This is a great piece of information. Thanks Chris. Christopher Schmidt a écrit : > On Wed, Sep 10, 2008 at 11:32:27AM +0200, Guillaume Sueur wrote: >> Hi, >> >> It seems that when layer's minResolution and maxResolution are set, the >> map's resolution are overriden and goes then from maxResolution to >> minResolution by x2 steps. >> Is it a normal behaviour or am I missing something ? > > This is normal behavior. > > OpenLayers has two different kind of layes: Base Layers, and Overlays. > Base layer resolutions control the resolutions available to the map: > when the base layer is switched, the available resolutions to zoom to > change. > > Overlays don't really care about hteir 'list' of resolutions: this list > is *only* used to determine whether a layer is in range or not. (In 2.7, > unless you pass layer-related resolution options *explicitly*, a layer > is always in range; this is a break from the past.) > > The map resolution options are used as a fallback to the layer > resolution options. When creating a layer, the initResolutions function > loops through all the resolution-relate properties, checking first if > the layer has such a property, then checking if the map has such a > property. In this way, it creates a 'complete' hash of all the > resolution related options. > > It then acts as if the layer has passed all those resolution options in > directly -- so, the map resolution parameters are just a fallback, which > is overridden by the layer. > > So, it is completely expected behavior that a layer will take the > feedback from the map, override it with its own settings, and call it > done. > > An easy way to prevent misbehavior is to simply always pass a list of > resolutions into your layer. Resolutions are the 'core' res properties > in OpenLayers, and override naything else set on the map or layer. you > don't *need* to go this far -- OpenLayers does a fair amount for you -- > but if you do that, you can never go wrong. > > (This isn't the first time a resolution-related question has been asked > which demosntrates a lack of understanding of this phenomen; This is > just a general response to the more general qustions we get.) > > Regards,
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