ielm read-only prompt.

[Luc Teirlinck]

What is the status of the optional read-only comint prompt about which
there was some discussion a year or so ago. (If I remember well.)  It
would be very easy for me to make some improvements to ielm's
read-only prompt, but I have never worried about that, since I always
thought that the ielm solution was extremely temporary.

Needed improvements to ielm's read-only prompt include making it
optional, making it "really" read-only (as opposed to just
non-erasable) by making the read-only property front-sticky, which
would avoid some very confusing accidents (which I had happen to me)
and making it easier to temporarily override the read-only property to
do some editing of the ielm buffer.  All of this would not be very
much work, but it makes little sense anyway, if a more general
solution would just be, say, weeks away.  However, if the more general
solution is to occur in some vague and distant future, it would make
sense.

In the intermediate case just adding "'front-sticky '(read-only)" to
the propertize form of the ielm-prompt defcustom would avoid accidents
where one yanks text just a little bit too far to the left. (Inside
the prompt, but invisibly so because the only part of the prompt that
is to the right of the yanked text is a space.  The yanked text itself
could start with a space, completely hiding the situation.)  Confusing
things can happen next.  Since we are talking about front-sticky, it
would not interfere with the rear-non-stickiness required for other
stuff to work right.  I could send a patch if this would be useful,
but again, if we go for this extremely limited change, we are only
talking about adding "'front-sticky '(read-only)" to the propertize
form.

Sincerely,

Luc.