UI access to persistent group ID

[haileyscommit]

I'm the developer of ThetaChat, a work-in-progress chatmail client for Android with a modern Material 3 design. Recently I added support for notification bubbles and shortcuts (these are related for some reason). Each shortcut (and therefore the "conversation" the bubble is made for) uses a shortcut ID, and currently I build that ID using the relevant account's configured_addr and the addresses of each participant in the chat using the list returned by getChatContacts. For 1-to-1 "single" chats, this works excellent, but for group chats, this ID breaks each time the membership changes, causing shortcuts to no longer apply and conversation notification settings to break:

An alternative approach, and one I'm taking everywhere else in the app, is to use the numeric account and chat IDs. This works well for everything else (think: starting Activities, getting messages, and showing profile pictures); however, it is not recommended for shortcuts on Android:

Because the system performs backup and restore on pinned shortcuts automatically, these shortcuts' IDs must contain stable, constant strings or server-side identifiers, rather than identifiers generated locally that might not make sense on other devices.

(source: Create shortcuts - Android Developers)

and yes, you can pin these shortcuts:

While reading the Chatmail core spec earlier, I noticed this:

To allow different groups with the same members, groups are identified by a group-id.

Of course, that would solve that problem I was having, so I looked to see if there was a way to access it over RPC or C FFI (which itself is over Java), and I could not find one. So, I would like a field or method that lets me read that group-id for the purpose of composing these shortcut IDs. (I was considering going ahead and doing the work but the contributing guidelines said to make an issue before doing that.)

[link2xt]

An alternative approach, and one I'm taking everywhere else in the app, is to use the numeric account and chat IDs. This works well for everything else (think: starting Activities, getting messages, and showing profile pictures); however, it is not recommended for shortcuts on Android: ...

Delta Chat on Android uses account ID and chat ID:
https://github.com/deltachat/deltachat-android/blob/43644b2f1bf8fca0af523a0e7fd5389417f8612c/src/main/java/org/thoughtcrime/securesms/ShareActivity.java#L208-L217

I think it is fine, if you backup the whole app, then these IDs are stable. You likely don't want to allow backing up the app though so it does not end up in some "google cloud", at least this is what Delta Chat Android does.

Is there a way that shortcuts get backed up, but app data (the databases used by chatmail core) is not?

cc @adbenitez @wchen342 @r10s maybe someone who knows how it works on Android in detail can confirm.

[wchen342]

On Android we do use local IDs and they are stable locally. The only problem is pinned shortcuts will become dead links after a device switch, but mostly harmless.

Using group-id can fix the membership change problem, but it is supported to be kept secret and embedding it in a shortcut ID will expose it to the launcher and other apps. Also ad-hoc groups can have different group-ids I think?

[iequidoo]

The right way of referencing chats across devices is

core/src/chat.rs

Lines 5174 to 5183 in 520ede1

	pub(crate) enum SyncId {
	/// E-mail address of the contact.
	ContactAddr(String),
	/// OpenPGP key fingerprint of the contact.
	ContactFingerprint(String),
	Grpid(String),
	/// "Message-ID"-s, from oldest to latest. Used for ad-hoc groups.
	Msgids(Vec<String>),

, but it contains things we definitely don't want to expose to other apps. Even "grpid" is unsafe to expose because this way we at least reveal that different users are members of some common chat.