Charts I: components 101-120

pie_chart.go

@@ -0,0 +1,146 @@
+package mujica
+
+import (
+	"fmt"
+	"math"
+
+	"github.com/egoist/mygo/ui"
+
+	"mujicaui/internal"
+	"mujicaui/theme"
+)
+
+// ChartSlice is one share of a PieChart or FunnelChart.
+type ChartSlice struct {
+	Label string
+	Value float64
+}
+
+// PieChartOptions configure a PieChart.
+type PieChartOptions struct {
+	Frame ChartFrame
+	// Donut cuts out the middle and writes the total there.
+	Donut bool
+	// MinAngle merges two or more narrower slices into Other.
+	MinAngle float64
+	Format   func(v float64) string
+}
+
+// PieChart shows shares as slices labeled with percents.
+func PieChart(c *ui.Context, slices []ChartSlice, opts PieChartOptions) ChartResult {
+	if opts.MinAngle < 0 || opts.MinAngle >= 360 {
+		panic("mujica: PieChart MinAngle must be in [0, 360)")
+	}
+	ch := newChart(c, opts.Frame)
+	k := Tokens(c)
+	pal := internal.Palette(k)
+	size := FontSize(c, theme.CaptionSize)
+	parts := chartMemo(ch, "parts", [2]any{chartID(slices), opts.MinAngle}, func() []ChartSlice {
+		return pieMerge(slices, opts.MinAngle, msg(c, "pie_chart.other"))
+	})
+	total := 0.0
+	for _, s := range parts {
+		total += s.Value
+	}
+	n := len(parts)
+	if total == 0 {
+		n = 0
+	}
+	keys := make([]chartKey, len(parts))
+	for i, s := range parts {
+		keys[i] = chartKey{Name: s.Label, Color: pal[i%len(pal)], Shape: i}
+	}
+	// angle returns slice i's start and end, clockwise.
+	angle := func(i int) (float64, float64) {
+		a := 0.0
+		for j := range i {
+			a += parts[j].Value
+		}
+		return 2 * math.Pi * a / total, 2 * math.Pi * (a + parts[i].Value) / total
+	}
+	geom := func(r ui.Rect) (cx, cy, r0, r1 float32) {
+		r1 = min(r.W, r.H)/2 - 8
+		if opts.Donut {
+			r0 = r1 * 0.58
+		}
+		return r.X + r.W/2, r.Y + r.H/2, r0, r1
+	}
+	share := func(i int) string { return fmt.Sprintf("%.1f%%", 100*parts[i].Value/total) }
+	spec := chartSpec{n: n, keys: keys}
+	spec.readout = func(i int) string {
+		return parts[i].Label + " · " + chartValue(c, parts[i].Value, opts.Format) + " · " + share(i)
+	}
+	spec.pick = func(r ui.Rect, x, y float32) int {
+		cx, cy, r0, r1 := geom(r)
+		d := float32(math.Hypot(float64(x-cx), float64(y-cy)))
+		if d < r0 || d > r1 {
+			return -1
+		}
+		a := math.Atan2(float64(x-cx), float64(cy-y))
+		if a < 0 {
+			a += 2 * math.Pi
+		}
+		for i := range parts {
+			if a0, a1 := angle(i); a >= a0 && a < a1 {
+				return i
+			}
+		}
+		return -1
+	}
+	spec.draw = func(p *ui.Painter, r ui.Rect, active int) {
+		cx, cy, r0, r1 := geom(r)
+		for i := range parts {
+			a0, a1 := angle(i)
+			if a1 <= a0 {
+				continue
+			}
+			grow := float32(0)
+			if i == active {
+				grow = 6
+			}
+			p.FillPath(internal.Sector(cx, cy, r0, r1+grow, a0, a1), keys[i].Color)
+			p.StrokePath(internal.Sector(cx, cy, r0, r1+grow, a0, a1), 1.5, k.Surface)
+			// Wide slices carry their shape and percent.
+			if a1-a0 > 0.38 {
+				mx, my := internal.Polar(cx, cy, (r0+r1)/2+float32(chartBool(r0 == 0))*r1*0.12, (a0+a1)/2)
+				ink := chartInk(k, keys[i].Color)
+				internal.Marker(p, i, mx, my-8, 9, ink)
+				chartText(p, share(i), mx, my+2, size, ink, 0.5, 0)
+			}
+		}
+		if opts.Donut {
+			chartText(p, chartValue(c, total, opts.Format), cx, cy, FontSize(c, theme.H3Size), k.Text, 0.5, 0.75)
+			chartText(p, msg(c, "pie_chart.total"), cx, cy+4, size, k.TextMuted, 0.5, 0)
+		}
+	}
+	res, _ := ch.build(spec)
+	return res
+}
+
+// pieMerge folds two or more narrow slices into other.
+func pieMerge(slices []ChartSlice, minAngle float64, other string) []ChartSlice {
+	total := 0.0
+	for _, s := range slices {
+		if s.Value < 0 || math.IsNaN(s.Value) || math.IsInf(s.Value, 0) || s.Label == "" {
+			panic("mujica: PieChart slices need a label and a finite value ≥ 0")
+		}
+		total += s.Value
+	}
+	var keep []ChartSlice
+	small, rest := 0, 0.0
+	for _, s := range slices {
+		if total > 0 && s.Value/total*360 < minAngle {
+			small++
+			rest += s.Value
+		}
+	}
+	for _, s := range slices {
+		if small < 2 || total == 0 || s.Value/total*360 >= minAngle {
+			keep = append(keep, s)
+		}
+	}
+	if small >= 2 {
+		keep = append(keep, ChartSlice{Label: other, Value: rest})
+	}
+	return keep
+}