Method Plot

plotter/polygon.go:54–90

Plot draws the polygon, implementing the plot.Plotter interface.

(c draw.Canvas, plt *plot.Plot)

// Plot draws the polygon, implementing the plot.Plotter
// interface.
func (pts *Polygon) Plot(c draw.Canvas, plt *plot.Plot) {
	trX, trY := plt.Transforms(&c)
	ps := make([][]vg.Point, len(pts.XYs))

	for i, ring := range pts.XYs {
		ps[i] = make([]vg.Point, len(ring))
		for j, p := range ring {
			ps[i][j].X = trX(p.X)
			ps[i][j].Y = trY(p.Y)
		}
		ps[i] = c.ClipPolygonXY(ps[i])
	}
	if pts.Color != nil && len(ps) > 0 {
		c.SetColor(pts.Color)
		// allocate enough space for at least 4 path components per ring.
		// 3 is the minimum but 4 is more common.
		pa := make(vg.Path, 0, 4*len(ps))
		for _, ring := range ps {
			if len(ring) == 0 {
				continue
			}
			pa.Move(ring[0])
			for _, p := range ring[1:] {
				pa.Line(p)
			}
			pa.Close()
		}
		c.Fill(pa)
	}

	for _, ring := range ps {
		if len(ring) > 0 && ring[len(ring)-1] != ring[0] {
			ring = append(ring, ring[0])
		}
		c.StrokeLines(pts.LineStyle, c.ClipLinesXY(ring)...)
	}
}

// DataRange returns the minimum and maximum
// x and y values, implementing the plot.DataRanger