Created attachment 1001 [details]
tl-shadow-notify with sv_SE.ISO-8859-1 locale
tl-shadow-notify seemingly assumes the system encoding to be UTF-8 making the dialog text render incorrectly. This is not a regression and can be reproduced in 4.13.0.
The attached screenshot shows tl-shadow-notify running on a Ubuntu 20.04 system with its locale set to `sv_SE.ISO-8859-1'.
I think it's actually the other way around. The code follows the system encoding, however FLTK always wants UTF-8. The screenshot shows Unicode replacement characters rather than the mojibake you would expect if you fed UTF-8 to a latin 1 system.