neovim/src/nvim/testdir/view_util.vim

" Functions about view shared by several tests

" Only load this script once.
if exists('*Screenline')
  finish
endif

" Get line "lnum" as displayed on the screen.
" Trailing white space is trimmed.
func Screenline(lnum)
  let chars = []
  for c in range(1, winwidth(0))
    call add(chars, nr2char(screenchar(a:lnum, c)))
  endfor
  let line = join(chars, '')
  return matchstr(line, '^.\{-}\ze\s*$')
endfunc

" ScreenLines(lnum, width) or
" ScreenLines([start, end], width)
function! ScreenLines(lnum, width) abort
  redraw!
  if type(a:lnum) == v:t_list
    let start = a:lnum[0]
    let end = a:lnum[1]
  else
    let start = a:lnum
    let end = a:lnum
  endif
  let lines = []
  for l in range(start, end)
    let lines += [join(map(range(1, a:width), 'nr2char(screenchar(l, v:val))'), '')]
  endfor
  return lines
endfunction

function! ScreenAttrs(lnum, width) abort
  redraw!
  if type(a:lnum) == v:t_list
    let start = a:lnum[0]
    let end = a:lnum[1]
  else
    let start = a:lnum
    let end = a:lnum
  endif
  let attrs = []
  for l in range(start, end)
    let attrs += [map(range(1, a:width), 'screenattr(l, v:val)')]
  endfor
  return attrs
endfunction

function! NewWindow(height, width) abort
  exe a:height . 'new'
  exe a:width . 'vsp'
  set winfixwidth winfixheight
  redraw!
endfunction

function! CloseWindow() abort
  bw!
  redraw!
endfunction