[Xastir] Help needed with proj library compatibility

[Tom Russo]

On Thu, Mar 14, 2019 at 09:57:22AM -0500, we recorded a bogon-computron collision of the <kg4wsv at gmail.com> flavor, containing:
> If I didn't have a clue if I were using these or not, is there some debug
> level and message that would tell me?

If you've got gdal installed, it's using the hacked version of 
GTIFProj4toLatLong.  To test out whether the hack is needed, you'd have to
change the ifdef in map_tif.c so the "else" is never used:

Comment this out at the top:

// Needed for GTIFProj4FromLatLong() replacement below
#ifdef HAVE_LIBGDAL
#  include "proj_api.h"
#endif  // HAVE_LIBGDAL

and then later:
#ifndef HAVE_LIBGDAL
#  define my_GTIFProj4FromLatLong GTIFProj4FromLatLong
#else


just change the "ifndef HAVE_GDAL" to "if 1".

If TIFF maps in UTM (e.g. USGS topos) display properly after that change, you 
wouldn't have a problem with removing the hack.

> e.g.:
> $ xastir -v X >xastir.log 2>&1
> [poke around until i display all my maps in xastir]
> $ grep "something" xastir.log

Nothing here would tell you anything useful.  This is entirely an issue of
TIFF maps not properly being georeferenced, because this "GTIFProj4ToLatLong"
is used to translate the coordinates stored in the TIFF file into coordinates
Xastir can work with.

> On Thu, Mar 14, 2019 at 9:25 AM Tom Russo <russo at bogodyn.org> wrote:
> 
> > We got a bug report on github that Xastir is using a deprecated API for the
> > proj.4 library.  A new API (in "proj.h") has been created in proj.5, the
> > old
> > is deprecated in proj.6, and will be removed in proj.7.  In keeping with
> > the
> > new normal of racing through major versions every 6 months or so, proj.7
> > is due out in 2020.
> >
> > I've looked into it, and it turns out that the only uses of proj.4's API
> > directly in Xastir source are the result of a hack that was put
> > in place to deal with a GDAL/libgeotiff issue, and another place where
> > we're including a "contrib" program for shapelib that the main shapelib
> > distribution has dropped altogether because it's not very useful.
> >
> > I could use a hand figuring out the best path forward here.
> >
> > In map_tif.c there is code that conditionally compiles in a substitute
> > function for GTIFProj4FromLatLong, because some 14 years ago there was
> > apparently sometimes a problem with this function if one compiled both
> > gdal
> > and libgeotiff into Xastir.  The reason for this is that both libraries
> > define
> > that function, and it was probably possible to compile them in
> > inconsistent
> > ways.  The question is whether the hack is still necessary, and
> > if the presence of both libraries still causes problems in the
> > map_tif.c code if the hack were removed.  This will require a lot of
> > testing using TIFF maps, and probably on multiple systems to make sure
> > it's safe to remove.  I will need a lot of help with that, as I have hardly
> > any time available to test things like this out myself.
> >
> > If this hack is no longer necessary, the easiest path forward to addressing
> > the future incompatibility with Proj.6 and Proj.7 will be to remove it
> > altogether.  If it is still necessary, then the best path forward might be
> > to use the GTIFProj4FromLatLong from the upcoming libgeotiff 1.5.0 instead
> > of the one we have, as the upcoming version has been modified to work with
> > the new proj.5 API.
> >
> > I also propose removing "shpproj" from our ancient "internal" shapelib
> > library's
> > contrib directory, because it is mostly useless and there are better tools
> > to get the job done (e.g. ogr2ogr, from the GDAL/OGR library).  Is anybody
> > depending on this program who would object to it disappearing?
> >
> > --
> > Tom Russo    KM5VY
> > Tijeras, NM
> >
> >  echo "prpv_a'rfg_cnf_har_cvcr" | sed -e 's/_/ /g' | tr [a-m][n-z]
> > [n-z][a-m]
> >
> > _______________________________________________
> > Xastir mailing list
> > Xastir at lists.xastir.org
> > http://xastir.org/mailman/listinfo/xastir
> >
> 
> 
> -- 
> -Jason
> kg4wsv

-- 
Tom Russo    KM5VY
Tijeras, NM  

 echo "prpv_a'rfg_cnf_har_cvcr" | sed -e 's/_/ /g' | tr [a-m][n-z] [n-z][a-m]