Tile opacity patch from tschaub: Fix for #235. Also includes tests to ensure

that code works.


git-svn-id: http://svn.openlayers.org/trunk/openlayers@1433 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/Layer.js

@@ -435,6 +435,18 @@ OpenLayers.Layer.prototype = {
                        Math.round(1/resolution * (extent.top - lonlat.lat))
                        );    
     },
+    
+    /**
+     * Sets the opacity for the entire layer (all images)
+     * @param {Float} opacity
+     */
+    setOpacity: function(opacity) {
+        this.opacity = opacity;
+        for(var i=0; i<this.div.childNodes.length; ++i) {
+            var element = this.div.childNodes[i];
+            OpenLayers.Util.setOpacity(element, opacity);
+        }
+    },
 
     /** @final @type String */
     CLASS_NAME: "OpenLayers.Layer"