Minor ChartOption changes

This changes the `parent` field to be internal only, specified only when `Children` are defined by the user.
There are other code simplifications are the OptionFunc usage was reviewed, but no functional changes.

chart_option.go

@@ -1,6 +1,7 @@
 package charts
 
 import (
+	"fmt"
 	"sort"
 
 	"github.com/golang/freetype/truetype"
@@ -29,8 +30,7 @@ type ChartOption struct {
 	// Font is the font to use for rendering the chart.
 	Font *truetype.Font
 	// Box specifies the canvas box for the chart.
-	Box    Box
-	Parent *Painter
+	Box Box
 	// SeriesList provides the data series.
 	SeriesList SeriesList
 	// RadarIndicators are radar indicator list for radar charts
@@ -47,8 +47,9 @@ type ChartOption struct {
 	BarWidth int
 	// BarHeight is the height of the bars for horizontal bar charts.
 	BarHeight int
-	// Children are child charts to pull options from.
+	// Children are child charts to render together.
 	Children []ChartOption
+	parent   *Painter
 	// ValueFormatter to format numeric values into labels.
 	ValueFormatter ValueFormatter
 }
@@ -227,35 +228,36 @@ func MarkPointOptionFunc(seriesIndex int, markPointTypes ...string) OptionFunc {
 	}
 }
 
-func (o *ChartOption) fillDefault() {
+func (o *ChartOption) fillDefault() error {
+	o.Width = getDefaultInt(o.Width, defaultChartWidth)
+	o.Height = getDefaultInt(o.Height, defaultChartHeight)
+
 	yaxisCount := 1
 	for _, series := range o.SeriesList {
-		if series.YAxisIndex >= yaxisCount {
+		if series.YAxisIndex == 1 {
 			yaxisCount++
+			break
+		} else if series.YAxisIndex > 1 {
+			return fmt.Errorf("series '%s' specified invalid y-axis index: %v", series.Name, series.YAxisIndex)
 		}
 	}
-	o.Width = getDefaultInt(o.Width, defaultChartWidth)
-	o.Height = getDefaultInt(o.Height, defaultChartHeight)
-
-	yAxisOptions := make([]YAxisOption, yaxisCount)
-	copy(yAxisOptions, o.YAxis)
-	o.YAxis = yAxisOptions
+	if len(o.YAxis) < yaxisCount {
+		yAxisOptions := make([]YAxisOption, yaxisCount)
+		copy(yAxisOptions, o.YAxis)
+		o.YAxis = yAxisOptions
+	}
 	// TODO - this is a hack, we need to update the yaxis based on the markpoint state
 	// TODO - but can't do this earlier due to needing the axis initialized
 	// TODO - we should reconsider the API for configuration
-	hasMarkpoint := false
 	for _, sl := range o.SeriesList {
-		if len(sl.MarkPoint.Data) > 0 {
-			hasMarkpoint = true
-			break
-		}
-	}
-	if hasMarkpoint {
-		for i := range o.YAxis {
-			if o.YAxis[i].RangeValuePaddingScale == nil {
-				defaultPadding := 2.5 // default a larger padding to give space for the mark point
-				o.YAxis[i].RangeValuePaddingScale = &defaultPadding
+		if len(sl.MarkPoint.Data) > 0 { // if graph has markpoint
+			// adjust padding scale to give space for mark point (if not specified by user)
+			for i := range o.YAxis {
+				if o.YAxis[i].RangeValuePaddingScale == nil {
+					o.YAxis[i].RangeValuePaddingScale = FloatPointer(2.5)
+				}
 			}
+			break
 		}
 	}
 
@@ -265,6 +267,7 @@ func (o *ChartOption) fillDefault() {
 	if o.Theme == nil {
 		o.Theme = GetDefaultTheme()
 	}
+	fillThemeDefaults(o.Theme, &o.Title, &o.Legend, &o.XAxis)
 
 	if o.Padding.IsZero() {
 		o.Padding = Box{
@@ -280,8 +283,7 @@ func (o *ChartOption) fillDefault() {
 	} else {
 		seriesCount := len(o.SeriesList)
 		for index, name := range o.Legend.Data {
-			if index < seriesCount &&
-				len(o.SeriesList[index].Name) == 0 {
+			if index < seriesCount && len(o.SeriesList[index].Name) == 0 {
 				o.SeriesList[index].Name = name
 			}
 		}
@@ -294,29 +296,39 @@ func (o *ChartOption) fillDefault() {
 			return nameIndexDict[o.SeriesList[i].Name] < nameIndexDict[o.SeriesList[j].Name]
 		})
 	}
+	return nil
+}
+
+func fillThemeDefaults(defaultTheme ColorPalette, title *TitleOption, legend *LegendOption, xaxis *XAxisOption) {
+	if title.Theme == nil {
+		title.Theme = defaultTheme
+	}
+	if legend.Theme == nil {
+		legend.Theme = defaultTheme
+	}
+	if xaxis.Theme == nil {
+		xaxis.Theme = defaultTheme
+	}
 }
 
 // LineRender line chart render
 func LineRender(values [][]float64, opts ...OptionFunc) (*Painter, error) {
-	seriesList := NewSeriesListDataFromValues(values, ChartTypeLine)
 	return Render(ChartOption{
-		SeriesList: seriesList,
+		SeriesList: NewSeriesListDataFromValues(values, ChartTypeLine),
 	}, opts...)
 }
 
 // BarRender bar chart render
 func BarRender(values [][]float64, opts ...OptionFunc) (*Painter, error) {
-	seriesList := NewSeriesListDataFromValues(values, ChartTypeBar)
 	return Render(ChartOption{
-		SeriesList: seriesList,
+		SeriesList: NewSeriesListDataFromValues(values, ChartTypeBar),
 	}, opts...)
 }
 
 // HorizontalBarRender horizontal bar chart render
 func HorizontalBarRender(values [][]float64, opts ...OptionFunc) (*Painter, error) {
-	seriesList := NewSeriesListDataFromValues(values, ChartTypeHorizontalBar)
 	return Render(ChartOption{
-		SeriesList: seriesList,
+		SeriesList: NewSeriesListDataFromValues(values, ChartTypeHorizontalBar),
 	}, opts...)
 }
 
@@ -329,17 +341,15 @@ func PieRender(values []float64, opts ...OptionFunc) (*Painter, error) {
 
 // RadarRender radar chart render
 func RadarRender(values [][]float64, opts ...OptionFunc) (*Painter, error) {
-	seriesList := NewSeriesListDataFromValues(values, ChartTypeRadar)
 	return Render(ChartOption{
-		SeriesList: seriesList,
+		SeriesList: NewSeriesListDataFromValues(values, ChartTypeRadar),
 	}, opts...)
 }
 
 // FunnelRender funnel chart render
 func FunnelRender(values []float64, opts ...OptionFunc) (*Painter, error) {
-	seriesList := NewFunnelSeriesList(values)
 	return Render(ChartOption{
-		SeriesList: seriesList,
+		SeriesList: NewFunnelSeriesList(values),
 	}, opts...)
 }
 

charts.go

@@ -106,6 +106,8 @@ type defaultRenderResult struct {
 }
 
 func defaultRender(p *Painter, opt defaultRenderOption) (*defaultRenderResult, error) {
+	fillThemeDefaults(getPreferredTheme(opt.Theme), &opt.Title, &opt.Legend, &opt.XAxis)
+
 	seriesList := opt.SeriesList
 	seriesList.init()
 	if !opt.backgroundIsFilled {
@@ -118,9 +120,6 @@ func defaultRender(p *Painter, opt defaultRenderOption) (*defaultRenderResult, e
 
 	legendHeight := 0
 	if len(opt.Legend.Data) != 0 {
-		if opt.Legend.Theme == nil {
-			opt.Legend.Theme = opt.Theme
-		}
 		legendResult, err := NewLegendPainter(p, opt.Legend).Render()
 		if err != nil {
 			return nil, err
@@ -129,10 +128,6 @@ func defaultRender(p *Painter, opt defaultRenderOption) (*defaultRenderResult, e
 	}
 
 	if opt.Title.Text != "" {
-		if opt.Title.Theme == nil {
-			opt.Title.Theme = opt.Theme
-		}
-
 		titleBox, err := NewTitlePainter(p, opt.Title).Render()
 		if err != nil {
 			return nil, err
@@ -248,7 +243,6 @@ func defaultRender(p *Painter, opt defaultRenderOption) (*defaultRenderResult, e
 			opt.XAxis.isValueAxis = true
 		}
 		reverseStringSlice(yAxisOption.Data)
-		// TODO - generate other positions and y-axis
 		child := p.Child(PainterPaddingOption(Box{
 			Left:  rangeWidthLeft,
 			Right: rangeWidthRight,
@@ -268,9 +262,6 @@ func defaultRender(p *Painter, opt defaultRenderOption) (*defaultRenderResult, e
 		}
 	}
 
-	if opt.XAxis.Theme == nil {
-		opt.XAxis.Theme = opt.Theme
-	}
 	xAxis := NewBottomXAxis(p.Child(PainterPaddingOption(Box{
 		Left:  rangeWidthLeft,
 		Right: rangeWidthRight,
@@ -300,11 +291,12 @@ func Render(opt ChartOption, opts ...OptionFunc) (*Painter, error) {
 	for _, fn := range opts {
 		fn(&opt)
 	}
-	opt.fillDefault()
+	if err := opt.fillDefault(); err != nil {
+		return nil, err
+	}
 
-	isChild := true
-	if opt.Parent == nil {
-		isChild = false
+	isChild := opt.parent != nil
+	if !isChild {
 		p, err := NewPainter(PainterOptions{
 			OutputFormat: opt.OutputFormat,
 			Width:        opt.Width,
@@ -314,9 +306,9 @@ func Render(opt ChartOption, opts ...OptionFunc) (*Painter, error) {
 		if err != nil {
 			return nil, err
 		}
-		opt.Parent = p
+		opt.parent = p
 	}
-	p := opt.Parent
+	p := opt.parent
 	if opt.ValueFormatter != nil {
 		p.valueFormatter = opt.ValueFormatter
 	}
@@ -329,7 +321,6 @@ func Render(opt ChartOption, opts ...OptionFunc) (*Painter, error) {
 	seriesList := opt.SeriesList
 	seriesList.init()
 
-	// line chart
 	lineSeriesList := seriesList.Filter(ChartTypeLine)
 	barSeriesList := seriesList.Filter(ChartTypeBar)
 	horizontalBarSeriesList := seriesList.Filter(ChartTypeHorizontalBar)
@@ -463,7 +454,7 @@ func Render(opt ChartOption, opts ...OptionFunc) (*Painter, error) {
 	}
 
 	for _, item := range opt.Children {
-		item.Parent = p
+		item.parent = p
 		if item.Theme == nil {
 			item.Theme = opt.Theme
 		}

pie_chart.go

@@ -145,7 +145,7 @@ func (p *pieChart) render(result *defaultRenderResult, seriesList SeriesList) (B
 		total += value
 	}
 	if total <= 0 {
-		return BoxZero, errors.New("The sum value of pie chart should gt 0")
+		return BoxZero, errors.New("the sum value of pie chart should greater than 0")
 	}
 	seriesPainter := result.seriesPainter
 	cx := seriesPainter.Width() >> 1

series.go

@@ -92,7 +92,7 @@ type Series struct {
 	Type string
 	// Data provides the series data list.
 	Data []SeriesData
-	// YAxisIndex is the index for the axis, it should be 0 or 1.
+	// YAxisIndex is the index for the axis, it must be 0 or 1.
 	YAxisIndex int
 	// Style represents the style for the series.
 	Style chart.Style
@@ -114,11 +114,8 @@ type Series struct {
 type SeriesList []Series
 
 func (sl SeriesList) init() {
-	if len(sl) == 0 {
-		return
-	}
-	if sl[len(sl)-1].index != 0 {
-		return
+	if len(sl) == 0 || sl[len(sl)-1].index != 0 {
+		return // already initialized
 	}
 	for i := 0; i < len(sl); i++ {
 		if sl[i].Type == "" {