allow notification of when a message has been read

[aaannndddyyy]

this could be disabled by the user, but when enabled, a similar confirmation like the receipt confirmation that already exists, should be sent and upon receiving of such the client be notified, such that the the sender of a message can see that a message has been read.

[GrayHatter]

This is blocked by the inablity of toxcore to track messages

Which is also blocking a few features in multi-device.

[aaannndddyyy]

Q1: Would it be hard to add such an ability to track messages by a hash of them?
Q2: Would adding this have unwanted side-effects?
Q3: Couldn't the clients track it and toxcore just provide a was of sending a custom system-message to the other contact, which the client then detects and intercepts as a read ack?
My original idea was that either it be analogous to current receipt confirmation, or as totally handled by client, except for the signaling itself

[GrayHatter]

Q1: Would it be hard to add such an ability to track messages by a hash of them?

Probably not.

Q2: Would adding this have unwanted side-effects?

Maybe? Very few people like change...

Q3: Couldn't the clients track it and toxcore just provide a was of sending a custom system-message to the other contact, which the client then detects and intercepts as a read ack?

Yes, but then client can do that already. The only reasonable solution is to let toxcore handle that.

My original idea was that either it be analogous to current receipt confirmation, or as totally handled by client, except for the signaling itself

Right, but the way it works now, all you're doing is getting an ACK from toxcore that the reciver has processed that packet. You don't currently even know if the client got the message in a callback.

[Renha]

we need unique message identifier per dialog to solve that right way