Subject: bug#69941: 30.0.50; Faulty fontification of radio button widgets

From: Stefan Monnier <[email-masked]>
Date: Thu, 09 May 2024 10:15:29 -0400

> I investigated the history of this code, and while the value t for the
> marker insertion type was used in the initial commit, it was changed to
> nil in commit e0f956935, with the message "Insert new text at the :from
> marker _after_ the marker, not before it."  But 18 days later it was
> changed back to t in commit 3bff434b8, that also added "Document need to
> put some text before the %v escape in :format string" of editable-field
> widgets.  (I looked at the bug-gnu-emacs and emacs-devel mailing list
> archives but found nothing relevant at the time just prior to these
> commits.)

I'm really not familiar with the widget code, but looking around that
code I see that we have

       (set-marker-insertion-type BLAfromBLA t)
       (set-marker-insertion-type BLAtoBLA nil)

at various places, and I think that makes a lot of sense when you
consider that we don't want text inserted right before or right after
the widget to suddenly become part of the widget.
But OTOH while "printing" the widget itself, we'd want the exact
opposite (i.e. nil for from and t for to).

Could it be that part of the problem is that the insertion of
a radio-button widget into a radio-button-choice widget is done "too
late", i.e. after the radio-button-choice widget has been printed?

        Stefan