I like to add my 2 cents of wisdom here. I am the author of IrScrutinizer, BTW.
IR receivers: The problem with almost all build-in IR receivers is that they are so limited. Not only are they using a demodulating receiver (like TSOP xxx38 or so), removing all information on the modulating frequency, most often the system, which is interested only on recognize its very own remote (in the Apple case the one with six buttons), more or less completely decodes the signal, outputting only the information it considers important, namely, if it recognized any of its own signals, not the received sequence of timings. AFAIK, that goes for the Mac Mini too. (I happen to have one too...)
IR databases: There are more than Logitech. A completely non-commercial is
http://irdb.tk, unfortunately a bit BBD (broken by design) since it orders the devices by protocol and parameters. The "old" GlobalCache data base
http://irdatabase.globalcache.com/ is free, after registration, but no longer mainted. These two are fully supported in IrScrutinizer, i.e. you can suck the codes with just a few key clicks. The new one
https://irdb.globalcache.com/ has a few problems for non-premium users (
[Link: harctoolbox.org]) but is a very nice, sort-of free data base. The latter two contains several Viewsonic devices, but I am not sure if any of these maps to your device. Trial and error.... (With hardware configured for sending, you can download and shoot the signal with just a few key clicks, without leaving IrScrutinizer.)