secondary axis works.

chart.go

@@ -155,6 +155,14 @@ func (c Chart) getRanges() (xrange, yrange, yrangeAlt Range) {
 		yrange.Min = globalMinY
 		yrange.Max = globalMaxY
 	}
+
+	if !c.YAxisSecondary.Range.IsZero() {
+		yrangeAlt.Min = c.YAxisSecondary.Range.Min
+		yrangeAlt.Max = c.YAxisSecondary.Range.Max
+	} else {
+		yrangeAlt.Min = globalMinYA
+		yrangeAlt.Max = globalMaxYA
+	}
 	return
 }
 
@@ -207,7 +215,7 @@ func (c Chart) getAxesTicks(r Renderer, xr, yr, yar Range, xf, yf, yfa ValueForm
 		yticks = c.YAxis.GetTicks(r, yr, yf)
 	}
 	if c.YAxisSecondary.Style.Show {
-		yticksAlt = c.YAxisSecondary.GetTicks(r, yr, yf)
+		yticksAlt = c.YAxisSecondary.GetTicks(r, yar, yf)
 	}
 	return
 }
@@ -348,7 +356,7 @@ func (c Chart) drawSeries(r Renderer, canvasBox Box, xrange, yrange, yrangeAlt R
 	if s.GetYAxis() == YAxisPrimary {
 		s.Render(r, canvasBox, xrange, yrange, c.getSeriesStyleDefaults(seriesIndex))
 	} else if s.GetYAxis() == YAxisSecondary {
-		s.Render(r, canvasBox, xrange, yrange, c.getSeriesStyleDefaults(seriesIndex))
+		s.Render(r, canvasBox, xrange, yrangeAlt, c.getSeriesStyleDefaults(seriesIndex))
 	}
 }
 

testserver/main.go

@@ -20,11 +20,11 @@ func chartHandler(rc *web.RequestContext) web.ControllerResult {
 		rc.Response.Header().Set("Content-Type", "image/svg+xml")
 	}
 
-	s1x := []float64{1.0, 2.0, 3.0, 4.0}
+	s1x := []float64{2.0, 3.0, 4.0, 5.0}
 	s1y := []float64{2.5, 5.0, 2.0, 3.3}
 
-	s2x := []float64{3.0, 4.0, 5.0, 6.0}
+	s2x := []float64{0.0, 0.5, 1.0, 1.5}
-	s2y := []float64{6.0, 5.0, 4.0, 1.0}
+	s2y := []float64{1.1, 1.2, 1.0, 1.3}
 
 	c := chart.Chart{
 		Title: "A Test Chart",
@@ -36,19 +36,26 @@ func chartHandler(rc *web.RequestContext) web.ControllerResult {
 		XAxis: chart.XAxis{
 			Style: chart.Style{
 				Show: true,
-				StrokeWidth: 1.0,
 			},
 		},
 		YAxis: chart.YAxis{
 			Style: chart.Style{
 				Show: true,
-				StrokeWidth: 1.0,
 			},
 			Range: chart.Range{
 				Min: 0.0,
 				Max: 7.0,
 			},
 		},
+		YAxisSecondary: chart.YAxis{
+			Style: chart.Style{
+				Show: true,
+			},
+			Range: chart.Range{
+				Min: 0.8,
+				Max: 1.5,
+			},
+		},
 		Series: []chart.Series{
 			chart.ContinuousSeries{
 				Name:    "a",
@@ -57,6 +64,7 @@ func chartHandler(rc *web.RequestContext) web.ControllerResult {
 			},
 			chart.ContinuousSeries{
 				Name:    "b",
+				YAxis:   chart.YAxisSecondary,
 				XValues: s2x,
 				YValues: s2y,
 			},
@@ -76,6 +84,7 @@ func chartHandler(rc *web.RequestContext) web.ControllerResult {
 			},
 			chart.AnnotationSeries{
 				Name:  "b - last value",
+				YAxis: chart.YAxisSecondary,
 				Style: chart.Style{
 					Show:        true,
 					StrokeColor: chart.GetDefaultSeriesStrokeColor(1),

yaxis.go

@@ -1,6 +1,7 @@
 package chart
 
 import (
+	"fmt"
 	"math"
 	"sort"
 )
@@ -54,6 +55,7 @@ func (ya YAxis) getTickStep(r Renderer, ra Range, vf ValueFormatter) float64 {
 func (ya YAxis) generateTicksWithStep(ra Range, step float64, vf ValueFormatter) []Tick {
 	var ticks []Tick
 	for cursor := ra.Min; cursor < ra.Max; cursor += step {
+		println("yaxis tick:", fmt.Sprintf("%.2f", cursor))
 		ticks = append(ticks, Tick{
 			Value: cursor,
 			Label: vf(cursor),
@@ -64,28 +66,24 @@ func (ya YAxis) generateTicksWithStep(ra Range, step float64, vf ValueFormatter)
 
 // Render renders the axis.
 func (ya YAxis) Render(r Renderer, canvasBox Box, ra Range, axisType YAxisType, ticks []Tick) {
-	var lx int
-	var tx int
-	if axisType == YAxisPrimary {
-		lx = canvasBox.Right
-		tx = canvasBox.Right + DefaultYAxisMargin
-	} else if axisType == YAxisSecondary {
-		lx = canvasBox.Left
-		tx = canvasBox.Left - DefaultYAxisMargin
-	}
-
 	r.SetStrokeColor(ya.Style.GetStrokeColor(DefaultAxisColor))
 	r.SetStrokeWidth(ya.Style.GetStrokeWidth(DefaultAxisLineWidth))
-
-	r.MoveTo(lx, canvasBox.Bottom)
-	r.LineTo(lx, canvasBox.Top)
-	r.Stroke()
-
 	r.SetFontColor(ya.Style.GetFontColor(DefaultAxisColor))
 	fontSize := ya.Style.GetFontSize(DefaultFontSize)
 	r.SetFontSize(fontSize)
 
 	sort.Sort(Ticks(ticks))
+
+	var lx int
+	var tx int
+	if axisType == YAxisPrimary {
+		lx = canvasBox.Right
+		tx = canvasBox.Right + DefaultYAxisMargin
+
+		r.MoveTo(lx, canvasBox.Bottom)
+		r.LineTo(lx, canvasBox.Top)
+		r.Stroke()
+
 		for _, t := range ticks {
 			v := t.Value
 			ly := ra.Translate(v) + canvasBox.Top
@@ -99,4 +97,31 @@ func (ya YAxis) Render(r Renderer, canvasBox Box, ra Range, axisType YAxisType,
 			r.LineTo(lx+DefaultVerticalTickWidth, ly)
 			r.Stroke()
 		}
+	} else if axisType == YAxisSecondary {
+		lx = canvasBox.Left
+
+		r.MoveTo(lx, canvasBox.Bottom)
+		r.LineTo(lx, canvasBox.Top)
+		r.Stroke()
+
+		for _, t := range ticks {
+			v := t.Value
+			ly := ra.Translate(v) + canvasBox.Top
+
+			ptw, _ := r.MeasureText(t.Label)
+
+			tw := ptw
+			th := int(fontSize)
+
+			tx = lx - (int(tw) + (DefaultYAxisMargin >> 1))
+			ty := ly + th>>1
+
+			r.Text(t.Label, tx, ty)
+
+			r.MoveTo(lx, ly)
+			r.LineTo(lx-DefaultVerticalTickWidth, ly)
+			r.Stroke()
+		}
+	}
+
 }