Using getcompletion function for insert mode autocompletion

Question

I recently became aware of the getcompletion function which can return autocompletion options for a variety of different things (shell commands, vim autocommand events, files, etc.). Many of the types of things that it can autocomplete are not available in insert mode completion (see ins-completion). Is there a way of harnessing getcompletion in insert mode autocompletion?

Answer 1

You can set up "user completion" (invoked with in insert mode with Ctrl-XCtrl-U) to do this:

function! CompleteColorschemes(findstart, base)
  if a:findstart
    " locate the start of the word
    let line = getline('.')
    let start = col('.') - 1
    while start > 0 && line[start - 1] =~ '\a'
      let start -= 1
    endwhile
    return start
  else
    " Use getcompletion() to complete colorschemes
    return getcompletion(a:base, 'color')
  endif
endfunction
set completefunc=CompleteColorschemes

This is a slight adaptation of the example given in :help complete-functions.

Omni completion (omnifunc, Ctrl-XCtrl-O) works in the same way, and is intended for filetype-specific completions