Propagating changes from pie to wedges

Chart must update wedges when its size or submorphs list changes:

layoutInPlace = (
	resend.layoutInPlace.
	wedges do: [| :w |
		 w center: 0@0.
		"+2 is workaround for display bug"
		 w radius: radius + 2.
	].
	updateWedges.
	self
).

Propagating changes from pie to wedges

We would like to pie chart to lay itself out whenever a pie wedge is added or removed and when the pie chart is resized. All of these operations cause the message layoutInPlace to be sent to the pie chart. Thus, we can get the desired behavior just by extending this method:

	layoutInPlace = (
		resend.layoutInPlace.
		wedges do: [| :w |
			 w center: 0@0.
			 w radius: radius + 2. "+2 is workaround for display bug"
		].
		updateWedges.
		self
	).

Note that the method sets the center of each wedge to 0@0, the center of the pie chart itself and the origin of the pie chart's coordinate system. The radius of each wedge is made a bit larger than the radius of the pie chart itself so that the wedges hide the underlying circle completely. (After the next step, try changing this to make the radius of the wedges smaller instead of larger. Try resizing a pie chart. What happens?)

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