Canvas renderer needs to return false from setExtent

lib/OpenLayers/Renderer/Canvas.js

@@ -70,6 +70,25 @@ OpenLayers.Renderer.Canvas = OpenLayers.Class(OpenLayers.Renderer, {
         }
     },
     
+    /**
+     * Method: setExtent
+     * Set the visible part of the layer.
+     *
+     * Parameters:
+     * extent - {<OpenLayers.Bounds>}
+     * resolutionChanged - {Boolean}
+     *
+     * Returns:
+     * {Boolean} true to notify the layer that the new extent does not exceed
+     *     the coordinate range, and the features will not need to be redrawn.
+     *     False otherwise.
+     */
+    setExtent: function() {
+        OpenLayers.Renderer.prototype.setExtent.apply(this, arguments);
+        // always redraw features
+        return false;
+    },
+    
     /** 
      * Method: eraseGeometry
      * Erase a geometry from the renderer. Because the Canvas renderer has