[GRASS-dev] Re: broken polygon fills with d.vect render=l

[Hamish]

Hamish wrote:
> I just threw up some new screenshots showing broken polygon fills with
> d.vect render=l. What should not be filled, is partially filled.
> 
> Look near the end of the page:
> 
>  http://bambi.otago.ac.nz/hamish/grass/bugs/d.vect/
> 
> from those pics, and assuming we have to use the display library and
> not the old libgis render functions, it appears that "c" would be a
> nicer pick than "l", if the two bands of white at the edges could be
> corrected.


Another d.vect issue, in 6.3cvs the new D_line_width() forces the
minimum line width to 1, which creates ugly jagged line output vs a line
width of 0.


This patch makes it nice again:

Index: lib/display/draw2.c
===================================================================
RCS file: /home/grass/grassrepository/grass6/lib/display/draw2.c,v
retrieving revision 1.11
diff -u -r1.11 draw2.c
--- lib/display/draw2.c 8 Apr 2007 18:03:29 -0000       1.11
+++ lib/display/draw2.c 13 Jun 2007 09:58:05 -0000
@@ -847,8 +847,8 @@
        int w = round(d);
        double m;
 
-       if (w < 1)
-               w = 1;
+       if (w < 0)
+               w = 0;
 
        R_line_width(w);


screenshots can be found at the URL at top of this email.
 (Spf roads buffered 5m)

The screenshots also show some north-south shift error in some lines
using different rendering methods.


see also previous talk about line width=0,1 WRT v.digit and tcl minimum
width inputs:

Glynn wrote:
 http://thread.gmane.org/gmane.comp.gis.grass.user/17458/focus=18731
> Odd. I initially suspected that Tk may have a different interpretation
> of "width" compared to X etc. However, having traced the Tk drawing
> routines with GDB, I can confirm that the width entered in the
> Settings dialog is passed directly[1] into the X GC.

then:
 http://thread.gmane.org/gmane.comp.gis.grass.devel/20444/focus=20503


finally:
 (11 May 2007)
Hamish:
>>> n.b. the smallest D_line_width is 0, not 1. width=1 still looks a
>>> little lumpy. (experiment with d.vect)
Maciej:
> > Are you absolutely sure? Glynn says it's really 1:
> > http://grass.itc.it/pipermail/grass-dev/2007-February/029336.html
Hamish:
> Well I was sure, but not so much anymore! I could have sworn I could
> see the difference in the past. Can't seem to now.

(by then R_line_width() had changed to D_line_width())



.. something is funny here. As seen in the screenshots linked above
there is a real difference, at least in the XDRIVER output.


Hamish