Add datetime components 196-215; Kit.At; inert stepper arrows

Calendars, date and time inputs, pickers, clocks, timers, a sun dial,
a season wheel, an agenda and a day schedule. Kit.At rebuilds at a
moment (relative times, midnight). Stepper and NumberInput arrows stop
under Inert. DateInput parks a popup focus as its own.

datetime/timer.go

@@ -0,0 +1,109 @@
+package datetime
+
+import (
+	"fmt"
+	"log/slog"
+	"time"
+
+	"github.com/egoist/mygo/ui"
+
+	"git.zacharyzhang.com/ZacharyZhang-NY/8bitMyGoUI/input"
+	"git.zacharyzhang.com/ZacharyZhang-NY/8bitMyGoUI/pixel"
+)
+
+type TimerOptions struct {
+	Disabled bool
+}
+
+type TimerResult struct {
+	Element *ui.Element
+	// Done is true in the frame the time runs out.
+	Done bool
+}
+
+type timerKey struct{}
+
+// ticking is time left when paused, the end, the ring.
+type ticking struct {
+	left       time.Duration
+	ends, rang time.Time
+}
+
+// Timer counts *set down; it flashes at zero.
+func Timer(c *ui.Context, text string, set *time.Duration, o TimerOptions) TimerResult {
+	k := pixel.K(c)
+	if *set < 0 || *set >= 100*time.Minute || *set%time.Second != 0 {
+		panic(fmt.Sprintf("datetime: Timer set %v is not whole seconds under 100 min", *set))
+	}
+	col := ui.Column(c).Gap(k.D(4)).Role(ui.RoleGroup).Label(text)
+	t := ui.Local(col, timerKey{}, func() ticking { return ticking{} })
+	now := k.Now()
+	running := !t.ends.IsZero()
+	left := t.left
+	res := TimerResult{Element: col}
+	if running {
+		left = max(0, t.ends.Sub(now))
+		k.Tick(c, 4)
+		if left == 0 {
+			t.ends, t.left, t.rang, res.Done, running = time.Time{}, 0, now, true, false
+			slog.Debug("8bit: timer done", "label", text)
+		}
+	}
+	// It flashes for three seconds after ringing.
+	flash := !t.rang.IsZero() && now.Sub(t.rang) < 3*time.Second
+	if flash {
+		k.Tick(c, 4)
+	}
+	if !running && !flash && t.left == 0 {
+		left = *set
+	}
+	col.Children(func() {
+		s := clock((left + time.Second - 1).Truncate(time.Second))
+		face := ui.Box(c).Size(k.D(pixel.Measure(s)*2), k.D(pixel.LineHeight*2)).Role(ui.RoleStatus).Label(s)
+		face.Draw(func(p *ui.Painter, r ui.Rect) {
+			g := k.Canvas(p, r)
+			if !flash {
+				g.Text(0, 0, s, pixel.Ink, 2)
+				return
+			}
+			// Reduced, the ring holds steady in Bad.
+			if k.Reduce() || g.Busy(4)%2 == 0 {
+				g.Text(0, 0, s, pixel.Bad, 2)
+			}
+		})
+		ui.Row(c).Gap(k.D(4)).AlignItems(ui.Center).Children(func() {
+			locked := o.Disabled || running
+			mins, secs := int(*set/time.Minute), int(*set%time.Minute/time.Second)
+			for _, f := range []struct {
+				name string
+				v    *int
+				top  int
+			}{{k.Msg("minutes"), &mins, 99}, {k.Msg("seconds"), &secs, 59}} {
+				pixel.Text(c, f.name, pixel.TextOptions{Slot: pixel.Faint})
+				if input.Stepper(c, f.name, f.v, input.StepperOptions{Max: f.top, Disabled: locked}).Changed {
+					*set, t.left = time.Duration(mins)*time.Minute+time.Duration(secs)*time.Second, 0
+					// The face above, built already, reads the new setting.
+					s = clock(*set)
+					face.Label(s)
+				}
+			}
+		})
+		toggle := k.Msg("start")
+		if running {
+			toggle = k.Msg("pause")
+		}
+		if input.Button(c, toggle, input.ButtonOptions{Size: input.Small, Variant: input.Primary, Disabled: o.Disabled}).Clicked {
+			switch {
+			case running:
+				t.left, t.ends = left, time.Time{}
+			case t.left > 0:
+				t.ends = now.Add(t.left)
+			default:
+				t.ends = now.Add(*set)
+			}
+			t.rang = time.Time{}
+			slog.Debug("8bit: timer", "label", text, "running", !running)
+		}
+	})
+	return res
+}