add polyline to drawing example

examples/drawing/drawing.go

@@ -6,6 +6,7 @@ package main
 
 import (
 	"log"
+	"math"
 )
 
 import (
@@ -88,6 +89,16 @@ func (mw *MyMainWindow) drawStuff(canvas *walk.Canvas, updateBounds walk.Rectang
 		return err
 	}
 
+	points := make([]walk.Point, 10)
+	dx := bounds.Width / (len(points) - 1)
+	for i := range points {
+		points[i].X = i * dx
+		points[i].Y = int(float64(bounds.Height) / math.Pow(float64(bounds.Width/2), 2) * math.Pow(float64(i*dx-bounds.Width/2), 2))
+	}
+	if err := canvas.DrawPolyline(linesPen, points); err != nil {
+		return err
+	}
+
 	bmpSize := bmp.Size()
 	if err := canvas.DrawImage(bmp, walk.Point{(bounds.Width - bmpSize.Width) / 2, (bounds.Height - bmpSize.Height) / 2}); err != nil {
 		return err