Bidi paragraph direction in terminal emulators

Egmont Koblinger via Unicode unicode at
Tue Feb 12 07:08:01 CST 2019

Hi Elias,

> For all the willingness to come up with ways to modernise the terminal, you've only spoken about trying to showhorn rtl text in to the vt102 basic terminal.

Yes, addressing BiDi was the exact thing that I did now. What's wrong with that?

I can't address all the imperfectnesses at once. If you take a look at
VTE's changelog, you'll see that I've done a lot more than this, and
chances are this won't be my last improvement either.

> What I mean is that f you're willing to go as far as introducing new escape codes to allow applications to better control the behaviour of this one feature, why do you stop there? Why still limit yourself to the bonds of vt102?

Did I stay I'll stop here? No, I presented one step, without saying
anything about what might be the next one I tackle. (Okay, I drafted
out some ideas for continuing this work, and I said things about what
will definitely _not_ be the next step, as far as I'm concerned.)

> Once you take that first step towards the new control codes, why not simply come up with a new scheme? Why not let me do:
> TERM=newfancything
> And then I'd have a system that supports everything I need: variable with fonts, proper rtl text, pixel-precise character positioning, all the colours, inline graphics, etc.

Because this would create a brand new world where practically every
application has to be heavily adjusted, if not built up from scratch
(e.g. for ncurses, I'd expect that a new replacement would have to be
designed and created).

Because this is not solely an engineering kind of task, but rather
something that would need buy-in from a critical set of people (the
maintainers of all these libs and apps, and the other popular
terminals), which I find unlikely to get, given that for most of these
apps the current platform is good enough, and something new would add
an significant amount of extra burden for marginal benefits.

Because, even if everyone supported the idea, the required amount of
design and implementation work would be magnitudes bigger than for

Because I'm doing one thing at a time. And I honestly just because I
came here to announce my work that addresses _one_ thing, I really
don't find it a fair question to ask why I didn't address suddenly
magnitudes more than that.

Because I'm doing this as a hobby project, not as a paid job. If
someone offers me a job to do this, we can discuss it.

> There is nothing magic about the grid of cells, and once you introduce new escape sequences, you might as well truly modernise the terminal.

The magic about the grid of cells is all the software that were built
up with this assumption during the last couple of decades.


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