allow protocols to be configured with a default filter, p=aabt, r=me (closes #2292)

git-svn-id: http://svn.openlayers.org/trunk/openlayers@9702 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/Protocol.js

@@ -29,6 +29,12 @@ OpenLayers.Protocol = OpenLayers.Class({
      */
     autoDestroy: true,
    
+    /**
+     * Property: defaultFilter
+     * {OpenLayers.Filter} Optional default filter to read requests
+     */
+    defaultFilter: null,
+    
     /**
      * Constructor: OpenLayers.Protocol
      * Abstract class for vector protocols.  Create instances of a subclass.
@@ -43,6 +49,28 @@ OpenLayers.Protocol = OpenLayers.Class({
         this.options = options;
     },
 
+    /**
+     * Method: mergeWithDefaultFilter
+     * Merge filter passed to the read method with the default one
+     *
+     * Parameters:
+     * filter - {OpenLayers.Filter}
+     */
+    mergeWithDefaultFilter: function(filter) {
+        if(filter) {
+            if(this.defaultFilter) {
+                filter = new OpenLayers.Filter.Logical({
+                    type: OpenLayers.Filter.Logical.AND,
+                    filters: [this.defaultFilter, filter]
+                });
+            }
+        } else {
+            filter = this.defaultFilter;
+        }
+        return filter;
+    },
+
+
     /**
      * APIMethod: destroy
      * Clean up the protocol.
@@ -64,7 +92,9 @@ OpenLayers.Protocol = OpenLayers.Class({
      * object, the same object will be passed to the callback function passed
      * if one exists in the options object.
      */
-    read: function() {
+    read: function(options) {
+        options = options || {};
+        options.filter = this.mergeWithDefaultFilter(options.filter);
     },