bug#57207: 29.0.50; Fontification is slow after e7b5912b23 (Improvements to long lines handling)

[Gregory Heytings]

> > > Maybe Org does something that frequently causes a window's redisplay 
> > > cycle to end prematurely, in which case the code that looks for long 
> > > lines could be called too frequently.  But in that case, your proposed 
> > > change will have the same problem, I think?
> >
> > That's possible indeed, let's see what Ihor tells us.
>
> I'm afraid that my knowledge of Emacs redisplay is not sufficient to 
> give any insight. I have no clue what "redisplay cycle end prematurely" 
> means and how it can be triggered.

I meant: let's see whether the patch I sent upthread solves your problem. 
Can you please try it?