bug#48439: 28.0.50; Support for the Alacritty terminal emulator

bug#48439: 28.0.50; Support for the Alacritty terminal emulator

[Tassilo Horn]

I use the Alacritty terminal emulator [1].  I've noticed that with
"emacs -nw" or "emacsclient -t" my terminal emacs was just white on
black, no colors at all.  It seems it's because emacs doesn't know how
to handle TERM=alacritty which Alacritty sets if the terminfo database
knows it, otherwise it'll set TERM=xterm-256color.

So I can either set TERM=xterm-256color in my Alacritty config or use
the following patch to alias alacritty to xterm in Emacs.

--8<---------------cut here---------------start------------->8---
1 file changed, 1 insertion(+), 1 deletion(-)
lisp/faces.el | 2 +-

modified   lisp/faces.el
@@ -46,7 +46,7 @@ term-file-aliases
     ("vt320" . "vt200")
     ("vt400" . "vt200")
     ("vt420" . "vt200")
-    )
+    ("alacritty" . "xterm"))
   "Alist of terminal type aliases.
 Entries are of the form (TYPE . ALIAS), where both elements are strings.
 This means to treat a terminal of type TYPE as if it were of type ALIAS."
--8<---------------cut here---------------end--------------->8---

IMHO, it would make sense to have that alias is place at least until
someone comes up with "proper" support for Alacritty.

[1] https://github.com/alacritty/alacritty


In GNU Emacs 28.0.50 (build 4, x86_64-pc-linux-gnu, GTK+ Version 3.24.29, cairo version 1.17.4)
 of 2021-05-15 built on thinkpad-t440p
Repository revision: 248ec838aa8b1a720a05b422be760f6ab32aa630
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12101001
System Description: Arch Linux

Configured using:
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Important settings:
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bug#48439: 28.0.50; Support for the Alacritty terminal emulator

[Eli Zaretskii]

> From: Tassilo Horn <tsdh@gnu.org>
> Date: Sat, 15 May 2021 13:07:59 +0200
> 
> So I can either set TERM=xterm-256color in my Alacritty config or use
> the following patch to alias alacritty to xterm in Emacs.
> 
> --8<---------------cut here---------------start------------->8---
> 1 file changed, 1 insertion(+), 1 deletion(-)
> lisp/faces.el | 2 +-
> 
> modified   lisp/faces.el
> @@ -46,7 +46,7 @@ term-file-aliases
>      ("vt320" . "vt200")
>      ("vt400" . "vt200")
>      ("vt420" . "vt200")
> -    )
> +    ("alacritty" . "xterm"))
>    "Alist of terminal type aliases.
>  Entries are of the form (TYPE . ALIAS), where both elements are strings.
>  This means to treat a terminal of type TYPE as if it were of type ALIAS."
> --8<---------------cut here---------------end--------------->8---
> 
> IMHO, it would make sense to have that alias is place at least until
> someone comes up with "proper" support for Alacritty.

Is Alacritty really similar to 256-color xterm?  What are the
differences?  Do you know where I can find the terminfo database for
Alacritty?

bug#48439: 28.0.50; Support for the Alacritty terminal emulator

[Tassilo Horn]

[-- Attachment #1: Type: text/plain, Size: 594 bytes --]

Eli Zaretskii <eliz@gnu.org> writes:

Hi Eli,

>> IMHO, it would make sense to have that alias is place at least until
>> someone comes up with "proper" support for Alacritty.
>
> Is Alacritty really similar to 256-color xterm?  What are the
> differences?

I don't know but given that it gives out itself as xterm-256color if
terminfo doesn't know it suggests it is similar enough.

> Do you know where I can find the terminfo database for Alacritty?

I've attached an archive of the 3 alacritty files in my
/usr/share/terminfo/a/ directory if that's what you were looking for.

Bye,
Tassilo


[-- Attachment #2: terminfo-alacritty.tar.gz --]
[-- Type: application/gzip, Size: 2583 bytes --]

bug#48439: 28.0.50; Support for the Alacritty terminal emulator

[Eli Zaretskii]

> From: Tassilo Horn <tsdh@gnu.org>
> Cc: 48439@debbugs.gnu.org
> Date: Sat, 15 May 2021 13:55:13 +0200
> 
> > Is Alacritty really similar to 256-color xterm?  What are the
> > differences?
> 
> I don't know but given that it gives out itself as xterm-256color if
> terminfo doesn't know it suggests it is similar enough.

The question is how close.  If it is 90% close, then using the alias
makes sense.  But if it has enough unique features, then using an
alias will rob users of those features for no good reason.

> > Do you know where I can find the terminfo database for Alacritty?
> 
> I've attached an archive of the 3 alacritty files in my
> /usr/share/terminfo/a/ directory if that's what you were looking for.

Thanks, but these files are not recognized by 'infocmp', which I tried
to use to decompile them (assuming they were terminfo files compiled
by 'tic').

Maybe someone else will be able to tell the differences between
alacritty and xterm256color.

bug#48439: 28.0.50; Support for the Alacritty terminal emulator

[Eli Zaretskii]

> Date: Sat, 15 May 2021 16:18:02 +0300
> From: Eli Zaretskii <eliz@gnu.org>
> Cc: 48439@debbugs.gnu.org
> 
> The question is how close.  If it is 90% close, then using the alias
> makes sense.  But if it has enough unique features, then using an
> alias will rob users of those features for no good reason.
> 
> > > Do you know where I can find the terminfo database for Alacritty?
> > 
> > I've attached an archive of the 3 alacritty files in my
> > /usr/share/terminfo/a/ directory if that's what you were looking for.
> 
> Thanks, but these files are not recognized by 'infocmp', which I tried
> to use to decompile them (assuming they were terminfo files compiled
> by 'tic').

Sorry, it seems I gave up too soon.  Here are the results of comparing
alacritty+common (the only file my infocmp recognized) with
xterm-256color:

  comparing alacritty+common to xterm-256color.
      comparing booleans.
	  ccc: F:T.
	  hs: T:F.
	  km: F:T.
      comparing numbers.
	  colors: 8, 256.
	  pairs: 64, 32767.
      comparing strings.
	  dim: '\E[2m', NULL.
	  dsl: '\E]2;\007', NULL.
	  fsl: '^G', NULL.
	  initc: NULL, '\E]4;%p1%d;rgb\:%p2%{255}%*%{1000}%/%2.2X/%p3%{255}%*%{1000}%/%2.2X/%p4%{255}%*%{1000}%/%2.2X\E\\'.
	  kbs: '\177', '^H'.
	  kmous: '\E[<', '\E[M'.
	  rep: '%p1%c\E[%p2%{1}%-%db', NULL.
	  ritm: '\E[23m', NULL.
	  rmcup: '\E[?1049l\E[23;0;0t', '\E[?1049l'.
	  setab: '\E[4%p1%dm', '\E[%?%p1%{8}%<%t4%p1%d%e%p1%{16}%<%t10%p1%{8}%-%d%e48;5;%p1%d%;m'.
	  setaf: '\E[3%p1%dm', '\E[%?%p1%{8}%<%t3%p1%d%e%p1%{16}%<%t9%p1%{8}%-%d%e38;5;%p1%d%;m'.
	  setb: '\E[4%?%p1%{1}%=%t4%e%p1%{3}%=%t6%e%p1%{4}%=%t1%e%p1%{6}%=%t3%e%p1%d%;m', NULL.
	  setf: '\E[3%?%p1%{1}%=%t4%e%p1%{3}%=%t6%e%p1%{4}%=%t1%e%p1%{6}%=%t3%e%p1%d%;m', NULL.
	  sgr: '%?%p9%t\E(0%e\E(B%;\E[0%?%p6%t;1%;%?%p5%t;2%;%?%p2%t;4%;%?%p1%p3%|%t;7%;%?%p4%t;5%;%?%p7%t;8%;m', '%?%p9%t\E(0%e\E(B%;\E[0%?%p6%t;1%;%?%p2%t;4%;%?%p1%p3%|%t;7%;%?%p4%t;5%;%?%p7%t;8%;m'.
	  sitm: '\E[3m', NULL.
	  smcup: '\E[?1049h\E[22;0;0t', '\E[?1049h'.
	  tsl: '\E]2;', NULL.
	  u8: '\E[?%[;0123456789]c', '\E[?1;2c'.

Looks quite extensive to me.  Of particular importance are: the number
of colors (not 256 but only 8 in alacritty), and different commands to
set fore- and back-ground colors.

Is there any way to raise these issues with the Alacritty developers?
Maybe there's something here I don't understand (I don't consider
myself an expert on terminal capabilities).

Thanks.

bug#48439: 28.0.50; Support for the Alacritty terminal emulator

[Andreas Schwab]

On Mai 15 2021, Eli Zaretskii wrote:

> Looks quite extensive to me.  Of particular importance are: the number
> of colors (not 256 but only 8 in alacritty), and different commands to
> set fore- and back-ground colors.

Both are overridden in the alacritty description.

comparing alacritty+common to alacritty.
    comparing booleans.
        ccc: F:T.
    comparing numbers.
        colors: 8, 256.
        pairs: 64, 65536.
    comparing strings.
        initc: NULL, '\E]4;%p1%d;rgb\:%p2%{255}%*%{1000}%/%2.2X/%p3%{255}%*%{1000}%/%2.2X/%p4%{255}%*%{1000}%/%2.2X\E\\'.
        oc: NULL, '\E]104\007'.
        rs1: '\Ec', '\Ec\E]104\007'.
        setab: '\E[4%p1%dm', '\E[%?%p1%{8}%<%t4%p1%d%e%p1%{16}%<%t10%p1%{8}%-%d%e48;5;%p1%d%;m'.
        setaf: '\E[3%p1%dm', '\E[%?%p1%{8}%<%t3%p1%d%e%p1%{16}%<%t9%p1%{8}%-%d%e38;5;%p1%d%;m'.
        setb: '\E[4%?%p1%{1}%=%t4%e%p1%{3}%=%t6%e%p1%{4}%=%t1%e%p1%{6}%=%t3%e%p1%d%;m', NULL.
        setf: '\E[3%?%p1%{1}%=%t4%e%p1%{3}%=%t6%e%p1%{4}%=%t1%e%p1%{6}%=%t3%e%p1%d%;m', NULL.

comparing xterm-256color to alacritty.
    comparing booleans.
        hs: F:T.
        km: T:F.
    comparing numbers.
    comparing strings.
        dsl: NULL, '\E]2;\007'.
        fsl: NULL, '^G'.
        tsl: NULL, '\E]2;'.

Andreas.

-- 
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 7578 EB47 D4E5 4D69 2510  2552 DF73 E780 A9DA AEC1
"And now for something completely different."

bug#48439: 28.0.50; Support for the Alacritty terminal emulator

[Eli Zaretskii]

> From: Andreas Schwab <schwab@linux-m68k.org>
> Cc: tsdh@gnu.org,  48439@debbugs.gnu.org
> Date: Sat, 15 May 2021 15:43:57 +0200
> 
> On Mai 15 2021, Eli Zaretskii wrote:
> 
> > Looks quite extensive to me.  Of particular importance are: the number
> > of colors (not 256 but only 8 in alacritty), and different commands to
> > set fore- and back-ground colors.
> 
> Both are overridden in the alacritty description.

OK, thanks.  Then I guess Alacritty is indeed close enough to
xterm-256color.  The only question I have is: does Alacritty offer any
capabilities that are not in xterm-256color?  Because if it does, then
adding it to the list of aliases will prevent users from taking
advantage of those additional capabilities, because AFAIU we use the
alias without checking first whether the original terminal name has a
library.  So if Alacritty has important additional features, it might
be better to prepare a separate alacritty.el file, using xterm.el as a
starting point (or even 'require'ing it).

bug#48439: 28.0.50; Support for the Alacritty terminal emulator

[Lars Ingebrigtsen]

Eli Zaretskii <eliz@gnu.org> writes:

> OK, thanks.  Then I guess Alacritty is indeed close enough to
> xterm-256color.

Since it's close enough, I've now applied Tassilo's patch.

> The only question I have is: does Alacritty offer any
> capabilities that are not in xterm-256color?  Because if it does, then
> adding it to the list of aliases will prevent users from taking
> advantage of those additional capabilities, because AFAIU we use the
> alias without checking first whether the original terminal name has a
> library.  So if Alacritty has important additional features, it might
> be better to prepare a separate alacritty.el file, using xterm.el as a
> starting point (or even 'require'ing it).

That's true -- but I guess we'll just have to wait and see whether
there's any request for supporting these additional features (if any).
If there is, removing the alias is easy enough.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no