[GRASS5] Bug: vector maps shifted (d.area / d.vect)

Bernhard Reiter bernhard at intevation.de
Sun Oct 21 09:58:03 EDT 2001

On Sun, Oct 21, 2001 at 01:55:33PM +0200, Markus Neteler wrote:
> On Sat, Oct 20, 2001 at 12:44:41PM +0100, Glynn Clements wrote:

> > If you remove the +0.5 from fastline(), d.vect and d.area coincide. 
> > However, G_plot_line() is used in many places, so changing it to suit
> > d.vect may break other things.
> Thanks for looking into it. But I wouldn't call it "breaking things":
> For 5.0 the display needs to be consistent in my opinion, we should
> not accept map shifts. I am willing to search-and-fix, but need a
> hint what route to follow.
> Raster and vector overlays should be 100% o.k.

Nobody will say no to this.
On the other hand Glynn's comment is correct:
Changing things in a core function which is used at various places
is not a change you want todo between a pre2 and a final release.
If this inconsistency was there for a long time other code might
work around it in places you cannot easily see. Fixing it in the
core fuction is very likely to break things at other places.
Therefore you need to test it intensively.

Not knowing the details of this case I recommend that adding a
workaround to d.vect for the 5.0.0 release should be considered.
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