bug#6922: 23.1; Setting read-only property in an overlay has no effect

[Marcin Borkowski <mbork@mbork.pl>]

For the record, the problem persists in GNU Emacs 25.1.50.1.  Neither
seems there to be any change in the manual (as RMS suggested in the
discussion at
http://lists.gnu.org/archive/html/emacs-devel/2008-01/msg01598.html).

Regards,
Marcin Borkowski


On 2010-08-26, at 17:46, "MT" <mt_void@warpmail.net> wrote:

> If I create an overlay in a buffer and set the 'read-only' property to
> t, it seems to make no difference, and I can still make changes to the
> text in the region where the overlay is active. Setting other overlay
> properties does have an effect. Setting the read-only property as a text
> property however works as expected.
>
> To demonstrate:
> 1. Type some text in an empty buffer.
> 2. (setq overlay (make-overlay 1 10)) ; Creates an overlay in this
> buffer between positions 1-10 named 'overlay'
> 3. (overlay-put overlay 'read-only t) ; Applies the read-only property
> to this overlay.
> 4. Type some characters at the beginning of the buffer. Emacs doesn't
> complain that the text is read-only, and text is edited as normal.
>
> I do this instead:
>    (put-text-property 1 10 'read-only t) ; Apply the read-only property
>    as a text property rather than an overlay
> Now if I try typing text in the same region as before, Emacs prevents me
> from doing so and says 'Text is read-only'.
>
>
>
> In GNU Emacs 23.1.1 (i486-pc-linux-gnu, GTK+ Version 2.20.0)
>  of 2010-03-29 on rothera, modified by Debian
> Windowing system distributor `The X.Org Foundation', version
> 11.0.10706000
> configured using `configure  '--build=i486-linux-gnu'
> '--host=i486-linux-gnu' '--prefix=/usr' '--sharedstatedir=/var/lib'
> '--libexecdir=/usr/lib' '--localstatedir=/var/lib'
> '--infodir=/usr/share/info' '--mandir=/usr/share/man' '--with-pop=yes'
> '--enable-locallisppath=/etc/emacs23:/etc/emacs:/usr/local/share/emacs/23.1/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/23.1/site-lisp:/usr/share/emacs/site-lisp:/usr/share/emacs/23.1/leim'
> '--with-x=yes' '--with-x-toolkit=gtk' '--with-toolkit-scroll-bars'
> 'build_alias=i486-linux-gnu' 'host_alias=i486-linux-gnu'
> 'CFLAGS=-DDEBIAN -g -O2' 'LDFLAGS=-g' 'CPPFLAGS=''
>
> Important settings:
>   value of $LC_ALL: nil
>   value of $LC_COLLATE: nil
>   value of $LC_CTYPE: nil
>   value of $LC_MESSAGES: nil
>   value of $LC_MONETARY: nil
>   value of $LC_NUMERIC: C
>   value of $LC_TIME: en_DK.UTF-8
>   value of $LANG: en_IN.UTF-8
>   value of $XMODIFIERS: nil
>   locale-coding-system: utf-8-unix
>   default-enable-multibyte-characters: t
>
> Major mode: Fundamental
>
> Minor modes in effect:
>   tooltip-mode: t
>   tool-bar-mode: t
>   mouse-wheel-mode: t
>   menu-bar-mode: t
>   file-name-shadow-mode: t
>   global-font-lock-mode: t
>   blink-cursor-mode: t
>   global-auto-composition-mode: t
>   auto-encryption-mode: t
>   auto-compression-mode: t
>   line-number-mode: t
>   transient-mark-mode: t
>
> Recent input:
> M-x r e p o r t - e m a c s - b u g <return>
>
> Recent messages:
> Setting up ede...
> Loading `eieio': old-style backquotes detected!
> Setting up ede...done
> Setting up eieio...done
> Setting up semantic...done
> Setting up speedbar...done
> Setting up cedet-contrib...done
> Loading /etc/emacs/site-start.d/55ecb.el (source)...done
> For information about GNU Emacs and the GNU system, type C-h C-a.
> /usr/bin/mail is not an executable.  Setting mail-interactive to t.