bug#49995: 28.0.50; EBDB Anniversaries do not appear marked in calendar

[Eric Abrahamsen]

Eric Abrahamsen <eric@ericabrahamsen.net> writes:

> Michael Heerdegen <michael_heerdegen@web.de> writes:
>
>> Eric Abrahamsen <eric@ericabrahamsen.net> writes:
>>
>>> Oof, EBDB's diary integration was "write once and back away slowly"
>>> code. I'm trying to understand diary-lib.el. So far as I can see, when
>>> you add diary entries to `diary-entry-list' [...]
>>
>> Suggestion: provide a new diary-sexp function, similar to
>> `diary-lunar-phases'.  Then marking would be handled by the diary.
>>
>> That function just has to return nil or a string (or a mark and a
>> string) depending on the dynamical variable DATE.  That's already the
>> whole diary related part.  People then have to add that function as sexp
>> entry to their diary if they want.
>
> Oh, huh: sort of inverting the prior approach. I find all this a little
> confusing, I've never spent any time with the diary, and its integration
> with Org always seemed very mysterious to me. But I do think the
> calendar integration is very useful.

Okay, here's a version of how it might work. I've learned a little bit
more about the diary (and as a result will likely use it more! I'd
always thought it was just a poor cousin to Org, but I see it has its
own strengths), and have a solution that is a bit funky, but might be
okay. If Michael or anyone with a better understanding of diary than me
would comment on this, I'd very much appreciate it.

So the user puts "%%(ebdb-diary-anniversaries)" as a sexp in their
diary. That function gets called in two situations: marking dates in the
calendar (it gets called *many* times but only has to return a boolean),
and listing diary entries for a particular date (it only gets called
once, but has to produce more detailed information). The function checks
(bound-and-true-p 'original-date) to know which situation it's in.

At load time EBDB builds some prep data in a hash table, and that data
feels messy, but the strategy is to do a medium amount of work at load
time, the absolute minimum amount of work when marking dates in the
*Calendar* (essentially checks "does this hash key have a value"), and
again a medium amount of work when displaying diary entries for a
particular day.

I would love some feedback on this!

Eric

rework-ebdb-diary-anniversaries.diff
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