Migrating the original QuasimondoLibs to Javascript. Mostly 2D Geometry.
For the drawing part and some of the UI elements Qlib uses EaselJS - for pure geometric operation it is not required though.
A big part of the intersection algorithms and their helper methods (most of which I still have to port from my ActionScript library) were originally taken from Kevin Lindsey: http://www.kevlindev.com/gui/math/intersection/index.htm