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An Introductory Mac OS X Leopard Review: Core Graphics and the New UI

Mac OS X 10.0 Quartz

In 1999, Apple demonstrated its new drawing system split into two segments: Core Graphics Rendering (Quartz 2D) for drawing, and Core Graphics Services (Quartz Compositor) for compositing together layers generated by both the new Quartz 2D and the existing QuickDraw and QuickTime. This allowed windows of existing Mac applications to seamlessly share the screen with new ones. In addition, Apple introduced support for OpenGL as its 3D interface.

Since Apple had already ported much of QuickDraw as part of its efforts to sell QuickTime on other platforms (including SGI's systems), some of the work to deliver backwards compatibility on the new system was already done. QuickDraw continued to outperform the new Quartz 2D for several years, because it was already highly optimized and had less work to do compared to the new Quartz 2D.

The innovative use of the Quartz Compositor engine to mix together images rendered by different technologies allowed all of the applications in Mac OS X to adopt the new Aqua appearance, with drop shadows and and translucency effects that were prominently exposed in early versions of Mac OS X (below).


Mac OS X 10.2 Jaguar: Quartz Extreme

In 2002, Apple released Jaguar with support for Quartz Extreme, which delegated the heavy lifting of compositing work to the graphics card. It describes the layers rendered by QuickDraw or Quartz 2D as texture maps spread across windows and, using OpenGL commands, has the video card itself render the desktop as if individual windows were 3D characters in a video game.

Because consumer video cards are designed for video gaming, this approach rapidly accelerated the graphics overall. However, Quartz Extreme didn't do anything to speed up actual graphics drawing within the context of a window. Apple continued to made incremental improvements to text, vector and bitmap drawing in Mac OS X 10.3 Panther, but it still remained as fast or faster to do drawing in the simpler, more mature QuickDraw.

Mac OS X 10.4 Tiger: Quartz 2D Extreme

In 2005, Apple released Tiger with major enhancements to Quartz 2D drawing. In addition, it introduced the beginnings of Quartz 2D Extreme, which similarly offered the potential to push drawing commands into the video card along with compositing work. However, this hardware acceleration wasn't yet ready for prime time, and graphics card requirements for supporting it were still too steep for many existing Macs. Even so, the new leap in Quartz 2D software performance allowed Apple to officially depreciate QuickDraw in Tiger, signaling that developers should begin their transition to using Quartz for drawing.

Along with improvements to drawing overall, Apple also released Core Image as a plugin architecture for accelerating specific effects to images using the OpenGL Shading Language. Core Image allows for specific hardware-accelerated functions called Image Units to apply stacks of filters and effects upon an image, and takes full advantage of video cards supporting GLSL to do this. A subset of the video hardware that can support Quartz Extreme can support Core Image.

Core Image can be used for color correction, applying color effects, to blur or sharpen, for create lighting effects such as highlight sheen, or to transform or warp images, among other applications.

Tiger also introduced Core Video, which serves as the new plumbing for QuickTime 7. Essentially, Core Video replaced much of the old QuickDraw in QuickTime, and provides a modern pipeline between video creation and video display, allowing for real time, hardware-accelerated transforms and effects. Like Quartz Extreme, Core Video similarly paints video onto an OpenGL surface, enabling the live window resizing during video playback demonstrated in QuickTime 7, as well as the application of live filters and effects on video, similar to Core Image.

Another major enhancement that resulted from the modernization in QuickTime 7 was support for out-of-order video frame compression. Earlier versions of QuickTime all assumed that frames would be delivered in the order they were to be displayed. However, MPEG-2 (used in DVDs) introduced the idea of sending "bidirectional predictive frames" that enabled greater compression at the expense of complexity.

QuickTime was never designed to handle such two-directional compression (described in greater detail in the article Apple TV: Using DVDs and other Video Sources), so QuickTime 7 incorporated new support using a wildly revamped architecture. In the process, Apple could deliver support for the new MPEG-4 H.264, which takes full advantage of bidirectional compression, while still maintaing QuickTime's characteristic frame-by-frame editing features.

Quicktime 7 also incorporated the use of Panther's Core Audio in place of the Classic Mac OS Sound Manager for audio within Quicktime, and introduced the QuickTime Kit (QTKit), an Objective-C Cocoa framework for developing QuickTime applications. Previously, the only interface for QuickTime was C.

What's New in Mac OS X 10.5 Leopard

Quartz 2D Extreme is now referred to in Apple's developer tools (specifically Quartz Debug) as Quartz GL (and sometimes QuartzGL). Applications can now activate hardware-acceleration as requested. This is important because some existing applications would actually be slowed down by Quartz GL if it were turned on system wide by default.

Leopard also introduces new Image Kit features for displaying, browsing, and editing collections of pictures, using the standard Picture Taker Panel (below), and applying Core Image filters. PDF Kit supplies similar tools for working with pages within PDF documents.


It also introduces Core Animation, originally called the Layer Kit on the iPhone as noted in iPhone OS X Architecture: Cocoa Frameworks and Mobile Mac Apps. Core Animation allows developers to map images or video from Quartz, OpenGL and QuickTime to OpenGL layers that can then be flipped, faded, resized, and otherwise animated around in space using OpenGL hardware acceleration, without requiring that developers be experts in low level graphics hardware. Core Animation is also Objective-C only, signaling a continued trend towards the use of Cocoa-based, object-oriented tools for high level development.

QuickTime now supplies full screen playback as a feature independent from the $30 QuickTime Pro upgrade (below), and QuickTime media playback is fully supported in both Cover Flow and Quick Look.


Leopard's OpenGL stack is updated to version 2.1 of the specification, and has been paired with LLVM to allow Apple to rapidly support new video hardware in addition to being optimized for "a dramatic increase in OpenGL performance by offloading CPU-based processing onto another thread which can then run on a separate CPU core feeding the GPU." New Core Image plugins, noted in An Introductory Mac OS X Leopard Review: Address Book and iChat, offer a starting point for taking advantage of the latest graphics hardware. Core Image, Core Animation, and OpenGL also all supply multicore support to take full advantage of new dual core processors.

Resolution Independence was introduced in Tiger as a way for developers to begin moving their applications toward an inevitable future where higher resolution displays increasingly cram so many pixels into the screen that existing icons and widgets become too small to use. In Leopard, support continues with high resolution 512 pixel icons (the original Mac icons were 32 pixels). In Leopard, even the icons have nice looking icons, such as the new desktop icon (below), with its highly detailed Dock and a menu bar with an Apple logo that's larger than the real menu bar's. Compare the legacy icons to the left.


Resolution Independence is mainly held up by the bitmapped graphics commonly used to build interfaces in today's applications. On the iPhone, Apple was able to deliver resolution independence in web pages and documents, allowing users to scale them by any factor and still see sharp, readable text. On the Mac desktop, developers (including Apple) will need to revisit all of their existing controls to get them ready. Apple has announced that this would be important by "2008," without offering more specifics. A new high density sub-compact laptop may be the reason.

Along the lines of getting ready, Apple has included a private Core UI framework in Leopard that builds interface elements from recipes of high resolution bitmap images, as John Siracusa describes in Ars Technica review: Core UI.

Leopard User Interface

Leopard introduces a more cohesive overall appearance than Tiger, while also incorporating new ideas pioneered within consumer applications such as iTunes and concepts first used on the iPhone. The most obvious example is the oversized new flick switch (below), which appears in various places in Leopard after debuting on the iPhone. The Time Machine preferences pane also shows off a new two-toned, indented page effect that appears to be unique to Leopard.


While brushed metal is now gone, there are still two window styles in Leopard: the standard window (below top) and the textured window (below bottom). Both cast a deeper, darker drop shadow when they are the frontmost window. This sets off the foreground window from inactive windows, and creates a more dimensional look to the desktop.



There are also two styles of panels: the standard mini-window panel (below top) and the translucent panel (below bottom) sometimes called a "heads up display." Apple's guidelines specify that developers use the standard panel for most normal applications, and reserve the translucent panel for use in applications that present editable documents in full screen mode, as iPhoto does. These panels also cast a much more limited shadow so they don't obscure the actual document you are working on.



Interface Builder supplies a wider variety of controls, including those that first appeared as unique interface elements in iTunes, Safari, or other Apple applications. Among the examples in the busy window below are NSPathControls from the iTunes Store along the top, NSRuleEditor for defining the rules of Smart Groups in the middle, and various alternative button styles.


The new Preview shows off a variety of Leopard's improvements. It uses the same grouped oval buttons from Tiger Mail, but they've been toned down with a neutral background rather than being light blue. In addition, it uses a new sidebar rather than a drawer, and that sidebar uses the new Leopard Image Kit to draw its icons. The result is that you can resize the sidebar to show multiple columns of icons in wide display, or zoom the preview icons as desired using the slider control however you want (series, below). Icons also support drag and drop reordering (as in the case of PDF pages), and sorting by name, size, or meta data information.




The best news related to changes and enhancements in the Leopard user interface is that despite all the subtle eye candy and animated effects, it is actually faster overall than Tiger because so much hardware acceleration is in use and so many improvements have been made to the underlying system, as noted in Ten Myths of Leopard: 1 Graphics Must Be Slow!.

There are also things that are harder to like. Stacks icons in the Dock look like, well, messy stacks. As items inside change, the Stacks change, which highlights new downloads, but also means that sorting your items will constantly change the display. Other notes on the Leopard user interface were made in the Road to Leopard series:

Road to Mac OS X Leopard: QuickTime, iTunes, and Media Features
System Preferences
Parental Controls and Directory Services
What's new in Mac OS X Leopard Server
Dashboard, Spotlight and the Desktop
Safari 3.0
iCal 3.0
iChat 4.0
Mail 3.0
Time Machine
Dock 1.6
Finder 10.5
Dictionary 2.0
Preview 4.0.

Leopard delivers measurable and obvious advances throughout its graphics and video features that not only improve and consolidate the appearance of existing applications, but also enable the development of more powerful new applications with innovative, animated interfaces. If you haven't, also check out earlier installments of our Leopard review series that followed our Road to Leopard series:

An Introductory Mac OS X Leopard Review: Meet Your New Desktop
An Introductory Mac OS X Leopard Review: Mail and iCal
An Introductory Mac OS X Leopard Review: Address Book and iChat