Re: Increase default `line-spacing' to 0.05, 0.10 or 0.15 [proposal]

[Stefan Kangas]

Daniele Nicolodi <daniele@grinta.net> writes:

>> C. A very conservative option is to use 0.05, which would be a small
>>    incremental improvement on what we already have. [58 lines, 3.33 %]
>>
>> D. The default. [60 lines, 0.0 %]
>
> On my system (macOS, Emacs 27.2 from https://emacsformacosx.com/) with
> some fonts, these two settings produce the same result. It seems that
> the "resolution" for this setting is 0.1 (thus 0.5 is rounded to 0.0).

I tested this on my macOS machine with a build from Homebrew, and one
built from the master branch.  In both these builds, 0.0 and 0.05 are
the same.  (0.1 and 0.15 are different, though.)

So I guess for this to matter on macOS, we would need to change this to
at least 0.1.

> In general, the visual distance between lines depends on the font: with
> some fonts I use a line-spacing of 0.0, while others require setting
> line-spacing to 0.15 to obtain roughly the same distance.

Yes, this will depend on the font.

Properly speaking, choosing the value should be a manual endeavor.  But
I don't think this is something we can easily do in Emacs as things
stand.  We would first need to build some infrastructure to change line
spacing depending on the font used.

Barring that, the best we can do is to find some happy average that
works okay most of the time.

    A true ideal line-height doesn’t exist, because every type-
    face is different.  You need to take into account the design of the
    typeface as well as the typesetting.  Is this a wide or decorative
    typeface?  You may need more space between lines to let the
    details breathe.  Is this a narrow text column, as you might see in
    hanging captions in an article’s margins?  You could use a smaller
    type size and keep the line-height tighter than the article text
    next to the caption.  By observing these factors, you can judge
    what a particular setting requires.

    A good starting point with line-height is about 1.2–1.8 ... It
    takes some trial and error to see what’s right for a given typeface
    at a given size in a given situation.  I find it useful to declare a
    line-height and see how it feels to read text at that setting.  Do
    letter ascenders and descenders crash into one another or run a
    little too close between lines? If so, more line-height is
    needed.  Are the spaces between the lines more prominent than the
    lines themselves?  If so, try reducing the line-height.  When you
    find an appropriate line-height, the text will seem to fall into a
    natural rhythm, feeling neither too far apart nor too close.

    - "On Web Typography", Jason Santa Maria, A Book Apart, 2014.