* bug#74091: 31.0.50; string-pixel-width in mode line disables region
@ 2024-10-29 17:27 Eshel Yaron via Bug reports for GNU Emacs, the Swiss army knife of text editors
2024-10-30 14:59 ` Eli Zaretskii
0 siblings, 1 reply; 2+ messages in thread
From: Eshel Yaron via Bug reports for GNU Emacs, the Swiss army knife of text editors @ 2024-10-29 17:27 UTC (permalink / raw)
To: 74091
The new implementation of string-pixel-width has some unexpected effect
when it is called from mode-line-format, as happens for example when
mode-line-format-right-align occurs in mode-line-format:
1. emacs -Q
2. (setq-default mode-line-format
'("" (:eval (progn (string-pixel-width "foo") nil))))
3. C-x C-f /path/to/emacs/lisp/subr.el
4. C-SPC
5. C-n
At this point the region is expected to be active since we activated it
in step 4. But in step 5 the mode line is updated, which calls
string-pixel-width, which in turn unexpectedly disables the region.
I'm not really sure why this happens... Also, if I now trace
string-pixel-width, then it no longer disables the region and everything
starts working as expected.
Thanks,
Eshel
^ permalink raw reply [flat|nested] 2+ messages in thread
* bug#74091: 31.0.50; string-pixel-width in mode line disables region
2024-10-29 17:27 bug#74091: 31.0.50; string-pixel-width in mode line disables region Eshel Yaron via Bug reports for GNU Emacs, the Swiss army knife of text editors
@ 2024-10-30 14:59 ` Eli Zaretskii
0 siblings, 0 replies; 2+ messages in thread
From: Eli Zaretskii @ 2024-10-30 14:59 UTC (permalink / raw)
To: Eshel Yaron; +Cc: 74091
> Date: Tue, 29 Oct 2024 18:27:05 +0100
> From: Eshel Yaron via "Bug reports for GNU Emacs,
> the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
>
>
>
> The new implementation of string-pixel-width has some unexpected effect
> when it is called from mode-line-format, as happens for example when
> mode-line-format-right-align occurs in mode-line-format:
>
> 1. emacs -Q
> 2. (setq-default mode-line-format
> '("" (:eval (progn (string-pixel-width "foo") nil))))
> 3. C-x C-f /path/to/emacs/lisp/subr.el
> 4. C-SPC
> 5. C-n
>
> At this point the region is expected to be active since we activated it
> in step 4. But in step 5 the mode line is updated, which calls
> string-pixel-width, which in turn unexpectedly disables the region.
Thanks, should be fixed now.
> I'm not really sure why this happens...
It happens because string-pixel-width modifies a buffer, and that sets
deactivate-mark, which then causes the region to be deactivated when
a command finishes. When you inject string-pixel-width into
mode-line-format, you indirectly cause it to be called from C-n and
the like, because those evaluate the mode-line format. So doing that
is quite a risky thing, in general.
^ permalink raw reply [flat|nested] 2+ messages in thread
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2024-10-29 17:27 bug#74091: 31.0.50; string-pixel-width in mode line disables region Eshel Yaron via Bug reports for GNU Emacs, the Swiss army knife of text editors
2024-10-30 14:59 ` Eli Zaretskii
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