Calling a function when timeoutlen expires and retrieving the input command

Question

This might be quite challenging, but I would like to achieve the following behavior. Imagine that I have two mappings that overlap:

• dcb := delete comment block := delete comment block (all adjacent comment lines)
• dcl := delete comment line := delete comment line

if I type in normal mode 'dc' and the timeout expires, I would like to provide help showing the different options. I have all the mappings documented so it would be easy to write a program that filters out what the verb is and what the text object is, but as I'm not very experienced with vimscript the challenging part for me is:

• Triggering the function when timeoutlen expires
• Retrieving the input command:
  • If I could get that the user input was 'dc' then I easy parse my documentation and provide the information.

Less challenging (still challenging for me but definitely possible as this is very common in many plugins:

• Presenting the different options to the user and letting them choose
• Executing the final command

Any ideas or guidance on how to achieve this would be very much appreciated.

Answer 1

Create map for dc, if you type in only dc, it will be triggered after timeoutlen ms.

nnoremap dcb :echo "dcb"<cr>
nnoremap dcl :echo "dcl"<cr>
nnoremap dc :call <sid>suggest('dc')<cr>

function! s:suggest(cmd)
  " get second column of `map dc`
  let l = map(split(execute('map ' . a:cmd), "\n"), {i,v->split(v)[1]})
  echo 'possible commands : ' . join(l[1:], " ")
endfunction