Add better documentation for the 'ratio' property of WFS layers.

git-svn-id: http://svn.openlayers.org/trunk/openlayers@9596 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/Layer/WFS.js

@@ -34,8 +34,13 @@ OpenLayers.Layer.WFS = OpenLayers.Class(
     
     /**
      * APIProperty: ratio
-     * {Float} the ratio of image/tile size to map size (this is the untiled
+     * {Float} The ratio property determines the size of the serverside query
-     *     buffer)
+     *    relative to the map viewport size. By default, we load an area twice
+     *    as big as the map, to allow for panning without immediately reload.
+     *    Setting this to 1 will cause the area of the WFS request to match
+     *    the map area exactly. It is recommended to set this to some number
+     *    at least slightly smaller than 1, otherwise accidental clicks can
+     *    cause a data reload, by moving the map only 1 pixel.
      */
     ratio: 2,