add getDataExtent() method to layer (experimental) and to markers layer (api supported). thanks for the feature request and original patch, anonymous ol-er :-) (Closes #750)

git-svn-id: http://svn.openlayers.org/trunk/openlayers@4051 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/Layer.js

@@ -723,6 +723,18 @@ OpenLayers.Layer = OpenLayers.Class({
         return this.getZoomForResolution(idealResolution);
     },
     
+    /** 
+     * Method: getDataExtent
+     * Calculates the max extent which includes all of the data for the layer.
+     *     This function is to be implemented by subclasses.
+     * 
+     * Returns:
+     * {<OpenLayers.Bounds>}
+     */
+    getDataExtent: function () {
+        //to be implemented by subclasses
+    },
+
     /**
      * APIMethod: getZoomForResolution
      * 

lib/OpenLayers/Layer/Markers.js

@@ -139,6 +139,27 @@ OpenLayers.Layer.Markers = OpenLayers.Class(OpenLayers.Layer, {
             }
         }
     },
+    
+    /** 
+     * APIMethod: getDataExtent
+     * Calculates the max extent which includes all of the markers.
+     * 
+     * Returns:
+     * {<OpenLayers.Bounds>}
+     */
+    getDataExtent: function () {
+        var maxExtent = null;
+        
+        if ( this.markers && (this.markers.length > 0)) {
+            var maxExtent = new OpenLayers.Bounds();
+            for(var i=0; i < this.markers.length; i++) {
+                var marker = this.markers[i];
+                maxExtent.extend(marker.lonlat);
+            }
+        }
+
+        return maxExtent;
+    },
 
     CLASS_NAME: "OpenLayers.Layer.Markers"
 });

tests/Layer/test_Markers.html

@@ -49,6 +49,34 @@
         layer.destroy();
         t.eq( layer.map, null, "layer.map is null after destroy" );
     }
+
+    function test_03_Layer_Markers_getDataExtent(t) {
+        t.plan( 4 );
+
+        var layer = {};
+        var ret = OpenLayers.Layer.Markers.prototype.getDataExtent.apply(layer, []);
+        t.eq(ret, null, "does not crash, returns null on layer with null 'this.markers'");
+
+        layer.markers = [];
+        ret = OpenLayers.Layer.Markers.prototype.getDataExtent.apply(layer, []);
+        t.eq(ret, null, "returns null on layer with empty 'this.markers'");
+        
+        layer.markers.push({
+            'lonlat': new OpenLayers.LonLat(4,5)
+        });
+        var expectedBounds = new OpenLayers.Bounds(4,5,4,5);
+        ret = OpenLayers.Layer.Markers.prototype.getDataExtent.apply(layer, []);
+        t.ok(ret.equals(expectedBounds), "returns expected bounds with only one marker");
+
+        layer.markers.push({
+            'lonlat': new OpenLayers.LonLat(1,2)
+        });
+        var expectedBounds = new OpenLayers.Bounds(1,2,4,5);
+        ret = OpenLayers.Layer.Markers.prototype.getDataExtent.apply(layer, []);
+        t.ok(ret.equals(expectedBounds), "returns expected bounds with multiple markers");
+
+    }
+
   // -->
   </script>
 </head>