Subject: bug#78120: 31.0.50; Calendar is not reliable with its marking

From: Eli Zaretskii <[email-masked]>
Date: Fri, 09 May 2025 10:47:57 +0300

> From: Michael Heerdegen <[email-masked]>
> Cc: Manuel Giraud <[email-masked]>,  [email-masked]
> Date: Fri, 09 May 2025 08:57:58 +0200
> 
> Eli Zaretskii <[email-masked]> writes:
> 
> > Surely, we need to make a decision like that if we want the results to
> > be completely deterministic?
> 
> I wonder how that could be done.  There are a lot of possible sources of
> marks besides diary entries (look for functions calling
> `calendar-mark-visible-date', for example).  Marks can also come from
> user functions.  Most of these can use arbitrary faces (the diary face
> is only a fallback) - and at least some of them are allowed to specify
> only attributes that should stack.  If you really intend to invent some
> kind of hierarchy to solve this, this will be a very complicated thing.

The priorities are per overlay, not per face.

How many places that create overlays are there in calendar and
diary-lib?  My suggestion is to assign a priority to each one of these
overlays, based on some reasonable estimation of their importance.  If
that is impossible, I'd need to see the detailed explanation why not.