[horde] Active sync: multiple calendars?

[Michael J Rubinsky]

Quoting Jan Schneider <jan at horde.org>:

> Zitat von Michael J Rubinsky <mrubinsk at horde.org>:
>
>> Quoting Gunnar Wrobel <wrobel at horde.org>:
>>
>>> Quoting Michael J Rubinsky <mrubinsk at horde.org>:
>>>
>>>> Quoting Andreas Ntaflos <daff at pseudoterminal.org>:
>>>>
>>>>> Hi,
>>>>>
>>>>> is it possible to access and sync multiple Horde calendars (on the same
>>>>> user account) with the new ActiveSync plugin? Or is this not supported
>>>>> by design or specification?
>>>>
>>>> By specification. The AS protocol does not support multiple  
>>>> calendars for a single user.
>>>
>>> But shouldn't there be ways to aggregate calendars? I'm pretty  
>>> certain the ActiveSync support on the Kolab server allows  
>>> selecting several.
>>
>> Sure, it would be possible to essentially combine all events from  
>> multiple calendars into a single AS collection. However, there are  
>> a number of issues that I ran into while trying to do this when I  
>> originally wrote the library:
>>
>> There is no way to differentiate the calendars on the client (AS  
>> only supports a single "calendar" folder) so no calendar names, no  
>> horde-centric calendar colors (in fact some clients might color the  
>> events based on the tags) - all events look like they are in the  
>> user's "main" calendar.
>>
>> There is no way to mark events as read only, no way to map back an  
>> event to the calendar it came from in the case that multiple  
>> calendars may have the same event uid (though this is not specific  
>> to AS), and no way on the client to select the calendar to add a  
>> new event to (all events are assumed to be on the user's "main"  
>> calendar). This last point _might_ also cause issues with both  
>> event invitations and recurring event exceptions on calendars other  
>> than the user's "main" calendar (don't have code or protocol docs  
>> in front of me at the moment to verify this one).
>>
>> There would also be issues when a user changes which calendars they  
>> want included after the initial setup (would basically require the  
>> user or admin to explicitly reset the AS account to force a  
>> complete replacement sync). For example - a user initially sets up  
>> two calendars, but then decides to remove one. All the events from  
>> the second calendar will still be present on the device. Similarly,  
>> adding a second calendar would not sync the events that were  
>> created/modified prior to the last successful sync time.
>>
>> Yes, some of these issues could be at least partially worked around  
>> by e.g., limiting the calendars allowed to be synched to calendars  
>> owned by the user, or adding user pref for the calendar to use when  
>> creating new events on an AS device, but these rather feel like  
>> hacks instead of implementations.
>>
>> If in fact kolab does allow this, I'd be interested in both how the  
>> kolab/activesync connector implements this and how robust this  
>> actually is. If you have any links to code or similar, I'd love to  
>> take a look. This is a sore point for me as well though even if we  
>> get minimal support for this, would likely not help me since it's  
>> calendars I have read only access to that I need to include (see  
>> note above about read only issues).
>>
>> Also, it's worth noting that I'm aware that Google's "activesync"  
>> support allows this - but this is not true activesync; they have  
>> added features to the protocol and these only work if using a  
>> Google client, not a generic activesync client.
>
> All what you said could be applied to contacts too, where we allow  
> several sources. In fact, synching several calendars can be  
> implemented transparently, i.e. for both SyncML and ActiveSync,  
> analogous to address books.

Except for the fact that the same event UID might exist in more than  
one calendar, though I guess that would be fairly rare if we limit to  
calendars the current user *owns* (which we have to do anyway). As  
long as this doesn't muck up invitations and recurring  
events/exceptions I'll add it to my list.

-- 
mike

The Horde Project (www.horde.org)
mrubinsk at horde.org