Add BarChart RoundedBarCaps option

axis.go

@@ -67,7 +67,7 @@ type AxisOption struct {
 
 func (a *axisPainter) Render() (Box, error) {
 	opt := a.opt
-	if isFalse(opt.Show) {
+	if flagIs(false, opt.Show) {
 		return BoxZero, nil
 	}
 	top := a.p
@@ -99,7 +99,7 @@ func (a *axisPainter) Render() (Box, error) {
 	}
 	dataCount := len(opt.Data)
 
-	centerLabels := !isFalse(opt.BoundaryGap)
+	centerLabels := !flagIs(false, opt.BoundaryGap)
 	isVertical := opt.Position == PositionLeft || opt.Position == PositionRight
 
 	// if less than zero, it means not processing

bar_chart.go

@@ -39,6 +39,8 @@ type BarChartOption struct {
 	Legend LegendOption
 	// BarWidth specifies the width of each bar.
 	BarWidth int
+	// RoundedBarCaps set to `true` to produce a bar graph where the bars have rounded tops.
+	RoundedBarCaps *bool
 }
 
 func (b *barChart) render(result *defaultRenderResult, seriesList SeriesList) (Box, error) {
@@ -115,7 +117,28 @@ func (b *barChart) render(result *defaultRenderResult, seriesList SeriesList) (B
 
 			seriesPainter.OverrideDrawingStyle(Style{
 				FillColor: fillColor,
-			}).Rect(chart.Box{
+			})
+			if flagIs(true, opt.RoundedBarCaps) {
+				radius := .5 * float64(barWidth)
+				top += int(radius)
+				seriesPainter.Circle(radius, x+int(radius), top)
+				if top+int(radius) > barMaxHeight {
+					// hide the part of the circle below the axis line
+					seriesPainter.OverrideDrawingStyle(Style{
+						FillColor: opt.Theme.GetBackgroundColor(),
+					}).Rect(chart.Box{
+						Top:    barMaxHeight,
+						Left:   x,
+						Right:  x + barWidth,
+						Bottom: top + int(radius),
+					})
+					seriesPainter.OverrideDrawingStyle(Style{
+						FillColor: fillColor,
+					})
+					top = barMaxHeight
+				}
+			}
+			seriesPainter.Rect(chart.Box{
 				Top:    top,
 				Left:   x,
 				Right:  x + barWidth,

legend.go

@@ -74,8 +74,7 @@ func NewLegendPainter(p *Painter, opt LegendOption) *legendPainter {
 
 func (l *legendPainter) Render() (Box, error) {
 	opt := l.opt
-	if opt.IsEmpty() ||
-		isFalse(opt.Show) {
+	if opt.IsEmpty() || flagIs(false, opt.Show) {
 		return BoxZero, nil
 	}
 

line_chart.go

@@ -54,7 +54,7 @@ func (l *lineChart) render(result *defaultRenderResult, seriesList SeriesList) (
 	opt := l.opt
 	seriesPainter := result.seriesPainter
 
-	boundaryGap := !isFalse(opt.XAxis.BoundaryGap)
+	boundaryGap := !flagIs(false, opt.XAxis.BoundaryGap)
 	xDivideCount := len(opt.XAxis.Data)
 	if boundaryGap && xDivideCount > 1 && seriesPainter.Width()/xDivideCount <= 10 {
 		// boundary gap would be so small it's visually better to disable the line spacing adjustment and just keep
@@ -164,7 +164,7 @@ func (l *lineChart) render(result *defaultRenderResult, seriesList SeriesList) (
 		}
 		drawingStyle.StrokeWidth = 1
 		seriesPainter.SetDrawingStyle(drawingStyle)
-		if !isFalse(opt.SymbolShow) {
+		if !flagIs(false, opt.SymbolShow) {
 			seriesPainter.Dots(points)
 		}
 		markPointPainter.Add(markPointRenderOption{

title.go

@@ -69,7 +69,7 @@ func NewTitlePainter(p *Painter, opt TitleOption) *titlePainter {
 func (t *titlePainter) Render() (Box, error) {
 	opt := t.opt
 	p := t.p
-	if isFalse(opt.Show) {
+	if flagIs(false, opt.Show) {
 		return BoxZero, nil
 	}
 

util.go

@@ -30,11 +30,12 @@ func FloatPointer(f float64) *float64 {
 	return &f
 }
 
-func isFalse(flag *bool) bool {
-	if flag != nil && !*flag {
-		return true
+// flagIs returns true if the flag is not-nil and matches the comparison argument.
+func flagIs(is bool, flag *bool) bool {
+	if flag == nil {
+		return false
 	}
-	return false
+	return *flag == is
 }
 
 func containsInt(values []int, value int) bool {