[GRASS5] Window Extents and region settings in X...

Roger Bivand rsb at reclus.nhh.no
Wed Feb 28 13:34:04 EST 2001

On Wed, 28 Feb 2001, Radim Blazek wrote:

> Eric G. Miller wrote:
> > I noticed after the bit of work I've done on d.area, that I still have a
> > small inconsistency with much of the rest of the display code.  Here's
> > the scenario:
> > 
> I think that region handling should be changed somehow. But that's task 
> for g51. My suggestion (not thought over deeply yet) is to distinguish region
> used by:
> 1) modules creating new data  
>     which would use current region saved in WIND
> and
> 2) monitor + display/query modules
>     which would use region stored in memory of monitor.
>     Each monitor would have it's own region.
> Monitor region would always cover whole area of monitor.
> New functions could be used for manipulating currend WIND, for example
> display WIND on monitor (by rectangle), set WIND to region of selected
> monitor, create WIND interactively on monitor, ...
> Some problems with one shared region as is used now:
> - user cannot rely on current state of monitor, if region was changed for
>    a while, d.erase must be run even if region was reset to original size.
> - it is impossible to run some script on data and at the same time
>    explore maps on monitor (I forgot several times about it and I was very
>    surprised why created data are incomplete)
> - write access to database is always required even if user want only
>    read/explore data.
> - (more?)

This issue also arises in interfacing with other programs in my case
R. This was also why, in discussion with Markus in Chatham in August, I
asked whether some kind of metadata checkin/checkout daemon might not be
an idea, so that each piece of data knew what was happening to the
others. In the same way as with WIND changing in relation to the display,
an external program can't know or update for region changes, and maybe it
should, so that regions stay harmonised. Something like a grassmaster,
that GRASS programs and external programs could ask for appropriate
metadata, to supplement (replace?) files in the present database
structure. This is very unclear, but some mechanism for ensuring coherence
seems to be needed.


Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Breiviksveien 40, N-5045 Bergen,
Norway. voice: +47 55 95 93 55; fax +47 55 95 93 93
e-mail: Roger.Bivand at nhh.no
and: Department of Geography and Regional Development, University of
Gdansk, al. Mar. J. Pilsudskiego 46, PL-81 378 Gdynia, Poland.

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