Custom msgtypes appear as "Unsupported event"

Your use case

What would you like to do?

When I execute the /fireworks woo hoo! command fireworks are displayed on Element for PC.
However, on Element X the message cannot be read at all, instead it displays "Unsupported event".
The same happens with other message types that have additional visual effects, namely /snowfall, /confetti or /rainfall.

Why would you like to do it?

At least see the message contents

How would you like to achieve it?

Idk

Have you considered any alternatives?

You can hold down the message and click "View Source" and then read the message from JSON, but this is inconvenient.

Additional context

Normal text message:

{
  "type": "m.room.message"
  "content": {
    "msgtype": "m.text"
    "body": "test",
  },
  "room_id": "[REDACTED]",
}

Fireworks text message:

{
  "type": "m.room.message",
  "content": {
    "msgtype": "nic.custom.fireworks",
    "body": "woo hoo!",
    "m.mentions": {}
  }
}

Are you willing to provide a PR?

No

[bmarty]

I agree that unknown msgtype should still display the body of the content in the timeline. This is what the spec is recommanding. I will see if I can do a quick fix for this.

[bmarty]

OK, I think we will need a change in the Rust SDK (or in the uniffi layer). There is a mix which is not clear to me on the mapping there between Event type and msgtype in the event content, when "type" = "m.room.message".

Anyway, for m.room.message, even if msgtype is not supported, the body field must be provided to the application for it to render the fallback properly.

[bmarty]

Actually I can fix for the room list and for the timeline, but not for the notification.

PR: #1549
Rust issue about adding notification support: matrix-org/matrix-rust-sdk#2703