Re: Low redisplay performance (23 regression)

[David Reitter]

On Apr 21, 2009, at 4:53 PM, Chong Yidong wrote:

> David Reitter <address@hidden> writes:
>
> > Without face-remapping and header line, I estimate the slowdown is
> > about 20% for me, a noticeable difference.
>
> Try something for me:
>
>  M-: (setq mode-line-format "") RET
>
> This removes everything from the mode-line.  Does it make any
> difference?

I tried (setq mode-line-format) and it doesn't make a noticeable  
difference.

I also tried (setq header-line-format "Hello"), which was reasonably  
fast.

Removing various face properties set for parts of the header line  
seems to make it go faster.

To recap, removing the more diverse face settings in face-remapping- 
alist helps, too.  Also, removing font-locking helps.

Given the evidence, I wonder

1. Is the header line is drawn more often than it should? (scrolling  
shouldn't redraw it).
2. Does changing / setting / finding faces now incur more of a penalty  
now compared to 22.3?

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