From b0cea7139b7f085cb57904d7e73573a4c6ecef28 Mon Sep 17 00:00:00 2001
From: Tim Schaub <tim.schaub@gmail.com>
Date: Mon, 23 Sep 2013 19:22:28 +0200
Subject: [PATCH 1/2] Function to buffer an extent

---
 src/ol/extent.js            | 13 +++++++++++++
 test/spec/ol/extent.test.js | 10 ++++++++++
 2 files changed, 23 insertions(+)

diff --git a/src/ol/extent.js b/src/ol/extent.js
index 25464d5e68..f4651b1f7d 100644
--- a/src/ol/extent.js
+++ b/src/ol/extent.js
@@ -52,6 +52,19 @@ ol.extent.boundingExtentXYs_ = function(xs, ys, opt_extent) {
 };
 
 
+/**
+ * Increase an extent by the provided value.
+ * @param {ol.Extent} extent The extent to buffer.
+ * @param {number} value The amount by wich the extent should be buffered.
+ */
+ol.extent.buffer = function(extent, value) {
+  extent[0] -= value;
+  extent[1] -= value;
+  extent[2] += value;
+  extent[3] += value;
+};
+
+
 /**
  * Creates a clone of an extent.
  *
diff --git a/test/spec/ol/extent.test.js b/test/spec/ol/extent.test.js
index a2f032f423..182491d9a6 100644
--- a/test/spec/ol/extent.test.js
+++ b/test/spec/ol/extent.test.js
@@ -3,6 +3,16 @@ goog.provide('ol.test.extent');
 
 describe('ol.extent', function() {
 
+  describe('buffer', function() {
+
+    it('buffers an extent by some value', function() {
+      var extent = [-10, -20, 10, 20];
+      ol.extent.buffer(extent, 15);
+      expect(extent).to.eql([-25, -35, 25, 35]);
+    });
+
+  });
+
   describe('clone', function() {
 
     it('creates a copy of an extent', function() {

From b355c1f412dfdcdf4c9bde1eb372617ef1571c72 Mon Sep 17 00:00:00 2001
From: Tim Schaub <tim.schaub@gmail.com>
Date: Mon, 23 Sep 2013 21:17:48 +0200
Subject: [PATCH 2/2] When expiring tiles, consider max symbol size

When an extent is invalidated, we have to expire tiles outside of that extent to account for symbolizer size.
---
 .../canvas/canvasvectorlayerrenderer.js       | 21 ++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

diff --git a/src/ol/renderer/canvas/canvasvectorlayerrenderer.js b/src/ol/renderer/canvas/canvasvectorlayerrenderer.js
index 8c3a1bb5e0..eb881e453d 100644
--- a/src/ol/renderer/canvas/canvasvectorlayerrenderer.js
+++ b/src/ol/renderer/canvas/canvasvectorlayerrenderer.js
@@ -1,5 +1,6 @@
 goog.provide('ol.renderer.canvas.VectorLayer');
 
+goog.require('goog.asserts');
 goog.require('goog.dom');
 goog.require('goog.dom.TagName');
 goog.require('goog.events');
@@ -101,6 +102,13 @@ ol.renderer.canvas.VectorLayer = function(mapRenderer, layer) {
    */
   this.tileArchetype_ = null;
 
+  /**
+   * The maximum symbol size ever rendered for this layer (in pixels).
+   * @private
+   * @type {number}
+   */
+  this.maxSymbolPixelDim_ = 0;
+
   /**
    * @private
    * @type {number}
@@ -168,12 +176,18 @@ goog.inherits(ol.renderer.canvas.VectorLayer, ol.renderer.canvas.Layer);
  * @private
  */
 ol.renderer.canvas.VectorLayer.prototype.expireTiles_ = function(extents) {
+  // buffer by max symbolizer size at rendered resolution
+  var resolution = this.renderedResolution_;
+  goog.asserts.assertNumber(resolution);
   var tileCache = this.tileCache_;
   var length = extents.length;
+  var extent;
   if (length > 0) {
     for (var i = 0; i < length; ++i) {
+      extent = ol.extent.clone(extents[i]);
+      ol.extent.buffer(extent, this.maxSymbolPixelDim_ * resolution / 2);
       tileCache.pruneTileRange(
-          this.tileGrid_.getTileRangeForExtentAndZ(extents[i], 0));
+          this.tileGrid_.getTileRangeForExtentAndZ(extent, 0));
     }
   } else {
     tileCache.clear();
@@ -509,6 +523,11 @@ ol.renderer.canvas.VectorLayer.prototype.renderFrame =
   var symbolSizes = sketchCanvasRenderer.getSymbolSizes(),
       maxSymbolSize = sketchCanvasRenderer.getMaxSymbolSize(),
       symbolOffsets = sketchCanvasRenderer.getSymbolOffsets();
+
+  // keep track of maximum pixel size for symbols rendered on this layer
+  this.maxSymbolPixelDim_ = Math.max(maxSymbolSize[0] / tileResolution,
+      maxSymbolSize[1] / tileResolution);
+
   for (key in tilesToRender) {
     tileCoord = tilesToRender[key];
     if (this.tileCache_.containsKey(key)) {