Can you turn a popup into a regular buffer?

Question

I have a popup / floating window open which is normally used for temporary jobs, like searching the code or opening a quick REPL. Is it possible to turn that into a regular buffer? While I have it open, it does not show up in :buffers, so I can't just move it to another tab or open a split above the popup; it remains in the centre of my screen. In fact, if I move away using <C-W><C-J> or similar, I can't even move back using the opposite direction, and have to find and plug in a mouse to get back into the popup!

My particular use-case is to keep the search results from fzf.vim's Rg command so that I can return to them after browsing some matches. However, this should apply equally well to any other uses of floating windows / popups.

I see that vim-floaterm allows you to store and then return to floating terminal buffers, with some hackery searching by index for buffers, but I don't fully understand why this logic is correct or necessary:

" find **one** visible floaterm window
function! floaterm#window#find() abort
  let found_winnr = 0
  for winnr in range(1, winnr('$'))
    if getbufvar(winbufnr(winnr), '&filetype') ==# 'floaterm'
      let found_winnr = winnr
      break
    endif
  endfor
  return found_winnr
endfunction

Can anyone explain the use of winbufnr, and how to use this to move a popup, or implement generalized store / load behaviour of popups?

Answer 1

A bit of a hack, but if you can get the window ID of the popup (popup_create returns it; popup_locate or popup_list might help find it), you can get the buffer contents and create a new one:

const popup_winid = …
const popup_bufnr = winbufnr(popup_winid)
const lines = getbufline(popup_bufnr, 1, '$')
" do something with them, like:
new
put =lines
1delete