go-chart/tick.go
Will Charczuk 98d3996b47 descending
2017-01-10 13:50:17 -08:00

116 lines
2.5 KiB
Go

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 {
panic("vf is nil; did you remember to set a default value formatter?")
}
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 := Math.GetRoundToForDelta(rangeDelta) / 10
intermediateTickCount = Math.MinInt(intermediateTickCount, 1<<10)
for x := 1; x < intermediateTickCount; x++ {
var tickValue float64
if ra.IsDescending() {
tickValue = max - Math.RoundUp(tickStep*float64(x), roundTo)
} else {
tickValue = min + Math.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
}