Ecma-48 proposed styling controls update updated & math expression representation proposal update

[Kent Karlsson]

Skickat från min iPhone

> 8 jan. 2024 kl. 14:00 skrev Giacomo Catenazzi via Unicode <unicode at corp.unicode.org>:
> 
> CSI is defined in Unicode and in other ECMA standards: it is the terminal command

Nothing restricts it to terminals or terminal emulators.

> usually send as `ESC [`

In modern terms, that is a character reference.

> (and if should be terminated by characters between 0x40 and 0x7E, but there were bugs and exceptions on some platforms), there is also one single character in C1 (so still two bytes in UTF-8), but many terminal disregard this alternate (which it is also very old).

Because in a terminal (emulator) the character encoding may change without notice. 

> But so we see the advantage of having elements (and tags) written as clear text (as in HTML, LaTeX, etc.): if we do not understand one element we can google it. With ECMA-48 code: either is standard, or good luck to find some references.

But HTML etc. are, and will continue to be, complete non-starters for terminal emulators.

However, ECMA-48 styling can be used to style enhance what is otherwise a plain text document, without getting entangled in a second level interpretation of tags, typesettig commands, similar, expressed in what would be “plain text”.

> ECMA-48-like syntax is bad, difficult to enhance without requiring updates on all programs (contrary to HTML: tags can be
> just ignored, without consequences to next ones,

I don’t see your point. I.e., I don’t see that there is any difference in principle.

> or previous *non-closed* one). Note: this fact is caused by a different reason, which modern mark-up languages shares: they are *structured* (which ECMA-48 is not,

Well, for the most part not, but tables (and Ruby) actually is structured also in ECMA-48. As are bidi controls. As are hyperlinks (OSC 8), proposed by others. And so are math expressions (in all three variants, separate proposal, but one variant is compatible with ECMA-48, another with HTML).

And most (major exception: CSI 0m, which should only be used for terminal emulators) styling controls have a start-(change)*-end structure, but unrelated styling controls need not nest. You may consider that last bit a flaw, but one that cannot be fixed for compatibility reasons.

/Kent K

> not TeX, but TeX is frozen). Past gives us a lesson, let's learn about it, and not doing the same errors. ECMA-48 is the past (still used on some appliances, but without expectation to enhance it too much: we have alternate graphical interfaces).
> 
> [Note: but I think there is a need for an update of ECMA-48: to standardise common behaviour, but it should be done by the maintainers of the different terminals].
> 
> cate
> 
> 
> 
>> On 8 Jan 2024 13:19, William_J_G Overington via Unicode wrote:
>> Previously I wrote:
>> > MORE NEEDED about Anne showing Patricia how to code the text in green and yellow.
>> I managed to download the PDF document to local storage and I have found on page 55 of the PDF document a table with codes in Kent's proposed enhanced system for setting the colours to alphanumerics green and alphanumerics yellow so that writing of the story can make progress.
>> It appears that for alphanumerics green SP? CSI 92m is needed and that for alphanumerics yellow that SP? CSI 93m is needed. I expect that the code alphanumerics green will be needed at the start of the line and after the name Gutenberg and that alphanumerics yellow will be needed before the name Gutenberg. A teletext alphanumerics colour code automatically generates a space in the display, so I am wondering if, for the possibility of making round-trip conversion back to teletext format that the space should be after the code rather than before it as is listed in Kent's document so that in a round trip the space following the colour code can be omitted when it is reached rather than needing to go back and remove it when the colour code is detected.
>> I do not currently know what CSI means in this context. There are 808 mentions of CSI is the PDF document and the first one is on page 6 but at present I do not understand it.
>> I am thinking that if this story can be completed and includes a reference to Kent's document and Anne and Patricia have a discussion about why Anne thinks it better to have the space after the colour code rather than before then the story might well be a good learning resource.
>> William