Re: [PATCH] Add function window-line-width

[Eli Zaretskii <eliz@gnu.org>]

> From: Sébastien Chapuis <sebastien@chapu.is>
> Date: Sun, 10 Nov 2019 06:09:56 +0800
> Cc: Eli Zaretskii <eliz@gnu.org>, emacs-devel@gnu.org

> After thinking about it, I am wondering if the current behavior of 'window-lines-pixel-dimensions' is correct ?
> As user of the function I do not expect the function to count glyphs that are inserted by redisplay only "for its
> own purpose",
> glyphs that are invisible and non-existent for the end user.

There are valid use cases where those glyphs do matter, see the use of
this function in Emacs's own code.

> I see that 'window-largest-empty-rectangle' uses this function, the widths of the rectangles it returns are
> smaller than they really are.

How do you mean "smaller"?  Can you show an example where the result
is incorrect in your opinion?

> I think it makes sense to change this behavior and make 'window-lines-pixel-dimensions' not counting these
> "redisplay only" glyphs.

I don't see the need, sorry.  If what that function does doesn't fit
your bill, it's probably because you should use another function
instead.

> `(time (test1))` returns 0.000004869
> `(time (test2))` returns 0.00376

So we are talking about 3 msec additional time?  Is that really
significant in your application?