WMS BBOX issues

[relliott]

When used as a WMS server mapserver will re-create the WMS BBOX by adding a -0.5pixel buffer to it (in fact its not a 0.5 pixel but a 0.5 unit so could be quite a distance). From the code I can see that it was done because mapserver uses the centre of the four corner pixels as its BBOX and not the outside of the pixels like WMS. This causes several problems: 1/ if you ask for a geoTiff the header will also be buffered by -0.5 and will not represent the original BBOX from the WMS request; 2/ if you have cascaded WMS layers in the map file the request they get uses the new buffered BBOX and not the original WMS one, this in itself can cause the returned image to be offset by half a unit.