Six months ago, Mac OS X Leopard was released to the public, bringing with it new technologies, features and problems for customization enthusiasts, and the issue of theming has been a complex one. Discoveries by forum members and other enthusiasts have made theming possible once again in 10.5, but to restore the culture of customization to Leopard, it will need something accessible to the masses.

Here’s the scoop for those of you not up to speed on why Leopard is themeless:

Starting in Mac OS X 10.5, Apple has changed the way the system draws the user interface, moving from a series of raster images, which have a specified number of pixels, to a combination of raster and vector images– images that can scale infinitely without losing resolution.

This move from a raster-based to a hybrid system marks the first steps to a resolution-independent interface: the idea that, if a display has such a high pixel count that the OS looks too small, you could just increase the size of the entire OS without any loss in sharpness. A screenshot of this enabled vector UI is off to the right. While “true” independence is still a few years off, this course in technology is inevitable; it is a huge advantage to Apple to have their independent interface in development now. The downside of its introduction, however, was that themers would need to start from scratch creating a total theming solution for 10.5.

And now for some vocabulary:

• Extras.rsrc and Extras2.rsrc are the deprecated resource files (for PowerPC and Intel, respectively) used to draw the user interface for Mac OS X versions 10.0 through 10.4. These resources contained raster bitmaps as well as text color dictation used for Aqua, and was the file modified by ShapeShifter for theming under these old operating system versions. By default, it is unused by Leopard, save for the scrollbars and global Save As PDF button.

• CoreUI is the framework for Leopard’s Aqua appearance. Its resources stem from three origins: a collection of vector PDFs and high-resolution PNGs used by the vector UI (disabled by default), as well as two packaged art files: ArtFile.bin and SArtFile.bin, which more or less contain all the resource elements used to draw 10.5’s user interface.

Now, here’s where the theming kicks in. By disabling CoreUI using a Terminal command, Leopard begins using the original Extras.rsrc files to draw the UI, allowing themers to manually port ShapeShifter themes (by manually merging their customized .rsrc files with the system’s) to Leopard; once it was revealed that the window chrome could also be reverted to “Tiger form”, applying themes without ShapeShifter became possible.

The elephant in the room, however, will be finding a solution in the long run. Because both Extras.rsrc files are approaching obsolescence by 10.6, any tool that makes itself dependent on these resource files will not last more than a couple years before something new will be needed again. Work has begun, however, on the encryption and decryption of the two ArtFiles, which may provide a new theming solution once Extras.rsrc is completely removed from Mac OS X.

If you’re interested in knowing the nitty-gritty details of all these files, take a look at the MacThemes Theming Wiki articles on ArtFile.bin, SArtFile.bin, ArtTools, Extras.rsrc, and the Vector UI. Contributions from CoreUI experts are also welcome.

Quite simply, none of this progress would have been possible without the help of the MacThemes forum community; discovering the workings of CoreUI has slowly begun to bring back themes to the Leopard front, and we hope the wiki will make the process just a bit easier for potential theme developers. But a successful theming movement requires more than members from this website.

After Mac OS X was released in 2001, customization was seldom done at all, restricted to a niche of a niche group who were brave enough to modify their own system files. This took two years to change, with the release of apps like CandyBar, ThemeChanger and ShapeShifter. But unlike the “manually replace files” way, these apps made customization– a daunting, archaic task– easy for users, turning out many great themers and artists as an effect. Sites like this wouldn’t have garnered the same success without the help of Unsanity and other independent developers.

This may be obvious to many of you, but to get that life back in the theming movement, Leopard needs its own ShapeShifter: not in the sense that it’s controlled by one entity, but that some easy-to-use tool does exist for safely replacing files; and without any Terminal or system folder pokery required from the user. Naturally, this thing takes time (by no means do I think the process is moving too slow), and as far as I’m concerned, theming seems to have a bright future on the Mac.

Oh, and let’s avoid haxies, shall we?