ANNOUNCE: GHC version 6.10.1 - EditLine / terminal incompatibility?

[Judah Jacobson]

On 11/21/08, Duncan Coutts <duncan.coutts at worc.ox.ac.uk> wrote:
> On Fri, 2008-11-21 at 11:59 +0100, Philip K.F. Hölzenspies wrote:
> > On Friday 21 November 2008 10:49:47 Jules Bean wrote:
>
> > > Something must be very very broken : surely it is not expected behaviour
> > > for editline to need configuration in this way?
> >
> > One can call it broken, another will say users should settle for the default
> > behaviour. Neither readline, nor editline *need* configuration this way,
> > because they do come with sensible defaults.
>
> But that's just it. It seems that readline does come with sensible
> defaults and editline does not. For example xterm is not a rare kind of
> terminal (basically every terminal in use claims to be xterm) and yet
> delete does not work with it out-of-the-box with editline. That is
> broken.
>
> [To add insult to injury, even when I look up the escape sequence for
> delete using the cat/telnet trick, I still cannot configure editline to
> recognise it.]

After further investigation, I think this technically isn't a terminal
compatibility issue, but rather a missing feature; i.e., editline just
doesn't intentionally support using the delete key.  The command
ed-delete-next-char which we found in the editrc manpage is really
meant to represent pressing 'x' in the vi bindings, which is why it
hasn't been working as expected.  AFAICT, editline has no command
equivalent to pressing 'delete'.

Of course, regardless of the cause, the net result (delete key not
working) is the same.  I just wanted to point out that editline does
use the same terminal capability libraries (termcap/terminfo) as
readline, so there's no fundamental reason this couldn't be
implemented portably other than (I'm guessing) the lack of motivation
or time from its authors/contributors.

-Judah