This was also my first thought, but looks like it's already designed to be toolkit-agnostic, like NetSurf. So it should be easy to port to fltk or anything else.

  $ ls -1 fixgui_\*.c
  fixgui_cocoa.c
  fixgui_gtk.c
  fixgui_haiku.c
  fixgui_win32.c

FLTK is c++, then a definitive nono?

Look at FLTK's source code. It's a minimal set of C++. Like C with classes.

Then it is c++, then a definitive nono.

Plain and simple C99+ port?

>Plain and simple C99+ port?

C89 bindings https://github.com/MoAlyousef/cfltk

The second your require a gigantic and insanely complex c++ and similar compiler for your SDK, it's over.

As for complexity and gigantism:

https://openhub.net/p/qt5 (8,876,034 lines of code)

https://openhub.net/p/gtk (1,031,203 lines of code)

https://openhub.net/p/fltk (467,564 lines of code)

You have an "amplification" due to the language used: you cannot compare the "cost" of C lines with c++ lines. They don't pull the same SDK dependency in the end.

Basically, to be fair, in qt5 and fltk cases you should add an amplification factor of at least "10" (probably not big enough since c++ syntax and tens of times more complex than plain C99+).

Compare dependencies:

GTK3 https://gitlab.archlinux.org/archlinux/packaging/packages/gt... GTK4 https://gitlab.archlinux.org/archlinux/packaging/packages/gt... and FLTK https://aur.archlinux.org/cgit/aur.git/tree/PKGBUILD?h=fltk-...

If you build FLTK with Wayland support, then add deps: wayland, libxkbcommon, pango.

You don't seem to understand my point: the second you are using c++, it is over.

>Then it is c++, then a definitive nono.

Language with OOP is good for GUI!

Language with OOP like c++ and similar (rust/java/etc) is ultra-complexity builtin the syntax itself which spills to their compilers (basically clang(apple)|gcc). That reasons alone is enough to do GUI with other languages.