Assuming the arc is defined with respect to an ellipse with major axis A
unfortunately I did not express myself very clearly in that comment. My comment made it sound as though the problem at hand is conversion of an arc to a Bezier. But of course that is not true, the problem at hand is the conversion of an arbitrary sbasis curve to a Bezier without having any knowledge at all of what the original function was that led to the sbasis in the first place. That function may have been an elliptical arc or it may have been something else like a Hypotrochoid, not very likely but still conceivable. So one needs a measure of size that does not presuppose anything, and it needs to behave well in the case that one dimension disappears entirely, like when you convert a square to a straight line. One possibility might be to borrow an idea from the filter code where a blur % is converted to an absolute size in pixels. The way this is done, roughly, is to first get the bbox, then calculate the perimeter of the bbox, then divide it by 4, and then think of that length as being the length of a side of a square which represents the "normalized" object. This is a bit "quick and dirty" but it works well for an object that actually is square and it does not behave pathologically in the case where one dimension goes to zero. It might serve as a measure of size so that the absolute tolerance could be converted into a dimensionless tolerance.
Alvin
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