api: cffi api to create account manager with existing events channel to see events emitted during startup. dc_event_channel_new, dc_event_channel_unref, dc_event_channel_get_event_emitter and dc_accounts_new_with_event_channel

[Simon-Laux]

closes #7606

• fix broken ci tests
• test it manually

[Simon-Laux]

Is this still the case?, rust code looks like it allows multiple listeners: it uses and async broadcast.

[Hocuri]

Looks like it, probably it was forgotten in #5478 to update the documentation. But of course, the only way to be totally sure is actually trying it out.

[Simon-Laux]

Tried it, the assumption was correct: the comment is outdated, in cffi and rust api it is possible to have multiple event channels, only in jsonrpc api it is currently not possible.

[iequidoo]

Suggested change

	* The account manager takes an directory
	* The account manager takes a directory

Maybe it's better not to duplicate the documentation, but just add a reference to dc_account_new() and explain the difference. Otherwise API users need to read both and build a diff in their head, and we have more text to maintain.

[Simon-Laux]

@r10s what's your opinion on references vs duplication in cffi docs?

[iequidoo]

I think it depends on amount of text. Huge texts should never be duplicated because users then have more work to read the docs and understand the difference between functions. E.g. see https://pubs.opengroup.org/onlinepubs/9799919799/functions/open.html, it documents two functions at the same time and explains which and when should be used, would be good if we can do the same, w/o duplication and extra cross-references.

EDIT: But i couldn't quickly find a way how to do this in Rust ideomatically.

[link2xt]

You don't need tokio mutex, just a std::sync::Mutex (or parking_lot::Mutex to avoid unwrap(), but then you need to add it as a dependency for deltachat_ffi). You call .blocking_lock() anyway.

See also https://docs.rs/tokio/latest/tokio/sync/struct.Mutex.html#which-kind-of-mutex-should-you-use, even in async code you don't necessarily need an async mutex.