Re: size of the slider bar

[David Reitter]

On 25 Dec 2005, at 20:06, Richard M. Stallman wrote:

>       The length of the slider bar, the blue bar that slides inside
> > the scroll bar track (I'm not sure about the terminology) changes
> > randomly as you scroll up and down the text. I'm sure you know that
> > the ratio of the length of this bar to the total length of the scroll
> > bar must represent the ratio between the number of lines in the  
> > window
> > to the number of lines in the file.
>
> That would take too long, for large files; he would not like this  
> either,
> but he has not realized this would be the price of what he wants.

I'm aware of that and I told him so.

The current situation isn't as bad as it was (Carbon port), so I  
don't think it's a pressing problem right now (but in the long run).

For Emacs 23, you may want to consider one of the following solutions:

1) Keep an index with line numbers for every 5000th character in a  
buffer and use the index to get a good approximate translation from  
char-position to line number (or char-position to pixel height count,  
i.e. lines x char-height) by using the index and counting the  
remaining few lines. The index could be updated through one mean or  
the other, but it's enough to keep it approximately right.
This solution is likely to make sense if the slider size isn't the  
only thing it's good for.

2) Do not change the slider size WHILE it is being dragged, because  
that is confusing from an UI point of view. I think it would be less  
confusing to adapt it AFTER dragging.

I'm sorry I can't implement either of them lacking knowledge about  
Emacs internals and time.