In January 2009, both MacRumors and Daring Fireball's John Gruber began hearing rumors that Apple was working on a project code-named "Marble" that was believed to be an overhaul of the Mac OS X interface set to appear with Snow Leopard later that year.
As time went by, however, Gruber noted that "Marble" was unlikely to appear in Mac OS X Snow Leopard, and indeed the new operating system did not carry the significant overhaul many had been hoping for, leading to speculation that it could still appear in Mac OS X 10.7 whenever that sees the light of day.
Yesterday, Gruber revealed that "Marble" actually appears not to be a Mac OS X interface revamp but an overhaul of Xcode, Apple's developer tools for Mac OS X and iOS. A beta version of Xcode 4 was previewed at Apple's Worldwide Developer Conference earlier this month, but with the sessions covered by non-disclosure agreements, it was taken some time for details on the update to come out. One of the major changes in Xcode 4 is the integration of Interface Builder into the larger Xcode application, creating a unified interface that comprises the "Marble" project.
Xcode 4 is still in beta, Apple doesn't have screenshots available, and what was shown at WWDC 2010 is covered by NDA. But if you have a developer account, you can get a tour of the new interface by watching the Developer Tools State of the Union session. It is, to say the least, a major overhaul - primarily focused on doing more within a single window, even going so far as to bake Interface Builder into Xcode itself. According to several informed sources at WWDC, that's the "Marble" project.
It is unknown when Xcode 4 will make its official debut, but it appears to promise a significantly enhanced development environment for creating and testing applications.
