From 040e67d16610808533bb45a71b2c5b184528ed29 Mon Sep 17 00:00:00 2001
From: Andreas Hocevar <andreas.hocevar@gmail.com>
Date: Fri, 1 Sep 2017 11:27:53 +0200
Subject: [PATCH] Only load source tiles that intersect the source tile grid's
 extent

---
 src/ol/vectorimagetile.js            |  4 ++++
 test/spec/ol/vectorimagetile.test.js | 21 +++++++++++++++++++++
 2 files changed, 25 insertions(+)

diff --git a/src/ol/vectorimagetile.js b/src/ol/vectorimagetile.js
index 5a782fa5d0..2b8a2b0210 100644
--- a/src/ol/vectorimagetile.js
+++ b/src/ol/vectorimagetile.js
@@ -94,6 +94,10 @@ ol.VectorImageTile = function(tileCoord, state, src, format, tileLoadFunction,
     sourceTileGrid.forEachTileCoord(extent, sourceZ, function(sourceTileCoord) {
       var sharedExtent = ol.extent.getIntersection(extent,
           sourceTileGrid.getTileCoordExtent(sourceTileCoord));
+      var sourceExtent = sourceTileGrid.getExtent();
+      if (sourceExtent) {
+        sharedExtent = ol.extent.getIntersection(sharedExtent, sourceExtent);
+      }
       if (ol.extent.getWidth(sharedExtent) / resolution >= 0.5 &&
           ol.extent.getHeight(sharedExtent) / resolution >= 0.5) {
         // only include source tile if overlap is at least 1 pixel
diff --git a/test/spec/ol/vectorimagetile.test.js b/test/spec/ol/vectorimagetile.test.js
index 20ed04e9f9..77a5e42f98 100644
--- a/test/spec/ol/vectorimagetile.test.js
+++ b/test/spec/ol/vectorimagetile.test.js
@@ -7,6 +7,7 @@ goog.require('ol.events');
 goog.require('ol.format.GeoJSON');
 goog.require('ol.proj');
 goog.require('ol.tilegrid');
+goog.require('ol.tilegrid.TileGrid');
 
 
 describe('ol.VectorImageTile', function() {
@@ -109,6 +110,26 @@ describe('ol.VectorImageTile', function() {
     });
   });
 
+  it('only loads tiles within the source tileGrid\'s extent', function() {
+    var format = new ol.format.GeoJSON();
+    var url = 'spec/ol/data/point.json';
+    var tileGrid = new ol.tilegrid.TileGrid({
+      resolutions: [0.02197265625, 0.010986328125, 0.0054931640625],
+      origin: [-180, 90],
+      extent: [-88, 35, -87, 36]
+    });
+    var sourceTiles = {};
+    var tile = new ol.VectorImageTile([1, 0, -1], 0, url, format,
+        ol.VectorImageTile.defaultLoadFunction, [1, 0, -1], function(zxy) {
+          return url;
+        }, tileGrid,
+        ol.tilegrid.createXYZ({extent: [-180, -90, 180, 90], tileSize: 512}),
+        sourceTiles, 1, ol.proj.get('EPSG:4326'), ol.VectorTile, function() {});
+    tile.load();
+    expect(tile.tileKeys.length).to.be(1);
+    expect(tile.getTile(tile.tileKeys[0]).tileCoord).to.eql([0, 16, -10]);
+  });
+
   it('#dispose() while loading', function() {
     var format = new ol.format.GeoJSON();
     var url = 'spec/ol/data/point.json';