what does "\033]110\007\033]111\007" mean

Question

I found this snippet online which is apparently a way to make vim a little faster if your terminal background is the same as what vim's is meant to be (right?)

" General colors
if has('gui_running') || has('nvim')
  hi Normal             guifg=#a89984 guibg=#282828
else
  " Set the terminal default background and foreground colors, thereby
  " improving performance by not needing to set these colors on empty cells.
  hi Normal guifg=NONE guibg=NONE ctermfg=NONE ctermbg=NONE
  let &t_ti = &t_ti . "\033]10;#a89984\007\033]11;#282828\007"
  let &t_te = &t_te . "\033]110\007\033]111\007"
endif

What are t_ti and t_te?

I looked up :help t_te and found out that these t_ti and t_te "put terminal in termcap mode", looking up :help termcap didn't help me (I don't really understand what it is/means). Also looking up :help & didn't help me understand why t_ti etc. have had & prepended.

I thought this kind of stuff \033]... were escape codes so I also did :helpgrep escape code but didn't find anything useful. Probably they're a part of the terminal/shell so not in vim's help, but then I don't know how to try to find out more about them.

Is someone able to explain what exactly the snippet is doing/how it does it?

Answer 1

t_ti and t_te are used by Vim (in the terminal) to switch between the different screens. The whole detail of this is described at :h xterm-screens and those are xterm terminal control sequences.

The usual effect of this is, that after you quit vim in the terminal, you do not see your old vim screen anymore, but the last commands you issued before starting vim (because the screens have been switched).

I am not sure, what your snippet is doing, it looks like it is requesting to set some foreground and background colors, using #rgb format. This is not supported by all terminals (and I think xterm does not yet completely support that according to this gist). So this might or not might work, depending on the terminal you are using. The full details of the terminal escape sequences can be read at Thomas Dickeys website: https://invisible-island.net/xterm/ctlseqs/ctlseqs.html

Neovim does not support setting terminal capabilities that way and in the gui it doesn't make any sense. Therefore it makes sense to distinguish them as you did in your snippet.