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

[Daniele Nicolodi]

On 08/05/2021 10:06, Eli Zaretskii wrote:
>> 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.

I have no idea what the author of the patch had in mind, I wa trying to
offer an interpretation. But, indeed simply dividing by 100 does not
work. Dividinng by 100 and subtracting 1 results in a number in the
correct range. However, I agree that "line spacing 100%" is a very bad
description of what the setting does.

Either the setting is called line "line height" with suggested values an
a neighborhood of 100%, or "line spacing" with values in a neighborhood
of 0% (ie 0%, 5%, 10% or so).

Cheers,
Dan