context can now be given as argument in StyleMap.addUniqueValueRules()

this, for example, allows user to access to properties that are not part of the feature attributes.
r=elemoine (closes #1548)

git-svn-id: http://svn.openlayers.org/trunk/openlayers@7216 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

examples/styles-unique.html

@@ -47,6 +47,42 @@
             
             layer.addFeatures(features);
             map.addLayer(layer);
+            
+            // create 20 random features with a random state property.
+            var features = new Array(20);
+            var states = [
+                OpenLayers.State.UNKNOWN,
+                OpenLayers.State.UPDATE,
+                OpenLayers.State.DELETE,
+                OpenLayers.State.INSERT
+            ];
+            for (var i=0; i<20; i++) {
+                features[i] = new OpenLayers.Feature.Vector(
+                    new OpenLayers.Geometry.Point(Math.random()*360-180, Math.random()*180-90)
+                );
+                features[i].state = states[parseInt(Math.random()*4)];
+            }
+            
+            var context = function(feature) {
+                return feature;
+            }
+            var styleMap = new OpenLayers.StyleMap();
+            
+            // create a lookup table with different symbolizers for the diffent
+            // state values
+            var lookup = {};
+            lookup[OpenLayers.State.UNKNOWN] = {fillColor: "green"};
+            lookup[OpenLayers.State.UPDATE] = {fillColor: "green"};
+            lookup[OpenLayers.State.DELETE] = {fillColor: "red"};
+            lookup[OpenLayers.State.INSERT] = {fillColor: "orange"};
+
+            styleMap.addUniqueValueRules("default", "state", lookup, context);
+            layer = new OpenLayers.Layer.Vector('Points', {
+                styleMap: styleMap
+            });
+            
+            layer.addFeatures(features);
+            map.addLayer(layer);
         }
     </script>
   </head>
@@ -56,7 +92,11 @@
     <div id="tags"></div>
 
     <p id="shortdesc">
-      Shows how to create a style based on unique feature attribute values.
+      Shows how to create a style based :
+      <ul> 
+        <li>on unique feature attribute values (markers),</li>
+        <li>on feature state values (circles).</li>
+      </ul>
     </p>
 
     <div id="map" class="smallmap"></div>

lib/OpenLayers/Rule.js

@@ -173,6 +173,9 @@ OpenLayers.Rule = OpenLayers.Class({
         if (!context) {
             context = feature.attributes || feature.data;
         }
+        if (typeof this.context == "function") {
+            context = this.context(feature);
+        }
         return context;
     },
         

lib/OpenLayers/StyleMap.js

@@ -130,12 +130,17 @@ OpenLayers.StyleMap = OpenLayers.Class({
      *                rules for
      * symbolizers  - {Object} Hash of symbolizers, keyed by the desired
      *                property values 
+     * context      - {Object} An optional object with properties that
+     *                symbolizers' property values should be evaluated
+     *                against. If no context is specified, feature.attributes
+     *                will be used
      */
-    addUniqueValueRules: function(renderIntent, property, symbolizers) {
+    addUniqueValueRules: function(renderIntent, property, symbolizers, context) {
         var rules = [];
         for (var value in symbolizers) {
             rules.push(new OpenLayers.Rule({
                 symbolizer: symbolizers[value],
+                context: context,
                 filter: new OpenLayers.Filter.Comparison({
                     type: OpenLayers.Filter.Comparison.EQUAL_TO,
                     property: property,

tests/Rule.html

@@ -14,6 +14,33 @@
         t.eq(typeof rule.evaluate, "function", "rule has an evaluate function"); 
     }
     
+    function test_Rule_getContext(t) { 
+        t.plan(2);
+        var rule, options;
+        
+        var feature = {
+            attributes: {
+                'dude': 'hello'
+            },
+            'foobar': 'world'
+        }
+        
+        rule = new OpenLayers.Rule();
+        var context = rule.getContext(feature);
+        t.eq(context.dude, "hello", "value returned by getContext is correct"
+            + " if no context is specified"); 
+        
+        var options = {
+            context: function(feature){
+                return feature;
+            }
+        };
+        rule = new OpenLayers.Rule(options);
+        var context = rule.getContext(feature);
+        t.eq(context.foobar, "world", "value returned by getContext is correct"
+            + " if a context is given in constructor options"); 
+    }
+
     function test_Rule_destroy(t) {
         t.plan(1);