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

[Jim Porter <jporterbugs@gmail.com>]

On Thu, May 6, 2021 at 1:21 PM Stefan Kangas <stefankangas@gmail.com> wrote:
>
> Jim Porter <jporterbugs@gmail.com> writes:
>
> > On 5/4/2021 9:12 AM, Óscar Fuentes wrote:
> >> There are some negative consequences, though, like the "line" of
> >> display-fill-column-indicator-mode losing any apparience of continuity.
>
> Given how that mode is implemented, by setting
> `display-fill-column-indicator' to ?\u2502, I don't see how it could be
> improved without a complete redesign.  It doesn't look like this was
> implemented with `line-spacing' in mind.

Yeah, Emacs' reliance on using characters to draw lines would probably
lead me to set `line-spacing' back to 0 if this were changed. It would
be interesting if Emacs were able to handle these issues, e.g. by
adding some special handling when it sees box-drawing characters, but
that would probably be a lot of work.

> > I'm not sure if there's an easy way to ensure the fill line looks
> > continuous in this case, but if that could be improved, it would help in
> > a few other areas even if line-spacing weren't increased. For example,
> > with `org-prettify-entities' set to t, subscripts add a bit to the line
> > height, causing the fill line to appear discontinuous. Likewise, I
> > believe overlines add a bit to the line height too.
>
> Do you have a recipe to reproduce this?

Sure, here it is. This might depend on the font used, though:

  emacs -Q
  C-x C-f file.org RET
  x_subscript RET
  foo RET
  bar RET
  M-x display-fill-column-indicator-mode
  ;; The fill column line should be continuous for most fonts
  M-x org-toggle-pretty-entities
  ;; The fill column line should be discontinuous between lines 1 and 2

Even on fonts where the fill column indicator is always discontinuous
(e.g. Deja Vu Sans Mono for me), `M-x org-toggle-pretty-entities'
makes the gap larger.

- Jim