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bug#51776: master 9741924: In insert_file_contents, always set windows'
From: |
Stefan Monnier |
Subject: |
bug#51776: master 9741924: In insert_file_contents, always set windows' point markers. |
Date: |
Fri, 12 Nov 2021 19:27:29 -0500 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/28.0.50 (gnu/linux) |
Hi Alan,
Alan Mackenzie [2021-11-12 13:44:52] wrote:
> In insert_file_contents, always set windows' point markers.
> This fixes bug #51776.
>
> * src/fileio.c (restore_window_points): Restore a w->mpoint even
> when that marker originally pointed into the unchanged area near
> BOB or EOB. This prevents that window's point being moved a long
> way from its starting place due to the removal of the central part
> of the buffer by insert_file_contents.
Hmm... my understanding of the code says that if `oldppos <= same_at_beg` then
your change is harmless but unnecessary because the marker
is still at `oldpos` anyway.
But when `oldppos > same_at_beg` your change is harmful because the
marker has properly preserved its exact position in the text whereas
your code will arbitrarily move it to `oldpos` (which is even
potentially past Z if the revert shortened the buffer).
So maybe the better fix is to just change
XFIXNUM (oldpos) < same_at_end
into
XFIXNUM (oldpos) <= same_at_end
Or am I missing something?
[ Not sure what we should do when `oldpos == same_at_beg == same_at_end`, OTOH.
I suspect staying at `same_at_beg` might be the better choice in that
case. ]
Stefan
> src/fileio.c | 9 ++++++---
> 1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/src/fileio.c b/src/fileio.c
> index 3c13d3f..a7b1649 100644
> --- a/src/fileio.c
> +++ b/src/fileio.c
> @@ -3827,6 +3827,7 @@ restore_window_points (Lisp_Object window_markers,
> ptrdiff_t inserted,
> Lisp_Object car = XCAR (window_markers);
> Lisp_Object marker = XCAR (car);
> Lisp_Object oldpos = XCDR (car);
> + ptrdiff_t newpos;
> if (MARKERP (marker) && FIXNUMP (oldpos)
> && XFIXNUM (oldpos) > same_at_start
> && XFIXNUM (oldpos) < same_at_end)
> @@ -3834,10 +3835,12 @@ restore_window_points (Lisp_Object window_markers,
> ptrdiff_t inserted,
> ptrdiff_t oldsize = same_at_end - same_at_start;
> ptrdiff_t newsize = inserted;
> double growth = newsize / (double)oldsize;
> - ptrdiff_t newpos
> - = same_at_start + growth * (XFIXNUM (oldpos) - same_at_start);
> - Fset_marker (marker, make_fixnum (newpos), Qnil);
> + newpos = same_at_start
> + + growth * (XFIXNUM (oldpos) - same_at_start);
> }
> + else
> + newpos = XFIXNUM (oldpos);
> + Fset_marker (marker, make_fixnum (newpos), Qnil);
> }
> }
>
- bug#51776: master 9741924: In insert_file_contents, always set windows' point markers.,
Stefan Monnier <=