Emacs doesn't use only terminfo database to identify a terminal

Emacs doesn't use only terminfo database to identify a terminal

[Akib Azmain Turja]

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Emacs uses something more than just a terminfo database to determine the
capabilities of a terminal.  For example, if I run Emacs in St, keys
like C-<left>, M-<up> work.  Then I modified the terminal name by
changing the terminfo source file (st-256color -> est-256color).  If I
run Emacs with the new terminfo database, keys like C-<down>, M-<right>
no longer work, although infocmp shows that both (st-256color and
est-256color) terminfo databases contain identical capabilities.  Now if
I rename the terminal name to something like "st-..." (I used
"st-foo-bar-baz"), those keys work again.

But why?  Who is the culprit here, Emacs or ncurses?

-- 
Akib Azmain Turja

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Re: Emacs doesn't use only terminfo database to identify a terminal

[Eli Zaretskii]

> From: Akib Azmain Turja <akib@disroot.org>
> Date: Sat, 10 Sep 2022 16:11:51 +0600
> 
> Emacs uses something more than just a terminfo database to determine the
> capabilities of a terminal.  For example, if I run Emacs in St, keys
> like C-<left>, M-<up> work.  Then I modified the terminal name by
> changing the terminfo source file (st-256color -> est-256color).  If I
> run Emacs with the new terminfo database, keys like C-<down>, M-<right>
> no longer work, although infocmp shows that both (st-256color and
> est-256color) terminfo databases contain identical capabilities.  Now if
> I rename the terminal name to something like "st-..." (I used
> "st-foo-bar-baz"), those keys work again.
> 
> But why?  Who is the culprit here, Emacs or ncurses?

See lisp/term/st.el, it's part of the puzzle, I think.

Re: Emacs doesn't use only terminfo database to identify a terminal

[Akib Azmain Turja]

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Eli Zaretskii <eliz@gnu.org> writes:

>> From: Akib Azmain Turja <akib@disroot.org>
>> Date: Sat, 10 Sep 2022 16:11:51 +0600
>> 
>> Emacs uses something more than just a terminfo database to determine the
>> capabilities of a terminal.  For example, if I run Emacs in St, keys
>> like C-<left>, M-<up> work.  Then I modified the terminal name by
>> changing the terminfo source file (st-256color -> est-256color).  If I
>> run Emacs with the new terminfo database, keys like C-<down>, M-<right>
>> no longer work, although infocmp shows that both (st-256color and
>> est-256color) terminfo databases contain identical capabilities.  Now if
>> I rename the terminal name to something like "st-..." (I used
>> "st-foo-bar-baz"), those keys work again.
>> 
>> But why?  Who is the culprit here, Emacs or ncurses?
>
> See lisp/term/st.el, it's part of the puzzle, I think.
>

Yeah, it is.  Putting the following in my early-init.el make those
C-<up> keys work:

--8<---------------cut here---------------start------------->8---
(setq term-file-aliases
      '(("apollo" . "vt100")
        ("vt102" . "vt100")
        ("vt125" . "vt100")
        ("vt201" . "vt200")
        ("vt220" . "vt200")
        ("vt240" . "vt200")
        ("vt300" . "vt200")
        ("vt320" . "vt200")
        ("vt400" . "vt200")
        ("vt420" . "vt200")
        ("alacritty" . "xterm")
        ("est" . "st")
        ("foot" . "xterm")))
--8<---------------cut here---------------end--------------->8---

Thanks, I just found that those keys are defined in xterm-function-map
in lisp/term/xterm.el.

-- 
Akib Azmain Turja

Find me on Mastodon at @akib@hostux.social.

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