refactor range checking into map and store a state variable in layer so that we dont fire changelayer every time user zooms

git-svn-id: http://svn.openlayers.org/trunk/openlayers@1606 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/Control/LayerSwitcher.js

@@ -130,7 +130,7 @@ OpenLayers.Control.LayerSwitcher.prototype =
                 inputElem.layer = layer;
                 inputElem.control = this;
 
-                if (!baseLayer && !layer.inRange()) {
+                if (!baseLayer && !layer.inRange) {
                     inputElem.disabled = true;
                 }
                 OpenLayers.Event.observe(inputElem, "mouseup", 
@@ -138,7 +138,7 @@ OpenLayers.Control.LayerSwitcher.prototype =
                 
                 // create span
                 var labelSpan = document.createElement("span");
-                if (!baseLayer && !layer.inRange()) {
+                if (!baseLayer && !layer.inRange) {
                     labelSpan.style.color = "grey";
                 }
                 labelSpan.innerHTML = layer.name;

lib/OpenLayers/Layer.js

@@ -47,6 +47,14 @@ OpenLayers.Layer.prototype = {
      */
     visibility: true,
 
+    /** Whether or not the map's current resolution is within this layer's
+     *   min/max range -- this is set in map's setCenter() whenever zoom
+     *   changes
+     * 
+     * @type Boolean
+     */
+    inRange: false,
+
   // OPTIONS
 
     /** @type Array */
@@ -186,10 +194,7 @@ OpenLayers.Layer.prototype = {
      * @param {Boolean} dragging
      */
     moveTo:function(bounds, zoomChanged, dragging) {
-        if (zoomChanged) {
+        this.display(this.visibility && this.inRange);
-            this.display(this.visibility && this.inRange());
-            this.map.events.triggerEvent("changelayer");
-        }
     },
 
     /** Set the map property for the layer. This is done through an accessor
@@ -266,7 +271,7 @@ OpenLayers.Layer.prototype = {
      *          current resolution
      * @type Boolean
      */
-    inRange: function() {
+    calculateInRange: function() {
         var inRange = false;
         if (this.map) {
             var resolution = this.map.getResolution();

lib/OpenLayers/Map.js

@@ -691,7 +691,14 @@ OpenLayers.Map.prototype = {
             var bounds = this.getExtent();
             for (var i = 0; i < this.layers.length; i++) {
                 var layer = this.layers[i];
-                if (zoomChanged || (layer.display && layer.inRange())) {
+                
+                var inRange = layer.calculateInRange();
+                if (layer.inRange != inRange) {
+                    layer.inRange = inRange;
+                    this.events.triggerEvent("changelayer");
+                }
+                
+                if (zoomChanged || (layer.display && layer.inRange)) {
                     layer.moveTo(bounds, zoomChanged, dragging);
                 }
             }