
I think this widget could have been designed better.
A dial is a handy thing, but the interaction with this particular
widget requires two changes in mouse direction in order to drag
from minimum to maximum values. Ideally I would think a dial should
be controlled with a single drag: Up or Right to increase, and
Down or Left to decrease. The only way I know how to accomplish
a smooth drag is by setting angles(90,270), as shown with the fill
dial, but then you have visual use of only half the dial. Say liver.

This dial could be useful as a read-only output, though, such as
a visual representation of a pressure gauge.
