bug#62275: 28.2; Changing major mode changes the current text scaling

[Drew Adams]

> > > But that's what text-scaling does: it enlarges
> > > the default face's font.
> >
> > You seem to be dancing around this.
> 
> Why the sarcasm/insult?  I don't have to have this conversation, and I
> certainly won't if you keep this attitude.

There's neither any sarcasm nor any insult there.
You're apparently seeing what you want to see.
Why do that?

> > Text-scaling does NOT "customize the default face".
> 
> Of course, it does.

For some meaning of "customize", perhaps.  I didn't
see any use of any `custom*' functions.  But I may
not have read the code carefully enough.

> > What's more, actually changing the font of face
> > `default' is the same as changing frame property
> > `font'.
> 
> Yes, and that's equivalent to what text-scaling does.
> 
> > And doing that changes the text size for ALL
> > windows in the frame - whatever buffers they
> > show, not just a single buffer.
> 
> Yes, as expected.  Text-scaling, by contrast, is a buffer-local
> behavior, and buffer-local behaviors get reset when the major mode
> changes.

I think you're confirming what I said.  Text-scaling
doesn't just change face `default' for a given frame.
If it did then that would affect only that frame, and
it would affect all windows showing any buffer in
that frame.

> > These are different things: (1) zooming a buffer
> > (everywhere) and (2) zooming a frame (all its
> > windows, whatever the buffers) and zooming
> > nothing in any other frame.
> 
> Not very different, since we now have
> global-text-scale-adjust and friends. 

Interesting.  I know nothing about such a command.
I don't see it in Emacs 28.2 (the latest release).
Does it zoom all windows (any buffers) in a frame?
Does it zoom only the current frame?
_____

At any rate, feel free to close this bug, as you
don't want to provide an easy option to make text
scaling be unaffected by major-mode changes in a
buffer.  By doing that I mean in a friendlier way
for users than them finding out they can do it by
(put 'face-remapping-alist 'permanent-local t).

Reminder: I proposed doing it.  All it takes is a
minor mode with a one-sexp body.  I've added that
to my face-remap+.el.  If you change your mind
then I'll be glad to be able to remove it.

(define-minor-mode text-scale-keep-mode
  "Keep the same text-scaling when a buffer changes major mode.
Disabling the mode restores the vanilla Emacs behavior, where changing
the major mode loses a buffer's current text-scaling.  This minor mode
is global: it affects all buffers."
  :init-value nil :global t
  (put 'face-remapping-alist 'permanent-local text-scale-keep-mode))