Oops, never checked this in

earcut.cpp

@@ -0,0 +1,91 @@
+#include "geometry.hpp"
+#include "mapbox/geometry/earcut.hpp"
+
+using Coord = long long;
+using N = size_t;
+using Point = std::array<Coord, 2>;
+
+drawvec fix_by_triangulation(drawvec const &dv, int z, int detail) {
+	std::vector<std::vector<Point>> polygon;
+	drawvec out;
+	double scale = 1LL << (32 - z - detail);
+
+	for (size_t i = 0; i < dv.size(); i++) {
+		if (dv[i].op == VT_MOVETO) {
+			size_t j;
+			for (j = i + 1; j < dv.size(); j++) {
+				if (dv[j].op != VT_LINETO) {
+					break;
+				}
+			}
+
+			std::vector<Point> ring;
+			// j - 1 because earcut docs indicate that it doesn't expect
+			// a duplicate last point in each ring
+			for (size_t k = i; k < j - 1; k++) {
+				Point p = {(long long) dv[k].x, (long long) dv[k].y};
+				ring.push_back(p);
+				out.push_back(dv[k]);
+			}
+			polygon.push_back(ring);
+
+			i = j - 1;
+		}
+	}
+
+	std::vector<N> indices = mapbox::earcut<N>(polygon);
+
+	bool again = true;
+	while (again) {
+		again = false;
+		for (size_t i = 0; i + 2 < indices.size(); i += 3) {
+			for (size_t j = 0; j < 3; j++) {
+				size_t v1 = i + j;
+				size_t v2 = i + ((j + 1) % 3);
+
+				if (std::llround(out[indices[v1]].x / scale) == std::llround(out[indices[v2]].x / scale) &&
+				    std::llround(out[indices[v1]].y / scale) == std::llround(out[indices[v2]].y / scale)) {
+					double ang = atan2(out[indices[v2]].y - out[indices[v1]].y, out[indices[v2]].x - out[indices[v1]].x);
+
+					printf("at %zu/%zu: %zu and %zu: ", i, j, v1, v2);
+					printf("z%d: was %f,%f to %f,%f ",
+					       z,
+					       out[indices[v1]].x / scale, out[indices[v1]].y / scale,
+					       out[indices[v2]].x / scale, out[indices[v2]].y / scale);
+
+					out[indices[v1]].x -= scale * cos(ang) * sqrt(2);
+					out[indices[v1]].y -= scale * sin(ang) * sqrt(2);
+					out[indices[v2]].x += scale * cos(ang) * sqrt(2);
+					out[indices[v2]].y += scale * sin(ang) * sqrt(2);
+					again = true;
+
+					printf("now %f,%f to %f,%f\n",
+					       out[indices[v1]].x / scale, out[indices[v1]].y / scale,
+					       out[indices[v2]].x / scale, out[indices[v2]].y / scale);
+				}
+			}
+		}
+	}
+
+	drawvec out2;
+	for (size_t i = 0; i < out.size(); i++) {
+		if (out[i].op == VT_MOVETO) {
+			size_t j;
+			for (j = i + 1; j < out.size(); j++) {
+				if (out[j].op != VT_LINETO) {
+					break;
+				}
+			}
+
+			for (size_t k = i; k < j; k++) {
+				out2.push_back(out[k]);
+			}
+
+			// re-close the ring
+			out2.push_back(draw(VT_LINETO, out[i].x, out[i].y));
+			i = j - 1;
+		}
+	}
+
+	return out2;
+}