[fusion-commits] r2605 - sandbox/ol212/lib

[svn_fusion at osgeo.org]

Author: jng
Date: 2012-09-19 02:46:11 -0700 (Wed, 19 Sep 2012)
New Revision: 2605

Modified:
   sandbox/ol212/lib/Map.js
Log:
Document the new client-zoom capabilities

Modified: sandbox/ol212/lib/Map.js
===================================================================
--- sandbox/ol212/lib/Map.js	2012-09-18 07:06:11 UTC (rev 2604)
+++ sandbox/ol212/lib/Map.js	2012-09-19 09:46:11 UTC (rev 2605)
@@ -168,7 +168,7 @@
     /** flag to indicate if fractional zoom is supported, ie. allow any scale
     *   value rather than a fixed set of scales
     */
-    fractionalZoom: true,
+    fractionalZoom: false,
     
     /** The DOM object that holds the map */
     maxScale: null, //set this to a large number in AppDef to zoom out beyond maxExtent, e.g. 1 billion
@@ -410,41 +410,69 @@
         this.oMapOL.setBaseLayer(this.aMaps[0].oLayerOL);
       }
 
-      if (this.fractionalZoom) {
-        var newResolutions = null;
-        var mgResolutions = null;
-        for (var i = 0; i < this.aMaps.length; i++) {
-            if (this.aMaps[i].arch == 'MapGuide') {
-                mgResolutions = this.aMaps[i].oLayerOL.resolutions;
-            }
-        }
-        for (var i = 0; i < this.aMaps.length; i++) {
-            if (this.aMaps[i].arch == 'Generic') {
-                var oLayer = this.aMaps[i].oLayerOL;
-                oLayer.serverResolutions = oLayer.resolutions;
-                if (newResolutions == null) {
-                    newResolutions = [];
-                    for (var j = 0; j < oLayer.serverResolutions.length; j++) {
-                        newResolutions.push(oLayer.serverResolutions[j]);
-                    }
-                    for (var j = 0; j < mgResolutions.length; j++) {
-                        if (mgResolutions[j] < oLayer.minResolution) {
-                            newResolutions.push(mgResolutions[j]);
-                        }
-                    }
-                }
-                oLayer.resolutions = newResolutions;
-                var newScales = [];
-                for (var i = 0; i < newResolutions.length; i++) {
-                    newScales.push(OpenLayers.Util.getScaleFromResolution(newResolutions[i], oLayer.units));
-                }
-                oLayer.scales = newScales;
-                oLayer.minResolution = newResolutions[newResolutions.length - 1];
-                oLayer.maxScale = newScales[newScales.length - 1];
-                oLayer.numZoomLevels = newScales.length;
-            }
-        }
+      //Take advantage of new client-zoom capabilities introduced in OpenLayers 2.12
+      //
+      //What we do here is for every grid-based commerical layer, we tack on extra resolutions
+      //of the MapGuide OL Layer that is below the minimum supported resolution of the commercial
+      //layers. The existing resolutions array is shifted to the layer's serverResolutions array.
+      //
+      //When we go below the minimum supported resolution of these commercial layers, 
+      //client-zoom kicks in and stretches the commerical layers appropriately.
+      //
+      //A small side-effect is that if fractionalZoom = true, and the layer setup is such that
+      //this won't be set to false during initialization (eg. fractionalZoom = true + 
+      //A MapGuide dynamic map + OSM layers), then the OSM layers will almost always be slightly 
+      //stretched, as any zoom scale is allowed and OL will be stretching the OSM layers to match.
+      //
+      //This technique does not work with Google layers (as they aren't grid-based). The mere presence
+      //of Google layers (or any non-Grid layers) will disable client-zoom, and your map will be snapping
+      //to whatever discrete scale list that is imposed by the commercial layer
+      //
+      //With these changes the behaviour is like so (OSM is interchangeable with any other grid-based layer):
+      //
+      // - MapGuide + OSM (fractionalZoom = true): Fully dynamic map and OSM tiles are stretched accordingly. OSM 
+      //                                           tiles will most likely never be un-stretched due to the fully dynamic
+      //                                           nature of the map.
+      // - MapGuide + OSM (fractionalZoom = false): Scales "snap" to OSM scales and are stretched accordingly 
+      //                                            when going below the minimum supported OSM scale
+      // - MapGuide + OSM + Explicit Scale List: Scales "snap" to OSM scales (any MG scales within the OSM scale 
+      //                                         list are disregarded). OSM tiles are stretched accordingly when 
+      //                                         going below the minimum supported OSM scale
+      //                                         
+      //TODO: Yet to observe this behaviour with tiled MG maps or maps with tiled/untiled mixtures
+      var newResolutions = null;
+      var mgResolutions = null;
+      for (var i = 0; i < this.aMaps.length; i++) {
+          if (this.aMaps[i].arch == 'MapGuide') {
+              mgResolutions = this.aMaps[i].oLayerOL.resolutions;
+          }
       }
+      for (var i = 0; i < this.aMaps.length; i++) {
+          if (this.aMaps[i].arch == 'Generic') {
+              var oLayer = this.aMaps[i].oLayerOL;
+              oLayer.serverResolutions = oLayer.resolutions;
+              if (newResolutions == null) {
+                  newResolutions = [];
+                  for (var j = 0; j < oLayer.serverResolutions.length; j++) {
+                      newResolutions.push(oLayer.serverResolutions[j]);
+                  }
+                  for (var j = 0; j < mgResolutions.length; j++) {
+                      if (mgResolutions[j] < oLayer.minResolution) {
+                          newResolutions.push(mgResolutions[j]);
+                      }
+                  }
+              }
+              oLayer.resolutions = newResolutions;
+              var newScales = [];
+              for (var i = 0; i < newResolutions.length; i++) {
+                  newScales.push(OpenLayers.Util.getScaleFromResolution(newResolutions[i], oLayer.units));
+              }
+              oLayer.scales = newScales;
+              oLayer.minResolution = newResolutions[newResolutions.length - 1];
+              oLayer.maxScale = newScales[newScales.length - 1];
+              oLayer.numZoomLevels = newScales.length;
+          }
+      }
       
       var initialExtent = this.setInitialExtents();
       this.setExtents(initialExtent);