Re: Scrolling commands and skipping redisplay, was: Re: emacs rendering comparisson between emacs23 and emacs26.3

[Eli Zaretskii]

> From: Stefan Monnier <address@hidden>
> Cc: Dmitry Gutov <address@hidden>,  address@hidden,  address@hidden,
>   address@hidden,  address@hidden,  address@hidden
> Date: Mon, 20 Apr 2020 13:47:10 -0400
> 
> If you do `C-n C-n C-n` quickly, the redisplay between the second and
> the third might very well be skipped, OTOH (since the second and third
> `C-n` might arrive while we're processing the first, in which case
> `input_was_pending` will be true when processing the second).

Btw, "line" in this context is actually the amount of pixels equal to
the canonical line height, not a physical line.  When the display
engine counts "lines" for the purpose of comparison with the value of
scroll-conservatively, it actually counts pixels and then divides that
by the canonical line height, it doesn't count screen lines.  So if
some lines in the buffer are displayed taller than the default face,
you will see a lot of recentering regardless of what you do.