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" <bug-gnu-emacs@gnu.org>]

Eli Zaretskii <eliz@gnu.org> writes:

>> > The variable deactivate-mark only becomes buffer-local if set;
>> > otherwise the global value will be changed.
>> 
>> Could you perhaps elaborate?  I see that running a command that modifies
>> a different buffer does not deactivate the region in the current buffer,
>> which is basically what I would expect.
>
> You are asking me to elaborate about what? about the local value of
> deactivate-mark or about why you see what you see (in a scenario you
> haven't described)?

What I'm asking is: under what circumstances is it expected that
after changing deactivate-mark in another buffer the mark is deactivated
in the current buffer?

> Look, you are welcome to keep debugging this if you are interested.  I
> invested enough of my time into figuring out why the region was
> deactivated by C-n, and the solution I installed satisfies me.  But
> you are welcome to keep digging, and let me tell you what I found to
> save you some non-trivial tinkering:

Thank you, I'll keep digging and let you know if I figure it out.