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

[Eli Zaretskii <eliz@gnu.org>]

> From: Daniele Nicolodi <daniele@grinta.net>
> Date: Sat, 8 May 2021 09:51:12 +0200
> 
> On 08/05/2021 08:19, Eli Zaretskii wrote:
> > On the implementation side, I'm not sure I understand how do you
> > intend to implement these values: 110% of what?  Line spacing is
> > eventually a pixel value; you can, of course, compute it in percents
> > of the font size, but then the nominal spacing will not have the 100%
> > or 1.0 value, right?  So how do you intend to convert the value in the
> > menu into the actual line-spacing value?
> 
> The documentation for the line-spacing variable says:
> 
> Documentation:
> Additional space to put between lines when displaying a buffer. The
> space is measured in pixels, and put below lines on graphic displays,
> see ‘display-graphic-p’.
> If value is a floating point number, it specifies the spacing relative
> to the default frame line height.  A value of nil means add no extra space.
> 
> I think the values in the menu would simply be divided by 100.

So you are saying that 100% would mean line-spacing equal to the
default frame line height?  That would mean the line height that is
twice as high as the default, so (a) 100% is hardly a good
description, and (b) how do you provide an option to get back to the
default value?

IOW, the default is that we add zero spacing, and that makes percent
notation not trivially convertible.  As the doc string says, this is
_additional_ space.