Disco is software for burning disks that illustrates a new approach to interfaces: It smokes while it burns. If you blow into your computer's microphone, the smoke blows across your desktop. When Steve Jobs takes the stage Monday at Apple's programmers conference, he's likely to give the world a glimpse of an upgraded Mac operating system that could herald the biggest changes to the machine's interface in 30 years.

At the annual Worldwide Developers Conference in San Francisco, Jobs will probably show off Leopard, a Mac OS X update due in October that he has promised contains "top secret" features. But perhaps the most important feature is one that has been overlooked by many Apple fans: a new set of tools for building program interfaces called Core Animation.

(Editor's note: See our Leopard preview story, "Apple to Show Off Leopard's Claws at WWDC.")

Core Animation will allow programmers to give their applications flashy, animated interfaces. Some developers think Core Animation is so important, it will usher in the biggest changes to computer interfaces since the original Mac shipped three decades ago.

"The revolution coming with Core Animation is akin to the one that came from the original Mac in 1984," says Wil Shipley, developer of the personal media-cataloging application Delicious Library. "We're going to see a whole new world of user-interface metaphors with Core Animation."

Shipley predicts that Core Animation will kick-start a new era of interface experimentation, and may lead to an entirely new visual language for designing desktop interfaces. The traditional desktop may become a multilayered three-dimensional environment where windows flip around or zoom in and out. Double-clicks and keystrokes could give way to mouse gestures and other forms of complex user input.

The Core Animation "revolution" is already starting to happen. Apple's iPhone at the end of the month will see people using their fingers to flip through media libraries, and pinching their fingers together to resize photos.

The "Delicious generation" is a breed of young developers who embrace interface experimentation and brash marketing. The term "Delicious generation" was meant as an insult, but they wear it as a badge of honor.

Image: Adam BettsShipley's initial release of Delicious Library, with its glossy, highly refined interface, gave birth to a new breed of developers dubbed the "Delicious generation." For these Mac developers, interface experimentation is one of the big appeals of programming.

Applications like AppZapper have taken traditional tasks (deleting application files) and added a fun layer of animation to the mix – this isn't your father's rm command. Disco is a disc-burning program that features smoke animation that reacts to sound – blow into the mike, and the smoke blows away.

But creating animations like those in AppZapper or Disco is presently a complex and difficult task.

Leopard's Core Animation will change that, giving the next generation of developers a set of tools that will allow them to easily create new, nonstandard, interactive interfaces.

Some Mac developers are so excited by Core Animation they are going to drop support for previous versions of their software, which won’t display their new interfaces on older versions of OS X.

"Our customers are going to have to upgrade their OS if they want to upgrade our program," Shipley says. "We realized any app we released based on Tiger (the current version of OS X) was going to look really pathetic when Leopard came out."

After getting a peek at Delicious Library 2, which hasn’t yet been shown publicly, Mac programmer Scott Stevenson wrote that the program is "going to be a major eye-opener for Mac developers. This last point is important. Whatever you thought was state-of-the-art in Tiger is going to be blown to bits with all of the new API (application programming interface) available in Leopard."

Allan Odgaard, the developer of TextMate, says the next version of the text editor will only work on Leopard. Because of Apple's nondisclosure agreements, most of the Mac developers approached by Wired News declined to discuss Core Animation or any interface changes they might be planning. None would provide screenshots.

The shift toward nonstandard interfaces isn't necessarily new. Kai's Power Tools, a set of plug-ins for Adobe Systems' Photoshop, featured what was at the time a revolutionary interface for editing image files. But the developer, Kai Kruse, was too far ahead of his time – the majority of Mac users disliked the novel interface, which broke with conventions and ignored Apple's Human Interface Guidelines, or HIG.

The HIG is a set of rules published by Apple to ensure consistency across different applications. It's become the bible of Mac programmers.

However, with the growing popularity of "widgets" – mini, task-specific applications for checking sports scores or finding cheap gas – users are starting to accept novel interfaces. And they often expect the sort of highly graphical interaction that Apple's new Core Animation enables.

With many developers already moving toward smaller, single-task applications, the addition of Core Animation tools may signal a revolution in Mac application design: lightweight, heavily animated, widgetlike applications are the future of the platform.

And while some longtime Mac developers have decried the Delicious generation of apps, Apple seems to be embracing the changes.

Apple has been ignoring its own HIG for some time in applications like QuickTime, and is abandoning them completely in upcoming Leopard applications like Time Machine.

Functionality-wise, Time Machine is a banal program – a content-version-control system that makes periodic, automated backups of a computer's hard drive.

But Apple's take on the age-old task of incremental backups features a 3-D visual browser that allows users to move forward and backward through time using a virtual "time tunnel" reminiscent of a Doctor Who title sequence. It's completely unlike any interface currently used in Mac OS X.

Spaces, also new to Leopard, lets users manage several virtual workspaces and flip between them using a navigation system that's pure eye candy.

Austin Sarner, an interface designer and engineer at software company madebysofa, says that the new style of Apple apps isn't just about glossy effects – there's a usability payoff as well.

"Animation in general creates continuity and more direct feedback to a user experience. In addition to obvious graphical speed boosts, the elegance (that animation) can add to a UI is pretty substantial," he says.

Sarner points to the Apple TV as an example of how animation is making interface navigation more intuitive.

"Your selection glides into place, as opposed to immediately snapping to the next item. Midway through the split-second animation, you can neatly cancel out and go in the other direction."

Shipley predicts the new user-interface paradigm will also include the direct manipulation of documents – instead of fumbling for a scrollbar, users will be able to grab a document and "throw" it upward with their mouse in order to scroll through it.

Upcoming small-screen devices like the iPhone will force designers to further abandon traditional elements associated with the window metaphor, such as pull-down menus and scrollbars, in favor of more innovative designs emphasizing mouse gestures and click-and-drag actions.

Core Animation will only make it easier to translate these new ways of thinking onto the desktop.

Mac developer and Panic co-founder Cabel Sasser has no doubt that developers will embrace Core Animation.

"A fast, Apple-maintained way to do the kind of animations we now rely on heavily is a brilliant and well-welcome idea," he says.

In order to run applications that utilize Core Animation, users will need to upgrade to Mac OS X version 10.5, as the graphics engine will only be available in the new OS.

While it seems logical to speculate that interfaces like those of Time Machine and Spaces will lead to the end of the familiar "window" framework for desktop applications altogether, many Mac developers predict that the most basic elements of the current user interface forms won't disappear entirely.

Flying desktops and animated scrolling actions can enhance a user interface in many instances, but applications like browsing the web and writing an e-mail will still require a traditional environment.

"I really don't think that the desktop will ever become 'windowless,'" says Panic's Sasser. "Windows present a very familiar and natural way to work and multitask, and to radically change it might just mean desktop suicide."

Even though we're still tied to the traditional computer desktop, Shipley agrees that the limitations of what that desktop can do are eroding.

"I don't think we'll abandon the old way as much as supplement our armory with a whole new arsenal of tools," Shipley says. "It's an awesome time to be a Mac developer, and, by extension, a Mac user."

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