Adjust how the parameters are calculated for the GETVISIBLEMAPEXTENT call for overlays so that existing parameters are safely overwritten with the required parameters for this call. r=me (Closes #1647)

git-svn-id: http://svn.openlayers.org/trunk/openlayers@7928 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/Layer/MapGuide.js

@@ -28,7 +28,7 @@ OpenLayers.Layer.MapGuide = OpenLayers.Class(OpenLayers.Layer.Grid, {
      * {Boolean} use tile server or request single tile image. Note that using
      *    singleTile *and* isBaseLayer false is *not recommend*: it uses synchronous
      *    XMLHttpRequests to load tiles, and this will *lock up users browsers*
-     *    during requests.
+     *    during requests if the server fails to respond.
      **/
     singleTile: false,
     
@@ -63,18 +63,29 @@ OpenLayers.Layer.MapGuide = OpenLayers.Class(OpenLayers.Layer.Grid, {
      * Constructor: OpenLayers.Layer.MapGuide
      * Create a new Mapguide layer, either tiled or untiled.  
      *
-     * For tiled layers, the 'groupName' and 'mapDefnition' options 
+     * For tiled layers, the 'groupName' and 'mapDefinition' values 
-     * must be specified as options.
+     * must be specified as parameters in the constructor.
      *
-     * For untiled layers, specify either combination of 'mapName' and
+     * For untiled base layers, specify either combination of 'mapName' and
      * 'session', or 'mapDefinition' and 'locale'.  
      *
+     * For untiled overlay layers (singleTile=true and isBaseLayer=false), 
+     * mapName and session are required parameters for the Layer constructor.  
+     * Also NOTE: untiled overlay layers issues a synchronous AJAX request 
+     * before the image request can be issued so the users browser may lock
+     * up if the MG Web tier does not respond in a timely fashion.
+     *
+     * NOTE: MapGuide OS uses a DPI value and degrees to meters conversion 
+     * factor that are different than the defaults used in OpenLayers, 
+     * so these must be adjusted accordingly in your application.  
+     * See the MapGuide example for how to set these values for MGOS.
+     *
      * Parameters:
      * name - {String} Name of the layer displayed in the interface
      * url - {String} Location of the MapGuide mapagent executable
      *            (e.g. http://localhost:8008/mapguide/mapagent/mapagent.fcgi)
      * params - {Object} hashtable of additional parameters to use. Some
-     *     parameters may require additional code on the serer. The ones that
+     *     parameters may require additional code on the server. The ones that
      *     you may want to use are: 
      *   - mapDefinition - {String} The MapGuide resource definition
      *            (e.g. Library://Samples/Gmap/Maps/gmapTiled.MapDefinition)
@@ -116,6 +127,7 @@ OpenLayers.Layer.MapGuide = OpenLayers.Class(OpenLayers.Layer.Grid, {
                            this.params,
                            this.SINGLE_TILE_PARAMS
                            );
+                           
         } else {
             //initialize for tiled layers
             OpenLayers.Util.applyDefaults(
@@ -196,16 +208,15 @@ OpenLayers.Layer.MapGuide = OpenLayers.Class(OpenLayers.Layer.Grid, {
             
             //but we first need to call GETVISIBLEMAPEXTENT to set the extent
             var getVisParams = {};
+            getVisParams = OpenLayers.Util.extend(getVisParams, params);
             getVisParams.operation = "GETVISIBLEMAPEXTENT";
             getVisParams.version = "1.0.0";
             getVisParams.session = this.params.session;
             getVisParams.mapName = this.params.mapName;
             getVisParams.format = 'text/xml';
-            getVisParams = OpenLayers.Util.extend(getVisParams, params);
+            url = this.getFullRequestString( getVisParams );
             
-            OpenLayers.Request.GET({
+            OpenLayers.Request.GET({url: url, async: false});
-                url: this.url, params: getVisParams, async: false
-            });
           }
           
           //construct the full URL
@@ -225,7 +236,7 @@ OpenLayers.Layer.MapGuide = OpenLayers.Class(OpenLayers.Layer.Grid, {
                            tilerow: rowidx,
                            scaleindex: this.resolutions.length - this.map.zoom - 1
                         });
-         }
+           }
         
         return url;
     },