refactor: support customize legend function

axis.go

@@ -23,6 +23,7 @@
 package charts
 
 import (
+	"github.com/dustin/go-humanize"
 	"github.com/wcharczuk/go-chart/v2"
 	"github.com/wcharczuk/go-chart/v2/drawing"
 )
@@ -80,7 +81,13 @@ func GetYAxis(theme string) chart.YAxis {
 		A: 255,
 	}
 	return chart.YAxis{
-
+		ValueFormatter: func(v interface{}) string {
+			value, ok := v.(float64)
+			if !ok {
+				return ""
+			}
+			return humanize.Commaf(value)
+		},
 		AxisType: chart.YAxisSecondary,
 		GridMajorStyle: chart.Style{
 			StrokeColor: strokeColor,

charts.go

@@ -68,7 +68,6 @@ func ToPNG(c *chart.Chart) ([]byte, error) {
 func ToSVG(c *chart.Chart) ([]byte, error) {
 	return render(c, chart.SVG)
 }
-
 func New(opt Option) *chart.Chart {
 	xAxis, xValues := GetXAxisAndValues(opt.XAxis, opt.Theme)
 
@@ -90,22 +89,11 @@ func New(opt Option) *chart.Chart {
 		YAxis:  GetYAxis(opt.Theme),
 		Series: GetSeries(opt.Series, opt.Theme),
 	}
+	// 设置secondary的样式
+	c.YAxisSecondary.Style = c.YAxis.Style
 	if legendSize != 0 {
 		c.Elements = []chart.Renderable{
-			chart.LegendThin(c, chart.Style{
+			DefaultLegend(c),
-				FillColor: hiddenColor,
-				// FillColor:   drawing.ColorWhite,
-				// FontColor:   DefaultTextColor,
-				FontSize:    8.0,
-				StrokeColor: hiddenColor,
-				// StrokeWidth: DefaultAxisLineWidth,
-				// Padding: Box{
-				// 	Top:    2,
-				// 	Left:   7,
-				// 	Right:  7,
-				// 	Bottom: 5,
-				// },
-			}),
 		}
 	}
 	return c

legend.go

@@ -0,0 +1,196 @@
+// MIT License
+
+// Copyright (c) 2021 Tree Xie
+
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+
+package charts
+
+import (
+	"github.com/wcharczuk/go-chart/v2"
+)
+
+type LegendOption struct {
+	Style        chart.Style
+	Align        string
+	TextPosition string
+	Theme        string
+	IconDraw     LegendIconDraw
+}
+
+type LegendIconDrawOption struct {
+	Box   chart.Box
+	Style chart.Style
+	Index int
+	Theme string
+}
+
+const (
+	LegendAlignLeft   = "left"
+	LegendAlignCenter = "center"
+	LegendAlignRight  = "right"
+)
+
+const (
+	LegendTextPositionRight = "right"
+)
+
+type LegendIconDraw func(r chart.Renderer, opt LegendIconDrawOption)
+
+func DefaultLegendIconDraw(r chart.Renderer, opt LegendIconDrawOption) {
+	if opt.Box.IsZero() {
+		return
+	}
+	r.SetStrokeColor(opt.Style.GetStrokeColor())
+	stokeWidth := opt.Style.GetStrokeWidth()
+	r.SetStrokeWidth(stokeWidth)
+	height := opt.Box.Bottom - opt.Box.Top
+	ly := (height / 2) + 1
+	r.MoveTo(opt.Box.Left, ly)
+	r.LineTo(opt.Box.Right, ly)
+	r.Stroke()
+	r.SetFillColor(chart.ColorWhite)
+	r.Circle(5, (opt.Box.Left+opt.Box.Right)/2, ly)
+	r.FillStroke()
+}
+
+func DefaultLegend(c *chart.Chart) chart.Renderable {
+	return LegendCustomize(c, LegendOption{
+		TextPosition: LegendTextPositionRight,
+		IconDraw:     DefaultLegendIconDraw,
+	})
+}
+
+func LegendCustomize(c *chart.Chart, opt LegendOption) chart.Renderable {
+	return func(r chart.Renderer, cb chart.Box, chartDefaults chart.Style) {
+		legendDefaults := chart.Style{
+			FontColor:   chart.DefaultTextColor,
+			FontSize:    8.0,
+			StrokeColor: chart.DefaultAxisColor,
+		}
+
+		legendStyle := opt.Style.InheritFrom(chartDefaults.InheritFrom(legendDefaults))
+
+		r.SetFont(legendStyle.GetFont())
+		r.SetFontColor(legendStyle.GetFontColor())
+		r.SetFontSize(legendStyle.GetFontSize())
+
+		var labels []string
+		var lines []chart.Style
+		for _, s := range c.Series {
+			if !s.GetStyle().Hidden {
+				if _, isAnnotationSeries := s.(chart.AnnotationSeries); !isAnnotationSeries {
+					labels = append(labels, s.GetName())
+					lines = append(lines, s.GetStyle())
+				}
+			}
+		}
+
+		var textHeight int
+		var textWidth int
+		var textBox chart.Box
+		labelWidth := 0
+		for x := 0; x < len(labels); x++ {
+			if len(labels[x]) > 0 {
+				textBox = r.MeasureText(labels[x])
+				labelWidth += textBox.Width()
+				textHeight = chart.MaxInt(textBox.Height(), textHeight)
+				textWidth = chart.MaxInt(textBox.Width(), textWidth)
+			}
+		}
+
+		legendBoxHeight := textHeight + legendStyle.Padding.Top + legendStyle.Padding.Bottom
+		chartPadding := cb.Top
+		legendYMargin := (chartPadding - legendBoxHeight) >> 1
+
+		lineLengthMinimum := 25
+
+		labelWidth += lineLengthMinimum * len(labels)
+
+		left := 0
+		switch opt.Align {
+		case LegendAlignLeft:
+			left = 0
+		case LegendAlignRight:
+			left = cb.Width() - labelWidth
+		default:
+			left = (cb.Width() - labelWidth) / 2
+		}
+
+		legendBox := chart.Box{
+			Left:   left,
+			Right:  left + labelWidth,
+			Top:    0,
+			Bottom: 0 + legendBoxHeight,
+		}
+
+		chart.Draw.Box(r, legendBox, legendDefaults)
+
+		r.SetFont(legendStyle.GetFont())
+		r.SetFontColor(legendStyle.GetFontColor())
+		r.SetFontSize(legendStyle.GetFontSize())
+
+		lineTextGap := 5
+
+		startX := legendBox.Left + legendStyle.Padding.Left
+		ty := legendYMargin + legendStyle.Padding.Top + textHeight
+		var label string
+		var x int
+		iconDraw := opt.IconDraw
+		if iconDraw == nil {
+			iconDraw = DefaultLegendIconDraw
+		}
+		for index := range labels {
+			label = labels[index]
+			if len(label) > 0 {
+				x = startX
+
+				// 如果文本靠左显示
+				if opt.TextPosition != LegendTextPositionRight {
+					textBox = r.MeasureText(label)
+					r.Text(label, x, ty)
+					x = startX + textBox.Width() + lineTextGap
+				}
+
+				// 图标
+				iconDraw(r, LegendIconDrawOption{
+					Theme: opt.Theme,
+					Index: index,
+					Style: lines[index],
+					Box: chart.Box{
+						Left:   x,
+						Top:    ty,
+						Right:  x + lineLengthMinimum,
+						Bottom: ty + textHeight,
+					},
+				})
+				x += (lineLengthMinimum + lineTextGap)
+
+				// 如果文本靠右显示
+				if opt.TextPosition == LegendTextPositionRight {
+					textBox = r.MeasureText(label)
+					r.Text(label, x, ty)
+				}
+
+				// 计算下一个legend的位置
+				startX += textBox.Width() + chart.DefaultMinimumTickHorizontalSpacing + lineTextGap + lineLengthMinimum
+			}
+		}
+	}
+}