ticks refactor.

tick.go

@@ -1,21 +1,10 @@
 package chart
 
-// GenerateTicksWithStep generates a set of ticks.
-func GenerateTicksWithStep(ra Range, step float64, vf ValueFormatter) []Tick {
-	var ticks []Tick
-	min, max := ra.GetMin(), ra.GetMax()
-	for cursor := min; cursor <= max; cursor += step {
-		ticks = append(ticks, Tick{
-			Value: cursor,
-			Label: vf(cursor),
-		})
+import "math"
 
-		// this guard is in place in case step is super, super small.
-		if len(ticks) > DefaultTickCountSanityCheck {
-			return ticks
-		}
-	}
-	return ticks
+// TicksProvider is a type that provides ticks.
+type TicksProvider interface {
+	GetTicks(vf ValueFormatter) []Tick
 }
 
 // Tick represents a label on an axis.
@@ -41,3 +30,46 @@ func (t Ticks) Swap(i, j int) {
 func (t Ticks) Less(i, j int) bool {
 	return t[i].Value < t[j].Value
 }
+
+// GenerateContinuousTicksWithStep generates a set of ticks.
+func GenerateContinuousTicksWithStep(ra Range, step float64, vf ValueFormatter) []Tick {
+	var ticks []Tick
+	min, max := ra.GetMin(), ra.GetMax()
+	for cursor := min; cursor <= max; cursor += step {
+		ticks = append(ticks, Tick{
+			Value: cursor,
+			Label: vf(cursor),
+		})
+
+		// this guard is in place in case step is super, super small.
+		if len(ticks) > DefaultTickCountSanityCheck {
+			return ticks
+		}
+	}
+	return ticks
+}
+
+// CalculateContinuousTickStep calculates the continous range interval between ticks.
+func CalculateContinuousTickStep(r Renderer, ra Range, isVertical bool, style Style, vf ValueFormatter) float64 {
+	r.SetFont(style.GetFont())
+	r.SetFontSize(style.GetFontSize())
+	if isVertical {
+		label := vf(ra.GetMin())
+		tb := r.MeasureText(label)
+		count := int(math.Ceil(float64(ra.GetDomain()) / float64(tb.Height()+DefaultMinimumTickVerticalSpacing)))
+		return ra.GetDelta() / float64(count)
+	}
+
+	// take a cut at determining the 'widest' value.
+	l0 := vf(ra.GetMin())
+	ln := vf(ra.GetMax())
+	ll := l0
+	if len(ln) > len(l0) {
+		ll = ln
+	}
+	llb := r.MeasureText(ll)
+	textWidth := llb.Width()
+	width := textWidth + DefaultMinimumTickHorizontalSpacing
+	count := int(math.Ceil(float64(ra.GetDomain()) / float64(width)))
+	return ra.GetDelta() / float64(count)
+}