[Xastir] OSM scaling 'bug' / limit

[Jerry Dunmire]

If you are using a large display (lucky you) and large window for
Xastir and then the area selected for a zoom is a high aspect ratio,
you may get an OSM map that does not fill the display and is not
aligned with the vector layers. The specific aspect ratio where the
problem occurs depends on your window size. I expect the problem to
occur both for short/wide areas and tall/narrow areas though the
problem has only been demonstrated for tall/narrow area selections.

The problem is due to limits at the site where the OSM image is
generated. That site limits the image to 2000 pixels in either
direction. If more than 2000 pixels is requested, the value is
truncated to a default value (different for X and Y).

The work around is to avoid high aspect ratio selections. To recover
after selecting a high aspect ratio, use the "Last Map Pos/Zoom"
option on the mouse menu or resize your display window.

The 'correct' fix for this problem will be to assemble the image from
tiles. Since I expect tile support to take some time, I will put in
some code to work around the problem.

73,
...jerry
KA6HLD