4 ms·

(Not a language or Unicode expert, the following likely has important mistakes.) > Off the top of my head, I don't know of a terminal that actually implements

(Not a language or Unicode expert, the following likely has important mistakes.) > Off the top of my head, I don't know of a terminal that actually implements the entire (very complex) set of Unicode text rendering behaviors There are at least two reasons for this: First, nobody actually seems to know how bidirectional text should interact with terminal control sequences, or indeed how it should be typeset on a terminal in the first place (what is the primary direction? where are the reordering boundaries?). There is the pre-Unicode bidirectional support mode (BDSM, I kid you not) in ECMA-48[1] and TR/53[2], which AFAIK nobody implements nor cares about; there are terminal emulators endorsed by bidi-language users[3], which AFAIK nobody has written down the behaviour of; there is the Freedesktop bidi terminal spec[4], which is a draft and AFAIK nobody implements yet either but at least some people care about; finally, there are bidi-language users who say that spec is a mistake[5]. Second, aside from bidi and a smattering of other things such as emoji, there is no detailed “Unicode text rendering behaviour”, only standards specific to font formats—the most recent among them being OpenType, which is dubiously compatible across implementations, decently documented only through painstaking reverse engineering (sometimes in words[6], sometimes only in Freetype library code), and generally full of snakes[7]. And it has no notion of a monospace font—only of a (proportional) font where all Lat/Cyr/Grk characters just happen to have the same advance. AFAICT that is not negligence or an oversight, but rather a concession to the fact that there are scripts which don’t really have a notion of monospace in the typographic tradition and in fact are written such that it’s extremely unclear what monospace would even mean—certainly not one or two cells per codepoint (e.g. Burmese or Tibetan; apparently there are Arabic monospace fonts[8] but I’ve no idea how the hell they work). Not coincidentally, those are the scripts where you really, really need that shaper, otherwise nothing looks anywhere close to correct. [This post could have been titled “Contra Muratori on Unicode in terminal emulators”.] [1] https://www.ecma-international.org/publications-and-standards/standards/ecma-48/ https://www.ecma-international.org/publications-and-standard... [2] https://www.ecma-international.org/publications-and-standards/technical-reports/ecma-tr-53/ https://www.ecma-international.org/publications-and-standard... [3] https://news.ycombinator.com/item?id=8086417 https://news.ycombinator.com/item?id=8086417 [4] https://terminal-wg.pages.freedesktop.org/bidi/ https://terminal-wg.pages.freedesktop.org/bidi/ [5] http://litcave.rudi.ir/ http://litcave.rudi.ir/ [6] https://github.com/n8willis/opentype-shaping-documents https://github.com/n8willis/opentype-shaping-documents [7] https://litherum.blogspot.com/2019/03/addition-font.html https://litherum.blogspot.com/2019/03/addition-font.html [8] https://news.ycombinator.com/item?id=10395464 https://news.ycombinator.com/item?id=10395464

csande17 4y ago
Here's another fun Unicode pitfall: does any terminal provide a way to display Chinese and Japanese text simultaneously, using the appropriate versions of the glyphs for each language's characters?
- mananaysiempre 4y ago
  As far as existing terminals are concerned, I don’t know. FWIW, there are similar problems (though only to the point of looking wrong, not of misunderstanding) in other scripts: Cyrillic as used in Bulgarian and a number of other languages[1] and even Latin as used in Polish[2]. Even the Han version, though, does not seem to me to be the sort of “what does it even mean?” problem like those I listed above; more like what you want the input to be. You can make your terminal keep language state, e.g. using the deprecated language tags. Pro: some form of this likely already needs to happen for bidi support; similar to what HTML does. Con: no text file or program ever did this; your nice UTF-8-only terminal is now stateful and goes mad after `head /dev/urandom`. Alternatively, you can require the driving program to emit variation selectors for each Han character. Pro: the state and the ensuing madness is now limited; you can still pretend you’re looking at a stream of characters. Con: no text file or program ever did this; neither does HTML although it theorerically could. [1] https://commons.wikimedia.org/wiki/File:Cyrillic_alternates.svg https://commons.wikimedia.org/wiki/File:Cyrillic_alternates.... [2] https://www.twardoch.com/download/polishhowto/kreska.html https://www.twardoch.com/download/polishhowto/kreska.html
- a1369209993 4y ago
  > does any terminal provide a way to display Chinese and Japanese text simultaneously, using the appropriate versions of the glyphs Does any terminal provide a way to display (say) two consecutive lines in different fonts? Because according to Unicode (and for once I don't particularly disagree), Chinese versus Japanese ideographs are the same characters, drawn in two different fonts.
  - hnfong 4y ago
    https://www.facebook.com/appliedphilosophy/photos/a.828540073892609/891825587564057 https://www.facebook.com/appliedphilosophy/photos/a.82854007... Many years ago I thought the highlighted text was a light hearted joke. Now I see what it is actually quite serious. (And now I understand why, among all people, a Japanese philosopher brought up the issue) I personally think Unicode didn't go essentialist enough though. There's lots of obscure CJK characters in unicode that, when you look up a dictionary, just says it's another form of a common character. What I heard from people in the know was that the CJK committee basically made an exception for the Japanese because they were threatening to withdraw from the Unicode effort unless their demands were met, and for the most part they got what they wanted. The "Chinese versus Japanese ideographs are the same characters, drawn in two different fonts" is actually a minority of those cases, which I personally interpret as clerical errors instead of a philosophical disagreement. For example if Unicode were actually thorough with the essentialist philosophy, 關 and 関 would have the same code point.

csande17 4y ago

Here's another fun Unicode pitfall: does any terminal provide a way to display Chinese and Japanese text simultaneously, using the appropriate versions of the glyphs for each language's characters?

mananaysiempre 4y ago
As far as existing terminals are concerned, I don’t know. FWIW, there are similar problems (though only to the point of looking wrong, not of misunderstanding) in other scripts: Cyrillic as used in Bulgarian and a number of other languages[1] and even Latin as used in Polish[2]. Even the Han version, though, does not seem to me to be the sort of “what does it even mean?” problem like those I listed above; more like what you want the input to be. You can make your terminal keep language state, e.g. using the deprecated language tags. Pro: some form of this likely already needs to happen for bidi support; similar to what HTML does. Con: no text file or program ever did this; your nice UTF-8-only terminal is now stateful and goes mad after `head /dev/urandom`. Alternatively, you can require the driving program to emit variation selectors for each Han character. Pro: the state and the ensuing madness is now limited; you can still pretend you’re looking at a stream of characters. Con: no text file or program ever did this; neither does HTML although it theorerically could. [1] https://commons.wikimedia.org/wiki/File:Cyrillic_alternates.svg https://commons.wikimedia.org/wiki/File:Cyrillic_alternates.... [2] https://www.twardoch.com/download/polishhowto/kreska.html https://www.twardoch.com/download/polishhowto/kreska.html
a1369209993 4y ago
> does any terminal provide a way to display Chinese and Japanese text simultaneously, using the appropriate versions of the glyphs Does any terminal provide a way to display (say) two consecutive lines in different fonts? Because according to Unicode (and for once I don't particularly disagree), Chinese versus Japanese ideographs are the same characters, drawn in two different fonts.
- hnfong 4y ago
  https://www.facebook.com/appliedphilosophy/photos/a.828540073892609/891825587564057 https://www.facebook.com/appliedphilosophy/photos/a.82854007... Many years ago I thought the highlighted text was a light hearted joke. Now I see what it is actually quite serious. (And now I understand why, among all people, a Japanese philosopher brought up the issue) I personally think Unicode didn't go essentialist enough though. There's lots of obscure CJK characters in unicode that, when you look up a dictionary, just says it's another form of a common character. What I heard from people in the know was that the CJK committee basically made an exception for the Japanese because they were threatening to withdraw from the Unicode effort unless their demands were met, and for the most part they got what they wanted. The "Chinese versus Japanese ideographs are the same characters, drawn in two different fonts" is actually a minority of those cases, which I personally interpret as clerical errors instead of a philosophical disagreement. For example if Unicode were actually thorough with the essentialist philosophy, 關 and 関 would have the same code point.