Re: redisplay - very long lines

[David Reitter]

On 17 Feb 2009, at 14:41, Eli Zaretskii wrote:
> If by ``wrapped lines'' you mean continuation lines, then (AFAIK) we
> still need to walk to the end of a line before we are able to display
> it and all the lines after it.  If by ``wrapped lines'' you mean
> something else, perhaps that belongs to the recent features whose
> effect on display engine I didn't yet have time to grasp, so I cannot
> answer the question.

I understood Stefan to refer to soft-wrapped (`word-wrap') lines,  
which necessitate the optimization we're talking about.

Displaying any lines "after it" would not be relevant, because we'd  
stop processing the line if the end of the portion of the buffer is  
reached that is shown in the window.

As for displaying the actual line (wrapped): can you give an example  
how the previous visual lines of a line are affected something that  
could come afterwards?
(I'm not doubting you, I just want to understand.)


> > [ Also, I'd much rather see occasional jumping than unbearably
> >  slow display.  In many cases (e.g. unibyte fundamental-mode for  
> > binary
> >  files), the likelihood of varying line height is pretty low. ]
>
> [How come you are suddenly in favor of unibyte operations?]
>
> FWIW, I think editing binary files other than via hexl is playing with
> fire, anyway.  But that's me.

It is, but Emacs shouldn't slow down to the point where undoing the  
find-file operation is impossible.
Also, I gave the example of XML files w/o newlines.