How can I determine the maximum possible number of threads?

Question

What factors determine the maximum possible number of threads mysqld will create?

I only care about consideration for mysql and not limitations that may be imposed by the operating system. Further, I only care about Linux, though if you want to include information specific to Windows, feel free.

As far as I can tell, threads can be created for replication, aspects of innodb, one per client connection up to max_connections, with an additional +1 to handle super connections. What else is there, or is that it?

threads_max =   max_connections  
              + 1 for super  
              + 2 for replication slave threads  
              + ? for InnoDB ?