[GRASS-dev] Re: [GRASS GIS] #254: wxpython Layer Manager: higher raster hides the lower (GRASS GIS)

[Michael Barton]

On Aug 14, 2008, at 8:19 PM, Glynn Clements wrote:

>
> Michael Barton wrote:
>
>>>> I think the mistake is the fact that in the wxGUI the raster is
>>> displayed without -o flag as default, as it is in the tcltk GUI.
>>>
>>> You can change default settings in GUI Preferences dialog, tab
>>> "Command",
>>> "Raster settings". I am not quite sure if '--o' should be defaut for
>>> d.rast as it is in TCL/TK GUI.
>>
>> I think that the default behavior of d.rast and the subsequent
>> addition of the -o flag is an historical artifact of the days before
>> GRASS rasters had null support. At that time, "0" values could mean a
>> values of 0 OR null values. Or nulls could be indicated by other
>> values like -999.
>>
>> Now that there is null support for rasters, the default behavior of
>> rasters should be that nulls are transparent during overlays,  
>> although
>> the option to make them opaque should be retained.
>>
>> The -o flag is additionally problematic in that it is very similar to
>> the --o flag which means "overwrite" in other contexts. We will need
>> to keep the -o flag for the GRASS 6 series, but I would recommend
>> changing it to something else for GRASS 7.
>
> Change in r32771. d.rast now makes nulls transparent by default; use
> -n to make them opaque. The -o flag no longer exists.
>
> The GUIs will need to be updated accordingly.

Thanks!

Michael

>
>
>> Do we need to keep opaque nulls the default for GRASS 6?
>
> For 6.x? d.rast can't change, but the default state of the checkbox in
> wxGUI could be changed (gis.m already makes -o the default).
>
> -- 
> Glynn Clements <glynn at gclements.plus.com>