Attribute Macro horizon_mod 

#[horizon_mod]

Mark a trait mod and derive its hook subscriptions.

A hook method may carry #[listener(priority = <i32>, receive_cancelled)], both optional: mods run by descending priority (0 when omitted), then in dependency order, and a mod that receives cancelled events is still called after an earlier mod cancels, with event.cancelled to read and clear. receive_cancelled compiles only on a hook a mod may cancel.