From 3bdcc3ca908c5b70a2bd8666a2963a9c39fee3f3 Mon Sep 17 00:00:00 2001
From: Eric Fischer <enf@pobox.com>
Date: Wed, 15 Oct 2014 17:03:30 -0700
Subject: [PATCH] Heavy-handedly fix clipping errors at the edges of z0 and z1
 tiles

---
 geojson.c | 27 +++++++++++++++++++++++++--
 tile.cc   | 12 ++++++------
 2 files changed, 31 insertions(+), 8 deletions(-)

diff --git a/geojson.c b/geojson.c
index 0664f42..827e7b0 100644
--- a/geojson.c
+++ b/geojson.c
@@ -61,8 +61,31 @@ void latlon2tile(double lat, double lon, int zoom, unsigned int *x, unsigned int
 	double lat_rad = lat * M_PI / 180;
 	unsigned long long n = 1LL << zoom;
 
-	*x = n * ((lon + 180) / 360);
-	*y = n * (1 - (log(tan(lat_rad) + 1/cos(lat_rad)) / M_PI)) / 2;
+	long long llx = n * ((lon + 180) / 360);
+	long long lly = n * (1 - (log(tan(lat_rad) + 1/cos(lat_rad)) / M_PI)) / 2;
+
+	if (lat >= 85.0511) {
+		lly = 0;
+	}
+	if (lat <= -85.0511) {
+		lly = n - 1;
+	}
+
+	if (llx < 0) {
+		llx = 0;
+	}
+	if (lly < 0) {
+		lly = 0;
+	}
+	if (llx >= n) {
+		llx = n - 1;
+	}
+	if (lly >= n) {
+		lly = n - 1;
+	}
+
+	*x = llx;
+	*y = lly;
 }
 
 // http://wiki.openstreetmap.org/wiki/Slippy_map_tilenames
diff --git a/tile.cc b/tile.cc
index 85bebf1..e281d67 100644
--- a/tile.cc
+++ b/tile.cc
@@ -373,8 +373,8 @@ void douglas_peucker(drawvec &geom, int start, int n, double e) {
 	}
 }
 
-static bool inside(draw d, int edge, int area) {
-	int clip_buffer = area / 64;
+static bool inside(draw d, int edge, long long area) {
+	long long clip_buffer = area / 64;
 
 	switch (edge) {
 		case 0: // top
@@ -408,8 +408,8 @@ static draw get_line_intersection(draw p0, draw p1, draw p2, draw p3) {
 	return draw(VT_LINETO, p0.x + (t * s1_x), p0.y + (t * s1_y));
 }
 
-static draw intersect(draw a, draw b, int edge, int area) {
-	int clip_buffer = area / 64;
+static draw intersect(draw a, draw b, int edge, long long area) {
+	long long clip_buffer = area / 64;
 
 	switch (edge) {
 		case 0: // top
@@ -437,9 +437,9 @@ static draw intersect(draw a, draw b, int edge, int area) {
 static drawvec clip_poly1(drawvec &geom, int z, int detail) {
 	drawvec out = geom;
 
-	unsigned area = 0xFFFFFFFF;
+	long long area = 0xFFFFFFFF;
 	if (z != 0) {
-		area = 1 << (32 - z);
+		area = 1LL << (32 - z);
 	}
 
 	for (int edge = 0; edge < 4; edge++) {