complete_flicker.vim

" save this as complete_flicker.vim
" vim -u complete_flicker.vim -c "startinsert"

let s:months = ['January', 'February', 'March', 'April', 'May', 'June', 'July', 'August', 'September', 'October', 'November', 'December']
let s:cycle = 1

let s:last_tick = []

function! s:current_tick()
    return [b:changedtick, getcurpos()]
endfunction

function! s:check_changes(...)
    let l:current_tick = s:current_tick()
    if s:last_tick != l:current_tick
        let s:last_tick = l:current_tick
        call s:on_changed()
    endif
endfunction

function! s:start_check_changes_timer()
    let s:last_tick = []
    let s:check_change_timer = timer_start(30, function('s:check_changes'), {'repeat': -1})
endfunction

function! s:stop_check_changes_timer()
    if exists('s:check_change_timer')
        call timer_stop(s:check_change_timer)
        unlet s:check_change_timer
    endif
endfunction

function! s:on_changed()
    if mode() != 'i'
        return
    endif
    setlocal completeopt-=longest
    setlocal completeopt+=menuone
    setlocal completeopt-=menu
    setlocal completeopt+=noselect
    call complete(1, s:months[: s:cycle])
    let s:cycle = (s:cycle + 3) % len(s:months)
endfunction

autocmd TextChangedI * call s:check_changes()
autocmd InsertEnter * call s:start_check_changes_timer()
autocmd InsertLeave * call s:stop_check_changes_timer()