feat: support rect and legend line point render

examples/painter/main.go

@@ -373,6 +373,42 @@ func main() {
 		},
 	})
 
+	// rect
+	top += 30
+	p.Child(
+		charts.PainterBoxOption(charts.Box{
+			Top:    top,
+			Left:   1,
+			Right:  200,
+			Bottom: top + 50,
+		}),
+	).OverrideDrawingStyle(charts.Style{
+		StrokeColor: drawing.ColorBlack,
+		FillColor:   drawing.ColorBlack,
+	}).Rect(charts.Box{
+		Left:   10,
+		Top:    0,
+		Right:  110,
+		Bottom: 20,
+	})
+	// legend line dot
+	p.Child(
+		charts.PainterBoxOption(charts.Box{
+			Top:    top,
+			Left:   200,
+			Right:  p.Width() - 1,
+			Bottom: top + 50,
+		}),
+	).OverrideDrawingStyle(charts.Style{
+		StrokeColor: drawing.ColorBlack,
+		FillColor:   drawing.ColorBlack,
+	}).LegendLineDot(charts.Box{
+		Left:   10,
+		Top:    0,
+		Right:  50,
+		Bottom: 20,
+	})
+
 	buf, err := p.Bytes()
 	if err != nil {
 		panic(err)

painter.go

@@ -687,3 +687,29 @@ func (p *Painter) Dots(points []Point) *Painter {
 	p.FillStroke()
 	return p
 }
+
+func (p *Painter) Rect(box Box) *Painter {
+	p.MoveTo(box.Left, box.Top)
+	p.LineTo(box.Right, box.Top)
+	p.LineTo(box.Right, box.Bottom)
+	p.LineTo(box.Left, box.Bottom)
+	p.LineTo(box.Left, box.Top)
+	p.FillStroke()
+	return p
+}
+
+func (p *Painter) LegendLineDot(box Box) *Painter {
+	width := box.Width()
+	height := box.Height()
+	strokeWidth := 3
+	dotHeight := 5
+
+	p.render.SetStrokeWidth(float64(strokeWidth))
+	center := (height - strokeWidth) >> 1
+	p.MoveTo(box.Left, box.Top+center)
+	p.LineTo(box.Right, box.Top+center)
+	p.Stroke()
+	p.Circle(float64(dotHeight), box.Left+width>>1, center)
+	p.FillStroke()
+	return p
+}