Disappearing messages are not disappearing

[link2xt]

There is a report of non-disappearing "disappearing messages" in #6355
The issue is closed because it essentially consisted of two issues, but disappearing messages problem is still unsolved

@kdltr has cases where in active chats some messages do not disappear even though they are read. Message info contains "Ephemeral timer: 604800" and "Expires: 2024.12.29 10:45:46" lines as if the timer started just now and will expire in 7 days.

The reason why the timer is not started is unclear, but the problem may be that the message was not actually marked as read by any UI. We should start the timer for all messages when the message is marked as noticed to make this more reliable. This way just opening a chat or marking any message as seen from another device should be enough to start the timer for all messages in a chat.

[r10s]

This way just opening a chat or marking any message as seen from another device should be enough to start the timer for all messages in a chat.

reason for staring the counter only for actually seen messages might be that that we have comparable short timeouts (1 minute, not long ago even 30 seconds) -- not sure about the usecases of these short timeouts, maybe fine also with start-ephemeral-timer-on-noticed (== start-ephemeral-timer-opening-chat), just saying

sending read receipts should not be touched and stay on-mark-seen (== really displayed on the screen), at least at a first glance.

[r10s]

not sure about the usecases of these short timeouts

the settings might have been inspired by signal, also having 30 seconds and 1 minute. telegram and whatsapp have minimums of 1 day

[link2xt]

Fix is at #6365

[iequidoo]

or marking any message as seen from another device should be enough to start the timer for all messages in a chat.

Couldn't find any code marking a chat or older messages as noticed if a chat message has been seen on another device.

[iequidoo]

Still, we don't start ephemeral timers when messages are noticed on another device and when DC_CHAT_ID_ARCHIVED_LINK is marked as noticed, isn't it a problem?

[link2xt]

Opened follow-up PR #6367

Also opened an issue #6368 but it's not that important, read synchronization may not work anyway and if the chat has unnoticed messages and a badge with a number then it is expected that the timer did not start.