centering_position in redisplay_window?

centering_position in redisplay_window?

[Po Lu]

Does anyone know what `centering_position' in redisplay_window means?
Is it some kind of row number that describes where to recenter point
should it move outside the window?

Thanks.

Re: centering_position in redisplay_window?

[Eli Zaretskii]

On December 1, 2021 9:19:14 AM GMT+02:00, Po Lu <luangruo@yahoo.com> wrote:
> Does anyone know what `centering_position' in redisplay_window means?
> Is it some kind of row number that describes where to recenter point
> should it move outside the window?
> 
> Thanks.
> 
> 

It is a distance in pixels from point to the position of window-start that would cause point to be displayed in the middle of the window.

IOW, if window-start is set to the position whose Y coordinate is centering_position pixels above or below point, the window will show point at its center.  (Whether it's above or below depends on where point is wrt the current window display.)

Note that "centering" is not necessarily literally the middle of the window  it could be elsewhere subject to scroll-aggressively and scroll-conservatively.

Re: centering_position in redisplay_window?

[Po Lu]

Eli Zaretskii <eliz@gnu.org> writes:

> It is a distance in pixels from point to the position of window-start
> that would cause point to be displayed in the middle of the window.
>
> IOW, if window-start is set to the position whose Y coordinate is
> centering_position pixels above or below point, the window will show
> point at its center.  (Whether it's above or below depends on where
> point is wrt the current window display.)
>
> Note that "centering" is not necessarily literally the middle of the
> window it could be elsewhere subject to scroll-aggressively and
> scroll-conservatively.

Thanks for the explanation, I think I understand now.