set-buffer-major-mode: how to use on buffer without file?

set-buffer-major-mode: how to use on buffer without file?

[Jean Louis]

I would like to set major mode for the buffer which only displays a
revision in a buffer without associated file. The buffer name may end
with let us say .scm for scheme or .org for Org mode, I would like to
invoke the major mode based on the file extension.

Maybe `set-buffer-major-mode' is right function?

Or maybe some other?

Jean

Re: set-buffer-major-mode: how to use on buffer without file?

[Stefan Monnier]

> I would like to set major mode for the buffer which only displays a
> revision in a buffer without associated file.

Your use of "the buffer" above is hilarious: it makes it sound like we
all should know, as a matter of course, which buffer it is you're
talking about, like if it had been on the front page of the newspaper
or something.

> The buffer name may end with let us say .scm for scheme or .org for
> Org mode, I would like to invoke the major mode based on the
> file extension.

You may want to do: `C-h o C-x v ~` and then look at the implementation
of that command (since that command does something closely related to
what you describe).


        Stefan

Re: set-buffer-major-mode: how to use on buffer without file?

[Jean Louis]

* Stefan Monnier <monnier@iro.umontreal.ca> [2021-03-25 17:31]:
> > I would like to set major mode for the buffer which only displays a
> > revision in a buffer without associated file.
> 
> Your use of "the buffer" above is hilarious: it makes it sound like we
> all should know, as a matter of course, which buffer it is you're
> talking about, like if it had been on the front page of the newspaper
> or something.

I have not expressed myself clearly, I have buffers that come from
database, and are not associated to the file within Emacs
context. Within program they are associated with the file with
specific extension.

vcfiles_filename entry may be "/home/admin/new.scm"

and buffer name becomes something like:

RCD VC Revision ID: 12, /home/admin/new.scm

so buffer is not really associated within Emacs context to file name,
within program's context it is directly associated. Now when I entered
the sphere of auto mode settings I can see that for buffers that
function is missing, or is not there. Am I right?

set-auto-mode function does not verify anything for buffers how I see
it. Maybe it would be better to have something for buffers not
associated to files.

Right now I am doing that trick to associate the file to buffer and
then set auto mode, and then I can disassociate file from buffer. I am
then associating the above example with
/home/admin/RCD-VC-Revision-ID-12-new.scm as that way it becomes
unique file.

So it is solved on my side.

But I still think that auto mode should also work in buffers without
file, at least when user enables it.

Jean