bug#51580: hl-line-mode doesn't override global-hl-line-mode in current buffer

bug#51580: hl-line-mode doesn't override global-hl-line-mode in current buffer

[Stefan Kangas]

It seems like there is currently no way to use `global-hl-line-mode'
while disabling it for individual buffers.

Steps to reproduce:

0. emacs -Q
1. M-x global-hl-line-mode
2. M-x hl-line-mode

Now, `global-hl-line-mode' is still in effect, and lines are still
highlighted.  I expect that running `hl-line-mode' turns off line
highlighting.

There is a comment in hl-line.el saying:

    ;; You could make variable `global-hl-line-mode' buffer-local and set
    ;; it to nil to avoid highlighting specific buffers, when the global
    ;; mode is used.

However, if I say M-x global-hl-line-mode and then

    M-: (setq-default global-hl-line-mode nil)

the highlighting overlay is left on the current line.

bug#51580: hl-line-mode doesn't override global-hl-line-mode in current buffer

[Gregory Heytings]

>
> It seems like there is currently no way to use `global-hl-line-mode' 
> while disabling it for individual buffers.
>

There is one: (setq-local global-hl-line-mode nil).

bug#51580: hl-line-mode doesn't override global-hl-line-mode in current buffer

[Stefan Kangas]

Gregory Heytings <gregory@heytings.org> writes:

> > It seems like there is currently no way to use `global-hl-line-mode'
> > while disabling it for individual buffers.
>
> There is one: (setq-local global-hl-line-mode nil).

Here, that leaves an overlay in the buffer.  Does it not do that for you?

[You didn't quote it, but I wrote "(setq-default global-hl-line-mode
nil)" in the bug report.  That was a typo.  I meant to write
"(setq-local global-hl-line-mode nil)".]

bug#51580: hl-line-mode doesn't override global-hl-line-mode in current buffer

[Gregory Heytings]

>>> It seems like there is currently no way to use `global-hl-line-mode' 
>>> while disabling it for individual buffers.
>>
>> There is one: (setq-local global-hl-line-mode nil).
>
> Here, that leaves an overlay in the buffer.  Does it not do that for 
> you?
>
> [You didn't quote it, but I wrote "(setq-default global-hl-line-mode 
> nil)" in the bug report.  That was a typo.  I meant to write 
> "(setq-local global-hl-line-mode nil)".]
>

Oh, now I see what you mean.  Indeed I had seen your setq-default, but did 
not guess it meant setq-local.  Indeed, M-: (setq-local 
global-hl-line-mode nil) leaves an overlay in the buffer.  I use this in 
buffer setup hooks, so the overlay is not created.  If you want to remove 
that overlay, you also need to call global-hl-line-unhighlight:

(defun buffer-deactivate-global-hl-line-mode ()
   (interactive)
   (global-hl-line-unhighlight)
   (setq-local global-hl-line-mode nil))

bug#51580: hl-line-mode doesn't override global-hl-line-mode in current buffer

[Gregory Heytings]

And of course this could become a command:

(defun buffer-toggle-global-hl-line-mode ()
   (interactive)
   (make-variable-buffer-local 'global-hl-line-mode)
   (if global-hl-line-mode
       (global-hl-line-unhighlight)
     (global-hl-line-highlight))
   (setq global-hl-line-mode (not global-hl-line-mode)))

bug#51580: hl-line-mode doesn't override global-hl-line-mode in current buffer

[Gregory Heytings]

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And just in case, here's a patch with that command.

[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
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From c747dd022d133133ae9d43ca137f87f2e8203e4d Mon Sep 17 00:00:00 2001
From: Gregory Heytings <gregory@heytings.org>
Date: Wed, 3 Nov 2021 13:07:05 +0000
Subject: [PATCH] Add command to toggle global-hl-line-mode locally.

* lisp/hl-line.el (global-hl-line-mode-toggle): New command.
---
 lisp/hl-line.el | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/lisp/hl-line.el b/lisp/hl-line.el
index 26cfcc3f9c..e63313128e 100644
--- a/lisp/hl-line.el
+++ b/lisp/hl-line.el
@@ -215,6 +215,16 @@ global-hl-line-mode
     (remove-hook 'post-command-hook #'global-hl-line-highlight)
     (remove-hook 'change-major-mode-hook #'global-hl-line-unhighlight)))
 
+;;;###autoload
+(defun global-hl-line-mode-toggle ()
+  "Toggle line highlighting in this buffer with Global Hl-Line mode."
+  (interactive)
+  (make-variable-buffer-local 'global-hl-line-mode)
+  (if global-hl-line-mode
+      (global-hl-line-unhighlight)
+    (global-hl-line-highlight))
+  (setq global-hl-line-mode (not global-hl-line-mode)))
+
 (defun global-hl-line-highlight ()
   "Highlight the current line in the current window."
   (when global-hl-line-mode	; Might be changed outside the mode function.
-- 
2.33.0

bug#51580: hl-line-mode doesn't override global-hl-line-mode in current buffer

[Stefan Kangas]

Gregory Heytings <gregory@heytings.org> writes:

>>>> It seems like there is currently no way to use `global-hl-line-mode' while
>>>> disabling it for individual buffers.
>>>
>>> There is one: (setq-local global-hl-line-mode nil).
>>
>> Here, that leaves an overlay in the buffer.  Does it not do that for you?
>>
>> [You didn't quote it, but I wrote "(setq-default global-hl-line-mode nil)" in
>> the bug report.  That was a typo.  I meant to write "(setq-local
>> global-hl-line-mode nil)".]
>>
>
> Oh, now I see what you mean.  Indeed I had seen your setq-default, but did not
> guess it meant setq-local.  Indeed, M-: (setq-local global-hl-line-mode nil)
> leaves an overlay in the buffer.  I use this in buffer setup hooks, so the
> overlay is not created.  If you want to remove that overlay, you also need to
> call global-hl-line-unhighlight:
>
> (defun buffer-deactivate-global-hl-line-mode ()
>   (interactive)
>   (global-hl-line-unhighlight)
>   (setq-local global-hl-line-mode nil))

My understanding is that our convention for minor modes that provide
both a global and local variant is that calling the local mode should
disable the global mode in the current buffer.

See for example `show-paren-mode' and `show-paren-local-mode'.

So in line with this convention, I expect that no new command is needed:
I should just be able call `M-x hl-line-mode' to disable it.

bug#51580: hl-line-mode doesn't override global-hl-line-mode in current buffer

[Lars Ingebrigtsen]

Stefan Kangas <stefan@marxist.se> writes:

> So in line with this convention, I expect that no new command is needed:
> I should just be able call `M-x hl-line-mode' to disable it.

Yup.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

bug#51580: hl-line-mode doesn't override global-hl-line-mode in current buffer

[Lars Ingebrigtsen]

Stefan Kangas <stefan@marxist.se> writes:

> It seems like there is currently no way to use `global-hl-line-mode'
> while disabling it for individual buffers.
>
> Steps to reproduce:
>
> 0. emacs -Q
> 1. M-x global-hl-line-mode
> 2. M-x hl-line-mode
>
> Now, `global-hl-line-mode' is still in effect, and lines are still
> highlighted.  I expect that running `hl-line-mode' turns off line
> highlighting.

I've now fixed this in Emacs 29.