Bidi paragraph direction in terminal emulators (was: Proposal for BiDi in terminal emulators)

Egmont Koblinger via Unicode unicode at
Mon Feb 4 15:27:39 CST 2019

Hi Richard,

> The concept appears to exist in the form of the fields of the
> fifth edition of ECMA-48.  Have you digested this ambitious standard?

To be honest: No, I haven't. And I have no idea what those "fields" are.

I spent (read: wasted) way too much time studying ECMA TR/53 to get to
understand what it's talking about, to realize that the good parts
were already obvious to me, and to be able to argue why I firmly
believe that the bad parts are bad. Remember: These documents were
created in 1991, that is, 28 years ago. (I'm emphasizing it because I
did the math wrong for a long time, I though it was 18 years ago :-D.)
Things have a changed a lot since then.

As for the BiDi docs, I found that the current state of the art,
current best practices, exisiting BiDi algorithm differ so much from
ECMA's approach (which no one I'm aware of cared to implement for 28
years) that the standard is of pretty little use. Only a few good
parts could be kept (but needed tiny corrections), and plenty of other
things needed to be build up anew. This is the only reasonable way to
move forward.

If you designed a house 2 or 3 years ago, and finally have the money
to get it built, you can reasonably start building it. If you designed
a house 28 years ago and finally have the chance to build it
(including the exact same heating technologies, electrical system
etc.), you wouldn't, would you? I'm sure you looked at those plans,
and started at the very least heavily updating them, or started to
design a brand new one, perhaps somewhat based on your old ideas.

I don't expect it to be any different with "fields" of ECMA-48. I'm
not aware of any terminal emulator implementing anything like them,
whatever they are. Probably there's a good reason for that. Whatever
purpose they aimed to serve apparently wasn't important enough for
such a long time. By now, if they're found important, they should
probably be solved by some new design (or at the very least, just like
I did with TR/53, the work should begin by evaluating that standard to
see if it's still feasible).

Instead of spending a huge amount of work on my BiDi proposal, I could
have just said: "guys, let's go with ECMA for BiDi handling". The
thing is, I'm pretty sure it wouldn't have taken us anywhere. I don't
expect it to be different with "fields" either.

The starting point for my work was the current state of terminal
emulators and the surrounding ecosystem, plus the current BiDi
algorithm; not some ancient plan that was buried deep in some drawer
for almost three decades. I hope this makes sense.

That being said, I'd really, honestly love to see if someone evaluated
ECMA's "fields" and created a feasibility study for current terminal
emulators, similarly to how I did it with TR/53.


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