From a14418f53f72a46341168ea9e25e0112e1e5f485 Mon Sep 17 00:00:00 2001
From: Tim Schaub <tim.schaub@gmail.com>
Date: Mon, 28 Jan 2008 16:28:21 +0000
Subject: [PATCH] Modifying initResolutions so that minResolution and
 numZoomLevels are respected if they are set as layer options.  Note that if
 only minResolution and maxResolution are specified, minResolution will still
 not be respected in general.  r=pspencer (closes #1300)

git-svn-id: http://svn.openlayers.org/trunk/openlayers@5918 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf
---
 lib/OpenLayers/Layer.js | 31 +++++++++++++++++++++++--------
 tests/test_Layer.html   | 18 ++++++++++++++++++
 2 files changed, 41 insertions(+), 8 deletions(-)

diff --git a/lib/OpenLayers/Layer.js b/lib/OpenLayers/Layer.js
index 1314c2871b..b037391c88 100644
--- a/lib/OpenLayers/Layer.js
+++ b/lib/OpenLayers/Layer.js
@@ -663,9 +663,7 @@ OpenLayers.Layer = OpenLayers.Class({
 
         } else {
           //maxResolution and numZoomLevels based calculation
-            
-            confProps.resolutions = [];
-            
+
             // determine maxResolution
             if (confProps.minScale) {
                 confProps.maxResolution = 
@@ -691,8 +689,9 @@ OpenLayers.Layer = OpenLayers.Class({
                 confProps.minResolution = Math.max(wRes, hRes);
             } 
 
-            // determine numZoomLevels
-            if (confProps.minResolution != null) {
+            // determine numZoomLevels if not already set on the layer
+            if (confProps.minResolution != null &&
+                this.options.numZoomLevels == undefined) {
                 var ratio = confProps.maxResolution / confProps.minResolution;
                 confProps.numZoomLevels = 
                     Math.floor(Math.log(ratio) / Math.log(2)) + 1;
@@ -700,10 +699,26 @@ OpenLayers.Layer = OpenLayers.Class({
             
             // now we have numZoomLevels and maxResolution, 
             //  we can populate the resolutions array
+            confProps.resolutions = new Array(confProps.numZoomLevels);
+            var base = 2;
+            if(typeof confProps.minResolution == "number" &&
+               this.options.numZoomLevels > 1) {
+                /**
+                 * If numZoomLevels is explicitly set in the layer options,
+                 * respect it.  If numZoomLevels is not specified, we use
+                 * exponential scaling with a base of 2.  If numZoomLevels
+                 * is specified, we use exponential scaling and determine the
+                 * appropriate base so minResolution is reached.
+                 */
+                base = Math.pow(
+                    (confProps.maxResolution / confProps.minResolution),
+                    (1 / (confProps.numZoomLevels - 1))
+                );
+            }
             for (var i=0; i < confProps.numZoomLevels; i++) {
-                var res = confProps.maxResolution / Math.pow(2, i);
-                confProps.resolutions.push(res);
-            }    
+                var res = confProps.maxResolution / Math.pow(base, i);
+                confProps.resolutions[i] = res;
+            }
         }
         
         //sort resolutions array ascendingly
diff --git a/tests/test_Layer.html b/tests/test_Layer.html
index 3ee58d4deb..8498ba179a 100644
--- a/tests/test_Layer.html
+++ b/tests/test_Layer.html
@@ -118,6 +118,24 @@
         t.eq(layer.maxResolution, maxResolution, "maxResolution set correctly");
         t.eq(layer.numZoomLevels, numZoomLevels, "numZoomLevels set correctly");
     }
+    
+    function test_Layer_initResolutions(t) {
+        t.plan(3);
+        var map = new OpenLayers.Map("map");
+        var options = {
+            minResolution: 1,
+            maxResolution: 10,
+            numZoomLevels: 5
+        };
+        var layer = new OpenLayers.Layer("test", options);
+        layer.map = map;
+        layer.initResolutions();
+        t.eq(layer.minResolution.toPrecision(9), (1).toPrecision(9),
+             "layer minResolution preserved");
+        t.eq(layer.maxResolution.toPrecision(9), (10).toPrecision(9),
+             "layer maxResolution preserved");
+        t.eq(layer.numZoomLevels, 5, "layer numZoomLevels preserved"); 
+    }
 
     function test_05_Layer_visibility(t) {