Appearance Manager

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 bundled with Mac OS 8 and 9. However, the Appearance Manager is also available free as part of a downloadable SDK for System 7. The current version of the operating system, macOS, no longer directly supports the Appearance Manager.

The Appearance Manager is 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 the Appearance Manager, these elements are abstracted into a series of APIs that 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 allows the system to support the concept of switchable "themes", since client code simply requests the image of an interface element (a button or scroll bar, for example) and draws its appearance. Kaleidoscope, a 3rd party application, was the first to utilize this functionality with via "scheme" files, followed by an updated Appearance Control Panel in Mac OS 8.5, which acted similarly via "theme" files. Schemes and themes are similar in concept, but they are not internally compatible. The Appearance Manager remains as part of Carbon, but switchable themes are no longer supported in Mac OS X.

The default look and feel of the Appearance Manager in the Mac OS 8 - 9 era is Apple Platinum, which was intended to be the primary GUI for Copland. Platinum retains many of the shapes and positions of elements from System 7 and earlier, like window control widgets and buttons and while Charcoal is the default system font, Chicago was available via a menu option. However, various shades of grey are used extensively throughout the interface, as opposed to previous interfaces which are mostly monochrome black and white. Apple Platinum is not a theme, however. It is actually embedded into the Appearance Manager. The Appearance Control Panel has the ability to attach a theme to the Appearance Manager. There is an Apple Platinum file in the themes folder in the System Folder which acts as a stub, but no functional theme elements are embedded into it. Customizable palettes ('clut' resources) are used for progress bars, scroll thumbs, slider tabs and menu selections in Apple Platinum and this unique option is not available to real themes. The Appearance Control Panel uses the type code 'pltn' to identify if a file should act like a palette modification stub to Apple Platinum and the type code 'thme' to identify if a file should act like an Appearance Theme. An important distinction is that the Appearance Control Panel implements themes into the Appearance Manager. Kaleidoscope is a third party software that implements schemes into the Appearance Manager. Kaleidoscope is not a substitute for the Appearance Manager. It is a substitute for the Appearance Control Panel.

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