My OpenLayers map was disabling layers with no minScale only at the most
zoomed-in level. Some firebug debugging showed that at that level, in
OpenLayers.Layer.calculateRange, this.map.getResolution() returns
0.14999999999999977 while this.minResolution is 0.15. My map
initialization parameters include { minResolution: 0.15 } so it would
seem paradoxical that this.map.getResolution() can return a value < 0.15.
Obviously there is a small roundoff problem here, which could be brushed
over by putting a very small tolerance (epsilon) value into the
calculateRange calculation:
inRange = ( (resolution >= this.minResolution /* - tolerance */) &&
(resolution <= this.maxResolution /* + tolerance */) );
My approach was to change the layer's minResolution from 0.15 to
Number.NEGATIVE_INFINITY. It unfortunately accomplishes this specious
task in a rather blunt way, clobbering the value of any
{min,max}Resolution parameters passed to Layer constructors.
Maybe this.map.getResolution() should just be tweaked to snap its value
to {min,max}Resolution if it's ever-so-slightly beyond one. Any
thoughts on the best course of action?
Thanks,
Dave Fuhry
P.S. Full map initialization params are: { maxExtent: new
OpenLayers.Bounds(-20000000,-20000000,20000000,20000000), maxResolution:
10000, minResolution: 0.15, numZoomLevels: 16, units: "m" }. I'm using
a spherical mercator projection.
Index: Layer.js
===================================================================
--- Layer.js (revision 7555)
+++ Layer.js (working copy)
@@ -797,8 +797,11 @@
this.resolutions = confProps.resolutions;
this.maxResolution = confProps.resolutions[0];
+ if (this.options.minScale == null) this.maxResolution = Number.POSITIVE_INFINITY;
var lastIndex = confProps.resolutions.length - 1;
this.minResolution = confProps.resolutions[lastIndex];
+ if (this.options.maxScale == null) this.minResolution = Number.NEGATIVE_INFINITY;
+
this.scales = [];
for(var i = 0; i < confProps.resolutions.length; i++) {
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