bug#45248: 28.0.50; Emacs freezes with big C functions

[Ravine Var]

Alan Mackenzie <acm@muc.de> writes:
> Sorry it's taken a little while to reply.  I've been preoccupied with
> another bug in the meantime.

No problem.

> By "scrolling becomes slower", do you mean (1) that the time for an
> isolated single full screen scroll becomes longer, the further you are
> through that struct?  Or do you mean (2) that on auto-repeat of the C-v
> or PageDown key, the scrolling becomes slower?

The second behavior. Opening the file and scrolling from the
the beginning with C-v becomes progressively slower.

> If you mean (2), from emacs -Q without enabling
> fast-but-imprecise-scrolling, then you are just seeing the normal
> expected, but unfortunate behaviour of Emacs: Emacs will not redisplay a
> screen as long as there is keyboard input unprocessed, but Emacs is
> spending its time fontifying the intermediate screens (which are not
> about to be displayed) as part of processing that input.  30 characters
> per second is faster than CC Mode can paint a single screen.

Ok.

> For problem (2) I recommend, again, enabling
> fast-but-imprecise-scrolling.

Without the patch in message 11, scrolling is bad
even when fast-but-imprecise-scrolling is enabled.

With the patch, things are much better and there
is no lockup, once fast-but-imprecise-scrolling is enabled.

I think this is enough for this bug - thanks for
looking into this issue.