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

Egmont Koblinger via Unicode unicode at
Thu Feb 7 06:29:09 CST 2019

Hi Philippe,

> There's some rules for correct display including with Bidi:

In what sense are these "rules"? Where are these written, in what kind
of specification or existing practice?

> - Separate paragraphs that need a different default Bidi by double newlines (to force a hard break)

There is currently no terminal emulator I'm aware of that uses empty
lines as boundaries of BiDi treatment.

While my recommendation uses a one smaller unit (logical lines), and I
understand as per Eli's request that it would be desireable to go with
emptyline-delimited boundaries, what in fact all the current
self-proclaimed BiDi-aware terminal emulators that I came across do is
use a unit two steps smaller than yours: they do BiDi on physical
lines of the terminal, no matter how a logical line of the output had
to wrap into physical ones because didn't fit in the width. (It's a
terrible behavior.)

The current behavior of terminal emulators is very far from what you describe.

> - use a single newline on continuation

Continuation of what exactly?

But let's take a step back: Should the output be pre-formatted by some
means, or do we rely on the terminal emulator wrapping overlong lines?
(If pre-formatted then for what width? 80 columns, so that I waste
precious real estate if my terminal is wider? Or is it a requirement
for any app that produces output to implement a decent dynamic
wrapping engine for nice formatting according to the actual width?)

There's precedence for both of these different approaches. I don't
think it's feasible to pick one, and claim that the other approach is

> - if technical items are untranslatable, make sure they are at the begining of lines and indented by some leading spaces, before translated ones.

I firmly disagree. There shouldn't be any restriction on how a
translator wishes to translate a sentence. The computer world has to
adapt to the requirements of human languages, not the other way

> - Don't use any Bidi control !

Why not? They do exist for a reason, for the very reason that any
logical translation, which a translator might want to write (see my
previous point) is presentable in a visually correct way. Use them for
that, whenever needed.


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