Re: Changing line widths in the Emacs source code

[Stefan Monnier <monnier@iro.umontreal.ca>]

> Keeping track of indentation level adds to cognitive load, so we can't
> dismiss leading unused columns as irrelevant.

I don't think we was saying they're irrelevant.  But just that the 55-60
"optimum" has to do with the difficulty for your visual system to jump
from the end of one line to the beginning of the next and that it was in
a context of "plain text", so it doesn't necessarily carry over to code
because of the indentation.

The indentation could both help (in the sense that a text indented by 40
columns should be able to use a fill-column of about 95-100 and result
in an "optimal" legibility) and hinder (in the sense that it might be
harder for the visual system to find the beginning of the line when
every line starts at a different indentation level, tho I don't know if
that's the case, nor even if it has been studied).

In any case, my experience is that regardless of issues of legibility it
is usually easy to make code fit within 80 columns so I don't see
a strong reason to increase that number (given that such an increase
would likely result in a decrease of visual code density, i.e. less
efficient use of screen real estate, and may encourage nesting code more
deeply which would be detrimental to the readability of the code).

I don't think there's anything magical about 80, but experience just
seems to show that it works well.


        Stefan