Add Mapguide Layer http served tile support. Patch from madair, positive

comments on usage from community members, r=me. (Closes #1622) 


git-svn-id: http://svn.openlayers.org/trunk/openlayers@9004 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/Layer/MapGuide.js

@@ -23,6 +23,16 @@ OpenLayers.Layer.MapGuide = OpenLayers.Class(OpenLayers.Layer.Grid, {
      **/
     isBaseLayer: true,
     
+    /**
+     * APIProperty: useHttpTile
+     * {Boolean} use a tile cache exposed directly via a webserver rather than the 
+	   *    via mapguide server. This does require extra configuration on the Mapguide Server,
+	   *    and will only work when singleTile is false. The url for the layer must be set to the
+	   *    webserver path rather than the Mapguide mapagent.	  
+	   *    See http://trac.osgeo.org/mapguide/wiki/CodeSamples/Tiles/ServingTilesViaHttp 
+     **/
+    useHttpTile: false,
+    
     /** 
      * APIProperty: singleTile
      * {Boolean} use tile server or request single tile image. Note that using
@@ -53,6 +63,19 @@ OpenLayers.Layer.MapGuide = OpenLayers.Class(OpenLayers.Layer.Grid, {
         version: '1.0.0'
     },
     
+    /** 
+     * Constant: FOLDER_PARAMS
+     * {Object} Hashtable of parameter key/value pairs which describe 
+     * the folder structure for tiles as configured in the mapguide 
+     * serverconfig.ini section [TileServiceProperties]
+     */
+    FOLDER_PARAMS: {
+        tileColumnsPerFolder: 30,
+        tileRowsPerFolder: 30,
+        format: 'png',
+        querystring: null
+    },	
+
     /** 
      * Property: defaultSize
      * {<OpenLayers.Size>} Tile size as produced by MapGuide server
@@ -130,10 +153,17 @@ OpenLayers.Layer.MapGuide = OpenLayers.Class(OpenLayers.Layer.Grid, {
                            
         } else {
             //initialize for tiled layers
-            OpenLayers.Util.applyDefaults(
-                           this.params,
-                           this.TILE_PARAMS
-                           );
+            if (this.useHttpTile) {
+                OpenLayers.Util.applyDefaults(
+                               this.params,
+                               this.FOLDER_PARAMS
+                               );
+            } else {
+                OpenLayers.Util.applyDefaults(
+                               this.params,
+                               this.TILE_PARAMS
+                               );
+            }
             this.setTileSize(this.defaultSize); 
         }
     },
@@ -230,15 +260,24 @@ OpenLayers.Layer.MapGuide = OpenLayers.Class(OpenLayers.Layer.Grid, {
           var rowidx = Math.floor((this.maxExtent.top-bounds.top)/currentRes);
           rowidx = Math.round(rowidx/this.tileSize.h);
 
-          url = this.getFullRequestString(
-                       {
-                           tilecol: colidx,
-                           tilerow: rowidx,
-                           scaleindex: this.resolutions.length - this.map.zoom - 1
-                        });
-           }
-        
-        return url;
+          if (this.useHttpTile){
+	          url = this.getImageFilePath(
+                   {
+                       tilecol: colidx,
+                       tilerow: rowidx,
+                       scaleindex: this.resolutions.length - this.map.zoom - 1
+                    });
+		  
+          } else {
+            url = this.getFullRequestString(
+                   {
+                       tilecol: colidx,
+                       tilerow: rowidx,
+                       scaleindex: this.resolutions.length - this.map.zoom - 1
+                    });
+          }
+       }
+       return url;
     },
 
     /**
@@ -305,6 +344,68 @@ OpenLayers.Layer.MapGuide = OpenLayers.Class(OpenLayers.Layer.Grid, {
         return requestString;
     },
 
+     /** 
+     * Method: getImageFilePath
+     * special handler to request mapguide tiles from an http exposed tilecache 
+     *
+     * Parameters:
+     * altUrl - {String} Alternative base URL to use.
+     *
+     * Returns:
+     * {String} A string with the url for the tile image
+     */
+    getImageFilePath:function(newParams, altUrl) {
+        // use layer's url unless altUrl passed in
+        var url = (altUrl == null) ? this.url : altUrl;
+        
+        // if url is not a string, it should be an array of strings, 
+        //  in which case we will randomly select one of them in order
+        //  to evenly distribute requests to different urls.
+        if (typeof url == "object") {
+            url = url[Math.floor(Math.random()*url.length)];
+        }   
+        // requestString always starts with url
+        var requestString = url;        
+
+        var tileRowGroup = "";
+        var tileColGroup = "";
+        
+        if (newParams.tilerow < 0) {
+          tileRowGroup =  '-';
+        }
+          
+        if (newParams.tilerow == 0 ) {
+          tileRowGroup += '0';
+        } else {
+          tileRowGroup += Math.floor(Math.abs(newParams.tilerow/this.params.tileRowsPerFolder)) * this.params.tileRowsPerFolder;
+        }
+          
+        if (newParams.tilecol < 0) {
+          tileColGroup =  '-';
+        }
+        
+        if (newParams.tilecol == 0) {
+          tileColGroup += '0';
+        } else {
+          tileColGroup += Math.floor(Math.abs(newParams.tilecol/this.params.tileColumnsPerFolder)) * this.params.tileColumnsPerFolder;
+        }					
+        
+        var tilePath = '/S' + Math.floor(newParams.scaleindex)
+                + '/' + this.params.basemaplayergroupname
+                + '/R' + tileRowGroup
+                + '/C' + tileColGroup
+                + '/' + (newParams.tilerow % this.params.tileRowsPerFolder) 
+                + '_' + (newParams.tilecol % this.params.tileColumnsPerFolder) 
+                + '.' + this.params.format;
+    
+        if (this.params.querystring) {
+               tilePath += "?" + this.params.querystring;
+        }
+        
+        requestString += tilePath;
+        return requestString;
+    },
+    
     /** 
      * Method: calculateGridLayout
      * Generate parameters for the grid layout. This