[Xastir] Here's a puzzle: Map metadata in map border?

[Tom Russo]

On Mon, Jul 07, 2008 at 07:37:28PM -0400, we recorded a bogon-computron collision of the <mckeehan at mckeehan.homeip.net> flavor, containing:
> I'll take a stab at it.
> 
> The code that you are looking at is only called when not in UTM mode. Have a
> look at draw_grid()

Well, that would 'splain it.

> On Mon, July 7, 2008 6:16 pm, Tom Russo wrote:
> > Ok, so I usually run my station with coordinate system UTM, since that's
> > what I like to use most often.  But sometimes I need to switch to Lat/Lon
> > in DMS or DDMM.MM format when working with some groups who need things that
> > way.
> >
> > I just this moment noticed something truly bizarre about how Xastir displays
> > the screen extents in its map border (enabled with Map->Enable Map Border and
> > Enable Map Grid).
> >
> > With UTM, the extents appear to be displayed correctly, but with lat/lon
> > the extents displayed are both (roughly) the coordinates of the lower right
> > corner.  See for example these two screen shots, which differ only by the
> > setting of coordinate system:
> >  http://www.swcp.com/~russo/imgs/utm.jpg
> >  http://www.swcp.com/~russo/imgs/ll.jpg
> >
> > Note that the lat/lon coordinates displayed for upper left corner are the
> > same as the lat/lon coordinates for the lower right.  That's just plain
> > wrong.
> >
> > What's puzzling, though, is the code for this, in maps.c:
> >
> >
> >         // Put metadata in top border.
> >         // find location of upper left corner of map, convert to Lat/Long
> >         convert_lon_l2s(xx2, grid_label1, sizeof(grid_label1),
> > coordinate_format
> > );
> >         convert_lat_l2s(yy2, grid_label2, sizeof(grid_label2),
> > coordinate_format
> > );
> >         xastir_snprintf(grid_label,
> >             sizeof(grid_label),
> >             "%s %s",
> >             grid_label1,grid_label2);
> >         // find location of lower right corner of map, convert to Lat/Long
> >         convert_lon_l2s(xx2, grid_label1, sizeof(grid_label1),
> > coordinate_format
> > );
> >         convert_lat_l2s(yy2, grid_label2, sizeof(grid_label2),
> > coordinate_format
> > );
> >
> > Note that both sets of "convert_lon_l2s" are working on the same pair of
> > coordinates, xx2 and yy2, with nothing intervening to change them.  In earlier
> > code we have:
> >
> >     // Find xastir coordinates of upper left and lower right corners.
> >     xx = NW_corner_longitude  + (border_width * scale_x);
> >     yy = NW_corner_latitude   + (border_width * scale_y);
> >     xx2 = NW_corner_longitude  + ((screen_width - border_width) * scale_x);
> >     yy2 = NW_corner_latitude   + ((screen_height - border_width) * scale_y);
> >
> >
> > It *looks* like the two pairs of convert_lon_l2s should be working on
> > xx,yy and xx2,yy2 instead, but that doesn't explain at all how the UTM version
> > of this code actually produces a banner at the top that is correct.  They
> > should all be wrong.
> >
> > Can anyone spot what's going on here?
> >
> > --
> > 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
> >  "It's so simple to be wise: just think of something stupid to say and
> >   then don't say it."  --- Sam Levinson
> >
> > _______________________________________________
> > Xastir mailing list
> > Xastir at xastir.org
> > http://lists.xastir.org/cgi-bin/mailman/listinfo/xastir
> >
> >

-- 
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
 "It's so simple to be wise: just think of something stupid to say and
  then don't say it."  --- Sam Levinson