keyboard.c: Overriding binding to only `(kdb "S")`

[Artur Zochniak]

Hello Emacs Community!

So I am trying to fight with RSI and 

I would like to have sticky modifier key for Emacs25

https://www.emacswiki.org/emacs/StickyModifiers

http://ergoemacs.org/emacs/emacs_pinky.html#Use_Sticky_Keys 

with a debouncer, this means: 

  (global-set-key (kdb "S") 'debounced-shift)

  ; if user presses shift - keep it pressed till either another 

  ;key is pressed (make it upper char) or elapsed 30 sec

  ; pseudo-code ofc

  (defn debounced-shift []

    (set-modifier-key 'shift)

    (setq last-pressed-key 'shift)

    (run-with-timer '30 sec' (lambda () (unset-modifier-key 'shift)))

  )

so far I have digged to this moment https://github.com/emacs-mirror/emacs/blob/b3e1b38/src/keyboard.c#L3470-L3479 

Can somebody instruct me what has to be done so I am able to get for example (global-set-key (kdb "S") 'newline-and-indent)?

Thanks!

BR

Artur