[GRASS-dev] how to display a vector map for d.path in gis.m?

[Otto Dassau]

On Tue, 30 Jan 2007 11:19:18 +0100
Moritz Lennert <mlennert at club.worldonline.be> wrote:

> On 30/01/07 10:43, Otto Dassau wrote:
> > Hi Moritz,
> > 
> > On Tue, 30 Jan 2007 10:03:10 +0100
> > Moritz Lennert <mlennert at club.worldonline.be> wrote:
> > 
> >> On 30/01/07 08:37, Otto Dassau wrote:
> >>> Hi, 
> >>>
> >>> I used the d.path module in gis.m and found that the map I chose for
> > calculating
> >>> the shortest path is not automatically displayed in the background. So I
> > have a
> >>> white monitor where I can select my starting and end nodes to display a
red
> >>> line.
> >>>
> >>> Is this missing or how do I have to use the module correctly in gis.m to
> > display
> >>> a vector map in the background? I used a grass cvs snapshot from today and
> > tried
> >>> with spearfish roads map.
> >>
> >> d.path uses the old monitor system, not the new gis.m display, so when 
> >> you launch it through the gis.m menu, an x-monitor opens (with something 
> >> like Monitor: x0 written in the title bar). You can display whatever you 
> >> want in this monitor by using the command line, e.g.:
> >>
> >> d.vect roads
> > 
> > thanks for your help,
> > 
> > yes I saw that, but I think that it might  be more intuitive for a user to
> > have the selected map for d.path visualized directly in the new x-monitor,
when
> > when you click on start.  
> > 
> > I mean, it is not an error, and of course one can easily type a d.vect roads
> > command or whatever, but I found it strange that klicking on start you get
an
> > empty x-monitor and a usage desription for the mouse buttons in the Output
> > monitor, but the map you selected in the d.path popup is not automatically
> > displayed.
> > 
> > Maybe it is just my impression, so for me there is simply sth. missing.
Could
> > that not be added or is this difficult or not wanted?
> > 
> > maybe I should add a wish to the bugtracker... but I wanted to ask, if there
is
> > a special reason, why the selected map isn't displayed in the new x-monitor.
> 
> You are right that this is currently a bit counter-intuitive. The 
> problem is that d.path was developed for the old monitoring system, 
> where you would display your maps and then run d.path on them. Now that 
> users use gis.m, and display their maps in the gis.m display, this 
> obviously causes a problem. This said the man page actually states: " 
> The user needs to display a vector map before using d.path."
> 
> d.path could be rewritten to display the chosen vector map 
> automatically, but there might be situations where you don't want this 
> map to be in the background, so imposing this might not be a good idea 
> either...
> 
> In any case, I don't think we should invest any more development time 
> into modules which depend on the x-monitors, so in my eyes the best 
> solution would be to start from the non-interactive v.net.path and 
> possibly write an interactive GUI wrapper around it which would allow 
> you to click on start and end points and would then create a temporary 
> vector file for display which it either discards afterwards or saves it 
> to a given filename. I don't think this would be too complicated, maybe 
> something for a python-programmer to try for the wxpython gui.

ok, now I understand and I totally agree.

thanks for the info, Moritz!

regards,
 Otto
 
> Moritz