Adding upstream version 2.1.2.

Signed-off-by: Daniel Baumann <daniel@debian.org>

tick.go

@@ -0,0 +1,115 @@
+package chart
+
+import (
+	"fmt"
+	"math"
+	"strings"
+)
+
+// TicksProvider is a type that provides ticks.
+type TicksProvider interface {
+	GetTicks(r Renderer, defaults Style, vf ValueFormatter) []Tick
+}
+
+// Tick represents a label on an axis.
+type Tick struct {
+	Value float64
+	Label string
+}
+
+// Ticks is an array of ticks.
+type Ticks []Tick
+
+// Len returns the length of the ticks set.
+func (t Ticks) Len() int {
+	return len(t)
+}
+
+// Swap swaps two elements.
+func (t Ticks) Swap(i, j int) {
+	t[i], t[j] = t[j], t[i]
+}
+
+// Less returns if i's value is less than j's value.
+func (t Ticks) Less(i, j int) bool {
+	return t[i].Value < t[j].Value
+}
+
+// String returns a string representation of the set of ticks.
+func (t Ticks) String() string {
+	var values []string
+	for i, tick := range t {
+		values = append(values, fmt.Sprintf("[%d: %s]", i, tick.Label))
+	}
+	return strings.Join(values, ", ")
+}
+
+// GenerateContinuousTicks generates a set of ticks.
+func GenerateContinuousTicks(r Renderer, ra Range, isVertical bool, style Style, vf ValueFormatter) []Tick {
+	if vf == nil {
+		vf = FloatValueFormatter
+	}
+
+	var ticks []Tick
+	min, max := ra.GetMin(), ra.GetMax()
+
+	if ra.IsDescending() {
+		ticks = append(ticks, Tick{
+			Value: max,
+			Label: vf(max),
+		})
+	} else {
+		ticks = append(ticks, Tick{
+			Value: min,
+			Label: vf(min),
+		})
+	}
+
+	minLabel := vf(min)
+	style.GetTextOptions().WriteToRenderer(r)
+	labelBox := r.MeasureText(minLabel)
+
+	var tickSize float64
+	if isVertical {
+		tickSize = float64(labelBox.Height() + DefaultMinimumTickVerticalSpacing)
+	} else {
+		tickSize = float64(labelBox.Width() + DefaultMinimumTickHorizontalSpacing)
+	}
+
+	domain := float64(ra.GetDomain())
+	domainRemainder := domain - (tickSize * 2)
+	intermediateTickCount := int(math.Floor(float64(domainRemainder) / float64(tickSize)))
+
+	rangeDelta := math.Abs(max - min)
+	tickStep := rangeDelta / float64(intermediateTickCount)
+
+	roundTo := GetRoundToForDelta(rangeDelta) / 10
+	intermediateTickCount = MinInt(intermediateTickCount, DefaultTickCountSanityCheck)
+
+	for x := 1; x < intermediateTickCount; x++ {
+		var tickValue float64
+		if ra.IsDescending() {
+			tickValue = max - RoundUp(tickStep*float64(x), roundTo)
+		} else {
+			tickValue = min + RoundUp(tickStep*float64(x), roundTo)
+		}
+		ticks = append(ticks, Tick{
+			Value: tickValue,
+			Label: vf(tickValue),
+		})
+	}
+
+	if ra.IsDescending() {
+		ticks = append(ticks, Tick{
+			Value: min,
+			Label: vf(min),
+		})
+	} else {
+		ticks = append(ticks, Tick{
+			Value: max,
+			Label: vf(max),
+		})
+	}
+
+	return ticks
+}