Emacs 27 - Changing the "selective display character" (also called "ellipsis")

Emacs 27 - Changing the "selective display character" (also called "ellipsis")

[A M]

Hello

I would like to change the "selective display character" (also called 
"ellipsis", default is "...") to some other character, an arrow 
character would be nice.

Up until Emacs 27, I used the code below in my init.el , it worked just 
great.

;Change the default selective display ("folding") character "..." to " »".
(set-display-table-slot standard-display-table
                         'selective-display (string-to-vector " »"))

With Emacs 27 this no longer works. I have tested by using 
'selective-display' (C-x $) on my init.el as a simple test, I get the 
default "...".
Could you help me by providing a working method for Emacs 27?


Additional information:
I have noticed that some changes were introduced in Emacs 27 pertaining 
to Selective Display / Hidden Text. Some relevant links to the GNU Emacs 
Lisp Reference Manual:

Invisible Text - "Hiding part of the buffer text."
Selective Display - "Hiding part of the buffer text (the old way)."
https://www.gnu.org/software/emacs/manual/html_node/elisp/Invisible-Text.html
https://www.gnu.org/software/emacs/manual/html_node/elisp/Selective-Display.html

Best Regards

Re: Emacs 27 - Changing the "selective display character" (also called "ellipsis")

[Eli Zaretskii]

> From: A M <alex334599@gmail.com>
> Date: Sun, 25 Jul 2021 12:07:07 +0200
> 
> I would like to change the "selective display character" (also called 
> "ellipsis", default is "...") to some other character, an arrow 
> character would be nice.
> 
> Up until Emacs 27, I used the code below in my init.el , it worked just 
> great.
> 
> ;Change the default selective display ("folding") character "..." to " »".
> (set-display-table-slot standard-display-table
>                          'selective-display (string-to-vector " »"))
> 
> With Emacs 27 this no longer works. I have tested by using 
> 'selective-display' (C-x $) on my init.el as a simple test, I get the 
> default "...".
> Could you help me by providing a working method for Emacs 27?

I cannot reproduce the problem you are reporting: the above works for
me in Emacs 27 (and in Emacs 28).  The "..." is replaced with the
arrow character.

Just to be sure: to test this you invoke "C-x $" with a numeric
argument that determines the column past which you want to have the
ellipsis, yes?

I suggest to try this in "emacs -Q"; if it works there, there are some
customizations of yours that get in the way.

Re: Emacs 27 - Changing the "selective display character" (also called "ellipsis")

[A M]

[-- Attachment #1: Type: text/plain, Size: 2079 bytes --]

Hello

Sorry, there was one thing I forgot to mention which is a requirement 
for the problem to appear.
I have also enabled automatic byte-compilation, using the following line 
of lisp code:

;; Automatic byte-compilation when starting emacs.
(byte-recompile-directory (expand-file-name "~/.emacs.d") 0)

A minimal emacs dotfile that demonstrates my described problem is thus 
the code snippet I gave in the first message combined with the one 
above. (I am checking that myself right now.) It is when an init.elc has 
been generated I get this error specifically in Emacs 27.

I will attach the error message I get in Emacs and also the stack trace 
from 'emacs --debug-init', please see the attached file.

Eli, yes you guess correctly. invoke "C-x $" with a numeric argument on 
init.el as a way of testing.

On 7/25/21 3:51 PM, Eli Zaretskii wrote:
>> From: A M <alex334599@gmail.com>
>> Date: Sun, 25 Jul 2021 12:07:07 +0200
>>
>> I would like to change the "selective display character" (also called
>> "ellipsis", default is "...") to some other character, an arrow
>> character would be nice.
>>
>> Up until Emacs 27, I used the code below in my init.el , it worked just
>> great.
>>
>> ;Change the default selective display ("folding") character "..." to " »".
>> (set-display-table-slot standard-display-table
>>                           'selective-display (string-to-vector " »"))
>>
>> With Emacs 27 this no longer works. I have tested by using
>> 'selective-display' (C-x $) on my init.el as a simple test, I get the
>> default "...".
>> Could you help me by providing a working method for Emacs 27?
> I cannot reproduce the problem you are reporting: the above works for
> me in Emacs 27 (and in Emacs 28).  The "..." is replaced with the
> arrow character.
>
> Just to be sure: to test this you invoke "C-x $" with a numeric
> argument that determines the column past which you want to have the
> ellipsis, yes?
>
> I suggest to try this in "emacs -Q"; if it works there, there are some
> customizations of yours that get in the way.
>

[-- Attachment #2: error-message_and_stack-trace.txt --]
[-- Type: text/plain, Size: 989 bytes --]


Warning (initialization): An error occurred while loading ‘/home/user/.emacs.d/init.elc’:

Wrong type argument: char-table-p, nil

To ensure normal operation, you should investigate and remove the
cause of the error in your initialization file.  Start Emacs with
the ‘--debug-init’ option to view a complete error backtrace.


$ emacs --debug-init

Debugger entered--Lisp error: (wrong-type-argument char-table-p nil)
set-char-table-extra-slot(nil 4 [32 187])
set-display-table-slot(nil selective-display [32 187])
byte-code("\301\302\303!\304\"\210\305\10\306\307\310\1!\262\1#\210\10\204\31\0\311 \20\301\207" [standard-display-table byte-recompile-directory expand-file-name "~/.emacs.d" 0 set-display-table-slot selective-display " »" vconcat make-display-table] 6)
load("/home/user/.emacs.d/init" noerror nomessage)
startup--load-user-init-file(#f(compiled-function () #<bytecode 0x5c1655>) #f(compiled-function () #<bytecode 0x5c1669>) t)
command-line()
normal-top-level()

Re: Emacs 27 - Changing the "selective display character" (also called "ellipsis")

[Eli Zaretskii]

> From: A M <alex334599@gmail.com>
> Date: Mon, 26 Jul 2021 12:42:41 +0200
> 
> Sorry, there was one thing I forgot to mention which is a requirement 
> for the problem to appear.
> I have also enabled automatic byte-compilation, using the following line 
> of lisp code:
> 
> ;; Automatic byte-compilation when starting emacs.
> (byte-recompile-directory (expand-file-name "~/.emacs.d") 0)
> 
> A minimal emacs dotfile that demonstrates my described problem is thus 
> the code snippet I gave in the first message combined with the one 
> above. (I am checking that myself right now.) It is when an init.elc has 
> been generated I get this error specifically in Emacs 27.
> 
> I will attach the error message I get in Emacs and also the stack trace 
> from 'emacs --debug-init', please see the attached file.

I think the error message explains itself, no?  It means that your
setting didn't take effect, most probably because you didn't load
disp-table before referencing standard-display-table.

Re: Emacs 27 - Changing the "selective display character" (also called "ellipsis")

[A M]

Adding this line of code solved the problem:
(require 'disp-table)

Thanks for the help.

On 7/26/21 3:00 PM, Eli Zaretskii wrote:
>> From: A M <alex334599@gmail.com>
>> Date: Mon, 26 Jul 2021 12:42:41 +0200
>>
>> Sorry, there was one thing I forgot to mention which is a requirement
>> for the problem to appear.
>> I have also enabled automatic byte-compilation, using the following line
>> of lisp code:
>>
>> ;; Automatic byte-compilation when starting emacs.
>> (byte-recompile-directory (expand-file-name "~/.emacs.d") 0)
>>
>> A minimal emacs dotfile that demonstrates my described problem is thus
>> the code snippet I gave in the first message combined with the one
>> above. (I am checking that myself right now.) It is when an init.elc has
>> been generated I get this error specifically in Emacs 27.
>>
>> I will attach the error message I get in Emacs and also the stack trace
>> from 'emacs --debug-init', please see the attached file.
> I think the error message explains itself, no?  It means that your
> setting didn't take effect, most probably because you didn't load
> disp-table before referencing standard-display-table.
>