Function ovrt_sys::cmd::sink::global_command_sink

pub fn global_command_sink(
    may_set_listener: Option<Listener>
) -> &'static CommandSink

This function has two use-cases: getting the CommandSink or initializing it.

The "get it" usage is simple and is used internally by ovrt-sys to forward commands received from events/callbacks/etc.

The "initialize it" usage needs more elaboration:

The initialization occurs in the first global call to this function. The caller may decide if a listener should be registered (by passing Some Listener), otherwise, None Listener will be registered.
Note: This None Listener will ignore all commands, but will at least log them.
Note: to see if there is Some registered listener, you may call the has_listener function on CommandSink.

So with the exception of the first global call, all other remaining calls should pass in None as a listener parameter, since the CommandSink would already be initialized by the first global call.
Otherwise, if other calls are made passing a new Listener as a parameter, that parameter will simply be ignored and CommandSink will not change it's already registered Listener (even if it's registered as None).