Re: Why emacs rendering is slow when encountering long lines?

[Dan Espen]

Jiaxin Cao <jiaxin.cao@gmail.com> writes:

> On Sunday, October 20, 2013 1:00:45 PM UTC+8, Jiaxin Cao wrote:
>> When I open a file containing long lines, it is not smooth to scroll up and 
>> down, even if the file is not large. 
>> 
>> 
>> 
>> Does anyone know how to configure emacs to make it smoother?
>
> Specifically, scroll-down is way worse than scroll-up. 
> I did a little test for it. A single scroll up takes about 15ms to finish, 
> while a scroll down takes about 50ms. 
> So if you press down pageup to trigger consecutive scroll-downs, the screen 
> will basically not respond to anything. 
> Anyone can explain why?

I just opened /usr/bin/ls.  It has pretty long lines.
It also scrolls pretty fast in both directions.

I think you need to provide more information, including emacs version
and the mode that emacs goes into.
Also see if the problem is still there when you start with emacs -Q.

-- 
Dan Espen