Tag system : Chat warning

[Citillara]

Hello,

Following the reading of this PR : #1294

I was thinking somethings is missing from both protocol and clients. This would be a warning to alert the user that the chat he's reading/typing into has entered a degraded mode (bridge down/whatever)
Features for the protocol :

• A notice that can be attached a channel and is part of the ACL management

Features for the client :

• When the notice is non null : it's displayed above the chatbox when the user starts writing a message for the first time since the notice went into effect

Features for the servers :

• When the notice is non null : notice gets published in the chatlog history
• When the notice becomes null : it's removal is published in the chatlog history

Example : "IRC bridge to this channel is currently down. Only matrix users will be able to read your discussions for now"

[Half-Shot]

Hiya, the feature in #1294 to disable the bridge upon membership mismatch is already mentioned by the bridge in the room via a org.matrix.appservice-irc.connection state event. It just needs clients to present this information to Matrix users to make it useful. I would suggest making an issue to https://github.com/vector-im/element-web/issues to ask them to present this information.

The state event is currently outside the matrix spec, because it's fairly particular to the IRC bridge. In the past there have been efforts to build a signalling system on Matrix for bridge state (matrix-org/matrix-spec-proposals#2162), but that hasn't gone anywhere in a while.

[Citillara]

That feature is not bad but seems very bridge oriented. Can I suggest instead of a custom flag system where a room could have a certain amount of informations in a key-value system.

This would allow bridges and clients to look for specific information about a room state while letting the protocol ignorant of those problems.

Tag add/edit/delete would be sumitted to the normal ACL (default admin ?)

Server would define a max number of custom tags placable on room (i.e 50) with a maximum key/value length (50/200)
A simple announcement system would broadcast in the room whenever a tag is added/edited/removed

Tag example : irc.bridge.offline:2021-06-28T12:00:00

Clients could themselves look for well known tags and read them