Proposal for BiDi in terminal emulators

[Eli Zaretskii via Unicode]

> From: Egmont Koblinger <egmont at gmail.com>
> Date: Fri, 1 Feb 2019 13:54:02 +0100
> Cc: Adam Borowski <kilobyte at angband.pl>, unicode at unicode.org
> 
> For this behavior, the only feature you need from a terminal emulator
> is to have a mode where it doesn't shuffle the characters. Currently
> every emulator I'm aware of has such a mode, although in some of them
> you have to tweak the settings to get to this mode (in my firm opinion
> it's an unacceptable user experience), while in emulators according to
> my specification there'll be an escape sequence for text-mode apps to
> automatically switch to this mode.

Like I said, as long as not every emulator supports this control, an
application will need to detect its support, and that in itself is a
complication.

> > This is indeed a significant issue, because it means applications
> > cannot force the terminal use a certain non-default base paragraph
> > direction.
> 
> They can, since there's a dedicated escape sequence (SCP) for setting
> the base paragraph.

Does this change the base direction globally for the whole screen, or
only for the current text?  The latter is what's needed.

And again, just detecting whether this is supported is a
complication.  Emitting LRM or RLM as needed is much easier.