func newBox(cvs *canvas.Canvas, r draw.Rectangle) *box { var b box red := image.Uniform{image.Red} b.n = canvas.NewLine(red, r.Min, draw.Pt(r.Max.X, r.Min.Y), 1) b.e = canvas.NewLine(red, draw.Pt(r.Max.X, r.Min.Y), r.Max, 1) b.s = canvas.NewLine(red, r.Max, draw.Pt(r.Min.X, r.Max.Y), 1) b.w = canvas.NewLine(red, draw.Pt(r.Min.X, r.Max.Y), r.Min, 1) cvs.AddItem(b.n) cvs.AddItem(b.e) cvs.AddItem(b.s) cvs.AddItem(b.w) return &b }