feat: support padding for legend

examples/line_chart/main.go

@@ -89,7 +89,13 @@ func main() {
 			"Video Ads",
 			"Direct",
 			"Search Engine",
-		}, charts.PositionCenter),
+		}, "50"),
+		func(opt *charts.ChartOption) {
+			opt.Legend.Padding = charts.Box{
+				Top:    5,
+				Bottom: 10,
+			}
+		},
 	)
 
 	if err != nil {

legend.go

@@ -59,6 +59,8 @@ type LegendOption struct {
 	FontColor Color
 	// The flag for show legend, set this to *false will hide legend
 	Show *bool
+	// The padding of legend
+	Padding Box
 }
 
 // NewLegendOption returns a legend option
@@ -111,9 +113,11 @@ func (l *legendPainter) Render() (Box, error) {
 	if opt.Left == "" {
 		opt.Left = PositionCenter
 	}
-	p := l.p.Child(PainterPaddingOption(Box{
+	padding := opt.Padding
-		Top: 5,
+	if padding.IsZero() {
-	}))
+		padding.Top = 5
+	}
+	p := l.p.Child(PainterPaddingOption(padding))
 	p.SetTextStyle(Style{
 		FontSize:  opt.FontSize,
 		FontColor: opt.FontColor,
@@ -242,6 +246,6 @@ func (l *legendPainter) Render() (Box, error) {
 
 	return Box{
 		Right:  width,
-		Bottom: height,
+		Bottom: height + padding.Bottom + padding.Top,
 	}, nil
 }