From 47e799ced0b580f1e369c13c1e7450dae3097251 Mon Sep 17 00:00:00 2001
From: Tom Payne <twpayne@gmail.com>
Date: Thu, 21 Feb 2013 16:14:51 +0100
Subject: [PATCH] Mark all low resolution tiles as used to prevent cache
 expiration

---
 .../canvas/canvastilelayerrenderer.js         |  1 +
 src/ol/renderer/dom/domtilelayerrenderer.js   |  1 +
 src/ol/renderer/layerrenderer.js              | 23 +++++++++++++++++++
 .../renderer/webgl/webgltilelayerrenderer.js  |  1 +
 4 files changed, 26 insertions(+)

diff --git a/src/ol/renderer/canvas/canvastilelayerrenderer.js b/src/ol/renderer/canvas/canvastilelayerrenderer.js
index e7c48f044c..c60ef7e49a 100644
--- a/src/ol/renderer/canvas/canvastilelayerrenderer.js
+++ b/src/ol/renderer/canvas/canvastilelayerrenderer.js
@@ -199,6 +199,7 @@ ol.renderer.canvas.TileLayer.prototype.renderFrame =
   }
 
   this.updateUsedTiles(frameState.usedTiles, tileSource, z, tileRange);
+  this.useLowResolutionTiles(tileSource, z, frameState.extent);
   this.scheduleExpireCache(frameState, tileSource);
 
   var transform = this.transform_;
diff --git a/src/ol/renderer/dom/domtilelayerrenderer.js b/src/ol/renderer/dom/domtilelayerrenderer.js
index faeb67d47d..3821f2a22b 100644
--- a/src/ol/renderer/dom/domtilelayerrenderer.js
+++ b/src/ol/renderer/dom/domtilelayerrenderer.js
@@ -217,6 +217,7 @@ ol.renderer.dom.TileLayer.prototype.renderFrame =
   }
 
   this.updateUsedTiles(frameState.usedTiles, tileSource, z, tileRange);
+  this.useLowResolutionTiles(tileSource, z, frameState.extent);
   this.scheduleExpireCache(frameState, tileSource);
 
 };
diff --git a/src/ol/renderer/layerrenderer.js b/src/ol/renderer/layerrenderer.js
index f1477ac8d7..beb91f376a 100644
--- a/src/ol/renderer/layerrenderer.js
+++ b/src/ol/renderer/layerrenderer.js
@@ -3,6 +3,7 @@ goog.provide('ol.renderer.Layer');
 goog.require('goog.events');
 goog.require('goog.events.EventType');
 goog.require('ol.Attribution');
+goog.require('ol.Extent');
 goog.require('ol.FrameState');
 goog.require('ol.Image');
 goog.require('ol.ImageState');
@@ -258,3 +259,25 @@ ol.renderer.Layer.prototype.updateWantedTiles =
   }
   wantedTiles[tileSourceKey][coordKey] = true;
 };
+
+
+/**
+ * @protected
+ * @param {ol.source.TileSource} tileSource Tile source.
+ * @param {number} z Z.
+ * @param {ol.Extent} extent Extent.
+ */
+ol.renderer.Layer.prototype.useLowResolutionTiles =
+    function(tileSource, z, extent) {
+  var tileGrid = tileSource.getTileGrid();
+  var tileRange, x, y, zKey;
+  // FIXME this should loop up to tileGrid's minZ when implemented
+  for (; z >= 0; --z) {
+    tileRange = tileGrid.getTileRangeForExtentAndZ(extent, z);
+    for (x = tileRange.minX; x <= tileRange.maxX; ++x) {
+      for (y = tileRange.minY; y <= tileRange.maxY; ++y) {
+        tileSource.useTile(new ol.TileCoord(z, x, y));
+      }
+    }
+  }
+};
diff --git a/src/ol/renderer/webgl/webgltilelayerrenderer.js b/src/ol/renderer/webgl/webgltilelayerrenderer.js
index 53405ca10a..0e939f8665 100644
--- a/src/ol/renderer/webgl/webgltilelayerrenderer.js
+++ b/src/ol/renderer/webgl/webgltilelayerrenderer.js
@@ -459,6 +459,7 @@ ol.renderer.webgl.TileLayer.prototype.renderFrame =
   }
 
   this.updateUsedTiles(frameState.usedTiles, tileSource, z, tileRange);
+  this.useLowResolutionTiles(tileSource, z, frameState.extent);
   this.scheduleExpireCache(frameState, tileSource);
 
   goog.vec.Mat4.makeIdentity(this.texCoordMatrix_);