feat: support title render function

range.go

@@ -0,0 +1,75 @@
+// MIT License
+
+// Copyright (c) 2022 Tree Xie
+
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+
+package charts
+
+import (
+	"math"
+)
+
+type Range struct {
+	divideCount int
+	Min         float64
+	Max         float64
+	Size        int
+	Boundary    bool
+}
+
+func NewRange(min, max float64, divideCount int) Range {
+	r := math.Abs(max - min)
+
+	// 最小单位计算
+	unit := 5
+	if r > 100 {
+		unit = 20
+	}
+	unit = int((r/float64(divideCount))/float64(unit))*unit + unit
+
+	if min != 0 {
+		min = float64(int(min/float64(unit)) * unit)
+		// 如果是小于0，int的时候向上取整了，因此调整
+		if min < 0 {
+			min -= float64(unit)
+		}
+	}
+	max = min + float64(unit*divideCount)
+	return Range{
+		Min:         min,
+		Max:         max,
+		divideCount: divideCount,
+	}
+}
+
+func (r *Range) getHeight(value float64) int {
+	v := 1 - (value-r.Min)/(r.Max-r.Min)
+	return int(v * float64(r.Size))
+}
+
+func (r *Range) getWidth(value float64) int {
+	v := value / (r.Max - r.Min)
+	// 移至居中
+	if r.Boundary &&
+		r.divideCount != 0 {
+		v += 1 / float64(r.divideCount*2)
+	}
+	return int(v * float64(r.Size))
+}