Disclosure bars are an alternative to disclosure triangles and the blue buttons currently used by Aqua. I originally got the idea in October 2000, while trying to solve some problems with the Dock.
The disclosure bar has two arrows rather than one, for increased discoverability ("lookie here!") as well as to add uniqueness since single-triangle arrows are already overloaded in the UI.
The arrows have the same orientation as existing Aqua blue buttons, but since the disclosure bar actually moves in the direction of its arrows (unlike Apple's existing buttons which only flip upside down), the arrow orientation actually makes sense.
(Hmm... should the arrows be centered in the bar, or kept on the left where a disclosure triangle would've been under traditional Mac OS?)
Disclosure bar, collapsed:
Disclosure bar, expanded:
Inspired by a message from Kevin Grant on the HI Developers list.
Changes on 7/26/2001 after reading a message from Jon Thompson: Added Lucida 9 descriptive text to the bar, and shading to the disclosed area.
-Walter
