hacking mc. key shortcuts

[Vladimir Dark Proger Kirillov]

Good evening to everyone! 

Recently, i thought that bingind toggle_show_hidden() to a hotkey would
be useful, so i have a question about working with keybinding at mc.
As i've looked through the src/key.c sources, keybinding is used via
int define_sequence (int code, const char *seq, int action) function.
So, if i wish to setup a keybind, 
i have to do something like 
define_sequence (KEY_M_ALT  | KEY_F(12),   ESC_STR "[28~", /*action
here*/);

So that's my question: what should i pass to define_sequence as int
action to perform something like toggle_show_hidden()?
What should i look for for examples or else?

Thank you in advance

-- 
Sincerely,
Vladimir 'Dark Proger' Kirillov, darkproger at gmail.com
http://darkproger.org.ua