javascript - Min/max zoom level in OpenLayers

Question

I'm using OpenLayers to display a map in a web page. I am using tiles from CloudMade, but the same issues occur with the Mapnik tiles from OpenStreetMap.

I'm trying to restrict the map so that the user cannot zoom all the way out to world view -- I want them to stay at roughly a city level zoom at minimum.

I have tried using the minZoomLevel / maxZoomLevel / numZoomLevels properties; only the maxZoomLevel and numZoomLevels properties seem to work, whereas the minZoomLevel property seems to be completely ignored.

Is there another way to accomplish this?

Answer 1

You could override the isValidZoomLevel function. Something like this (not tested):

OpenLayers.Map.isValidZoomLevel = function(zoomLevel) {
   return ( (zoomLevel != null) &&
      (zoomLevel >= 2) && // set min level here, could read from property
      (zoomLevel < this.getNumZoomLevels()) );
}

EDIT

Or you would need to override the available resolutions, see the example here: http://dev.openlayers.org/examples/zoomLevels.html