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

[Eli Zaretskii]

> Date: Mon, 19 Oct 2015 13:11:58 +0000
> Cc: address@hidden
> From: Alan Mackenzie <address@hidden>
> 
> > > I'm only really looking at the problem of getting to the correct
> > > beginning of line.  Moving to a specific column (with a cons argument to
> > > vertical-motion) seems to be less of a problem.
> 
> > If that's in a continuation line, you have the same problem: the
> > display engine and the move_it_* functions count coordinates and
> > columns from their BOL, not from your "actual" BOLs.
> 
> That's not what I see.  Having set `it' in Fvertical_motion to an
> iterator based at WS, the column movement remains based on `it', i.e.
> based on "actual" BOLs.

When move_it_by_lines returns, you are on the goal line, at zero X
coordinate.  That zero is in "xdisp coordinates".