go-chart/tick.go

82 lines
2.0 KiB
Go

package chart
import "math"
// TicksProvider is a type that provides ticks.
type TicksProvider interface {
GetTicks(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
}
// GenerateContinuousTicksWithStep generates a set of ticks.
func GenerateContinuousTicksWithStep(ra Range, step float64, vf ValueFormatter, includeMax bool) []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
}
}
if includeMax {
ticks = append(ticks, Tick{
Value: ra.GetMax(),
Label: vf(ra.GetMax()),
})
}
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)
}