Please explain the AddArc parameters, e.g. to make a "pie part"

[metal3d]

Hi,
I spent hours making tests and trying to understand the parameters, and the "points" content and I didn't find my way to make a "pie part". Whatever I do, the path becomes a circle.

Using this

	cx, cy := float64(w/2.0), float64(h/2.0)
	r := float64(w / 3.0)
	angle := 45.0
	rot := angle * math.Pi / 180.0

	// find the point on circle of radius r at angle rot
	px := cx + r*math.Cos(rot)
	py := cy + r*math.Sin(rot)

	points := []float64{r, r, angle, 1, 0, px, py}

	stroker.Start(rasterx.ToFixedP(cx, cy))
	//stroker.Line(rasterx.ToFixedP(cx, cy+r))
	stroker.Start(rasterx.ToFixedP(px, py))
	rasterx.AddArc(points, cx, cy, px, py, stroker)
	//stroker.Stop(false)
	//stroker.Line(rasterx.ToFixedP(cx, cy))
	stroker.Stop(false)
	stroker.Draw()

With this:

	stroker.Start(rasterx.ToFixedP(cx, cy))
	stroker.Line(rasterx.ToFixedP(cx, cy+r))
	stroker.Start(rasterx.ToFixedP(px, py))
	rasterx.AddArc(points, cx, cy, px, py, stroker)
	stroker.Line(rasterx.ToFixedP(cx, cy))
	stroker.Stop(false)
	stroker.Draw()

I made several other tests to start the path somewhere else, with no idea of how to make a "pie chart element".

This is the wanted shape:

The goal is to make a pie chart (of course :) ) but (sorry to say this) the code is not well documented... Can you please give a simple example of a pie chart element?