bug#64730: 30.0.50; Mark activation doesn't work after insert

[Bruno Boal]

Thank you for such a quick and helpful reply.
Best regards,
BB

Eli Zaretskii <eliz@gnu.org> writes:

> tags 64730 notabug
> thanks
>
>> Cc: public@protesilaos.com
>> From: Bruno Boal <egomet@bboal.com>
>> Date: Wed, 19 Jul 2023 12:17:21 +0100
>> 
>> I'm trying to evaluate the following snippet in emacs -Q, however as
>> soon as I try to insert a character, the region is not highlighted
>> anymore. `activate- mark' doesn't make it work either. Whereas
>> interactively with `exchange-point-and-mark' the region gets proper 
>> highlight.
>> 
>>        (progn
>>          (insert "")
>>          (push-mark (line-beginning-position) :no-message :activate))
>> 
>>        (progn
>>          (insert "a")
>>          (push-mark (line-beginning-position) :no-message :activate))
>
> This is the intended behavior.  The ELisp manual says in the node "The
> Mark":
>
>  -- Variable: deactivate-mark
>      If an editor command sets this variable non-‘nil’, then the editor
>      command loop deactivates the mark after the command returns (if
>      Transient Mark mode is enabled).  All the primitives that change
>      the buffer set ‘deactivate-mark’, to deactivate the mark when the
>      command is finished.  Setting this variable makes it buffer-local.
>
>      To write Lisp code that modifies the buffer without causing
>      deactivation of the mark at the end of the command, bind
>      ‘deactivate-mark’ to ‘nil’ around the code that does the
>      modification.  For example:
>
>           (let (deactivate-mark)
>             (insert " "))