Sticky shift - or getting <shift> with letter combinations

Question

I use the shift keys a lot and it is an unnecessary strain on the pinky. The enter and backspace functionalities are conveniently located under a dominant finger (ctrl-m and ctrl-h). Similarly:

Is there a way to map the shift function to a dominant finger?

But in the vim spirit I want to get this functionality with a key combination rather than finger acrobatics; e.g., lets use the extremely rare key combination fd (in insert mode!).

For the alphanumerical keys one could dump an entire list of imaps: fd1 !, fd2 @, ..., fda A etc. into vimrc. I'm hoping there is a better way.

Ideally, fd would be mapped to a "sticky shift" that waits for a one letter input, shifts it, then turns off the sticky shift. Is this possible?

Many thanks!

Post mortem

Rich has a function down below which can be modified to have the complete effect. Last night someone wrote a neat solution and then erased it so I will include it here:

imap <expr> fd nr2char(getchar()-32)

This does the trick if all you want to capitalize letters. Otherwise it seems like a good way to do function calls.

Another good suggestion in the comments below is modifying the keyboard at the firmware level using this.

Thanks for the help everyone!

Answer 1

I'm not sure if a clean implementation of this feature is possible in Vimscript. (I suspect it's not, and I fully agree with the commenters who suggest it's better to implement this outside of Vim.)

Nevertheless, here's a proof-of-concept of a hacky function that maps insert-mode fd to a function which waits for a single character of input, and capitalises it if it's a-z before re-entering insert mode and writing it back out. This is marginally nicer than your "create all the mappings individually" idea.

It would need a bit more logic to handle all the other keyboard keys, but this should be sufficient to demonstrate the general concept. Note that getchar() returns an ASCII value, so all the if block is doing is converting the ASCII values for lowercase letters into uppercase ones.

Let me know if you decide to go down this path and need any more help filling the rest of it in.

inoremap fd <Esc>:call StickyShift()<CR>

function! StickyShift()
  let l:key_pressed = getchar()
  " Capitalise a-z
  if l:key_pressed >= 97 && l:key_pressed <= 122
    let l:key_pressed -= 32
  endif
  call feedkeys("a". nr2char(l:key_pressed))
endfunction

Answer 2

inoremap fd <C-o>gUl

Would allow you to type afd and get A etc. if you are open to reverse the order of your bind.

Does not work for the 1 to ! etc unfortunately.