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Re: setnu-mode and Emacs 21.

From: Miles Bader
Subject: Re: setnu-mode and Emacs 21.
Date: 15 Nov 2001 10:01:12 +0900

Juanma Barranquero <address@hidden> writes:
> Not just setnu.el and other elisp packages that try to put
> line-numbers in the margin are (or could be) affected by the
> performance problems derived from managing lots of overlays.


> Any package that tries to put data in the margin on a line-by-line
> basis (for example, the length of each line, or a mark to show if the
> line is modified, or whatever) either sets the margin through the use
> of overlays, or through text-properties. Neither form is convenient,
> both can cause (I believe) slowdowns.

True, but I'm saying that, in general, a design that tries to put an
overlay for _every line_ of the file is going to be a dog, no matter how
fast overlays are.  I think it's much better to think about how such
designs can be avoided (for instance, in the line-numbering case, using
jit-lock to add overlays only to displayed lines).

> There is no easy way to associate margin content with line content.

I said nothing about the margin.

It seems that you think I was saying overlays are bad -- I was not.

I think overlays are a _good_ way to do things like display line
numbers; what I think is _bad_ is a design that requires _every_ line of
the file to have an overlay (even if never display or modified), rather
than somehow adding overlays on a more `as needed' basis.

Love is a snowmobile racing across the tundra.  Suddenly it flips over,
pinning you underneath.  At night the ice weasels come.  --Nietzsche

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