Bidi paragraph direction in terminal emulators

[Richard Wordingham via Unicode]

On Sun, 10 Feb 2019 14:54:39 +0100
Philippe Verdy via Unicode <unicode at unicode.org> wrote:

> Le sam. 9 févr. 2019 à 20:55, Egmont Koblinger via Unicode <
> unicode at unicode.org> a écrit :  
> 
> > Hi Asmus,
> >  
> > > On quick reading this appears to be a strong argument why such
> > > emulators  
> > will  
> > > never be able to be used for certain scripts. Effectively, the
> > > model  
> > described works  
> > > well with any scripts where characters are laid out (or can be
> > > laid out)  
> > in fixed  
> > > width cells that are linearly adjacent.  
> >
> > I'm wondering if you happen to know:
> >
> > Are there any (non-CJK) scripts for which a mechanical typewriter
> > does not exist due to the complexity of the script?
> >  
> 
> Look into South Asian scripts (Lao, Khmer, Tibetan...) and...

The Khmer script is an interesting case - see
http://onkhmertype.com/the-cambodian-typewriter.  The problem there is
that deep cells are needed.  What's the VTE algorithm for the vertical
extent of the cell?

The only problem I can see for Lao is that there can be two marks below
a consonant. Otherwise, a straightforward adaptation of a Thai
typewriter should suffice.

There's a Tai Tham typewriter in the National Museum in Bangkok.
However, spelling may have been adapted to cope with any limitations.

>... large syllabaries (CANS, Ethiopian).

That's more a matter of extent than complexity.

Sesquidimensional Egyptian hieroglyphs could be tricky - they'll be like
producing 2-D renderings of ideographic description sequences.

There could be a problem with standardising cuneiform character widths.

Richard.