I am posting this here because I don't know where else to post it, and I don't expect a solution because it's a complex interaction between older software versions, but I at least wanted a record of it in case it ever happens to anyone else. This affects at least Starling 1.5.1 and Feathers 1.3.1, but I haven't tested any other versions because those are the versions my client's project is using :). For all I know it's been fixed on github long ago.
When I export a font from the Littera web-based bitmap font tool (http://kvazars.com/littera/), it includes space characters (charCode 32) in the
.fnt file that show up in the XML with width and height both
0. I'm not sure if this is a problem with the
.fnt file or not, but when Feathers tries to render any string with spaces, the
Image for the spaces is set to width and height both 0, and Starling complains in the
Quad constructor and throws an error.
My kludgy solution is to manually edit the
.fnt files and change the
width/height for charCode 32 to
There may be other/better solutions out there, but mine works for me on this project.