Update calculateInRange: Only turn layers off if they have some scale-related

properties set directly in their creation options. By default, layers will 
be "always on", with an overridable "alwaysInRange" parameter.

To maintain the old behavior, set:
   OpenLayers.Layer.prototype.alwaysInRange = false;

r=euzuro
(Closes #987)


git-svn-id: http://svn.openlayers.org/trunk/openlayers@7863 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/Layer.js

@@ -37,6 +37,23 @@ OpenLayers.Layer = OpenLayers.Class({
      */
     opacity: null,
 
+    /**
+     * APIProperty: alwaysInRange
+     * {Boolean} If a layer's display should not be scale-based, this should 
+     *     be set to true. This will cause the layer, as an overlay, to always 
+     *     be 'active', by always returning true from the calculateInRange() 
+     *     function. 
+     * 
+     *     If not explicitly specified for a layer, its value will be 
+     *     determined on startup in initResolutions() based on whether or not 
+     *     any scale-specific properties have been set as options on the 
+     *     layer. If no scale-specific options have been set on the layer, we 
+     *     assume that it should always be in range.
+     * 
+     *     See #987 for more info.
+     */
+    alwaysInRange: null,   
+
     /**
      * Constant: EVENT_TYPES
      * {Array(String)} Supported application event types.  Register a listener
@@ -615,14 +632,20 @@ OpenLayers.Layer = OpenLayers.Class({
      * 
      * Returns:
      * {Boolean} The layer is displayable at the current map's current
-     *     resolution.
+     *     resolution. Note that if 'alwaysInRange' is true for the layer, 
+     *     this function will always return true.
      */
     calculateInRange: function() {
         var inRange = false;
-        if (this.map) {
+
-            var resolution = this.map.getResolution();
+        if (this.alwaysInRange) {
-            inRange = ( (resolution >= this.minResolution) &&
+            inRange = true;
-                        (resolution <= this.maxResolution) );
+        } else {
+            if (this.map) {
+                var resolution = this.map.getResolution();
+                inRange = ( (resolution >= this.minResolution) &&
+                            (resolution <= this.maxResolution) );
+            }
         }
         return inRange;
     },
@@ -677,6 +700,15 @@ OpenLayers.Layer = OpenLayers.Class({
           'numZoomLevels', 'maxZoomLevel'
         );
 
+        //these are the properties which do *not* imply that user wishes 
+        // this layer to be scale-dependant
+        var notScaleProps = ['projection', 'units'];    
+
+        //should the layer be scale-dependant? default is false -- this will 
+        // only be set true if we find that the user has specified a property
+        // from the 'props' array that is not in 'notScaleProps'
+        var useInRange = false;
+
         // First we create a new object where we will store all of the 
         //  resolution-related properties that we find in either the layer's
         //  'options' array or from the map.
@@ -684,9 +716,28 @@ OpenLayers.Layer = OpenLayers.Class({
         var confProps = {};        
         for(var i=0, len=props.length; i<len; i++) {
             var property = props[i];
+            
+            // If the layer had one of these properties set *and* it is 
+            // a scale property (is not a non-scale property), then we assume
+            // the user did intend to use scale-dependant display (useInRange).
+            if (this.options[property] && 
+                OpenLayers.Util.indexOf(notScaleProps, property) == -1) {
+                useInRange = true;
+            }
+                   
             confProps[property] = this.options[property] || this.map[property];
         }
 
+        //only automatically set 'alwaysInRange' if the user hasn't already 
+        // set it (to true or false, since the default is null). If user did
+        // not intend to use scale-dependant display then we set they layer
+        // as alwaysInRange. This means calculateInRange() will always return 
+        // true and the layer will never be turned off due to scale changes.
+        //
+        if (this.alwaysInRange == null) {
+            this.alwaysInRange = !useInRange;
+        }
+
         // Do not use the scales array set at the map level if 
         // either minScale or maxScale or both are set at the
         // layer level

tests/Layer.html

@@ -145,11 +145,11 @@
     }
 
     function test_Layer_initResolutions(t) {
-        t.plan(12);
+        t.plan(15);
         var map = new OpenLayers.Map("map");
         var options, layer;
         
-        // three tests for minResolution, maxResolution, and numZoomLevels
+        // tests for minResolution, maxResolution, and numZoomLevels
         options = {
             minResolution: 1.5,
             maxResolution: 10.5,
@@ -163,7 +163,8 @@
         t.eq(layer.maxResolution.toPrecision(6), (10.5).toPrecision(6),
              "(with numZoomLevels) layer maxResolution preserved");
         t.eq(layer.numZoomLevels, 5, "(with numZoomLevels) layer numZoomLevels preserved");
-        
+        t.eq(layer.alwaysInRange, false, "Always in range is set to false due to passed options.")        
+
         // three tests for minResolution, and maxResolution
         options = {
             minResolution: 1.5,
@@ -206,6 +207,16 @@
         t.eq(layer.maxScale.toPrecision(6), (155).toPrecision(6),
              "(without numZoomLevels) layer maxScale preserved");
         t.eq(layer.numZoomLevels, 4, "(without numZoomLevels) layer numZoomLevels calculated");
+        
+        layer = new OpenLayers.Layer("test", {'projection': 'EPSG:4326', 'map': map});
+        layer.initResolutions();
+        t.eq(layer.alwaysInRange, true, "always in range true if only get projection.");     
+        
+        OpenLayers.Layer.prototype.alwaysInRange = false;
+        layer = new OpenLayers.Layer("test", {'projection': 'EPSG:4326', 'map': map});
+        layer.initResolutions();
+        t.eq(layer.alwaysInRange, false, "always in range true if overridden on prototype.");     
+        OpenLayers.Layer.prototype.alwaysInRange = null;
 
         map.destroy();