Re: troubleshoot C-M-/ key binding (dabbrev-completion)

[Michael V. Antosha]

On 1/21/24, Martin Marshall <law@martinmarshall.com> wrote:
> "Michael V. Antosha" <michael.antosha@gmail.com> writes:
>
>> 3. Using C-M-/ (i.e. pressing Ctrl+Alt+SLASH) seems to have the same
>> effect as M-/ (dabbrev-expand).
>
> What effect is that?

I prepared a description of a test procedure to specify the effect,
but I chose to skip sending it to keep my post shorter and because it
seems unnecessary now (explained below).


> Are you sure there are multiple completion candidates in the buffer?

Yes.


> If there's only one candidate in the buffer, `dabbrev-completion' will
> immediately complete the word without bringing up a "*Completions*"
> buffer.  That would look like the same thing `dabbrev-expand' does.

I understand differences and similarities between the two commands, I
first tested their behavior without key bindings, through M-x
dabbrev-*


> You can check which key Emacs thinks you pressed and which command it
> called by invoking `view-lossage' (bound to "C-h l").

Martin, thank you very much!
That's really useful.


What I'm seeing now proves my original suspicion:
 - when I press "Alt+SLASH" emacs interprets it as ESC / [dabbrev-expand]
 - when I press "Ctrl+Alt+SLASH" emacs interprets it, as ESC / [dabbrev-expand]

 ESC / [dabbrev-expand]
 C-h l [view-lossage]

What could I do further to find out why these different combinations
are understood by emacs as ESC / sequence?


For comparison, Ctrl+Alt+BACKSLASH works fine.
Below are keys/commands from C-h l after pressing Ctr+BACKSLASH, then
Alt+BACKSLASH, then Ctrl+Alt+BACKSLASH:

 C-\ [toggle-input-method]
 ...
 ESC \ [delete-horizontal-space]
 ...
 ESC C-\ [indent-region]
 C-h l [view-lossage]


I also tried to emulate C-M-/ by pressing ESC and then pressing Ctrl+SLASH,
the result is quite unexpected:

 ESC C-_ [nil]
 C-h l [view-lossage]


-- 
Michael V. Antosha