From 00a42796b4e3bf66d267f1a4aa45d6fc18655ed3 Mon Sep 17 00:00:00 2001
From: Eric Fischer <enf@pobox.com>
Date: Tue, 23 Sep 2014 10:57:01 -0700
Subject: [PATCH] Use lower resolution at lower zooms. Not sure it's worth it.

---
 geojson.c |  2 +-
 tile.cc   | 12 +++++-------
 tile.h    |  2 +-
 3 files changed, 7 insertions(+), 9 deletions(-)

diff --git a/geojson.c b/geojson.c
index 7153784..22d8497 100644
--- a/geojson.c
+++ b/geojson.c
@@ -334,7 +334,7 @@ void check(struct index *ix, long long n, char *metabase, unsigned *file_bbox) {
 
 			printf("%d/%u/%u    %x %x   %lld to %lld\n", z, tx, ty, wx, wy, (long long)(i - ix), (long long)(j - ix));
 
-			write_tile(i, j, metabase, file_bbox, z, tx, ty);
+			write_tile(i, j, metabase, file_bbox, z, tx, ty, z == 14 ? 12 : 10);
 		}
 	}
 }
diff --git a/tile.cc b/tile.cc
index e004d71..76b0848 100644
--- a/tile.cc
+++ b/tile.cc
@@ -12,9 +12,6 @@ extern "C" {
 	#include "tile.h"
 }
 
-#define XMAX 4096
-#define YMAX 4096
-
 #define CMD_BITS 3
 
 // https://github.com/mapbox/mapnik-vector-tile/blob/master/src/vector_tile_compression.hpp
@@ -46,7 +43,7 @@ static inline int compress(std::string const& input, std::string& output) {
 }
 
 
-void write_tile(struct index *start, struct index *end, char *metabase, unsigned *file_bbox, int z, unsigned tx, unsigned ty) {
+void write_tile(struct index *start, struct index *end, char *metabase, unsigned *file_bbox, int z, unsigned tx, unsigned ty, int detail) {
 	GOOGLE_PROTOBUF_VERIFY_VERSION;
 
         mapnik::vector::tile tile;
@@ -54,7 +51,8 @@ void write_tile(struct index *start, struct index *end, char *metabase, unsigned
 
         layer->set_name("name");
         layer->set_version(1);
-        layer->set_extent(XMAX);
+
+        layer->set_extent(1 << detail);
 
 	struct pool keys;
 	keys.n = 0;
@@ -124,8 +122,8 @@ void write_tile(struct index *start, struct index *end, char *metabase, unsigned
 					wwy -= ty << (32 - z);
 				}
 
-				wwx >>= (32 - 12 - z);
-				wwy >>= (32 - 12 - z);
+				wwx >>= (32 - detail - z);
+				wwy >>= (32 - detail - z);
 
 				int dx = wwx - px;
 				int dy = wwy - py;
diff --git a/tile.h b/tile.h
index 9d6f077..7c8945d 100644
--- a/tile.h
+++ b/tile.h
@@ -47,4 +47,4 @@ struct index {
 };
 
 
-void write_tile(struct index *start, struct index *end, char *metabase, unsigned *file_bbox, int z, unsigned x, unsigned y);
+void write_tile(struct index *start, struct index *end, char *metabase, unsigned *file_bbox, int z, unsigned x, unsigned y, int detail);