A source list is an area of window set off by a movable pane splitter to provide users a way to navigate data. Use a source list when the data presented in it is a primary means of navigating within the application, as in iTunes or the Finder. Users select objects in the source list that they act on in the main part of the window.
And source lists are apparently the reason that the Panther Finder’s windows are (sometimes) metal:
You can use a brushed metal window if your application:
- Provides an interface for a digital peripheral, such as a camera, or an interface for managing data shared with digital peripherals—iPhoto or iSync, for example.
- Strives to re-create a familiar physical device—Calculator or DVD Player, for example.
- Provides a source list to navigate information—for example, iTunes or the Finder.
Don’t use the brushed metal look indiscriminately. Although it works well for some types of applications, some applications appear too heavy when using this look. For example, it works well for the iSync application window, but it does not work very well for the TextEdit document window.
Of course, by this logic, Xcode and System Profiler windows would be metal, Safari browser windows would change to metal only when you viewed the bookmarks, the Safari Downloads window wouldn’t be metal, and on and on. It’s not worth thinking about this too deeply, because the brushed metal guidelines are more a retroactive justification for Apple’s design fetishes than a set of sound principles for designing usable, consistent interfaces.
Also note that they’re now called “brushed metal windows” rather than “textured windows.” Hopefully this is meant as a reassurance that the texture won’t be changed to Blue Dalmation in Mac OS X 10.4.