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/dayschedule.go

@@ -0,0 +1,86 @@
+package datetime
+
+import (
+	"fmt"
+	"slices"
+	"time"
+
+	"github.com/egoist/mygo/ui"
+
+	"git.zacharyzhang.com/ZacharyZhang-NY/8bitMyGoUI/pixel"
+)
+
+type DayScheduleOptions struct {
+	// From and To bound the hours; zeros mean 8–18.
+	From, To int
+}
+
+// hourH is an hour row's height; gutter holds labels.
+const hourH, gutter = pixel.LineHeight + 4, 24
+
+// DaySchedule places events on hour rows by start and length.
+func DaySchedule(c *ui.Context, events []Event, o DayScheduleOptions) *ui.Element {
+	k := pixel.K(c)
+	from, to := o.From, o.To
+	if from == 0 && to == 0 {
+		from, to = 8, 18
+	}
+	if from < 0 || to > 24 || from >= to {
+		panic(fmt.Sprintf("datetime: DaySchedule hours %d to %d", from, to))
+	}
+	sorted := slices.Clone(events)
+	slices.SortStableFunc(sorted, func(a, b Event) int { return a.Start.Compare(b.Start) })
+	// Chains of overlapping events share the width in lanes.
+	lanes, shared := make([]int, len(sorted)), make([]int, len(sorted))
+	var ends []time.Time
+	var last time.Time
+	head := 0
+	for i, e := range sorted {
+		if i > 0 && e.Start.Compare(last) >= 0 {
+			for j := head; j < i; j++ {
+				shared[j] = len(ends)
+			}
+			head, ends = i, nil
+		}
+		lane := slices.IndexFunc(ends, func(end time.Time) bool { return end.Compare(e.Start) <= 0 })
+		if lane < 0 {
+			lane, ends = len(ends), append(ends, time.Time{})
+		}
+		lanes[i], ends[lane] = lane, e.Start.Add(e.Length)
+		if end := ends[lane]; end.Compare(last) > 0 || i == head {
+			last = end
+		}
+	}
+	for j := head; j < len(sorted); j++ {
+		shared[j] = len(ends)
+	}
+	box := ui.Box(c).FillWidth().Height(k.D((to - from) * hourH)).Role(ui.RoleList)
+	w, check := pixel.WrapWidth(c, box)
+	return box.Draw(func(p *ui.Painter, r ui.Rect) {
+		check(r)
+		g := k.Canvas(p, r)
+		for h := from; h < to; h++ {
+			y := (h - from) * hourH
+			g.Micro(0, y+1, fmt.Sprintf("%02d:00", h), pixel.Faint, 1)
+			g.Checker(gutter, y, g.W-gutter, 1, pixel.Edge)
+		}
+	}).Children(func() {
+		for i, e := range sorted {
+			// Minutes from the top row, cut to the hours shown.
+			top := e.Start.Hour()*60 + e.Start.Minute() - from*60
+			end := min(top+int(e.Length/time.Minute), (to-from)*60)
+			if top = max(0, top); end <= top {
+				continue
+			}
+			h := max(3, (end-top)*hourH/60)
+			y := min(top*hourH/60, (to-from)*hourH-h)
+			laneW := max(4, (w-gutter)/shared[i])
+			ui.Box(c).Absolute().Left(k.D(gutter+lanes[i]*laneW)).Top(k.D(y)).Size(k.D(laneW-1), k.D(h)).Role(ui.RoleListItem).
+				Label(e.Start.Format("15:04") + " " + e.Title).Draw(func(p *ui.Painter, r ui.Rect) {
+				g := k.Canvas(p, r)
+				g.Frame(0, 0, g.W, g.H, pixel.Raised, pixel.AccentLit)
+				g.Clip(1, 1, g.W-2, g.H-2, func() { g.Text(3, 0, e.Title, pixel.Ink, 1) })
+			})
+		}
+	})
+}