[Xastir] Online Map Enhancements

[Lee Bengston]

After 11 years of avoiding attempting to modify Xastir's source code I took
the plunge.

Knowing there were alternative OSM-like tile sets available such as those
listed here, http://aprsisce.wikidot.com/tile-sets, I thought I would see
if I could get Xastir to  retrieve tiles from servers that reverse the x
and y parameter when storing the otherwise standard 256x256 tiles.  After
much teeth gnashing and attempts to fry my brain, which is mostly due to
zero experience programming in C, I got things working.

Next it was time to try some different URL's, and to my surprise and dismay
I found the nationalmap.gov sever didn't put an extension on the tiles,
which are jpg files.  So it was back to the source to deal with that
scenario, and I was able to get that working as well.

I looked at the Wiki article on how developers should use Git, but I guess
my brain is to tired for that to fully soak in, so for now I'm sharing the
modified source files via a web link.

http://www.175moonlight.com/xastir/new-Xastir-src.tar.gz

Also here are two sample geo files that use the new capabilities:

http://www.175moonlight.com/xastir/sample-geo-files.tar.gz

At this point I'm not recommending that new geo files for a bunch of
alternate tile sets should be included with Xastir's source code.  I don't
have a good handle on what the terms of use are for the ones on the
aprsisce site above.  I'm thinking the nationalmap.gov geo for the USGS
Topo Map, which is one of the samples provided is probably OK.  The URL for
that one is not on the aforementioned aprsisce site - perhaps because it's
one that doesn't use file extensions in the tile names.

I'm sure there are more efficient ways to code what I did, but I'll still
take the moral victory that it works.  :-)

Lee - K5DAT