mostly works.

xaxis.go

@@ -1,27 +1,101 @@
 package chart
 
-import "github.com/wcharczuk/go-chart/drawing"
+import (
+	"math"
+	"sort"
+
+	"github.com/wcharczuk/go-chart/drawing"
+)
 
 // XAxis represents the horizontal axis.
 type XAxis struct {
-	axis
+	Name           string
+	Style          Style
+	ValueFormatter ValueFormatter
+	Range          Range
+	Ticks          []Tick
+}
+
+// GetName returns the name.
+func (xa XAxis) GetName() string {
+	return xa.Name
+}
+
+// GetStyle returns the style.
+func (xa XAxis) GetStyle() Style {
+	return xa.Style
+}
+
+// GetTicks returns the ticks for a series. It coalesces between user provided ticks and
+// generated ticks.
+func (xa XAxis) GetTicks(r Renderer, ra Range, vf ValueFormatter) []Tick {
+	if len(xa.Ticks) > 0 {
+		return xa.Ticks
+	}
+	return xa.generateTicks(r, ra, vf)
+}
+
+func (xa XAxis) generateTicks(r Renderer, ra Range, vf ValueFormatter) []Tick {
+	step := xa.getTickStep(r, ra, vf)
+	return xa.generateTicksWithStep(ra, step, vf)
+}
+
+func (xa XAxis) getTickCount(r Renderer, ra Range, vf ValueFormatter) int {
+	fontSize := xa.Style.GetFontSize(DefaultFontSize)
+	r.SetFontSize(fontSize)
+
+	// take a cut at determining the 'widest' value.
+	l0 := vf(ra.Min)
+	ln := vf(ra.Max)
+	ll := l0
+	if len(ln) > len(l0) {
+		ll = ln
+	}
+	llw, _ := r.MeasureText(ll)
+	textWidth := drawing.PointsToPixels(r.GetDPI(), float64(llw))
+	width := textWidth + DefaultMinimumTickHorizontalSpacing
+	count := int(math.Ceil(float64(ra.Domain) / float64(width)))
+	return count
+}
+
+func (xa XAxis) getTickStep(r Renderer, ra Range, vf ValueFormatter) float64 {
+	tickCount := xa.getTickCount(r, ra, vf)
+	step := ra.Delta() / float64(tickCount)
+	return step
+}
+
+func (xa XAxis) generateTicksWithStep(ra Range, step float64, vf ValueFormatter) []Tick {
+	var ticks []Tick
+	for cursor := ra.Min; cursor < ra.Max; cursor += step {
+		ticks = append(ticks, Tick{
+			Value: cursor,
+			Label: vf(cursor),
+		})
+	}
+	return ticks
 }
 
 // Render renders the axis
-func (xa XAxis) Render(r Renderer, canvasBox Box, ra Range) {
+func (xa XAxis) Render(r Renderer, canvasBox Box, ra Range, ticks []Tick) {
 	tickFontSize := xa.Style.GetFontSize(DefaultFontSize)
 	tickHeight := drawing.PointsToPixels(r.GetDPI(), tickFontSize)
 	ty := canvasBox.Bottom + DefaultXAxisMargin + int(tickHeight)
 
+	r.SetStrokeColor(xa.Style.GetStrokeColor(DefaultAxisColor))
+	r.SetStrokeWidth(xa.Style.GetStrokeWidth(DefaultAxisLineWidth))
+
+	r.MoveTo(canvasBox.Left, canvasBox.Bottom)
+	r.LineTo(canvasBox.Right, canvasBox.Bottom)
+	r.Stroke()
+
 	r.SetFontColor(xa.Style.GetFontColor(DefaultAxisColor))
 	r.SetFontSize(tickFontSize)
 
-	ticks := xa.getTicks(ra)
-
+	sort.Sort(Ticks(ticks))
 	for _, t := range ticks {
 		v := t.Value
 		x := ra.Translate(v)
-		tx := canvasBox.Left + int(x)
+		tx := canvasBox.Right - x
 		r.Text(t.Label, tx, ty)
 	}
 }