Starting on my own polygon cleaner

polygon.cpp

@@ -0,0 +1,52 @@
+#include "geometry.hpp"
+
+struct point {
+	double x;
+	double y;
+
+	point(double x_, double y_)
+	    : x(x_), y(y_) {
+	}
+};
+
+drawvec clean_polygon(drawvec const &geom, int z, int detail) {
+	double scale = 1LL << (-(32 - detail - z));
+
+	// decompose polygon rings into segments
+
+	std::vector<std::pair<point, point>> segments;
+
+	for (size_t i = 0; i < geom.size(); i++) {
+		if (geom[i].op == VT_MOVETO) {
+			size_t j;
+
+			for (j = i + 1; j < geom.size(); j++) {
+				if (geom[i].op != VT_LINETO) {
+					break;
+				}
+			}
+
+			for (size_t k = i; k + 1 < j; k++) {
+				std::pair<point, point> segment = std::make_pair(
+					point(geom[k].x / scale, geom[k].y / scale),
+					point(geom[k + 1].x / scale, geom[k + 1].y / scale));
+
+				segments.push_back(segment);
+			}
+
+			i = j - 1;
+		}
+	}
+
+	// snap-round intersecting segments
+
+	// remove duplicate segments with opposite windings
+
+	// reassemble segments into rings
+
+	// remove collinear points?
+
+	// determine ring nesting
+
+	return drawvec();
+}