Re: emacs rendering comparisson between emacs23 and emacs26.3

[Eli Zaretskii]

> Cc: address@hidden, address@hidden, address@hidden, address@hidden
> From: martin rudalics <address@hidden>
> Date: Sun, 5 Apr 2020 17:50:33 +0200
> 
> I cannot nearly simulate the problem using a simple loop that steadily
> invokes say (forward-line 50) followed by a (sit-for 0).  50 such
> invocations take 16.7 seconds here, 22.7 with (forward-line -50).  And
> redisplay takes place as expected here.  So it's likely the mouse wheel
> input mounting up that inhibits redisplay.

Not forward-line, scroll-up.  That's what wheel.el calls.

> Do you at least see CPU activity significantly go up when you do such
> mouse wheel scrolling?

With what build?  With the -O0 build with --enable-checking, I don't
need the mouse: it's enough to lean on C-v and let the keyboard
auto-repeat do its job -- one execution unit of the CPU maxes out
after 5 to 10 C-v's.

But with a -O2 optimized production build, Emacs keeps up both when I
lean on C-v and when I turn the mouse wheel constantly.

Anyway, you don't need to work too hard to get me started on how slow
CC Mode is, especially when re-indentation is involved in addition to
font-lock.  Which is why I think we should move away of regexp-based
and SMIE-based engines towards fast parsers written in C.