
+.IP \(bu 2
+\fB\fC\-\-order\-smallest\-first\fR: Order features so the smallest geometry comes first in each tile. Multiple \fB\fC\-\-order\-by\fR and \fB\fC\-\-order\-descending\-by\fR options may be specified, the first being the primary sort key.
+.IP \(bu 2
+\fB\fC\-\-order\-largest\-first\fR: Order features so the largest geometry comes first in each tile. Multiple \fB\fC\-\-order\-by\fR and \fB\fC\-\-order\-descending\-by\fR options may be specified, the first being the primary sort key.
 .RE
 .SS Adding calculated attributes
 .RS

serial.cpp

@@ -517,7 +517,7 @@ int serialize_feature(struct serialization_state *sst, serial_feature &sf) {
 	}
 
 	double extent = 0;
-	if (additional[A_DROP_SMALLEST_AS_NEEDED] || additional[A_COALESCE_SMALLEST_AS_NEEDED]) {
+	if (additional[A_DROP_SMALLEST_AS_NEEDED] || additional[A_COALESCE_SMALLEST_AS_NEEDED] || order_by_size) {
 		if (sf.t == VT_POLYGON) {
 			for (size_t i = 0; i < sf.geometry.size(); i++) {
 				if (sf.geometry[i].op == VT_MOVETO) {

tile.cpp

@@ -96,6 +96,7 @@ struct coalesce {
 	double spacing = 0;
 	bool has_id = false;
 	unsigned long long id = 0;
+	long long extent = 0;
 
 	bool operator<(const coalesce &o) const {
 		int cmp = coalindexcmp(this, &o);
@@ -250,6 +251,13 @@ static int metacmp(const std::vector<long long> &keys1, const std::vector<long l
 }
 
 static mvt_value find_attribute_value(const struct coalesce *c1, std::string key) {
+	if (key == ORDER_BY_SIZE) {
+		mvt_value v;
+		v.type = mvt_double;
+		v.numeric_value.double_value = c1->extent;
+		return v;
+	}
+
 	const std::vector<long long> &keys1 = c1->keys;
 	const std::vector<long long> &values1 = c1->values;
 	const char *stringpool1 = c1->stringpool;
@@ -2285,6 +2293,7 @@ long long write_tile(FILE *geoms, std::atomic<long long> *geompos_in, char *meta
 					c.spacing = partials[i].spacing;
 					c.id = partials[i].id;
 					c.has_id = partials[i].has_id;
+					c.extent = partials[i].extent;
 
 					// printf("segment %d layer %lld is %s\n", partials[i].segment, partials[i].layer, (*layer_unmaps)[partials[i].segment][partials[i].layer].c_str());