2013-12-05-002215.vim

let s:V = vital#of('vital')
function! s:truncate(text, max_width, ellipsis)
  let ellipsis_width = strdisplaywidth(a:ellipsis)
  let text_width = strdisplaywidth(a:text)
  if text_width > a:max_width
    let truncated = s:V.strwidthpart(a:text, a:max_width - ellipsis_width)
    " for double width string
    if strdisplaywidth(truncated) != a:max_width - ellipsis_width
      let truncated .= ' '
    endif
    return truncated . a:ellipsis
  else
    return a:text
  endif
endfunction

echo repeat('|', 20) . '$'
echo s:truncate('ほげhogefuga', 20, '…  続きを読む') . '$'
echo s:truncate('ほげhogefugohogefugo', 20, '…  続きを読む') . '$'
echo s:truncate('ほげhogefugohogefugohogefugo', 20, '…  続きを読む') . '$'
echo s:truncate('ほげほげhogefugohogefugohogefugohogefugo', 20, '…  続きを読む') . '$'