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

[Glynn Clements]

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.

> 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>