From 38752f4700578242892136ee0dfed97f0bd4f666 Mon Sep 17 00:00:00 2001
From: Tim Schaub <tim.schaub@gmail.com>
Date: Fri, 17 May 2013 23:22:07 -0600
Subject: [PATCH] Properly reset the dirty flag

Currently, the dirty flag is never reset (to false).  This is a bug.  Because renderFrame is called very often (every layer render gets called when every other layer needs to re-render), it is criticial to know when we can bail out early.  The dirty flag is currently the way that the vector layer renderer knows that it needs to do more work.  On an empty cache, the renderFrame method of the vector layer renderer is called ~30 times for a single zoom in the vector layer example (due to tiles loading on other layers).  Without this change, we miss the fast path out and clear/re-render the canvas all 30 times.  With this change, we are only clear the canvas and redraw 6 times in a typical zoom animation.
---
 src/ol/renderer/canvas/canvasvectorlayerrenderer.js | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/ol/renderer/canvas/canvasvectorlayerrenderer.js b/src/ol/renderer/canvas/canvasvectorlayerrenderer.js
index 7a076406d1..167071625f 100644
--- a/src/ol/renderer/canvas/canvasvectorlayerrenderer.js
+++ b/src/ol/renderer/canvas/canvasvectorlayerrenderer.js
@@ -393,6 +393,7 @@ ol.renderer.canvas.VectorLayer.prototype.renderFrame =
   var filters = this.geometryFilters_,
       numFilters = filters.length,
       deferred = false,
+      dirty = false,
       i, geomFilter, tileExtent, extentFilter, type,
       groups, group, j, numGroups;
   for (x = tileRange.minX; x <= tileRange.maxX; ++x) {
@@ -420,10 +421,11 @@ ol.renderer.canvas.VectorLayer.prototype.renderFrame =
         }
         tilesOnSketchCanvas[key] = tileCoord;
       } else {
-        this.dirty_ = true;
+        dirty = true;
       }
     }
   }
+  this.dirty_ = dirty;
 
   renderByGeometryType:
   for (type in featuresToRender) {