implementing BIDI isolates, and make LRM and RLM visible

implementing BIDI isolates, and make LRM and RLM visible

[Uwe Brauer]

Hello

According
https://www.gnu.org/software/emacs/manual/html_node/elisp/Bidirectional-Display.html
the actual BIDI support «does not yet support the isolate directional
formatting».

I presume that has to do with fact that if in one line I mix say Hebrew
with English text and I want to switch editing between them then, in
order to do that in any comfortable way (cursor movements etc) I end up
that the whole buffer will be displayed either R2L or L2R and not the
individual paragraphs.

In any case I wish I could help implementing this missing feature, but I
cannot so I simply ask: any plans for the near future?

Meanwhile I try to use LRM and RLM to deal with such situations. However
is there a way to make them visible, at least buffer local?

thanks

Uwe Brauer 

Re: implementing BIDI isolates, and make LRM and RLM visible

[Eli Zaretskii]

> From: Uwe Brauer <oub@mat.ucm.es>
> Date: Mon, 02 May 2016 17:41:16 +0000
> 
> According
> https://www.gnu.org/software/emacs/manual/html_node/elisp/Bidirectional-Display.html
> the actual BIDI support «does not yet support the isolate directional
> formatting».

That's accurate for Emacs 24.5.  Emacs 25.1 has the full UBA
implemented, including the isolates.

> I presume that has to do with fact that if in one line I mix say Hebrew
> with English text and I want to switch editing between them then, in
> order to do that in any comfortable way (cursor movements etc) I end up
> that the whole buffer will be displayed either R2L or L2R and not the
> individual paragraphs.

I don't understand this, sorry.  Please show what you type, how it
looks on display, and how you wanted it to look, and we can take it up
from there.

In any case, I don't think the issue that bothers you has anything to
do with isolates, because those don't change how Emacs determines the
base paragraph direction.

> In any case I wish I could help implementing this missing feature, but I
> cannot so I simply ask: any plans for the near future?

It's done already.  We are already in the future, just use the latest
pretest of Emacs 25.1.

> Meanwhile I try to use LRM and RLM to deal with such situations. However
> is there a way to make them visible, at least buffer local?

They are visible: they are displayed as thin spaces.  If you want them
more visible, customize glyphless-char-display-control.

Re: implementing BIDI isolates, and make LRM and RLM visible

[Uwe Brauer]

>>> "Eli" == Eli Zaretskii <eliz@gnu.org> writes:


    > That's accurate for Emacs 24.5.  Emacs 25.1 has the full UBA
    > implemented, including the isolates.

    > I don't understand this, sorry.  Please show what you type, how it
    > looks on display, and how you wanted it to look, and we can take it up
    > from there.

Ok, I will send some screenshots, most likely tomorrow. I'd rather avoid
to send them, but it seems the fastest way to explain.


    > In any case, I don't think the issue that bothers you has anything
    > to do with isolates, because those don't change how Emacs
    > determines the base paragraph direction.

ok

    > It's done already.

Good :-D

    > We are already in the future, just use the latest pretest of Emacs
    > 25.1.

I do, the person I was discussing this issue with, however did not. He
still uses 24. But he was also bothered by the paragraph direction. For
example OO (OpenOffice) whose BIDI implementation does not seem to be
perfect, only changes the display paragraph wise. But I will elaborate
an example.


    >> Meanwhile I try to use LRM and RLM to deal with such situations.
    >> However is there a way to make them visible, at least buffer
    >> local?

    > They are visible: they are displayed as thin spaces.  If you want them
    > more visible, customize glyphless-char-display-control.

Ok, I realize that there is something, but for me that is to tiny. I
will try your advice.

Thanks again

Uwe 

Re: implementing BIDI isolates, and make LRM and RLM visible

[Uwe Brauer]

   > That's accurate for Emacs 24.5.  Emacs 25.1 has the full UBA
   > implemented, including the isolates.


   > I don't understand this, sorry.  Please show what you type, how it
   > looks on display, and how you wanted it to look, and we can take it up
   > from there.

I investigated this further, it seems that the behavior I find strange
only occurs in orgmode when outline is activated. I still have to look
into this further to get an working example, but I have the feeling that
the case is a bit pathological.

Re: implementing BIDI isolates, and make LRM and RLM visible

[Eli Zaretskii]

> From: Uwe Brauer <oub@mat.ucm.es>
> Date: Sat, 07 May 2016 16:55:07 +0000
> 
> I investigated this further, it seems that the behavior I find strange
> only occurs in orgmode when outline is activated. I still have to look
> into this further to get an working example, but I have the feeling that
> the case is a bit pathological.

AFAIR, Org forces bidi-paragraph-direction to the left-to-right value
by default, so maybe you want to set it to nil instead.