Expand description
The way for a client to pass focus to another toplevel is as follows.
The client that intends to activate another toplevel uses the xdg_activation_v1.get_activation_token request to get an activation token. This token is then passed to the client to be activated through a separate band of communication. The client to be activated will then pass the token it received to the xdg_activation_v1.activate request. The compositor can then use this token to decide how to react to the activation request.
The token the activating client gets may be ineffective either already at the time it receives it, for example if it was not focused, for focus stealing prevention. The activating client will have no way to discover the validity of the token, and may still forward it to the to be activated client.
The created activation token may optionally get information attached to it that can be used by the compositor to identify the application that we intend to activate. This can for example be used to display a visual hint about what application is being started.