new restrictedMinZoom property. r=bartvde (closes #3024)

git-svn-id: http://svn.openlayers.org/trunk/openlayers@11058 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/Layer.js

@@ -275,6 +275,18 @@ OpenLayers.Layer = OpenLayers.Class({
      */
     numZoomLevels: null,
     
+    /**
+     * Property: restrictedMinZoom
+     * {Integer} Restriction of the minimum zoom level. This is used for layers
+     *     that only use a subset of the resolutions in the <resolutions>
+     *     array. This is independent of <numResolutions>, which always starts
+     *     counting at zoom level 0. If restrictedMinZoom is e.g. set to 2,
+     *     the first two zoom levels (0 and 1) will not be used by this layer.
+     *     If the layer is a base layer, zooming to the map's maxExtent means
+     *     setting the map's zoom to 2.
+     */
+    restrictedMinZoom: 0,
+   
     /**
      * APIProperty: minScale
      * {Float}
@@ -740,7 +752,8 @@ OpenLayers.Layer = OpenLayers.Class({
         } else {
             if (this.map) {
                 var resolution = this.map.getResolution();
-                inRange = ( (resolution >= this.minResolution) &&
+                inRange = ( this.map.getZoom() >= this.restrictedMinZoom &&
+                            (resolution >= this.minResolution) &&
                             (resolution <= this.maxResolution) );
             }
         }
@@ -1171,7 +1184,7 @@ OpenLayers.Layer = OpenLayers.Class({
             }
             zoom = Math.max(0, i-1);
         }
-        return zoom;
+        return Math.max(this.restrictedMinZoom, zoom);
     },
     
     /**

lib/OpenLayers/Map.js

@@ -1801,7 +1801,7 @@ OpenLayers.Map = OpenLayers.Class({
      */
     isValidZoomLevel: function(zoomLevel) {
         return ( (zoomLevel != null) &&
-                (zoomLevel >= 0) && 
+                (zoomLevel >= this.getRestrictedMinZoom()) && 
                 (zoomLevel < this.getNumZoomLevels()) );
     },
     
@@ -1905,6 +1905,20 @@ OpenLayers.Map = OpenLayers.Class({
         return maxExtent;
     },
     
+    /**
+     * Method: getRestricteMinZoom
+     *
+     * Returns:
+     * {Integer} the minimum zoom level allowed for the current baseLayer.
+     */
+    getRestrictedMinZoom: function() {
+        var minZoom = null;
+        if (this.baseLayer != null) {
+            minZoom = this.baseLayer.restrictedMinZoom;
+        }
+        return minZoom;
+    },
+    
     /**
      * APIMethod: getNumZoomLevels
      * 

tests/Layer.html

@@ -556,7 +556,7 @@
 
     function test_Layer_getZoomForResolution(t) {
 
-        t.plan(12);
+        t.plan(13);
 
         var layer = new OpenLayers.Layer('Test Layer');
         layer.map = {};
@@ -585,6 +585,9 @@
         t.eq(layer.getZoomForResolution(1).toPrecision(6), (layer.resolutions.length - 1).toPrecision(6),
              "(fractionalZoom) doesn't return zoom above highest index");
         
+        layer.restrictedMinZoom = 1;
+        t.eq(layer.getZoomForResolution(200), 1, "zoom all the way out, but we have a restrictedMinZoom of 1");
+
     }
     
     function test_Layer_redraw(t) {

tests/Map.html

@@ -326,6 +326,34 @@
     }
  */
 
+    function test_Map_isValidZoomLevel(t) {
+        t.plan(6);
+        var map = new OpenLayers.Map("map");
+        map.addLayer(new OpenLayers.Layer(null, {
+            isBaseLayer: true, numZoomLevels: 19
+        }))
+        var valid;
+
+        valid = OpenLayers.Map.prototype.isValidZoomLevel.apply(map, [0]);
+        t.eq(valid, true, "0 is a valid zoomLevel when baseLayer has no restrictedMinZoom");
+
+        valid = OpenLayers.Map.prototype.isValidZoomLevel.apply(map, [18]);
+        t.eq(valid, true, "18 is a valid zoomLevel");
+
+        valid = OpenLayers.Map.prototype.isValidZoomLevel.apply(map, [19]);
+        t.eq(valid, false, "19 is not a valid zoomLevel");
+        
+        map.baseLayer.restrictedMinZoom = 1;
+        valid = OpenLayers.Map.prototype.isValidZoomLevel.apply(map, [0]);
+        t.eq(valid, false, "0 is not a valid zoomLevel when baseLayer has restrictedMinZoom of 1");
+
+        valid = OpenLayers.Map.prototype.isValidZoomLevel.apply(map, [1]);
+        t.eq(valid, true, "1 is a valid zoomLevel");
+
+        valid = OpenLayers.Map.prototype.isValidZoomLevel.apply(map, [19]);
+        t.eq(valid, false, "19 is not a valid zoomLevel when baseLayer has restrictedMinZoom of 1");
+    }
+    
     function test_Map_isValidLonLat(t) {
         t.plan( 3 );    
 
@@ -1234,6 +1262,27 @@
         t.ok(maxExtent == map.baseLayer.maxExtent, "null options, valid baseLayer returns map.baseLayer.maxExtent");     
     }
 
+    function test_Map_getRestrictedMinZoom(t){
+        t.plan(3);
+
+        var map = {};
+
+      //no baseLayer
+        var minZoom = OpenLayers.Map.prototype.getRestrictedMinZoom.apply(map);
+        t.eq(minZoom, null, "no baseLayer returns null");
+        
+        map.baseLayer = new OpenLayers.Layer(null, {isBaseLayer: true});
+
+      //baseLayer
+        minZoom = OpenLayers.Map.prototype.getRestrictedMinZoom.apply(map);
+        t.eq(minZoom, 0, "default baseLayer.restrictedMinZoom returns 0");     
+
+      //custom minZoomLevel on baseLayer
+        map.baseLayer.restrictedMinZoom = 1;
+        minZoom = OpenLayers.Map.prototype.getRestrictedMinZoom.apply(map);
+        t.eq(minZoom, map.baseLayer.restrictedMinZoom, "custom baseLayer.restrictedMinZoom returns map.baseLayer.restrictedMinZoom");     
+    }
+    
     function test_Map_zoomToMaxExtent(t){
         t.plan(4)