Re: Future of display engine and lines

[Alan Mackenzie]

Hello, Lars.

On Sun, Oct 24, 2021 at 14:38:07 +0200, Lars Ingebrigtsen wrote:
> Eli Zaretskii <eliz@gnu.org> writes:

> > Perhaps I misunderstand what "multiple columns" mean, then.  Doesn't
> > it mean that buffer text is displayed in separate rectangular
> > portions, like this:

> >    aaaaaaaaaaaa bbbbbbbb ccccccc    xxx xxxxxxxx xxxxxxxxxxxx
> >    dddddddd eeeeeeee fffffff ggg    yyyyyy yyyyyyyyy yyyyyyyy
> >    hhhhhhhh iiiiiiiiii jjjj kkkk    zzzzzzzzz zzzzzzzzzz zzzz

> > where buffer position of the first "xxx" follows the buffer position
> > of the last "kkkk"? 

> Well, it depends.  Perhaps these the next point after "xxx" is before
> "where".  Or perhaps if you enter more text after "kkk", that box should
> get a scroll bar, or perhaps it should extend downwards.

> We're basically in the same design territory that HTML + CSS 3 covers,
> and It's Just Very Difficult.  And as you say, the main problem isn't
> displaying the glyphs on the screen -- but it's defining the semantics
> about how the blocks interoperate, and making a command like `M-q' do
> something sensible within a block.

Err, aren't we talking about Follow Mode, here?  Follow Mode has been
around for a year or two now, and works very well (apart from the fact
there are no standard key bindings to enable it in 1/2/3 columns, or
disable it).  The semantics of the interoperating windows is indeed
somewhat involved, and unfortunately also somewhat slow, since
follow-mode is fighting the display engine over what goes where.

> Within the current Emacs structure, it would have to look like a bunch
> of buffers that we glue together as sub-panes inside one window, where
> your example ("xxx" follows "kkkk") would be as two sub-panes from one
> of these sub-buffers, and where the second sub-pane displays the text
> after line 3, with the layout in question.

> I mean...  it'd be great, but I think we're basically talking about a
> different editor.

> -- 
> (domestic pets only, the antidote for overdose, milk.)
>    bloggy blog: http://lars.ingebrigtsen.no

-- 
Alan Mackenzie (Nuremberg, Germany).