Comment by cosmos0072

Comment by cosmos0072 9 hours ago

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Author here :)

I've been using Twin as my everyday terminal emulator and terminal multiplexer since ~2000, slowly adding features as my free time - and other interests - allowed.

As someone pointed out, the look-and-feel reminds Borland Turbo Vision. The reason is simple: I started writing in in the early '90s on DOS with a Borland C compiler, and I used the Borland Turbo Vision look-and-feel as a visual guideline (never actually looked at the code, though).

The porting to linux happened in 1999 (it was basically dormant before that), and Unicode support was progressively added around 2015-2016 (initially UCS-2 i.e. only the lowest 64k codepoints, then full UTF-32 internally, with terminal emulator accepting UTF-8). There are still some missing features, most notably: no grapheme clusters, no fullwidth (asian etc.) support, no right-to-left support.

Right now I'm adding truecolor support (see https://github.com/cosmos72/twin/tree/truecolor) - it's basically finished, I'm ironing out some remaining bugs, and thinking whether wire compatibility with older versions is worth adding.

And yes, documentation has been stalled for a very long time.

Retrospectively, I should have switched C -> C++ much earlier: lots of ugly preprocessor macros accumulated over time, and while I rewrote the C widget hierarchy as C++ classes, several warts remain.

panzi 8 hours ago

Do symbols for legacy computing work with it? Especially the 1/8ths vertical/horizontal blocks?

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JdeBP 8 hours ago

Alas, it's not finished. You've made the mistakes that all of us have made, and haven't caught up with us, must of us having fixed those mistakes, a few years back when implementing 24-bit RGB was in vogue.

This is not, as the function name suggests, a colon, but per ITU/IEC T.416 it should be:

https://github.com/cosmos72/twin/blob/truecolor/server/hw/hw...

And not only should this have colons too, but per ITU/IEC T.416 there's a colour space parameter that goes in there:

https://github.com/cosmos72/twin/blob/truecolor/server/hw/hw...

The unfortunate part is that when rendering to a terminal, you don't have any available mechanism apart from hand-decoding the family part of the TERM environment variable, and knowing who made which mistakes, to determine which of the 7 possible colour mechanisms are supported. They are:

1. ECMA-48 standard 8 colour, SGRs 30 to 37, 39, 40 to 47, and 49

2. AIXTerm 16 colour, ECMA-48 plus SGRs 90 to 97 and 100 to 107

3. XTerm 256 colour, ITU T.416 done wrongly with SGR 38;5;n and SGR 48;5;n

4. XTerm 256 colour corrected, ITU T.416 done right with SGR 38:5:n and SGR 48:5:n

5. 24-bit colour take 1, ITU T.416 done wrongly with SGR 38;2;r;g;b and SGR 48;2;r;g;b

6. 24-bit colour take 2, ITU T.416 done wrongly with SGR 38:2:r:g:b and SGR 48:2:r:g:b

7. 24-bit colour take 3, ITU T.416 done right with SGR 38:2::r:g:b::: and SGR 48:2::r:g:b:::

Few people support 4, and although quite a lot of us have finally got to supporting 7 it isn't quite universal. Egmont Koblinger, I, and others have been spreading the word where we can over the last few years.

This is where I was at in 2019:

https://github.com/jdebp/nosh/blob/trunk/source/TerminalCapa...

There a few updates to that that are going to come out in 1.41, but when it comes to colour they're mainly things like recognizing the "ms-terminal" and "netbsd6" terminal types in the right places.

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  • cosmos0072 7 hours ago

    Yep, I am well aware of the `;` vs `:` confusion in both 256 color and 24-bit color control sequences.

    Short of hand-coding "which terminal supports which variant" I do not know any standard mechanism to detect that (beyond the well-known $TERM=...-256color and $COLORTERM=truecolor or $COLORTERM=24bit)

    I guess I'll have to add command line options to choose among the variants 1...7 you helpfully listed above.

    My main use it to render twin directly on X11, which avoids all these issues, and while rendering inside another terminal is important and is not going away, I am OK with a few minor color-related limitations (note: limitations, not bugs) in such setup, especially if the other terminal does not follow the relevant standards

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  • skissane 6 hours ago

    > This is not, as the function name suggests, a colon, but per ITU/IEC T.416 it should be

    Digressing, but I’m fascinated to see ODA still being referenced, even if only some small part of it

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