public bool wait_is_uris_available ()
Test to see if there is a list of URIs available to be pasted This is done by requesting the TARGETS atom and checking if it contains the URI targets.
This function waits for the data to be received using the main loop, so events, timeouts, etc, may be dispatched during the wait.
This function is a little faster than calling wait_for_uris since it doesn’t need to retrieve the actual URI data.
true is there is an URI list available, false otherwise.