From e6cb15c3f18c73cfc7aea2a797d3a33eedb946cd Mon Sep 17 00:00:00 2001
From: Ansis Brammanis <brammanis@gmail.com>
Date: Thu, 18 Feb 2016 19:18:01 -0800
Subject: [PATCH] look for loaded parent tiles in cache

This reduces the amount of the view not covered by tiles.
It makes tile loading look a lot faster.

It helps a lot when you:
- zoom in and the pan around
- zoom in quickly and then zoom out more slowly

ref #1918
---
 js/source/tile_pyramid.js | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/js/source/tile_pyramid.js b/js/source/tile_pyramid.js
index f241a3f9f82..06404013aa3 100644
--- a/js/source/tile_pyramid.js
+++ b/js/source/tile_pyramid.js
@@ -195,7 +195,12 @@ TilePyramid.prototype = {
             var tile = this._tiles[coord.id];
             if (tile && tile.loaded) {
                 retain[coord.id] = true;
-                return tile;
+                return true;
+            }
+            if (this._cache.has(coord.id)) {
+                this.addTile(coord);
+                retain[coord.id] = true;
+                return true;
             }
         }
     },