bug#71605: 30.0.50; [PATCH] Support variable-width text in 'visual-wrap-prefix-mode'

[Eli Zaretskii <eliz@gnu.org>]

> Date: Wed, 19 Jun 2024 12:53:33 -0700
> Cc: 71605@debbugs.gnu.org
> From: Jim Porter <jporterbugs@gmail.com>
> 
> On 6/19/2024 4:45 AM, Eli Zaretskii wrote:
> > If both the first line of the paragraph and the rest are aligned on
> > that width, they will all line up.  IOW, the idea is to make the text
> > of all the lines :align-to to the same column number, like this:
> > 
> >    * some text
> >      some other text
> > 
> > Then you don't care about the actual pixel width of "* ".
> 
> Just so I'm sure I understand this: the idea is that the buffer's 
> contents are "* some text some other text" and then we set the :align-to 
> property on "some text some other text" so that the result is displayed 
> like this?
> 
>       +---- Here is the align-to column
>       v
>    * _some text
>    ___some other text

Yes.

> The underscores represent the space added by :align-to. In practice, the 
> first line might not have any extra space from :align-to, but the 
> pixel-width of "* " could be less than 2 * <canonical character width> 
> for variable-pitch fonts.

The value calculated for :align-to needs to make sure that never
happens.

> I think that would work, provided :align-to were fixed so that it could 
> handle wrapping again.

Stay tuned.

> (And so long as we're ok with there being a bit of extra space after
> the first-line prefix when using some fonts, but I don't see why
> that would be an issue.)

We _should_ be ok with some extra white space, because that's what I
see in word processors all around me.  Their indentation of the
itemized lists always indents by more than just one SPC after the item
symbol (bullet or number or letter).