[OpenLayers-Users] mapExtents for Layer vs mapExtents for Map

[srweal]

Hi there,

I'm a new OpenLayers user and am struggling with the use of the mapExtent
setting.  I have a WMS that renders imagery for me, which is being accessed
through a TileCache.  The imagery only covers part of my entire map, so I
want to make sure OpenLayers is not requesting image tiles for areas beyond
the extent of the layer.  

However, when I set a mapExtent on my WMS layer to something like
(135,-45,180,0), it is still displaying 'pink tiles' over top of the base
layer of the map (which has mapExtent -something like 180,-90,180,90).  This
seems wrong, as the WMS layer may be set up to only return tiles inside the
BBOX (135,-45,180,0).  Am I missing something here with the way these
options are supposed to work?  Please explain.

The error response for the 'pink tiles' is "Lower left corner (90,-45) is
outside layer bounds [135,-45,180,0]. To remove this condition, set
extent_type=loose in your configuration."  

If I set the TileCache to extent_type=loose, all I get is blank
(transparent) tiles rendered everywhere which seems like a waste of server
resources to me.  I thought that by setting the mapExtent on the layer, I
would avoid OpenLayers requesting tiles beyond those extents.  Can someone
please explain how this works?  

Thanks.  Otherwise, everything is working great for me.  The combination of
TileCache, mod_python, OpenLayers is awesome.  Well done.

Steve

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