* bug#15659: 24.1; (wishlist) Simple method for preserving minor-mode
@ 2013-10-20 0:22 yary
2013-10-20 1:33 ` Stefan Monnier
2013-11-08 20:29 ` Stefan Monnier
0 siblings, 2 replies; 5+ messages in thread
From: yary @ 2013-10-20 0:22 UTC (permalink / raw)
To: 15659
There are times when I wish to set a minor-mode permanently for a
buffer, even through major-mode changes. They are display-related
minor-modes, such as buffer-face-mode or text-scale-mode.
Ideally I'd like a simple way to preserve a minor-mode between
major-mode changes. I started discussing this in Bug #15577, which is
about dir-locals, but am moving it here as this is a separate issue.
Also bug #15396 "permanent-local truncate-lines" is related, Stefan sets
a display-related local variable and would like it preserved across mode
changes (or in this case, revert-buffer). Yet setting `permanent-local'
on the `truncate-lines' variable does not protect it:
`toggle-truncate-lines' behaves like a minor mode.
A function could take a minor-mode to preserve, and then either set up
hooks needed to re-enable it after a major-mode change, or prevent
`kill-all-local-variables' from disabling it in the first place. Or
perhaps marking the minor-mode's function-symbol itself as
`permanent-local' could protect it, along with all its buffer-locals.
I have a personal workaround which works for modes I use posted at
http://stackoverflow.com/a/19439236/379333 - though it isn't fully
generalized and has other flaws. It checks if specified minor-modes
are active during `change-major-mode-hook', and if so, then tries to
figure out which variables they use, and then restores those variables
and minor modes in the `after-change-major-mode-hook'
Answering a question from bug #15577 about this issue:
>> a. Get all of that mode's customizable buffer-locals.
>
>Not sure what that is.
The modes I wanted to preserve have buffer-locals for the face, and
for the size adjustment. It's not enough to just re-enable the modes,
we have to know which buffer-locals the mode reads.
>> Ideally the minor-mode, or emacs core, would provide a function for
>> that purpose.
>
>It's probably not possible (not reliably at least) with the way minor
>modes are defined currently. Tho depending on what you mean it might be
>a non-issue.
What I meant was, since any proposed minor-mode-preserving mechanism
needs to know what buffer-local variables also would need to be set
`permanent-local', then "Ideally the minor-mode, or emacs core, would
provide a function" listing those variables. So for example, the
`define-minor-mode' macro might get a `:local-variables' keyword
allowing the author to declare that mode's buffer-locals, along with
their documentation and defaults. Would not be required in general,
but would make it easier for anything that wants to manipulate minor
modes.
>> b. Mark those variables as permanent-local
>
>There's no such thing, currently (we instead have to use a hack with
>change-major-mode-hook, along the lines of what you did).
Must be a mis-communication here. The docs to `kill-all-local-variables' say:
As a special exception, local variables whose names have
a non-nil `permanent-local' property are not eliminated by this function.
I just tried (put 'foo 'permanent-local 't) and `foo' survived
`kill-all-local-variables' and several mode changes. So we do have the
`permanent-local' property for keeping local variables around.
>But there are some issues:
>- we have to find out which buffer-local minor-modes are enabled, which
> presumes we have some kind of list of minor-modes. We can probably
> use minor-mode-list for that, tho.
Searching minor-mode-list would work, as would checking that the
symbol "name-of-minor-mide' is buffer-local and has a non-nil value.
>- some minor modes are mode-specific; e.g. it doesn't make much sense to
> preserve reftex-mode when switching from latex-mode to haskell-mode.
This sounds like another mis-communication- proposal is to let a user
(or by extension a minor-mode-author) to easily mark a minor-mode as
"to-be-preserved." As another example, I do not want flymake still on
when switching into css-mode. It's not up to this method to decide
which minor-modes to preserve; it is up to the user.
-y
^ permalink raw reply [flat|nested] 5+ messages in thread
* bug#15659: 24.1; (wishlist) Simple method for preserving minor-mode
2013-10-20 0:22 bug#15659: 24.1; (wishlist) Simple method for preserving minor-mode yary
@ 2013-10-20 1:33 ` Stefan Monnier
2013-10-20 13:26 ` yary
2013-11-08 20:29 ` Stefan Monnier
1 sibling, 1 reply; 5+ messages in thread
From: Stefan Monnier @ 2013-10-20 1:33 UTC (permalink / raw)
To: yary; +Cc: 15659
> There are times when I wish to set a minor-mode permanently for a
> buffer, even through major-mode changes. They are display-related
> minor-modes, such as buffer-face-mode or text-scale-mode.
Indeed, those two should probably be make "permanent local".
Stefan
^ permalink raw reply [flat|nested] 5+ messages in thread
* bug#15659: 24.1; (wishlist) Simple method for preserving minor-mode
2013-10-20 1:33 ` Stefan Monnier
@ 2013-10-20 13:26 ` yary
0 siblings, 0 replies; 5+ messages in thread
From: yary @ 2013-10-20 13:26 UTC (permalink / raw)
To: Stefan Monnier; +Cc: 15659
On Sat, Oct 19, 2013 at 9:33 PM, Stefan Monnier
<monnier@iro.umontreal.ca> wrote:
>> There are times when I wish to set a minor-mode permanently for a
>> buffer, even through major-mode changes. They are display-related
>> minor-modes, such as buffer-face-mode or text-scale-mode.
>
> Indeed, those two should probably be make "permanent local".
That's a better solution than prompting people to make permanent those
minor-modes themselves, via some new generic method for preserving any
minor mode.
I can still see a reason to have something like a `:local-variables'
keyword for any mode definition, minor or major- to help `desktop
save/recover' properly handle the buffer state. Doubtless there would
be yet more uses I haven't thought of.
^ permalink raw reply [flat|nested] 5+ messages in thread
* bug#15659: 24.1; (wishlist) Simple method for preserving minor-mode
2013-10-20 0:22 bug#15659: 24.1; (wishlist) Simple method for preserving minor-mode yary
2013-10-20 1:33 ` Stefan Monnier
@ 2013-11-08 20:29 ` Stefan Monnier
2021-12-04 3:37 ` Lars Ingebrigtsen
1 sibling, 1 reply; 5+ messages in thread
From: Stefan Monnier @ 2013-11-08 20:29 UTC (permalink / raw)
To: yary; +Cc: 15659
> A function could take a minor-mode to preserve, and then either set up
> hooks needed to re-enable it after a major-mode change, or prevent
> `kill-all-local-variables' from disabling it in the first place. Or
> perhaps marking the minor-mode's function-symbol itself as
> `permanent-local' could protect it, along with all its buffer-locals.
We could start with something like the following (guaranteed 100% untested):
(put 'after-change-major-mode-hook 'permanent-local-hook t)
(defvar permanent-local--modes nil)
(defun permanent-local--reenable ()
(mapc #'funcall permanent-local--modes))
(put 'permanent-local--reenable 'permanent-local-hook t)
(defun permanent-local-mode (mode)
"Enable MODE permanently in this buffer."
(interactive
(list
(intern
(completing-read "Minor mode: "
obarray
(lambda (sym)
(or (memq mode minor-mode-list)
(string-match "-mode\\'" (symbol-name sym))))
t))))
(funcall mode) ;Enable.
(add-hook 'after-change-major-mode-hook #'permanent-local--reenable nil t))
-- Stefan
^ permalink raw reply [flat|nested] 5+ messages in thread
* bug#15659: 24.1; (wishlist) Simple method for preserving minor-mode
2013-11-08 20:29 ` Stefan Monnier
@ 2021-12-04 3:37 ` Lars Ingebrigtsen
0 siblings, 0 replies; 5+ messages in thread
From: Lars Ingebrigtsen @ 2021-12-04 3:37 UTC (permalink / raw)
To: Stefan Monnier; +Cc: yary, 15659
Stefan Monnier <monnier@IRO.UMontreal.CA> writes:
>> A function could take a minor-mode to preserve, and then either set up
>> hooks needed to re-enable it after a major-mode change, or prevent
>> `kill-all-local-variables' from disabling it in the first place. Or
>> perhaps marking the minor-mode's function-symbol itself as
>> `permanent-local' could protect it, along with all its buffer-locals.
(I'm going through old bug reports that unfortunately weren't resolved
at the time.)
> We could start with something like the following (guaranteed 100% untested):
>
> (put 'after-change-major-mode-hook 'permanent-local-hook t)
>
> (defvar permanent-local--modes nil)
>
> (defun permanent-local--reenable ()
> (mapc #'funcall permanent-local--modes))
> (put 'permanent-local--reenable 'permanent-local-hook t)
>
> (defun permanent-local-mode (mode)
> "Enable MODE permanently in this buffer."
> (interactive
> (list
> (intern
> (completing-read "Minor mode: "
> obarray
> (lambda (sym)
> (or (memq mode minor-mode-list)
> (string-match "-mode\\'" (symbol-name sym))))
> t))))
> (funcall mode) ;Enable.
> (add-hook 'after-change-major-mode-hook #'permanent-local--reenable nil t))
I think this could work... but I don't really see it being used a lot.
Changing a major mode is a relatively rare thing to do, and I don't see
people using `permanent-local-mode' first -- because it'd be more work
than just re-enabling the minor modes.
And if you are in the habit of changing modes a lot (for instance,
between two modes like cperl-mode and perl-mode), then I think you'd be
more likely to want to put the minor modes into the major mode hooks.
So, while it would be possible to add something like this, I just don't
see the use case, so I don't think we should add this, and I'm closing
this bug report.
--
(domestic pets only, the antidote for overdose, milk.)
bloggy blog: http://lars.ingebrigtsen.no
^ permalink raw reply [flat|nested] 5+ messages in thread
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2013-10-20 0:22 bug#15659: 24.1; (wishlist) Simple method for preserving minor-mode yary
2013-10-20 1:33 ` Stefan Monnier
2013-10-20 13:26 ` yary
2013-11-08 20:29 ` Stefan Monnier
2021-12-04 3:37 ` Lars Ingebrigtsen
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