Re: "... the window start at a meaningless point within a line."

[Eli Zaretskii <eliz@gnu.org>]

> Date: Mon, 19 Oct 2015 10:45:07 +0000
> Cc: emacs-devel@gnu.org
> From: Alan Mackenzie <acm@muc.de>
> 
> > We are miscommunicating (because these diagrams are devilishly hard to
> > interpret).
> 
> Sorry, I didn't realise.  Obviously they're easy for me.  Could we
> possibly improve them somehow, since I find it difficult to think things
> through without some sort of diagram?
> 
> For example, would it help if the actual BOLs and the xdisp BOLs were
> written on separate lines?

Not really, not for me, anyway.

My problem is that you "flatten" the layout: where the actual layout
is 2-dimensional, you make it 1-dimensional, and replace visual cues
with those A2, L3 markers, that I can never remember which one is
which.  Reasoning about VERTICAL motion while using a HORIZONTAL
diagram doesn't help, either.

So if you want to use diagrams, let's make them reflect the screen
layout, like this:

  B--------------------WS----------
  A--------------------L1----------
  A2------\n
  C---------------------------\n
  C2-------------------------\n

etc., where a line without a \n at the end is continued on the next
one.

With this arrangement, the symbol's at the left can be discarded, and
we only need the ones that are in the middle of the lines.

If it's easier for you to have the lines start at WS and L1 instead of
B and A, that's okay, too; we should just agree which convention we
use.