bug#73005: [REGRESSION, BISECTED]: line numbers disappear when pressing `df` in evil-mode

[Konstantin Kharlamov <Hi-Angel@yandex.ru>]

On Tue, 2024-09-03 at 18:30 +0300, Eli Zaretskii wrote:
> > Cc: da_vid@orange.fr
> > From: Konstantin Kharlamov <Hi-Angel@yandex.ru>
> > Date: Tue, 03 Sep 2024 17:46:09 +0300
> > 
> > CCing the commit author.
> > 
> > Sorry for using external plugin, but master has two separate
> > unrelated
> > critical regressions (the other one is going via link in *Help*
> > buffer
> > and getting Emacs locked up with 100% CPU and quickly increasing
> > memory
> > usage, which complicates reducing the steps), and since there's a
> > clear
> > commit that introduced the problem I decided to report it as is.
> > 
> > # Steps to reproduce
> > 
> > 1. Make sure you're in the Emacs repository and `./build/src/emacs`
> > is
> > the built binary
> > 2. Execute `git clone --depth 1 https://github.com/emacs-evil/evil
> > /tmp/evil`
> > 3. Execute `PATH="$(pwd)/build/src/:$PATH" make -C /tmp/evil emacs`
> > (Emacs with Evil loaded will start)
> > 4. Press `n` to refuse running tests
> > 5. Turn line numbers on by evaluating: (setq-default display-line-
> > numbers 'visual)
> > 6. Press `df`
> 
> What does "df" do?

"df" is triggering the action "delete text up to" and it will wait for
the third key, the symbol to "delete text up to". But for the problem
to appear pressing the third key is not required.

As a matter of fact, sometimes it gets reproduced by just pressing "f"
which stands for "go to next symbol" (and it would similarly wait a
keypress to define a symbol to go to), but for some reason it happens
much less compared to pressing "df".

>   Does it somehow end up calling string-pixel-width?

It seems it doesn't. I used a `M-x debug-on-entry string-pixel-width`
and then pressed "df" which made line numbers disappear, but debugger
wasn't triggered.

> IOW, please show how string-pixel-width is related to the above.

Offhand I don't know. I would reduce steps, but I can't use *Help* for
reasons mentioned in my 1st email, and I still didn't find a commit
which does not hang upon following *Help* buffer, because 1000 commits
before dffdbc1f1fd6 Emacs fails to compile with some native-compilation
errors and `make clean` doesn't help. I presume finding the culprit for
this problem will take some time.

I don't know if it's of any help, but upon pressing "df" the caret
turns from a rectangle to a square (half the rectangle size). This is
indicating that Emacs is waiting for the next keypress, perhaps this
indication somehow triggers the problem…