[GRASS-dev] MASK_OVERRIDE

[Paul Kelly]

On Wed, 20 Feb 2008, Ivan Shmakov wrote:

>>>>>> Glynn Clements <glynn at gclements.plus.com> writes:
>
> > For this feature to be of real use, you need to allow MASK_OVERRIDE
> > to be used to disable reading a mask altogether. E.g. if
> > MASK_OVERRIDE is defined but empty, no mask should be used rather
> > than falling back to MASK. This would allow the GUI to operate
> > without a mask even when MASK has been created via the command line.
>
> 	The code doesn't ever fall back to `MASK' if `MASK_OVERRIDE' is
> 	defined.  If `MASK_OVERRIDE' doesn't point to a valid raster
> 	(e. g., if it's an empty string), the mask is ignored.
>
> 	However, I doubt if it's a reasonable behaviour.  It seems to be
> 	usual in the Unix world to ignore the environment variable's
> 	value if it's an empty string.  Using a non-existing raster
> 	(say, `.') is probably a better idea.

On Windows, an environment variable is unset by setting it to an empty 
string. There seems to be no difference between the two. So I don't think 
we could rely on the behaviour caused by MASK_OVERRIDE being an empty 
string. OTOH setting it to some garbage value seems a little unelegant, 
but as long as it's not a valid raster name there should be no problem I 
suppose.

Paul