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bug#12401: scroll-preserve-screen-position broken with font height faces
From: |
Eli Zaretskii |
Subject: |
bug#12401: scroll-preserve-screen-position broken with font height faces |
Date: |
Mon, 10 Sep 2012 21:05:27 +0300 |
> From: Stefan Monnier <monnier@iro.umontreal.ca>
> Cc: Le Wang <l26wang@gmail.com>, 12401@debbugs.gnu.org
> Date: Mon, 10 Sep 2012 09:26:42 -0400
>
> > scroll-preserve-screen-position? Is it just that doing N C-v's
> > followed by N M-v's brings point to the same location where it was
> > before this sequence of 2N commands?
>
> I think this should be the main point, yes.
For this to work, we would need to make sure that C-v followed by M-v
end up with a window that has the same window-start as the one before
C-v. But this is impossible to ensure with the way we compute
window-start, because the move_it family of functions used for that
can only move forward; therefore moving back is necessarily
implemented differently, and the results differ when variable-size
fonts are present.
IOW, this is a limitation of the current design of the
window-scrolling functions that can only be lifted by redesigning.