bug#55692: 29.0.50; delete-selection-mode: Replace region only if set using the mouse

[Visuwesh]

[ஞாயிறு மே 29, 2022] Eli Zaretskii wrote:

>> From: Visuwesh <visuweshm@gmail.com>
>> Cc: 55692@debbugs.gnu.org
>> Date: Sun, 29 May 2022 13:40:20 +0530
>> 
>> >>    By default, text insertion occurs normally even if the mark is
>> >>  active---for example, typing @kbd{a} inserts the character @samp{a},
>> >>  then deactivates the mark.  Delete Selection mode, a minor mode,
>> >>  modifies this behavior: if you enable that mode, then inserting text
>> >>  while the mark is active causes the text in the region to be deleted
>> >> -first.  To toggle Delete Selection mode on or off, type @kbd{M-x
>> >> -delete-selection-mode}.
>> >> +first.  If you want to replace only temporary regions, set by
>> >> +mouse-dragging or shift-selection, then change the variable
>> >
>> > There should be cross-references here to where these methods are
>> > described in the manual.
>> >
>> 
>> These methods as in "mouse-dragging" or "shift-selection".  I'm afraid I
>> don't fully understand what you mean.
>
> I mean to add @xref or @pxref to the places in the manual where mouse
> selection and shift-selection are described.  Those places are,
> respectively, the nodes "Setting Mark" and "Shift Selection".
>

Done.

>> >> @@ -251,6 +259,10 @@ delete-selection-pre-hook
>> >>  have this property won't delete the selection.
>> >>  See `delete-selection-helper'."
>> >>    (when (and delete-selection-mode (use-region-p)
>> >> +             (if delete-selection-temporary-regions-only
>> >> +                 (and (consp transient-mark-mode)
>> >> +                      (eq (car transient-mark-mode) 'only))
>> >> +               t)
>> >
>> > I wonder whether we should also optionally allow replacing text in
>> > regions activated by "C-u C-x C-x" when transient-mark-mode is off.
>> > Those cause transient-mark-mode to have the value 'lambda', not
>> > '(only...)'.  So maybe the new defcustom should be a tristate, not a
>> > boolean?
>> >
>> 
>> Sure, that could be useful.  But I have transient-mark-mode turned on
>> always so I can't comment much on it.  However, what would the third
>> state be?
>
> Some symbol.
>
>> When the defcustom is t, we could have it check for '(only . ...)'
>> and the value 'lambda', no?
>
> Yes, we could have:
>
>   . nil - always replace the region
>   . t   - replace region from mouse, shift-selection, and "C-u C-x C-x"
>   . selection - only replace  region from mouse and shift-selection
>

Done.

>> > Also, can we have the above condition in a more elegant form?  In
>> > general, whenever you have something like
>> >
>> >    (if SOMETHING foo t)
>> >
>> > it begs to be rewritten so the "t" part is not needed, because 'if'
>> > itself already returns a boolean value.
>> 
>> Sure.  I will factor out the condition into a separate function.  Is
>> that more elegant?
>
> No, that's overkill.  I meant that if you need an 'if' to return t or
> something else, you could instead make it return nil or something
> else, as in
>
>    (if SOMETHING foo)
>
> and reverse the condition.
>
> But if you still don't understand, just forget this comment.

I don't think I fully understood what you meant but I took a shot at it
anyway.  Please review updated patch.

0001-delete-selection-mode-Add-user-option-to-delete-temp.patch
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