bug#32281: shr.el align support patch

[Eli Zaretskii]

> From: Bad Blue Bull <ibmbull@yandex.ru>
> Cc: "npostavs@gmail.com" <npostavs@gmail.com>,
>       "32281@debbugs.gnu.org" <32281@debbugs.gnu.org>
> Date: Tue, 07 Aug 2018 19:54:58 +0300
> 
> I've escaped using of paragraph separator symbol by using narrowing

That's also fine.

> (can't just use constant position as
> fill-region-as-paragraph will change the text before it and it won't 
> correspond the end of paragraph anymore).

We have markers for that.  But if narrowing solves your problem, it's
okay to use that.

> Using a marker symbol to mark line breaks is still necessary, any attempt to 
> avoid it would lead to ridicously
> complicated solution.

Can you explain why?  I still don't think I understand.

> fill-region-as-paragraph disregards fill-collumn when aligns pic, all I can 
> do is not to justify images at all (but I'm
> really puzzled how to do it, I could use other marker just to determine where 
> image starts and ends and skip
> that region, but since you're against such approach... )
> Justification is badly implemented in fill, it's useless for proportional 
> fonts and you can see it's bad for images
> too. TBH would be good to make fill.el just ignore justify in such cases 
> (maybe giving a warning message).

To support proportional fonts, we need:

  . convert all the calculations to work in pixels instead of in
    columns (or, equivalently, in units of the canonical character
    width, in which case you then must use floating-point values)
  . put on some (or all?) SPC characters a :width display property,
    with the suitably calculated width in pixels

The infrastructure for all of that already exists, it's just a matter
of coding.