* Currently, the usleep() in the main event loop causes the knob to be
(often) redrawn slightly behind schedule after receiving an Expose event.
I'm not sure how this behavior may be improved without tighter polling.
Suggestions will be appreciated.

* Configuration via libPropList.

* Add a right-click menu that allows the knob's associated source to be
selected. This should be doable either with WINGs, or with menu.[hc] from
the Window Maker source distribution.

* Alternative knob graphics? (Contributions are welcome!)