type t = ..
type t +=
| Ignore(*

Ignore events are dropped, so no handler is called

*)
| Viewport_changed(*

Viewport_changed events are delivered to all visibility handlers

*)
| Stop_propagation(*

Stop_propagation prevents the underlying DOM event from propagating up to the parent elements

*)
| Prevent_default(*

Prevent_default prevents the default browser action from occurring as a result of this event

*)
| Many of t list(*

Allows one to represent a list of handlers, which will be individually dispatched to their respective handlers. This is so callbacks can return multiple events of whatever kind.

*)
module type Handler = sig ... end
module type Visibility_handler = sig ... end
module type S = sig ... end
module Define (Handler : Handler) : S with type action := Handler.Action.t and type t := t

For registering a new handler and a corresponding new constructor of the Event.t type

module Define_visibility (VH : Visibility_handler) : sig ... end

For registering a handler for Viewport_changed events. Note that if this functor is called multiple times, each handler will see all of the events.

module Expert : sig ... end