I refer you to the Web Plugin Programming Topics Guide
Beginning in Mac OS X v10.6, on 64-bit-capable computers, Netscape-style plug-ins execute in an out-of-process fashion. This means that each Netscape-style plug-in gets its own process separate from the application process. This design applies to all Netscape-style plug-ins. It does not apply to WebKit plug-ins, nor at present to WebKit-based applications when running in 32-bit mode.)
It goes on to enumerate a large number of new restrictions on how plugins are supposed to operate in their new out of process home. At this point, it becomes pretty hard to justify using a NPAPI style plugin for any but the simplest plugin for Safari; it is just too strangling. So the mind turns to WebKit plugins which are basically Cocoa NSViews with a few limitations and added message handlers. As the quote above says they are not (at present) limited in such a way as Netscape plugins; in this way Apple is nudging people to use WebKit plugins if for no other reason that they allow you to do things that the NPAPI plugin do not.
And here we come to the idea for this posting, it seems as though Apple is interested in locking down and rationalizing Safari plugins. It is also reasonable that at sometime in the future, they will allow plugins for Safari on the iPad. It is also almost a given that those plugins will not be NPAPI style plugins, but will instead be UIView or UIViewController derivatives. And at that point, the question becomes, wouldn't the UIView style plugin with its simpler and more modern object design make a cleaner foundation for plugins for Safari on the Mac? Apple already has an iPhone simulator on the Mac. Of course, there would have to be some extension allowing mouse hovering events.
- Code sharing between Mac and iPad
- Plugins are closer in scope to iPhone Apps then full blown Mac apps.
- At this point most Objective-C programmers are iPhone developers so developer pool would be larger
- Expand iPhone apps to the Mac
- iPhone Apps are used to being sandboxed
Anyway, just a thought.