Woopsi is a Nintendo DS GUI library for rapidly creating user interfaces for homebrew software. Modelled after the AmigaOS windowing system.

Release notes:

Woopsi version 0.99.1 has been released:

http://www.sourceforge.net/projects/woopsi

This version fixes bugs in the slider and scrollbar gadgets.

Fixes:
– Rewrote SliderVertical and SliderHorizontal again to improve accuracy.
– Removed jumpGrip() from all slider gagdets.
– Added setValueWithBitshift() to all slider gadgets.
– Added getMinimumStep() to SliderVertical and SliderHorizontal.
– Removed getValuesPerPixel() from all slider gadgets.

http://forum.gbadev.org/viewtopic.php?t=14332