Re: pixel-point-and-height-at-unseen-line

[Po Lu <luangruo@yahoo.com>]

Eli Zaretskii <eliz@gnu.org> writes:

> This function has several problems that IMO would be good to clean up:
>
>  . It's unnecessarily restricted to a very special use case: a single
>    screen line above the one where window-start is.  It could be much
>    more useful (and be moved to subr.el or simple.el) if it could at
>    least accept an argument to control on which line or position to
>    report.
>
>  . It changes important state variables without protecting itself from
>    errors and non-local exits, so a C-g at an opportune time will
>    disrupt the buffer/window state.
>
>  . It calls vertical-motion without checking its return value, which
>    could tell you whether it actually moved at all, and where.  (One
>    bonus of checking the return value is that you could perhaps drop
>    the bobp test there.)  vertical-motion can do some surprising
>    things around overlays and display properties, especially ones that
>    include newlines in their strings.
>
> Thanks.

I'll look into that.  I did not write that function, I only modified it
(and moved it) so I could reuse the code there in for precision pixel
scrolling.

Thanks.