[Xastir] Proposed change to handling of gps-downloaded shapefiles.

[Tom Russo]

On Mon, Dec 11, 2006 at 11:06:03AM -0700, we recorded a bogon-computron collision of the <russo at bogodyn.org> flavor, containing:
> 
> What I propose to change is to allow the dbfawk file to override the hard-coded
> stuff even when the  file is in the GPS directory.  The dbfawk file that is
> written out by xastir by default is set up to mimic the default behavior, 
> so this should be a user-invisible change.  If the user were to edit the dbfawk
> file and fine tune it, however, the changes would be visible immediately upon
> map redraw, and would not require clumsy name changing or moving the file to
> a different directory just to disable the default behavior.
> 
> So, if I were to make that change and let map_shp always use the dbfawk file
> if that feature is enabled and the file exists, and only use the default
> hard-coded behavior if dbfawk is disabled or there IS no dbfawk file, would 
> anyone be terribly offended?
> 
> I think that making this change would be a usability improvement.  But I'm 
> happy to listen to those who think otherwise.

I only heard one comment, and it was favorable.  I just committed a change.
It was very simple.

As of now, if a shapefile is in the GPS directory and there is a DBFAWK file
with the same base name, and Xastir is compiled with DBFAWK support, the 
DBFAWK file controls the rendering, period.

If there is no dbfawk file, or if DBFAWK is disabled at compile time, the 
old fixed-style, color-based-on-file-name behavior is still there.

Unfortunately, I discovered that the dbfawk file we've been writing out did
not match the style that the hard-coded stuff used.  It had 1 "lane" solid
lines instead of fat dashed lines.  I fixed that so new GPS downloads will 
create dbfawk files that render the gps tracks the same way as before this
change.  But it does mean that if you have a stock of downloaded GPS tracks
with associated dbfawk files, they will suddenly look different, because the
old dbfawk files will now be honored instead of mostly ignored.

If this happens to you, you can do one of two things:  remove the dbfawk file
to revert to the old behavior, or edit the dbfawk file to give the behavior
you want.  The variables to change are "pattern" (which should  be 1 to match
the old rendering) and "lanes" (which should be 3.

I hope that now that the rendering of gps downloads is controlled by the dbfawk
file instead of the file name and the name of the directory in which it lives,
users will have better control over the presentation of GPS data.

Now a question: is anyone aware of a good tool for tweaking shapefiles, as in
removing garbage points?  I downloaded a GPS track, and there was a single 
extra point at the beginning that was garbage --- several degrees jump from
the first and second point, and after that it was fine.  Xastir is drawing
a huge line from the starting point to the second point, and has a rendering 
problem at zoom levels below 8 when it tries to draw that line (fills the screen
with horizontal bars).  Unfortunately, I cannot find any tool that will let
me delete that first point from the shapefile.  I've tried qgis, but even
though it'll let me edit the layer and will flash the point when I click
the "delete vertex" tool on it, it doesn't actually do the deletion.  Grrr.
Any helpful hints would be welcome.

Of course, I could always write a quick tool that links with shapelib and 
writes out all but the first vertex, but that seems like too much of a hack, 
even for this simple task.

-- 
Tom Russo    KM5VY   SAR502   DM64ux          http://www.swcp.com/~russo/
Tijeras, NM  QRPL#1592 K2#398  SOC#236 AHTB#1 http://kevan.org/brain.cgi?DDTNM
"And, isn't sanity really just a one-trick pony anyway? I mean all you get is
 one trick, rational thinking, but when you're good and crazy, oooh, oooh,
 oooh, the sky is the limit!"  --- The Tick