Zinc is a Tk widget developed with Perl/Tk, Tcl/Tk and Python/Tk bindings.
Graphical items can be manipulated, and bindings can be associated with them to implement interaction behaviors. But unlike the canvas, zinc can structure the items in a hierarchy, and has support for affine 2D transforms.
Clipping can be set for sub-trees of the item hierarchy and the item set is quite more powerful, including field-specific items for Air Traffic systems.
Zinc is fast enough to allow the implementation of 2k2k radar displays with smooth animations. It is structured enough to allow the implementation of direct manipulation desktop GUIs.