feat: support subtext for title

axis.go

@@ -256,7 +256,7 @@ func (a *axis) axisTick(opt *axisOption) {
 	}
 	labelMargin := style.GetLabelMargin()
 	tickShow := true
-	if style.TickShow != nil && !*style.TickShow {
+	if isFalse(style.TickShow) {
 		tickShow = false
 	}
 
@@ -364,7 +364,7 @@ func (a *axis) measureAxis() int {
 
 func (a *axis) Render() {
 	style := a.style
-	if style.Show != nil && !*style.Show {
+	if isFalse(style.Show) {
 		return
 	}
 	textMaxWidth, textMaxHeight := a.axisMeasureTextMaxWidthHeight()
@@ -373,7 +373,7 @@ func (a *axis) Render() {
 		textMaxHeight: textMaxHeight,
 		boundaryGap:   true,
 	}
-	if style.BoundaryGap != nil && !*style.BoundaryGap {
+	if isFalse(style.BoundaryGap) {
 		opt.boundaryGap = false
 	}
 

chart.go

@@ -72,11 +72,14 @@ type ChartOption struct {
 
 func (o *ChartOption) FillDefault(theme string) {
 	t := NewTheme(theme)
-	f, _ := chart.GetDefaultFont()
+	if o.Font == nil {
-	o.Font = f
+		o.Font, _ = chart.GetDefaultFont()
+	}
 	if o.BackgroundColor.IsZero() {
 		o.BackgroundColor = t.GetBackgroundColor()
 	}
+
+	// 标题的默认值
 	if o.Title.Style.FontColor.IsZero() {
 		o.Title.Style.FontColor = t.GetTextColor()
 	}
@@ -84,7 +87,7 @@ func (o *ChartOption) FillDefault(theme string) {
 		o.Title.Style.FontSize = 14
 	}
 	if o.Title.Style.Font == nil {
-		o.Title.Style.Font = f
+		o.Title.Style.Font = o.Font
 	}
 	if o.Title.Style.Padding.IsZero() {
 		o.Title.Style.Padding = chart.Box{
@@ -94,12 +97,23 @@ func (o *ChartOption) FillDefault(theme string) {
 			Bottom: 5,
 		}
 	}
+	// 副标题
+	if o.Title.SubtextStyle.FontColor.IsZero() {
+		o.Title.SubtextStyle.FontColor = o.Title.Style.FontColor.WithAlpha(180)
+	}
+	if o.Title.SubtextStyle.FontSize == 0 {
+		o.Title.SubtextStyle.FontSize = 10
+	}
+	if o.Title.SubtextStyle.Font == nil {
+		o.Title.SubtextStyle.Font = o.Font
+	}
+
 	o.Legend.Theme = t
 	if o.Legend.Style.FontSize == 0 {
-		o.Legend.Style.FontSize =10 
+		o.Legend.Style.FontSize = 10
 	}
 	if o.Legend.Style.Font == nil {
-		o.Legend.Style.Font = f
+		o.Legend.Style.Font = o.Font
 	}
 	if o.Legend.Style.FontColor.IsZero() {
 		o.Legend.Style.FontColor = t.GetTextColor()

title.go

@@ -30,39 +30,71 @@ import (
 )
 
 type TitleOption struct {
-	Text  string
+	Text         string
-	Style chart.Style
+	Subtext      string
-	Left  string
+	Style        chart.Style
-	Top   string
+	SubtextStyle chart.Style
+	Left         string
+	Top          string
 }
 type titleMeasureOption struct {
 	width  int
 	height int
 	text   string
+	style  chart.Style
 }
 
-func drawTitle(d *Draw, opt *TitleOption) (chart.Box, error) {
+func splitTitleText(text string) []string {
+	arr := strings.Split(text, "\n")
+	result := make([]string, 0)
+	for _, v := range arr {
+		v = strings.TrimSpace(v)
+		if v == "" {
+			continue
+		}
+		result = append(result, v)
+	}
+	return result
+}
+
+func drawTitle(p *Draw, opt *TitleOption) (chart.Box, error) {
 	if len(opt.Text) == 0 {
 		return chart.BoxZero, nil
 	}
 
 	padding := opt.Style.Padding
-	titleDraw, err := NewDraw(DrawOption{
+	d, err := NewDraw(DrawOption{
-		Parent: d,
+		Parent: p,
 	}, PaddingOption(padding))
 	if err != nil {
 		return chart.BoxZero, err
 	}
 
-	r := titleDraw.Render
+	r := d.Render
-	opt.Style.GetTextOptions().WriteToRenderer(r)
+
-	arr := strings.Split(opt.Text, "\n")
+	measureOptions := make([]titleMeasureOption, 0)
+
+	// 主标题
+	for _, v := range splitTitleText(opt.Text) {
+		measureOptions = append(measureOptions, titleMeasureOption{
+			text:  v,
+			style: opt.Style.GetTextOptions(),
+		})
+	}
+	// 副标题
+	for _, v := range splitTitleText(opt.Subtext) {
+		measureOptions = append(measureOptions, titleMeasureOption{
+			text:  v,
+			style: opt.SubtextStyle.GetTextOptions(),
+		})
+	}
+
 	textMaxWidth := 0
 	textMaxHeight := 0
 	width := 0
-	measureOptions := make([]titleMeasureOption, len(arr))
+	for index, item := range measureOptions {
-	for index, str := range arr {
+		item.style.WriteTextOptionsToRenderer(r)
-		textBox := r.MeasureText(str)
+		textBox := r.MeasureText(item.text)
 
 		w := textBox.Width()
 		h := textBox.Height()
@@ -72,15 +104,12 @@ func drawTitle(d *Draw, opt *TitleOption) (chart.Box, error) {
 		if h > textMaxHeight {
 			textMaxHeight = h
 		}
-		measureOptions[index] = titleMeasureOption{
+		measureOptions[index].height = h
-			text:   str,
+		measureOptions[index].width = w
-			width:  w,
-			height: h,
-		}
 	}
 	width = textMaxWidth
 	titleX := 0
-	b := titleDraw.Box
+	b := d.Box
 	switch opt.Left {
 	case PositionRight:
 		titleX = b.Width() - textMaxWidth
@@ -102,9 +131,10 @@ func drawTitle(d *Draw, opt *TitleOption) (chart.Box, error) {
 		titleY += value
 	}
 	for _, item := range measureOptions {
+		item.style.WriteTextOptionsToRenderer(r)
 		x := titleX + (textMaxWidth-item.width)>>1
-		titleDraw.text(item.text, x, titleY)
+		d.text(item.text, x, titleY)
-		titleY += textMaxHeight
+		titleY += item.height
 	}
 	height := titleY + padding.Top + padding.Bottom
 	box := padding.Clone()

util.go

@@ -106,3 +106,10 @@ func convertPercent(value string) float64 {
 	}
 	return float64(v) / 100
 }
+
+func isFalse(flag *bool) bool {
+	if flag != nil && !*flag {
+		return true
+	}
+	return false
+}

xaxis.go

@@ -56,7 +56,7 @@ func drawXAxis(p *Draw, opt *XAxisOption) (int, *Range, error) {
 
 	boundary := true
 	max := float64(len(opt.Data))
-	if opt.BoundaryGap != nil && !*opt.BoundaryGap {
+	if isFalse(opt.BoundaryGap) {
 		boundary = false
 		max--
 	}