Re: Binding Home and End

["Benjamin R. Haskell" <zsh@xxxxxxxxxx>]

On Sun, 31 Jan 2010, Frank Terbeck wrote:

> Peter Stephenson wrote:
> > On Sat, 30 Jan 2010 12:25:15 +0100
> > Frank Terbeck <ft@xxxxxxxxxxxxxxxxxxx> wrote:
> >> Mikael Magnusson wrote:
> [...]
> 
> > (Although it's certainly arguable, it's not completely clear that a 
> > shell's line editor is an "application" in the strict sense, the 
> > whole distinction being a not very happy historical accident in the 
> > first place.  The way shells evolved means that to begin with they 
> > were just using raw input; at some point they crossed the boundary 
> > to become something more sophisticated.  The simple application / 
> > raw distinction doesn't really fit.)
> 
> Does somebody on the list actually know why such a distinction was 
> made at all? And why it would make sense to have a key like `HOME' 
> send different bytes depending on which mode is active?

(This problem came up on the Vim list, too in the past couple days).  
The XTerm FAQ has a short (possible) answer[1].  And I liked this ending 
to an email on an Apple mailing list[2]:

"""
  Confused yet? Read the relevant man pages terminfo, infocmp, tput.
  If still not sufficiently confused, read

  http://invisible-island.net/xterm/ctlseqs/ctlseqs.html

  and weep.

  - Harald
"""

As with most things terminal(-emulator)-related, it seems to mostly come 
down to hysterical raisins, but the purpose of the two modes seems 
similar to what the NumLock key tends to do nowadays.  (That is: lets 
you switch between two useful sets of keybindings for the same 
~18-key numerical keypad.)  AFAICT, the VT-100 didn't have a NumLock key[3].

And, from terminfo, it seems clear that that was the intent (to separate 
two different modes for the keypad itself, not to create a semantic 
distinction between 'application' and 'normal' modes)[4].

[1] http://invisible-island.net/xterm/xterm.faq.html#xterm_arrows
[2] http://lists.apple.com/archives/x11-users/2008/Apr/msg00253.html
[3] http://www.columbiauniversity.org/kermit/vt100-keyboard.jpg
[4] http://linux.die.net/man/5/terminfo (Â Keypad and Function Keys)

> > If you're not relying on the particular O / [ key sequence you're 
> > getting at the moment, however, as far as I know the shell code I 
> > gave should work fine for you (obviously, do let us know if you find 
> > a problem).
> 
> Sending smkx when zle starts should make the values from $terminfo 
> valid within the line editor. So no rewriting O to [ should be 
> necessary.
> 
> I've tested this with a number of terminals, with and without terminal 
> multiplexers (screen and tmux), and so far I have not seen any 
> breakages. (So far, only tried Linux, though.)

Just as more data: I can also confirm that on my system, the 'terminfo' 
values for 'Home' and 'End' match the 'application' mode values for: 
(u)rxvt, mlterm, and (u)xterm (=konsole, gnome-terminal, xfce's 
Terminal, and terminator).  Same is true under 'screen' and 'tmux'.

Of all those I just listed, only the ones that "faithfully" emulate 
XTerm ((u)xterm, konsole, gnome-terminal) actually emit a different code 
for Home/End under the different modes.  All the others match terminfo 
in both modes (as far as Home/End go).

-- 
Best,
Ben