Appearance Manager
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In the "classic" Mac OS, the Appearance Manager controlled the overall look of the Mac GUI widgets and supported several themes. The Appearance Manager was originally developed for Apple's failed Copland project, but with the cancellation of this project the system was moved into newer versions of the Mac OS, notably Mac OS 8, Mac OS 9. Mac OS X no longer directly supports the Appearance Manager, which can be considered "dead".
The Appearance Manager was implemented as an abstraction layer between the Control Manager and QuickDraw. Previously, controls made direct QuickDraw calls to draw user interface elements such as buttons, scrollbars, window title bars, etc. With Appearance, these elements were abstracted into a series of APIs that would draw the item as a distinct entity on behalf of the client code, thus relieving the Control Manager of the task. This extra level of indirection allowed the system to support the concept of switchable themes, since client code would simply request the image of an interface element (a button or scroll bar, for example) and draw its appearance. The Appearance Manager remains as part of Carbon (API), but switchable themes are no longer supported in Mac OS X.
The primary Appearance Manager theme was Platinum, which was intended to be the primary GUI for Copland. Platinum retained many of the shapes from previous operating systems, like the shapes of window control widgets and of buttons. However, various shades of grey were used extensively throughout the interface, as opposed to previous themes that were mostly black and white. Also, gradients of customizable colors were used for progress bars, and the colors of scroll thumbs could also be customized. The theme featured Charcoal as new default interface font.
Apple also widely demonstrated two other themes, Hi-Tech and Gizmo. Hi-Tech was based on a shades-of-black color scheme that made the interface look like a piece of stereo equipment. Gizmo was a "kids" interface, using lots of bright colors and "wiggly" interface elements. Both changed only a subset of the overall GUI, leaving other elements in their Platinum defaults. A fourth theme was later introduced, Drawing Board, developed at Apple Japan. This theme used elements that made the interface look like it had been drawn in pencil on a drafting-board, including small "pencil marks" around the windows, a barely-visible grid on the desktop, and "squarish" elements with low-contrast.
Similar UI-customization products had existed on Mac OS for some time, and many considered the Appearance Manager to be a direct copy of [Kaleidoscope], a shareware program that was similar in almost every way and supported schemes, which were essentially identical to Apple's themes. Apple apparently intended to offer a tool that would automatically convert Kaleidoscope schemes to Apple's theme format, but this tool went unreleased when theme support was later dropped. The creation of the Appearance Manager led to some bad blood in the Mac community, many of whom felt Apple was "beating up" on Kaleidoscope when they could have simply included it in the system. The anger was even sharper when Apple then cancelled the project outright, leaving Kaleidoscope unable to run on the new system.
The Platinum theme was also used on several versions of OpenStep while it was in the process of being turned into Mac OS X. In particular, both Rhapsody and, the final version of it, which was called Mac OS X Server 1.0, and also Mac OS X Developer Previews up to DR2 used a Platinum-based UI. In this case the effects were purely cosmetic; the Appearance Manager was not used, or supported, on either system.
OS X replaced Platinum, and the Appearance Manager, with a new interface style named Aqua. Some Platinum windows may still be seen in OS X, however: applications for Mac OS 9 running in Mac OS X run in the classic compatibility layer, which is effectively a stripped-down version of Mac OS 9 running as an application.
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