"There are not many comments."
The code should comment itself, and /* some comment for block */ really need
only for description the strongly non-obvious actions - like complex math,
optimization (with answer why optimize here) or factorization algorithm O(1) :-).

Dear Neal, I thank you for answer.

This issue's the main goal is getting an answer to a question - Do you plan
support FLTK. I suppose that it may be closed with comment "not need this
toolkit" - so I do not format according to the GNU coding standards - There are
many contentious issues about the format code - 80 chars per line is more then
enough for assembler, but for C++ with templates - not sure.
Your code is your rules, so If you plan to accept FLTK support - I fix all notes.

"Using email"
email "madrat@users.noreply.github.com" is also my email, which I use in
github.com and because I use local git, it will be inserted automatically.

"the rest of the code has a fair number of violations"
For my studies and knowledge - can you post sample of violation?

FL/fl_utf8.H in some distros is Fl/fl_utf8.h

D354: 774_fltk.patch

input field tests removed

D355: 773_fltk.patch

D356: 772_fltk.patch

forget add resources

D357: 771_fltk.patch

Patch adds fltk support to pinentry

D358: 770_fltk.patch