systemdict begin

/KnobItem Item  [
	/KnobMax	1	def
	/KnobMin	10	def
	/KnobInc	.00001	def
	/KnobWidth	75	def
	/KnobHeight	75	def
	/KnobRadis	25	def
	/KnobFrame	3	def
	/KnobValue	0	def
] classbegin
	/new { % min max initvalue notifyproc parent width hieght -> item
		/new super send begin
			/NotifyUser exch cvx def
			/ItemValue exch def
			/KnobMax exch def
			/KnobMin exch def
			currentdict
		end
	} def
	/KnobToValue { % (0...1) to value
		KnobMax KnobMin sub mul KnobMin add 
		1 KnobInc div mul round
		1 KnobInc div div
	} def
	/ValueToKnob { % value to (0...1)
			KnobMin sub KnobMax KnobMin sub div
	} def
	/PaintItem {
		0 0 ItemHeight ItemWidth ovalpath
		ItemFillColor setcolor fill
		KnobFrame 0 0 ItemHeight ItemWidth ovalframe
		ItemBorderColor setcolor eofill
		gsave 
		ItemHeight 2 div ItemWidth 2 div translate
		ItemValue ItemBorderColor PaintKnobValue
		grestore
	} def
	/SetKnobValue {
		gsave
		/ItemValue 
		CurrentEvent /XLocation get neg
		CurrentEvent /YLocation get neg
		atan 360 div KnobToValue store
		grestore
	} def
	/PaintKnobValue {
		setcolor 
		/ItemPaintedValue exch store
		gsave
		-270 rotate -1 1 scale
		0 0 moveto
		0 0 KnobRadis ItemPaintedValue ValueToKnob
		360 mul dup arc stroke
		0 0 KnobRadis 0 360 arc stroke
		grestore
		0 0 moveto ItemPaintedValue 16 string cvs cshow
	} def
	/ClientDown {
		gsave
		ItemHeight 2 div ItemWidth 2 div translate
		SetKnobValue
		ItemPaintedValue ItemFillColor PaintKnobValue
		ItemValue ItemBorderColor PaintKnobValue
		grestore
	} def
	/ClientDrag { ClientDown NotifyUser } def
	/ClientUp { ClientDown NotifyUser StopItem } def
classend def

end % systemdict