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

[Eli Zaretskii <eliz@gnu.org>]

> Date: Sun, 18 Oct 2015 14:53:56 +0000
> Cc: emacs-devel@gnu.org
> From: Alan Mackenzie <acm@muc.de>
> 
> > Is the following a correct definition of when Fvertical_motion
> > overshoots, i.e. lands one line below (for LINES > 0) the correct one:
> > when the offset between the "actual" window-start and the preceding
> > "xdisp" BOL is greater than the X coordinate of the last character of
> > the 1st physical line in the window.
> 
> Disentangling the words, what I think you're saying is that ....
> 
>    nlines = 3
> 8. B-------WS-------------A-------L1-------------A2----\nC--------C2--------C3
>    <---N--->                      <---------X--------->
> (a)                           ^                                   it,T
> (b)                                  ^                            it        T
> 
> 
>    nlines = 3
> 9. B-----------------WS---A-----------------L1---A2----\nC--------C2--------C3
>    <--------N-------->                      <----X---->
> (a)                           ^                                   it,T
> (b)                                            ^                  it        T
> 
> .... an overshoot occurs when N > X.  I'm assuming that by "X coordinate
> of ..." you're meaning the offset from an _actual_ BOL.
> 
> I don't see at all that this is the case.

We are miscommunicating (because these diagrams are devilishly hard to
interpret).

But let's leave this alone, and instead try to use my other idea.