bug#21453: 25.0.50; When font size is temporarily increased Emacs is slow

[Mark Karpov]

Eli Zaretskii <eliz@gnu.org> writes:

> Does the text have faces other than the default face?  What modes were
> active in that buffer?  Do you see the same slow-down in a buffer
> that's in Fundamental mode?

Well yes, since that test file is part of my Emacs configuration it has
some syntax highlighting (everything is by default since it's run with
‘-Q’ flag).

Modes? You can check yourself, I just started Emacs without config, then
opened one of my init files and pressed ‘C-x C-=’, then scrolled. That's
all.

Yes I can reproduce it in Fundamental mode too.