Attachment support

[profmaad]

One of the calendar features that I use a lot is attachments. These are supported well by Google Calendar, but for obvious reasons that's something many folks want to avoid using.

From the DAVx5 docs (https://manual.davx5.com/integration.html#extended-event-properties), I understand that the Android Calendar Provider has no proper support for attachments, and that DAVx5 thus can't sync them onto Android. Is this true? Would it be possible to sync Caldav attachments via a new custom property like DAVx5 does for URL?

Support in OSS calendar apps on Android is also missing, but can't really be implemented until there's an agreed-upon way of representing attachments under the limitations of Android Calendar Provider. For example, there's on open issue for this on Fossify calendar: FossifyOrg/Calendar#562.

On the Caldav server side, there seem to be a few implementations with attachment support, like Nextcloud.

[rfc2822]

The idea was discussed sometimes internally but there was no point to collect the ideas. I have now created #2031 for that purpose.

I understand that the Android Calendar Provider has no proper support for attachments, and that DAVx5 thus can't sync them onto Android. Is this true?

Yes, but depending on which type of attachment this is about, DAVx5 could provide a content provider that provides the attachments for other apps. The URLs for these attachments could then be a custom property.

So we would need a calendar app that supports DAVx5 attachments. However this can in theory be integrated into an open-source app like Etar (or also into a primitive calendar/attachment viewer within DAVx5).

For example, there's on open issue for this on Fossify calendar: FossifyOrg/Calendar#562 example, there's on open issue for this on Fossify calendar: FossifyOrg/Calendar#562.

Thanks for the hint. It would surely be a good if the feature could be supported by an external calendar since the beginning.

On the Caldav server side, there seem to be a few implementations with attachment support, like Nextcloud.

I would especially be interested in Managed attachments. There's a Nextcloud issue for that: nextcloud/calendar#5001

[profmaad]

This does indeed seem like an issue that needs coordination between Caldav server implementations (though that might be the easy part, as we have relevant Caldav standards for regular and managed attachments), Caldav Android apps and DAVx5. I'm willing to help out if I can, and have at least 2 developer friends who've also expressed interest in working on better OSS calendaring.

Likewise, I'd be particularly interested in getting managed attachments to work all the way from e.g. Nextcloud (or Radicale or similar, though they don't seem to have any attachment support currently) into Fossify or Etar calendar on Android.