A way for an addon to export data visible by others?
 

Is there a way for an addon to export some custom data that would be readable by another addon? The use case I'm looking at would be sharing some extended player-defined information - so that addon on the side of other players would be able to display it (after targeting the other addon user with the reticle). I've seen addons using it in roundabout way - synchronizing data through saved variables, custom external app and server; I wondered if there's a more direct way for doing the same. Thanks in advance. ^^

Not really, and definitely not in the way you are thinking of it. If there was, people wouldn't use those round about ways. All of the possible methods are pretty limited in bandwidth, and require you to be in group.

I think, it can be done via chat.
some addon sends a messages with some data. And recepients recieve that info and translate it to be a human-like.
That addon also need to remove that info from the actual chat tab, to prevent flood

But, if a player didn't use that addon, then his chat window would looks not good while being flooded with custom data from other players :D

I can identify several high-bandwidth methods of player-to-player data transfer, though they do have some drawbacks...

The most obvious is group and use libGroupSocket to transmit data. Slow, relatively speaking, but depending on your volume, not that slow. However, grouping probably kills it.

You can use chat -- whisper the target -- and transmit high volume data fairly quickly, even accounting for flooding limits. However, this requires the sender to hit enter every time you need to perform a send operation. If this is a one-shot-and-done sort of thing, that probably works.

You can use mail. I know you can send the stuff without human interaction, given another addon doing it for crown crate drop rate tracking, and the bandwidth of a mail is fairly large. I don't know if you can read it without the other player opening their mailbox, however, which may make it a bit more cumbersome.

I'd personally start by investigating the mail option: you can put an explanatory header in place, you can send fairly high bandwidth, and relatively frequent, messages, and you can certainly automate the other party ingesting the mail with your addon. Depending, you may even be able to communicate the data in a way that both humans and machines can process.

You could certainly use chat / whisper to handshake before the mail started, too, if you wished: an automated message to confirm they have your addon, and then the data exchange can proceed from there...

An addon can't send messages by itself, to prevent channel flooding.

All an addon can do is post text into the chat box for the user to hit enter. No automation allowed.

Mail is unreliable for time critical data, since new mails are not pulled from the server right away, or not at all until you change zone or relog.

Exactly as I said. Depending on the use-case, this may be sufficient.

Yup. Again, it isn't clear if that will be a huge issue or not for the user, since they didn't clarify those details of their use-case.