Originally posted by edvniow
Don't worry. I got it.
What I don't get is why they 'lock' the GUI so it's not easily modified.
I know that Quartz Extreme is not something you wanna f*ck with, but maybe I'd like a spherical Dock or something.
Is it for the OS's protection or something else.?
Well, you don't want an OS to be as tweakable as the Windows Registry. This is just a bad idea.
Things people genearally use to tweak (to be a little more specific) X are:
preference (.plist) files
BSD tools
Darwin tools
resources within packages
There are third-party tools as well, but these usually implement the above with published/non-published methods. If a program is asking for your password, it's probably issuing a superuser command to Darwin using sudo.
There are many different levels of X, each of which is increasingly harder to tweak. Darwin is based off FreeBSD and the mach microkernel. So basically all Apple did is stick its own proprietary OS on top of a modified FreeBSD. Darwin (the kernel level) is easily tweakable to the experienced *nix head, because it is open-sourced. That makes things like XPostFacto possible. The other part of the OS, Aqua, is guarded heavily.
The place where you find Aqua resources is in System> Library> Frameworks. Other processes implement these core libraries in CoreServices, Components, etc. So to heavily modify Aqua would be rather difficult. There are the apps governing Aqua (Dock.app, Finder.app, etc.) which are mostly compiled Cocoa code. Then there are the libraries themselves, which are probably the most heavily guarded part of the OS, since this is Apple's own "style".
So to go back to your original questions, Apple wants to keep their monopoly on their OS. Everything they do (excluding early projects like the Apple I) is supposed to reflect Apple's elegance. The only way they maintain this high-level of quality is with secrecy and closed code. Technically, the OS would not be harmed if tweaked properly in the hands of a professional but Apple doesn't want people modifying the "look" and "feel" of Apple.
You have to remember that Windows, an inferior OS, is implemented through .dll spaghetti code and archaic structures like the Windows Registry. Not only that, they have a web browser controlling the OS. This is a security nightmare. Sure, it is relatively easy to modify for good purposes, but also for bad. That's why there are patches every 2 minutes.
Apple has a top-quality OS, and the only way it will stay that way is if they lock it up tight. The Unix core is the only feasible thing that can be hacked "heavily" for now. But the results of such low-level hacking aren't too readily apparent in Aqua. Maybe something missing here and a little something more there, but nothing major. It works out better for the user this way.
Something like a spherical Dock is feasible, but would require a completely new Cocoa app. Applications Apple endorses because it augments their product, hence the Dev tools.