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bug#30028: 24.5; behavior and doc of `revert-buffer' wrt markers
From: |
Drew Adams |
Subject: |
bug#30028: 24.5; behavior and doc of `revert-buffer' wrt markers |
Date: |
Mon, 8 Jan 2018 09:35:48 -0800 (PST) |
That markers are typically restored when you revert is important.
This behavior is not very well documented, I think.
1. Doc: The elisp manual (node `Reverting'), but not the doc string,
mentions that markers at the beginning and end of the buffer (after
changes) are generally preserved (restored). The doc string should
mention this also - it says nothing about markers.
2. Doc: This restoring of markers happens for visited files, but not
necessarily for other buffers, presumably. The doc in at least the
manual should make this clear.
3. Behavior: The manual says that preserving other markers, besides
those described, "would be problematical". (You might want to change
that to "problematic", but this is not important -
http://grammarist.com/usage/problematic-problematical)
I can understand that in some cases restoring a marker would not
position it correctly. But I don't see why Emacs wouldn't/couldn't
restore all markers anyway. Or does it? The doc does not make clear
whether markers that are not "preserved" are deleted or just not
necessarily in the correct positions. Please make clear just how
(all) markers are handled.
What criteria does Emacs use for filtering out markers that it
decides not to restore?
4. Trying to track down where the marker handling
(e.g. saving/restoring) takes place sent me down multiple levels
of code. My guess (I don't have the C sources) is that it is
actually done in `insert-file-contents'. But the doc for that
function (both (elisp) `Reading from Files' and doc string) says even
less about marker handling than does the doc for `revert-buffer'.
Can we please get more informative doc about this handling?
In GNU Emacs 24.5.1 (i686-pc-mingw32)
of 2015-04-11 on LEG570
Windowing system distributor `Microsoft Corp.', version 6.1.7601
Configured using:
`configure --prefix=/c/usr --host=i686-pc-mingw32'
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