screen*() functions don't register floating windows

[echasnovski]

Neovim version (nvim -v)

NVIM v0.8.0-dev+441-ge651ae586

Vim (not Nvim) behaves the same?

Yes, with popup windows (8.2.5046)

Operating system/version

EndeavourOS 5.18.3-arch1-1

Terminal name/version

xfce4-terminal 1.0.4 (Xfce 4.16)

$TERM environment variable

xterm-256color

Installation

appimage

How to reproduce the issue

1. Create 'init-floating.lua' file with following content:

local buf_id = vim.api.nvim_create_buf(true, true)
vim.api.nvim_buf_set_lines(buf_id, 0, -1, true, { 'aaaaaaaaaa' })

vim.api.nvim_open_win(buf_id, false, {
  relative = 'editor',
  width = 10,
  height = 1,
  row = 0,
  col = 0,
})

2. nvim -u init-floating.lua. Should result in Neovim instance with aaaaaaaaaa in floating window in top left corner.
3. Run :lua print(vim.inspect(vim.fn.screenstring(1, 1))). It should be "a", but it is " ", which is a character under floating window. The same effect is for screenchar(), screenchars(), and screenattr().

On the other hand, Vim behaves as expected with its popup windows. Use equivalent 'init-popup.vim' file:

call popup_create("aaaaaaaaaa", {"line": 1, "col": 1})

Expected behavior

All screen*() functions respect floating windows, i.e. use them during computation of "what is displayed on the screen".

Actual behavior

neovim-issue_screenstring.mp4

[zeertzjq]

Is this related to your feature request in #19000?

[echasnovski]

Implicitly related, yes. I've built a straightforward get_screenshot() function by traversing all cells (within 1, vim.o.lines x 1, vim.o.columns) with screenstring() and screenattr(). Works like a charm (with couple of design drawbacks), but when testing it, found that it doesn't support floating windows (which is a must for modern plugin testing, unfortunately). As similar works on Vim's side, seems to be an undesirable behavior.

[zeertzjq]

This may be impossible because AFAIK how floating windows are displayed depends on what UIs are attached.

[clason]

(Remember that Neovim's floating windows are very different from Vim's popups.)

[zeertzjq]

Although duplicating the code for finding mouse click position may make this work.

[echasnovski]

This may be impossible because AFAIK how floating windows are displayed depends on what UIs are attached.

This is sad.

At least, this means a documentation of these functions are not really up to date. All of them have something like character ... at position [row, col] on the screen.

Although duplicating the code for finding mouse click position may make this work.

And this is better :)
If you, please, could point me to the right direction, I will be trying something. Really want to have the ability to do proper screen tests.

[bfredl]

there is also nvim__inspect_cell() which is not standardized yet, but allows you to address floating windows.

[zeertzjq]

I just noticed this comment:

neovim/src/nvim/eval.c

Lines 6854 to 6857 in cd9e08c

	// TODO(bfredl): this is a hack for legacy tests which use screenchar()
	// to check printed messages on the screen (but not floats etc
	// as these are not legacy features). If the compositor is refactored to
	// have its own buffer, this should just read from it instead.

[echasnovski]

there is also nvim__inspect_cell() which is not standardized yet, but allows you to address floating windows.

I tried incorporating it and did in fact succeed to get data from both main window and floating ones. But not so smartly: by looping grid id from 1 to 100 and seeing if there is a valid output. As I couldn't find a way to match window id to a grid id with exported Lua API (if this even makes sense). It also seem to lead to other hassles: manually computing which floating window is on top through z-index, aligning grids (as coordinates seem to be "per window"), dealing with occasional segfaults... Not as straightforward as I hoped with screenstring() and screenattr() :(