I'm not sure I understand what you mean by "prior disclosure" here. They filed a patent application: those are supposed to be public. The prior art Joel used was the documentation of the Win32 API from 5 years previously (and I'm pretty sure we've been using variable-resolution apps since earlier than 2008, and not just in Windows -- this was just an example). Could you clarify what the problem is?
App icons in OS X are interpolated between about 4 different sized images. I remember reading about this in the developer docs back in about 2002. I'd be surprised if Apple don't have pretty much the same patent on this already but registered 10 years earlier :-)
Mac OS has done this since much earlier. The classic Mac OS needed at least two different representations of the same icon, one for the desktop (32x32) and one for the application switcher (16x16). The application switcher, initially called MultiFinder, was introduced in 1987[1]. If memory serves, the various sizes of an icon were stored together in the ICNS resource of the app binary's resource fork. There was a developer tool provided by Apple called ResEdit which allowed you to view or change the icons of any application, in a nice GUI editor (of course).
I'm not 100% sure what you are confused about, but let me take a stab at it. Prior disclosure is public disclosure of the invention prior to the patent application. The one year rule states that once you publicly disclose an invention, you have one year from that date to file a patent application. Otherwise, your invention is considered public domain and cannot be patented. Does that clarify?
The problem I think you are referring to is that researchers run the risk of shooting themselves in the foot by prematurely presenting their findings unless they file an application in the process. Doing so would ruin their chances of being granted a patent.
I understand how prior disclosure works, my confusion is that nothing like that seems to have happened here. The patent was invalidated on the basis of documentation of a different piece of software with the same features released 5 years prior (albeit by the same company).
However, having read the ruling, I see it explicitly cites the prior-disclosure rule. So the bad patent system has invalidated a bad patent, but in a bad way.
