v.digit background errors

[clerici]

The d.vect command in the Background panel of v.digit gives an error regarding topology rebuilding
1) I inserted roads_copy (a copy of roads in Spearfish) in the GIS Manager
2) I entered v.digit by the r.digit/v.digit button.
3) The v.digit GUI was correctly opened and the display was ok.
4) In the background panel the command 'd.vect map=roads_copy@esercizi color=0:0:0 ..........' is displayed by default.
5) I moved a node in roads_copy.
6) Clicking the Redraw button the following error message was reported in the Output window(Fig.1.)

Entering v.digit through: Vector>Develop map>Digitize the Background panel is empty.
I added the command 'd.vect map=roads_copy disp=cat' and I moved a node. In redrawing, the cat values were not displayed and I had the same error as in Fig.1.

I entered at the GRASS prompt the command: v.digit map=roads_copy map=roads_copy bgcmd='d.vect map=roads_copy disp=cat'. Moving a node and redrawing, the cat values were correctly displayed and two WARNING were reported in the terminal (Fig.2).

The error is the same with GRASS6.3, 6.4 and 6.5.

[mmetz]

Replying to clerici:

The d.vect command in the Background panel of v.digit gives an error regarding topology rebuilding

Using the very same vector map that is edited as background does not work because it gets modified and topology info is only updated when v.digit is closed. The only way that would work is to update and write out topology every time something is changed. This is not an option because then v.digit would be incredibly slow. It also doesn't really make sense because the vector map to be digitized is displayed anyway.

Therefore...

4) In the background panel the command 'd.vect map=roads_copy@esercizi color=0:0:0 ..........' is displayed by default.

...is this a bug in the tcltk GUI.

Entering v.digit through: Vector>Develop map>Digitize the Background panel is empty.
I added the command 'd.vect map=roads_copy disp=cat' and I moved a node. In redrawing, the cat values were not displayed and I had the same error as in Fig.1.

..and this will not work, i.e. produce the error you observed.

I entered at the GRASS prompt the command: v.digit map=roads_copy map=roads_copy bgcmd='d.vect map=roads_copy disp=cat'. Moving a node and redrawing, the cat values were correctly displayed and two WARNING were reported in the terminal (Fig.2).

..same as above.

If you want to compare changes, the only option is to first create a copy of the vector map and use that as background.

As above, this won't fix because v.digit would become even slower than it is already. If possible, use the new wxGUI digitizer (more features, faster, less memory).

[clerici]

What's strange is that the procedure runs well on GRASS6.2. With 'd.vect vectorname disp=cat' as background I can have a very useful updated and fast display of the category numbers during digitation or editing. The rebuilding of topology doesn't seem to require more time even with large vector files.
PS. Actually I cannot use the new wxGUI as I have to write a small manual for students that attended a preliminary GRASS course two years ago using the tcltk GUI. I'll do it sure in future (for the new students). Thanks.

[hamish]

Replying to clerici:

What's strange is that the procedure runs well on GRASS6.2.

IIRC Glynn rewrote it after 6.2, underneath the UI it's a different module by the same name.

FWIW I had used the same background image trick in 6.2, but I seem to recall it would crash after digitizing about 100 points or so. So I would exit and restart often but still got caught every now and then when the file was resized on the disk to accomodate the new points.

Hamish