Bidi paragraph direction in terminal emulators

[Egmont Koblinger via Unicode]

On Tue, Feb 12, 2019 at 9:35 PM Richard Wordingham via Unicode
<unicode at unicode.org> wrote:

> Bash already seems to handle proportional fonts quite well when run
> under Emacs 'M-x shell',

Having never used bash inside Emacs's shell, here's my experience
after about a minute of trying it:

Cursor keys allow you to walk back to the prompt, backspace allows to
delete the prompt, typing letters lets you modify the prompt... Not
something that I consider a sensible behavior.

If I do so, I have no idea what the executed command will be. Coloring
gives some clue, but isn't always reliable. My prompt is blue, the
text I type after that is black. I type one letter and then press
Ctrl-T to transpose the last two letters (the trailing space of my
prompt, and the newly typed letter). The newly typed letter is black.
I press Enter, this one-letter command isn't executed, and becomes
blue.

I feel magnitudes safer in standard bash where I know it doesn't allow
me to walk back to the prompt, only allows me to edit whatever I'm
trying to execute.

I have not studied how this behavior is implemented, but as per [1] as
well as the behavior I experience, it seems that lot of bash's
behavior wrt. line editing is moved to Emacs itself. Pretty much none
of my preferred shortcuts work as they do in native bash, something
I'm not happy about either.

I've no idea how this (external editing) would be expected to be the
generic behavior when there's no Emacs (no external editor) in the
game, plus a whole bunch of other utilities are expected to run (ones
that fail big time in Emacs's M-x shell, or even refuse to start up).

[1] https://www.gnu.org/software/emacs/manual/html_node/emacs/Shell-Mode.html