Add text components 021-040 with demos and behavior tests

text/odometer.go

@@ -0,0 +1,89 @@
+package text
+
+import (
+	"fmt"
+	"math"
+	"strconv"
+
+	"github.com/egoist/mygo/ui"
+
+	"git.zacharyzhang.com/ZacharyZhang-NY/8bitMyGoUI/pixel"
+)
+
+type OdometerOptions struct {
+	// Digits is zero for as many as value has.
+	Digits int
+	Slot   pixel.Slot
+}
+
+type odoKey struct{}
+
+type odoState struct {
+	shown float64
+	last  int
+}
+
+const odoCell = 10
+
+// Odometer rolls its digits toward value, step by step.
+func Odometer(c *ui.Context, value int, o OdometerOptions) *ui.Element {
+	if value < 0 {
+		panic(fmt.Sprintf("text: Odometer value %d is negative", value))
+	}
+	k := pixel.K(c)
+	digits := orDef("Odometer Digits", o.Digits, len(strconv.Itoa(value)))
+	if value >= int(math.Pow10(digits)) {
+		panic(fmt.Sprintf("text: Odometer value %d needs more than %d digits", value, digits))
+	}
+	h := pixel.LineHeight + 2
+	e := ui.Box(c).Size(k.D(digits*odoCell), k.D(h)).Label(strconv.Itoa(value)).Role(ui.RoleText)
+	st := ui.Local(e, odoKey{}, func() odoState { return odoState{shown: float64(value), last: -1} })
+	target := float64(value)
+	switch {
+	case k.Reduce() || st.shown == target:
+		st.shown, st.last = target, -1
+	default:
+		tick := k.Tick(c, 30)
+		if st.last >= 0 {
+			for range tick - st.last {
+				st.shown = roll(st.shown, target)
+			}
+		}
+		st.last = tick
+	}
+	shown := st.shown
+	return e.Draw(func(p *ui.Painter, r ui.Rect) {
+		g := k.Canvas(p, r)
+		for i := range digits {
+			x := (digits - 1 - i) * odoCell
+			d, frac := wheel(shown, i)
+			g.Frame(x, 0, odoCell-1, h, pixel.Sunken, pixel.Well)
+			g.Clip(x+2, 2, odoCell-5, h-4, func() {
+				y := 1 - int(frac*float64(h))
+				g.Text(x+2, y, strconv.Itoa(d), o.Slot, 1)
+				g.Text(x+2, y+h, strconv.Itoa((d+1)%10), o.Slot, 1)
+			})
+		}
+	})
+}
+
+// roll moves shown a step toward target, faster when far.
+func roll(shown, target float64) float64 {
+	diff := target - shown
+	stride := max(0.25, math.Abs(diff)/6)
+	if math.Abs(diff) <= stride {
+		return target
+	}
+	return shown + math.Copysign(stride, diff)
+}
+
+// wheel is digit i of shown and its roll.
+func wheel(shown float64, i int) (d int, frac float64) {
+	place := math.Pow10(i)
+	v := shown / place
+	d = int(math.Floor(v)) % 10
+	if lower := math.Mod(shown, place); lower > place-1 {
+		frac = lower - (place - 1)
+	}
+	return d, frac
+}