terminfo

`terminfo`

Terminfo is a library and database that enables programs to use display terminals in a device-independent manner.

In layman's terms, your terminal emulator uses terminfo to diaplay CLI, or talk to tmux/Vim so they can display the text based interface.

Currently, Thomas E. Dickey maintains ncurses and the distributed terminfo database. Here are links to a table of content of terminfo database, a terminfo database, and a coloured terminfo database.

In this wiki page, all terminfo are compiled with this database with no alteration.

To get terminfo database:

$ curl -LO https://invisible-island.net/datafiles/current/terminfo.src.gz && gunzip terminfo.src.gz

The file is downloaded as a terminfo.src file. It includes basically all existent terminfo.

To see xterm-256color terminfo:

$ infocmp -x xterm-256color

The option -x includes user-defined capabilities which begins with capital letter (e.g. curly underline Smulx).

To compile database into ~/.terminfo:

$ tic -x terminfo.src

All the terminfo defined in terminfo.src will be compiled. Similar to infocmp, the option -x includes user-defined capabilities.

To compile only to one or some terminfo, into ~/.terminfo:

$ tic -xe xterm-256color,tmux-256color terminfo.src

Only xterm-256color and tmux-256color are compiled.

To compile for all users (into e.g. /usr/share/terminfo):

$ sudo tic -x terminfo.src

Italics, sitm=\E[3m entry. It's not in xterm-256color, but terminal emulators like iTerm2 enables italics in their software. It's in tmux-256color, but for iTerm2, this line needs to be added into tmux.conf:
```
set -as terminal-overrides ',*:sitm=\E[3m'
```
Curly underline, Smulx=\E[4\:%p1%dm entry, see https://github.com/tmux/tmux/issues/1492#issuecomment-427939241. This is a user-defined capability, and needs to be enabled by terminal emulators first. kitty and iTerm2 implemented curly underline. kitty has its own terminfo xterm-kitty which includes curly underline entry. tmux-256color also has it. But it's not available in xterm-256color. Therefore, kitty can show curly underline with xterm-kitty but iTerm2 cannot show curly underline with xterm-256color, but both can display curly underline in tmux with tmux-256color, provided this line is added into tmux.conf:
```
set -as terminal-overrides ',*:Smulx=\E[4::%p1%dm'
```
Coloured underline, Setulc=\E[38\:2\:\:%p1%{65536}%/%d\:%p1%{256}%/%{255}%&%d\:%p1%{255}%&%d%;m entry, see https://github.com/tmux/tmux/pull/1771#issuecomment-500906522. I'm not sure if it exists in which terminfo, but for tmux at least add this line into tmux.conf:
```
set -as terminal-overrides ',*:Setulc=\E[58::2::%p1%{65536}%/%d::%p1%{256}%/%{255}%&%d::%p1%{255}%&%d%;m'
```

Ref: