How to get line numbers of a different window

Question

I would like to get these line numbers of a different window without moving to that window.

line('w0')
line('w$')
line('.')
line('$')

As for the first two, we can use getwininfo([{winid}]) which returns a list including 'topline' and 'botline'. Is there any function or some workaround as for the last two?

Answer 1

As a partial answer, for line('.'), you can get the buffer number associated with a window with winbufnr({nr}) (carefull to pass the window number and not the window id) then pass it to getbufinfo([{expr}]) and get the lnum entry :

getbufinfo(winbufnr({nr}))[0]['lnum']

Thanks to @Luc Hermitte, we can get the last line number with

len(getbufline(winbufnr({nr}), 1, '$')

which gets all the lines of the buffer as a list of strings and returns its length.

Old original answer

Can't tell how to get line('$') without moving to the actual window. But we could achieve it with a function that restores the current and previous visited window, than get any line({expr}) :

function! WindowLine(winnr, expr)
    let curr_window = winnr()
    let prev_window = winnr('#')
    exec a:winnr . 'wincmd w'
    let line = line(a:expr)
    exec prev_window . 'wincmd w'
    exec curr_window . 'wincmd w'
    return line
endfunction
echo WindowLine(2, '$')

Answer 2

patch 8.1.1418 introduced :h win_execute() :

call win_execute(winid, 'let l:num_lines = line("$") | let l:current_line = line(".")')

It's fast, it has no window related side effect.