Confusion about Undo keybinding

Confusion about Undo keybinding

[Kevin Havener]

According to the tutorial and other places, undo is bound by default to 
C-/, C-_, and C-x u.  However in my newly installed emacs 24.5, C-/ is 
bound to DEL (backspace).  I don't think I have any .emacs type file 
overriding the defaults, so is this wrong or is the documentation wrong?

Wait just a minute.  C-/ is bound to undo in graphical mode and in xterm 
(-nw) mode.  C-/ is bound to DEL in my linux virtual consoles.  How is 
this possible?

Can you tell me what is going on?

Thank you,
Kevin Havener

Re: Confusion about Undo keybinding

[Barry Margolin]

In article <mailman.4403.1455218497.843.help-gnu-emacs@gnu.org>,
 Kevin Havener <havenerk@gmail.com> wrote:

> According to the tutorial and other places, undo is bound by default to 
> C-/, C-_, and C-x u.  However in my newly installed emacs 24.5, C-/ is 
> bound to DEL (backspace).  I don't think I have any .emacs type file 
> overriding the defaults, so is this wrong or is the documentation wrong?
> 
> Wait just a minute.  C-/ is bound to undo in graphical mode and in xterm 
> (-nw) mode.  C-/ is bound to DEL in my linux virtual consoles.  How is 
> this possible?

In terminal mode, only ASCII characters can be used, and there is no 
ASCII C-/ character. When you type C-/ it sends the DEL character, I 
think because this is what Teletype terminals in the 70's did (or maybe 
it's what DEC VTxxx terminals did).

-- 
Barry Margolin, barmar@alum.mit.edu
Arlington, MA
*** PLEASE post questions in newsgroups, not directly to me ***

Re: Confusion about Undo keybinding

[Emanuel Berg]

Kevin Havener <havenerk@gmail.com> writes:

> I don't think I have any .emacs type file overriding
> the defaults

You can check this with emacs -Q.

> C-/ is bound to undo in graphical mode and in xterm
> (-nw) mode.

I wouldn't call this "xterm mode" as just about any
terminal emulator (urxvt, Gnome terminal, etc.) should
be able to do this.

But actually the Emacs help mentions xterm:

    -nw, --no-window-system
            Tell Emacs not to create a graphical  frame.   If  you  use
            this  switch  when  invoking Emacs from an xterm(1) window,
            display is done in that window.

> C-/ is bound to DEL in my linux virtual consoles.
> How is this possible?

Here is a tutorial if you want to rebind it:

    http://user.it.uu.se/~embe8573/tty-emacs-keys.txt

use, e.g.:

    (define-key input-decode-map [?\u0114] [C-/])

> Can you tell me what is going on?

The Linux VTs are not the same as X. xterm may appear
closer to the Linux VTs but it is not: it *is*
"x"term, aye?

PS. I have `undo' M-0 - very fast, close, and
ergonomic if I may... DS.

-- 
underground experts united
http://user.it.uu.se/~embe8573