The SMDoubleSlider code consists of two Xcode project files, the source code itself, and this documentation. The source code is broken into four parts, but is all included in the Xcode projects.
The SMDoubleSlider code and the related files in this distribution are open source. They are not public domain; they are copyright © 2003-2010 Snowmint Creative Solutions LLC. They are governed by an open source license, which is intended to allow others reasonable freedom in using and modifying the sources, while allowing Snowmint Creative Solutions LLC to retain some control over the project. If you intend to use or modify the source code for this project, you must read and follow the license. The license should be included in this distribution; if not, you can find it at <http://developer.snowmintcs.com/OpenLicense.html>.
This framework provides both NSSlider and NSSliderCell subclasses which have two knobs instead of one. The user can slide either of the knobs along, with the limitation that the lower knob is always less than the higher knob. The SMDoubleSlider class also supports tabbing through both knobs if keyboard access is turned on.
Note: The SMDoubleSliderCell does not handle the tabbing through both knobs. Therefore, if a double slider is placed in a matrix or table column, the user tabbing through will only be able to adjust one of the knobs. This seems to be a general limitation of the NSCell class construction.