pim: personal information management, starting with a calendar

A calendar as a file tree, and tools that only know the tree:

	events/date/yyyy/mm/dd/hhmm-summary	as lived
	events/uuid/<uid>/			as stored
	ctl query alarm changed

lib/cal owns all of that. A backend supplies events and, where its
protocol allows, takes changes back -- six methods. cmd/icalfs is the
first: it reads .ics files from a directory and nothing else, because
fetching is rc/fetch's job and hget already exists. That keeps
net/http out of the binary and makes a subscribed calendar and a local
one the same thing.

The tools are rc on purpose. If the tree needs a compiled program to be
useful, the tree is the wrong shape. Three things were added to the
tree because the rc port needed them: a path from an occurrence to its
event, epoch seconds beside RFC3339, and a numeric slot for all-day
events so test(1) can compare it.

ctl reports caps, so a tool can say "read only" instead of trying and
failing. A published .ics is read only: nowhere to PUT, and no
METHOD:REQUEST to reply to. CalDAV would be read write rsvp schedule,
and that is the next backend.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

4 files changed, 1757 insertions, 0 deletions

diff --git a/pim/cmd/cal9/main.go b/pim/cmd/cal9/main.go
new file mode 100644
index 0000000..aa9a370
--- /dev/null
+++ b/pim/cmd/cal9/main.go
@@ -0,0 +1,1131 @@
+// cal: a calendar over the pim filesystem.
+//
+// Day, week and month views; < > step by the current unit; the wheel rolls
+// the time axis. There is no minimise button: rio has no iconify, so
+// "compact" is driven by how small you make the window instead.
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"path"
+	"sort"
+	"strconv"
+	"strings"
+	"time"
+
+	"9front/gui/draw"
+)
+
+const (
+	mtpt     = "/mnt/pim"
+	fontpath = "/lib/font/bit/lucidasans/unicode.8.font"
+
+	pad      = 6
+	gutter   = 52 // hour-label column
+	spanMin  = 11 * 60
+	compactH = 90 // below this window height, show the one-line view
+)
+
+type view int
+
+const (
+	vDay view = iota
+	vWeek
+	vMonth
+)
+
+var viewName = map[view]string{vDay: "Day", vWeek: "Week", vMonth: "Month"}
+
+// One colour per calendar. The fill is pale enough to take black text in
+// the day and week views; the ink is the same hue darkened, for the month
+// grid where events are text on the background rather than in a box.
+var calPalette = []struct{ fill, ink uint32 }{
+	{0x8888CCFF, 0x333388FF}, // purpleblue, the original event colour
+	{0x88CC88FF, 0x226622FF}, // green
+	{0xE0B080FF, 0x805000FF}, // tan
+	{0xCC8888FF, 0x883333FF}, // red
+	{0x88CCCCFF, 0x226666FF}, // cyan
+	{0xCCCC88FF, 0x666622FF}, // olive
+}
+
+type event struct {
+	min   int    // minutes past midnight
+	title string
+	file  string
+	cal   string // which calendar it came from
+}
+
+// selLine is one line of panel text, recorded so it can be selected.
+type selLine struct {
+	r    draw.Rectangle
+	text string
+}
+
+// hit is a clickable region recorded during redraw.
+type hit struct {
+	r  draw.Rectangle
+	do func(*state)
+}
+
+type state struct {
+	d    *draw.Display
+	win  *draw.Image
+	f    *draw.Font
+	col  map[string]*draw.Image
+	view view
+	cals []string        // every calendar mounted under mtpt
+	on   map[string]bool // the ones being shown
+	pick time.Time       // the day whose list is in the panel; zero for none
+
+	// Text selection in the panel, by line. Character granularity would
+	// need the font metrics per glyph; whole lines are what you want to
+	// snarf out of a calendar anyway.
+	panelR   draw.Rectangle
+	backAt   draw.Rectangle
+	openAt   draw.Rectangle
+	selLines []selLine
+	selA     int // first selected line, -1 for none
+	selB     int
+	at   time.Time // the anchor day
+	top  int       // first visible minute, day/week views
+	evs  map[string][]event
+	hits []hit
+	sel  *event // the opened event, if any
+	mc   *draw.Mousectl
+	quit bool
+}
+
+func now() time.Time { return time.Now() }
+
+func main() {
+	if err := run(); err != nil {
+		fmt.Fprintf(os.Stderr, "cal: %v\n", err)
+		os.Exit(1)
+	}
+}
+
+func run() error {
+	// -n: report what would be loaded and exit, so the calendar
+	// plumbing can be checked without a display
+	dry := false
+	want := vDay
+	args := os.Args[1:]
+	for len(args) > 0 {
+		switch {
+		case args[0] == "-n":
+			dry, args = true, args[1:]
+		case args[0] == "-v" && len(args) > 1:
+			switch args[1] {
+			case "day":
+				want = vDay
+			case "week":
+				want = vWeek
+			case "month":
+				want = vMonth
+			default:
+				return fmt.Errorf("usage: cal [-n] [-v day|week|month] [YYYY-MM-DD]")
+			}
+			args = args[2:]
+		default:
+			goto done
+		}
+	}
+done:
+
+	s := &state{view: want, at: time.Now(), top: 8 * 60, selA: -1, selB: -1}
+	s.cals = calendars()
+	s.on = map[string]bool{}
+	for _, c := range s.cals {
+		s.on[c] = true
+	}
+	if len(args) > 0 {
+		t, err := time.Parse("2006-01-02", args[0])
+		if err != nil {
+			return fmt.Errorf("usage: cal [-n] [-v day|week|month] [YYYY-MM-DD]")
+		}
+		s.at = t
+	}
+
+	if dry {
+		fmt.Printf("calendars: %v\n", s.cals)
+		for _, c := range s.cals {
+			evs, err := readDay(c, s.at)
+			fmt.Printf("%s: %d events on %s (err %v)\n",
+				c, len(evs), s.at.Format("2006-01-02"), err)
+		}
+		s.load()
+		k := s.at.Format("2006-01-02")
+		fmt.Printf("merged %s: %d\n", k, len(s.evs[k]))
+		for _, e := range s.evs[k] {
+			fmt.Printf("  %02d:%02d  %-40s [%s]\n", e.min/60, e.min%60, e.title, e.cal)
+		}
+		return nil
+	}
+
+	var err error
+	if s.d, err = draw.Init("/dev"); err != nil {
+		return err
+	}
+	defer s.d.Close()
+	if s.f, err = s.d.OpenFont(fontpath); err != nil {
+		return err
+	}
+	s.col = map[string]*draw.Image{}
+	for k, v := range map[string]uint32{
+		"bg":     0xFFFFEAFF, // acme body
+		"tag":    0xEAFFFFFF, // acme tag
+		"rule":   0x99994CFF,
+		"ink":    0x000000FF,
+		"event":  0x8888CCFF, // DPurpleblue
+		"today":  0xFFFFAAFF, // DPaleyellow
+		"pick":   0xDDE4FFFF, // the anchor day, when it is not today
+		"snarf":  0xAAC4FFFF, // selected text, on its way to /dev/snarf
+		"now":    0xCC0000FF,
+		"border": 0x8888CCFF,
+	} {
+		if s.col[k], err = s.d.Color(v); err != nil {
+			return err
+		}
+	}
+	// a fill and an ink for every calendar, wrapping if there are more
+	// calendars than colours
+	for i := range s.cals {
+		p := calPalette[i%len(calPalette)]
+		if s.col[fmt.Sprintf("fill%d", i)], err = s.d.Color(p.fill); err != nil {
+			return err
+		}
+		if s.col[fmt.Sprintf("ink%d", i)], err = s.d.Color(p.ink); err != nil {
+			return err
+		}
+	}
+
+	if s.win, err = s.d.Window("/dev"); err != nil {
+		return err
+	}
+
+	s.load()
+	s.redraw()
+
+	mc, err := draw.OpenMouse("/dev")
+	if err != nil {
+		return err
+	}
+	defer mc.Close()
+	s.mc = mc
+
+	// Consume the keyboard. Without this rio keeps its line editor on the
+	// window and paints what you type over the drawing.
+	kb, err := draw.OpenKeyboard("/dev")
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "cal: keyboard: %v\n", err)
+	} else {
+		defer kb.Close()
+	}
+	var keys <-chan rune
+	if kb != nil {
+		keys = kb.C
+	}
+
+	var wasDown, dragging bool
+	var pressed draw.Point
+	for {
+		select {
+		case m, ok := <-mc.C:
+			if !ok {
+				return nil
+			}
+			if m.Buttons&4 != 0 {
+				// Button 3 is the menu button on this system; Exit lives
+				// in there rather than owning the whole button.
+				s.menu(m.Point, mc)
+				if s.quit {
+					return nil
+				}
+				wasDown = false
+				continue
+			}
+			switch {
+			case m.Buttons&8 != 0: // wheel up
+				s.scroll(-30)
+			case m.Buttons&16 != 0: // wheel down
+				s.scroll(30)
+			}
+			down := m.Buttons&1 != 0
+			switch {
+			case down && !wasDown:
+				// A press inside the panel may be the start of a text
+				// selection, so it is not resolved until the release.
+				if i := s.lineAt(m.Point); i >= 0 && !s.inBack(m.Point) {
+					s.selA, s.selB = i, i
+					pressed = m.Point
+					dragging = true
+					s.redraw()
+				} else {
+					s.clearSel()
+					s.click(m.Point)
+				}
+			case down && dragging:
+				if i := s.lineAt(m.Point); i >= 0 && i != s.selB {
+					s.selB = i
+					s.redraw()
+				}
+			case !down && dragging:
+				dragging = false
+				if s.selA == s.selB {
+					// no drag: it was a click after all
+					s.clearSel()
+					s.click(pressed)
+				} else {
+					s.snarfSel()
+				}
+			}
+			wasDown = down
+		case r, ok := <-keys:
+			if !ok {
+				keys = nil
+				continue
+			}
+			switch r {
+			case 'q', 0x7F: // q or Del
+				return nil
+			case 't':
+				s.at = time.Now()
+				s.top = 8 * 60
+				s.load()
+				s.redraw()
+			case 'h':
+				s.step(-1)
+			case 'l':
+				s.step(1)
+			case 'd':
+				s.view = vDay
+				s.load()
+				s.redraw()
+			case 'w':
+				s.view = vWeek
+				s.load()
+				s.redraw()
+			case 'm':
+				s.view = vMonth
+				s.load()
+				s.redraw()
+			case 0x1B: // Esc clears whatever is showing
+				s.sel = nil
+				s.pick = time.Time{}
+				s.clearSel()
+				s.redraw()
+			}
+		case <-mc.Resize:
+			if s.win, err = s.d.Reattach("/dev", s.win); err != nil {
+				return err
+			}
+			s.redraw()
+		}
+	}
+}
+
+// step moves the anchor by one unit of the current view.
+func (s *state) step(n int) {
+	switch s.view {
+	case vDay:
+		s.at = s.at.AddDate(0, 0, n)
+	case vWeek:
+		s.at = s.at.AddDate(0, 0, 7*n)
+	case vMonth:
+		s.at = s.at.AddDate(0, n, 0)
+	}
+	s.load()
+	s.redraw()
+}
+
+// scroll rolls the time axis in day/week; in month it rolls whole weeks,
+// which is the only thing "up and down" can mean on a grid of days.
+func (s *state) scroll(mins int) {
+	if s.view == vMonth {
+		s.at = s.at.AddDate(0, 0, 7*sign(mins))
+		s.load()
+		s.redraw()
+		return
+	}
+	s.top += mins
+	if s.top < 0 {
+		s.top = 0
+	}
+	if s.top > 24*60-spanMin {
+		s.top = 24*60 - spanMin
+	}
+	s.redraw()
+}
+
+func sign(n int) int {
+	if n < 0 {
+		return -1
+	}
+	return 1
+}
+
+func (s *state) click(p draw.Point) {
+	for _, h := range s.hits {
+		if p.X >= h.r.Min.X && p.X < h.r.Max.X && p.Y >= h.r.Min.Y && p.Y < h.r.Max.Y {
+			h.do(s)
+			return
+		}
+	}
+}
+
+// ---------------------------------------------------------------- loading
+
+// days returns the days the current view covers.
+func (s *state) days() []time.Time {
+	switch s.view {
+	case vWeek:
+		start := s.at.AddDate(0, 0, -weekday(s.at))
+		out := make([]time.Time, 7)
+		for i := range out {
+			out[i] = start.AddDate(0, 0, i)
+		}
+		return out
+	case vMonth:
+		first := time.Date(s.at.Year(), s.at.Month(), 1, 0, 0, 0, 0, s.at.Location())
+		start := first.AddDate(0, 0, -weekday(first))
+		out := make([]time.Time, 42) // 6 weeks, the usual grid
+		for i := range out {
+			out[i] = start.AddDate(0, 0, i)
+		}
+		return out
+	}
+	return []time.Time{s.at}
+}
+
+func weekday(t time.Time) int { return int(t.Weekday()) }
+
+func (s *state) load() {
+	s.evs = map[string][]event{}
+	for _, d := range s.days() {
+		var all []event
+		for _, c := range s.cals {
+			if !s.on[c] {
+				continue
+			}
+			e, err := readDay(c, d)
+			if err != nil {
+				continue
+			}
+			all = append(all, e...)
+		}
+		if len(all) > 0 {
+			sort.Slice(all, func(i, j int) bool {
+				if all[i].min == all[j].min {
+					return all[i].title < all[j].title
+				}
+				return all[i].min < all[j].min
+			})
+			s.evs[d.Format("2006-01-02")] = all
+		}
+	}
+}
+
+// calendars names every live calendar. mntgen leaves the directory
+// behind when a server goes away, so a name only counts if something
+// still answers for ctl.
+func calendars() []string {
+	ents, err := os.ReadDir(path.Join(mtpt, "calendars"))
+	if err != nil {
+		return nil
+	}
+	var out []string
+	for _, e := range ents {
+		n := e.Name()
+		if _, err := os.Stat(path.Join(mtpt, "calendars", n, "ctl")); err == nil {
+			out = append(out, n)
+		}
+	}
+	sort.Strings(out)
+	return out
+}
+
+func readDay(cal string, t time.Time) ([]event, error) {
+	dir := path.Join(mtpt, "calendars", cal, "events", "date",
+		t.Format("2006"), t.Format("01"), t.Format("02"))
+	f, err := os.Open(dir)
+	if err != nil {
+		return nil, nil // a day with nothing on it is not an error
+	}
+	defer f.Close()
+	names, err := f.Readdirnames(-1)
+	if err != nil {
+		return nil, err
+	}
+	var evs []event
+	for _, n := range names {
+		if len(n) < 5 || n[4] != '-' {
+			continue
+		}
+		hh, e1 := strconv.Atoi(n[0:2])
+		mm, e2 := strconv.Atoi(n[2:4])
+		if e1 != nil || e2 != nil {
+			continue
+		}
+		ev := event{
+			min:   hh*60 + mm,
+			title: strings.ReplaceAll(n[5:], "-", " "),
+			file:  path.Join(dir, n),
+			cal:   cal,
+		}
+		if t := summary(ev.file); t != "" {
+			ev.title = t
+		}
+		evs = append(evs, ev)
+	}
+	sort.Slice(evs, func(i, j int) bool { return evs[i].min < evs[j].min })
+	return evs, nil
+}
+
+// summary reads only the header block, not the whole body.
+func summary(file string) string {
+	f, err := os.Open(file)
+	if err != nil {
+		return ""
+	}
+	defer f.Close()
+	sc := bufio.NewScanner(f)
+	for sc.Scan() {
+		line := sc.Text()
+		if line == "" {
+			break
+		}
+		if v, ok := strings.CutPrefix(line, "summary:"); ok {
+			return strings.TrimSpace(v)
+		}
+	}
+	return ""
+}
+
+// ---------------------------------------------------------------- drawing
+
+// fit truncates s to w pixels.
+// calKey names the colour registered for a calendar, falling back to the
+// generic event colour for anything that appeared since startup.
+func (s *state) calKey(what, cal string) string {
+	for i, c := range s.cals {
+		if c == cal {
+			k := fmt.Sprintf("%s%d", what, i)
+			if _, ok := s.col[k]; ok {
+				return k
+			}
+		}
+	}
+	if what == "fill" {
+		return "event"
+	}
+	return "ink"
+}
+
+func (s *state) fit(str string, w int32) string {
+	if s.f.Width(str) <= w {
+		return str
+	}
+	r := []rune(str)
+	for len(r) > 1 {
+		r = r[:len(r)-1]
+		if s.f.Width(string(r)+"..") <= w {
+			return string(r) + ".."
+		}
+	}
+	return ""
+}
+
+func (s *state) text(p draw.Point, c string, str string) {
+	s.f.String(s.win, p, s.col[c], str)
+}
+
+func (s *state) fill(r draw.Rectangle, c string) {
+	draw.Draw(s.win, r, s.col[c], nil, draw.ZP)
+}
+
+// button draws a labelled box and records its hit region.
+func (s *state) button(r draw.Rectangle, label string, on bool, do func(*state)) {
+	bg := "tag"
+	if on {
+		bg = "today"
+	}
+	s.fill(r, bg)
+	s.fill(draw.Rect(r.Min.X, r.Min.Y, r.Max.X, r.Min.Y+1), "border")
+	s.fill(draw.Rect(r.Min.X, r.Max.Y-1, r.Max.X, r.Max.Y), "border")
+	s.fill(draw.Rect(r.Min.X, r.Min.Y, r.Min.X+1, r.Max.Y), "border")
+	s.fill(draw.Rect(r.Max.X-1, r.Min.Y, r.Max.X, r.Max.Y), "border")
+	w := s.f.Width(label)
+	s.text(draw.Point{X: r.Min.X + (r.Dx()-w)/2, Y: r.Min.Y + 3}, "ink", label)
+	s.hits = append(s.hits, hit{r, do})
+}
+
+func (s *state) redraw() {
+	s.hits = s.hits[:0]
+	r := s.win.Rect()
+	s.fill(r, "bg")
+
+	if r.Dy() < compactH {
+		s.drawCompact(r)
+		s.d.Flush()
+		return
+	}
+
+	hdr := s.drawHeader(r)
+	body := draw.Rect(r.Min.X, hdr.Max.Y+pad, r.Max.X, r.Max.Y-pad)
+	if (s.sel != nil || (!s.pick.IsZero() && s.view != vDay)) && body.Dy() > 160 {
+		split := body.Max.Y - body.Dy()*2/5
+		s.drawDetail(draw.Rect(body.Min.X, split, body.Max.X, body.Max.Y))
+		body.Max.Y = split - pad
+	}
+	switch s.view {
+	case vDay:
+		s.drawTimeGrid(body, []time.Time{s.at})
+	case vWeek:
+		s.drawTimeGrid(body, s.days())
+	case vMonth:
+		s.drawMonth(body)
+	}
+	s.d.Flush()
+}
+
+func (s *state) drawHeader(r draw.Rectangle) draw.Rectangle {
+	h := int32(s.f.Height) + 8
+	hdr := draw.Rect(r.Min.X, r.Min.Y, r.Max.X, r.Min.Y+h)
+	s.fill(hdr, "tag")
+
+	// Buttons, right to left: Month Week Day  >  <
+	x := r.Max.X - pad
+	mk := func(label string, on bool, do func(*state)) {
+		w := s.f.Width(label) + 16
+		br := draw.Rect(x-w, hdr.Min.Y+2, x, hdr.Max.Y-2)
+		s.button(br, label, on, do)
+		x = br.Min.X - 4
+	}
+	for _, v := range []view{vMonth, vWeek, vDay} {
+		vv := v
+		mk(viewName[v], s.view == v, func(st *state) {
+			st.view = vv
+			if vv == vDay {
+				st.pick = time.Time{}
+			}
+			st.load()
+			st.redraw()
+		})
+	}
+	x -= 6
+	mk(">", false, func(st *state) { st.step(1) })
+	mk("<", false, func(st *state) { st.step(-1) })
+	x -= 6
+	mk("Today", false, func(st *state) {
+		st.at = time.Now()
+		st.top = 8 * 60
+		st.load()
+		st.redraw()
+	})
+
+	s.text(draw.Point{X: r.Min.X + pad, Y: hdr.Min.Y + 4}, "ink", s.fit(s.title(), x-r.Min.X-pad*2))
+	return hdr
+}
+
+func (s *state) title() string {
+	switch s.view {
+	case vWeek:
+		d := s.days()
+		return d[0].Format("2 Jan") + " - " + d[6].Format("2 Jan 2006")
+	case vMonth:
+		return s.at.Format("January 2006")
+	}
+	return s.at.Format("Monday 2 January 2006")
+}
+
+// drawTimeGrid renders one or more day columns against an hour axis.
+func (s *state) drawTimeGrid(r draw.Rectangle, days []time.Time) {
+	top, bot := r.Min.Y+int32(s.f.Height)+4, r.Max.Y
+	if bot <= top {
+		return
+	}
+	pxPerMin := float64(bot-top) / float64(spanMin)
+	yOf := func(m int) int32 { return top + int32(float64(m-s.top)*pxPerMin) }
+
+	// Hour rules across the whole body.
+	for m := (s.top/60 + 1) * 60; m < s.top+spanMin; m += 60 {
+		y := yOf(m)
+		s.fill(draw.Rect(r.Min.X+gutter, y, r.Max.X-pad, y+1), "rule")
+		s.text(draw.Point{X: r.Min.X + pad, Y: y - int32(s.f.Height)/2}, "ink",
+			fmt.Sprintf("%02d:00", m/60))
+	}
+
+	colw := (r.Dx() - gutter - pad) / int32(len(days))
+	today := time.Now().Format("2006-01-02")
+	for i, d := range days {
+		x0 := r.Min.X + gutter + int32(i)*colw
+		cr := draw.Rect(x0, top, x0+colw-2, bot)
+		key := d.Format("2006-01-02")
+
+		if len(days) > 1 {
+			lab := d.Format("Mon 2")
+			c := "ink"
+			hdr := draw.Rect(cr.Min.X, r.Min.Y, cr.Max.X, top-2)
+			switch {
+			case !s.pick.IsZero() && key == s.pick.Format("2006-01-02"):
+				s.fill(hdr, "pick")
+			case key == time.Now().Format("2006-01-02"):
+				s.fill(hdr, "today")
+			}
+			s.text(draw.Point{X: cr.Min.X + 4, Y: r.Min.Y}, c, s.fit(lab, colw-8))
+			dd := d
+			s.hits = append(s.hits, hit{hdr, func(st *state) { st.pickDay(dd) }})
+		}
+
+		for _, e := range s.evs[key] {
+			if e.min < s.top || e.min > s.top+spanMin {
+				continue
+			}
+			y := yOf(e.min)
+			box := draw.Rect(cr.Min.X+2, y+1, cr.Max.X, y+int32(s.f.Height)+6)
+			if box.Max.Y > bot {
+				continue
+			}
+			s.fill(box, s.calKey("fill", e.cal))
+			lab := fmt.Sprintf("%02d:%02d %s", e.min/60, e.min%60, e.title)
+			s.text(draw.Point{X: box.Min.X + 4, Y: box.Min.Y + 2}, "ink",
+				s.fit(lab, box.Dx()-8))
+			ev := e
+			s.hits = append(s.hits, hit{box, func(st *state) {
+				st.sel = &ev
+				st.redraw()
+			}})
+		}
+
+		// Now line.
+		if key == today {
+			m := time.Now().Hour()*60 + time.Now().Minute()
+			if m >= s.top && m <= s.top+spanMin {
+				y := yOf(m)
+				s.fill(draw.Rect(cr.Min.X, y, cr.Max.X, y+2), "now")
+			}
+		}
+	}
+}
+
+// drawMonth renders a 6x7 grid of days with as many titles as fit.
+func (s *state) drawMonth(r draw.Rectangle) {
+	days := s.days()
+	cw := r.Dx() / 7
+	ch := r.Dy() / 6
+	if cw < 20 || ch < 20 {
+		return
+	}
+	today := time.Now().Format("2006-01-02")
+	picked := ""
+	if !s.pick.IsZero() {
+		picked = s.pick.Format("2006-01-02")
+	}
+	lh := int32(s.f.Height) + 1
+	// A day cell covers its events, and click takes the first hit, so
+	// these are appended only once every event hit is already down.
+	var dayHits []hit
+	for i, d := range days {
+		cx := r.Min.X + int32(i%7)*cw
+		cy := r.Min.Y + int32(i/7)*ch
+		cell := draw.Rect(cx, cy, cx+cw-2, cy+ch-2)
+		key := d.Format("2006-01-02")
+
+		switch {
+		case key == picked:
+			s.fill(cell, "pick")
+		case key == today:
+			s.fill(cell, "today")
+		}
+		if d.Month() != s.at.Month() {
+			// Outside the anchor month: leave it on the background.
+			s.fill(draw.Rect(cell.Min.X, cell.Min.Y, cell.Max.X, cell.Min.Y+1), "rule")
+		} else {
+			s.fill(draw.Rect(cell.Min.X, cell.Min.Y, cell.Max.X, cell.Min.Y+1), "rule")
+		}
+		s.text(draw.Point{X: cell.Min.X + 3, Y: cell.Min.Y + 2}, "ink", d.Format("2"))
+
+		y := cell.Min.Y + 2 + lh
+		for _, e := range s.evs[key] {
+			if y+lh > cell.Max.Y {
+				break
+			}
+			lab := fmt.Sprintf("%02d:%02d %s", e.min/60, e.min%60, e.title)
+			s.text(draw.Point{X: cell.Min.X + 3, Y: y}, s.calKey("ink", e.cal),
+				s.fit(lab, cell.Dx()-6))
+			ev := e
+			s.hits = append(s.hits, hit{
+				draw.Rect(cell.Min.X, y, cell.Max.X, y+lh),
+				func(st *state) { st.sel = &ev; st.redraw() },
+			})
+			y += lh
+		}
+
+		dd := d
+		dayHits = append(dayHits, hit{cell, func(st *state) { st.pickDay(dd) }})
+	}
+	s.hits = append(s.hits, dayHits...)
+}
+
+func min(a, b int) int { if a < b { return a }; return b }
+func max(a, b int) int { if a > b { return a }; return b }
+
+func (s *state) clearSel() { s.selA, s.selB = -1, -1 }
+
+// openCal starts another cal in its own window. A second view is a
+// second process here, not a second window inside this one.
+func (s *state) openCal(v view, d time.Time) {
+	s.wctl(fmt.Sprintf("new -dx 820 -dy 620 cal9 -v %s %s",
+		strings.ToLower(viewName[v]), d.Format("2006-01-02")))
+}
+
+// openEvent pins one event in a window of its own.
+func (s *state) openEvent(e *event) {
+	s.wctl(fmt.Sprintf("new -dx 540 -dy 360 pim/showwin %s", e.file))
+}
+
+// inBack reports whether a point is on the panel's Back button, which
+// must act as a button rather than start a selection.
+func (s *state) inBack(p draw.Point) bool {
+	for _, r := range []draw.Rectangle{s.backAt, s.openAt} {
+		if p.X >= r.Min.X && p.X < r.Max.X && p.Y >= r.Min.Y && p.Y < r.Max.Y {
+			return true
+		}
+	}
+	return false
+}
+
+// lineAt finds the panel line under a point, -1 if there is none.
+func (s *state) lineAt(p draw.Point) int {
+	for i, l := range s.selLines {
+		if p.X >= l.r.Min.X && p.X < l.r.Max.X && p.Y >= l.r.Min.Y && p.Y < l.r.Max.Y {
+			return i
+		}
+	}
+	return -1
+}
+
+// snarfSel puts the selected lines on /dev/snarf.
+func (s *state) snarfSel() {
+	if s.selA < 0 {
+		return
+	}
+	var b strings.Builder
+	for i := min(s.selA, s.selB); i <= max(s.selA, s.selB) && i < len(s.selLines); i++ {
+		b.WriteString(strings.TrimRight(s.selLines[i].text, " "))
+		b.WriteByte('\n')
+	}
+	if err := draw.Snarf("/dev", b.String()); err != nil {
+		fmt.Fprintf(os.Stderr, "cal: snarf: %v\n", err)
+	}
+}
+
+// pickDay puts a whole day in the panel below. A month cell only has
+// room for the first few events, and this is how you see the rest without
+// losing the month.
+func (s *state) pickDay(d time.Time) {
+	s.pick = d
+	s.sel = nil
+	s.redraw()
+}
+
+// drawCompact is what you get by making the window small: the next thing
+// due. No minimise button, because rio has no iconify to hook one to.
+func (s *state) drawCompact(r draw.Rectangle) {
+	s.fill(r, "tag")
+	now := time.Now()
+	key := now.Format("2006-01-02")
+	cur := now.Hour()*60 + now.Minute()
+	var next *event
+	for i, e := range s.evs[key] {
+		if e.min >= cur {
+			next = &s.evs[key][i]
+			break
+		}
+	}
+	y := r.Min.Y + 2
+	if next == nil {
+		s.text(draw.Point{X: r.Min.X + pad, Y: y}, "ink",
+			s.fit("nothing else today", r.Dx()-pad*2))
+		return
+	}
+	in := next.min - cur
+	s.text(draw.Point{X: r.Min.X + pad, Y: y}, "ink",
+		s.fit(fmt.Sprintf("%02d:%02d  %s", next.min/60, next.min%60, next.title), r.Dx()-pad*2))
+	s.text(draw.Point{X: r.Min.X + pad, Y: y + int32(s.f.Height) + 2}, "ink",
+		s.fit(fmt.Sprintf("in %d min", in), r.Dx()-pad*2))
+}
+
+// drawDetail shows the opened event. The date tree carries only the basics;
+// everything else -- attendees, organizer, location, the full description --
+// lives in the per-event directory in the uuid tree, which the "event:"
+// header points at relative to the day directory.
+func (s *state) drawDetail(r draw.Rectangle) {
+	s.fill(r, "tag")
+	s.fill(draw.Rect(r.Min.X, r.Min.Y, r.Max.X, r.Min.Y+1), "border")
+	s.panelR = r
+	s.selLines = s.selLines[:0]
+
+	y := r.Min.Y + 4
+	lh := int32(s.f.Height) + 2
+	line := func(c, str string) {
+		if y+lh > r.Max.Y {
+			return
+		}
+		lr := draw.Rect(r.Min.X, y, r.Max.X, y+lh)
+		i := len(s.selLines)
+		if s.selA >= 0 && i >= min(s.selA, s.selB) && i <= max(s.selA, s.selB) {
+			s.fill(lr, "snarf")
+		}
+		s.selLines = append(s.selLines, selLine{lr, str})
+		s.text(draw.Point{X: r.Min.X + pad, Y: y}, c, s.fit(str, r.Dx()-pad*2))
+		y += lh
+	}
+
+	// A real button, like the ones in the header, rather than a line of
+	// text that happens to be clickable.
+	// Back, and Open beside it. Open means "put this in a window of its
+	// own and leave it there".
+	bar := func(back func(*state), open func(*state)) {
+		x := r.Min.X + pad
+		mk := func(label string, do func(*state)) draw.Rectangle {
+			bw := s.f.Width(label) + 20
+			br := draw.Rect(x, y, x+bw, y+lh+2)
+			s.button(br, label, false, do)
+			x = br.Max.X + 6
+			return br
+		}
+		s.backAt = mk("Back", back)
+		s.openAt = mk("Open", open)
+		y = s.openAt.Max.Y + 4
+	}
+
+	// A day was clicked and no single event chosen: list the day.
+	if s.sel == nil {
+		key := s.pick.Format("2006-01-02")
+		evs := s.evs[key]
+		// Back from a day means no panel at all; the month is behind it.
+		d := s.pick
+		bar(func(st *state) { st.pick = time.Time{}; st.clearSel(); st.redraw() },
+			func(st *state) { st.openCal(vDay, d) })
+		line("ink", s.pick.Format("Monday 2 January 2006")+
+			fmt.Sprintf("   (%d)", len(evs)))
+		y += 3
+		for _, e := range evs {
+			ev := e
+			top := y
+			lab := fmt.Sprintf("%02d:%02d  %s", e.min/60, e.min%60, e.title)
+			if e.min == 0 && strings.HasPrefix(path.Base(e.file), "0000-allday-") {
+				lab = "all day  " + e.title
+			}
+			line(s.calKey("ink", e.cal), lab)
+			if y > top {
+				s.hits = append(s.hits, hit{
+					draw.Rect(r.Min.X, top, r.Max.X, y),
+					func(st *state) { st.sel = &ev; st.redraw() },
+				})
+			}
+		}
+		if len(evs) == 0 {
+			line("ink", "nothing")
+		}
+		return
+	}
+
+	e := s.sel
+	hdrs, body := readEvent(e.file)
+
+	// A way back up. Coming from a month cell there is otherwise nothing
+	// to click but the menu, and no sign of which day this was.
+	day, haveDay := dayOf(hdrs["start"])
+	if haveDay && s.view != vDay {
+		d := day
+		ev := e
+		bar(func(st *state) { st.pick = d; st.sel = nil; st.clearSel(); st.redraw() },
+			func(st *state) { st.openEvent(ev) })
+		line("ink", d.Format("Monday 2 January 2006"))
+		y += 3
+	} else {
+		// In day view the grid behind is already the whole day, so
+		// there is nothing to go back to but the grid itself.
+		ev := e
+		bar(func(st *state) {
+			st.sel = nil
+			st.pick = time.Time{}
+			st.clearSel()
+			st.redraw()
+		}, func(st *state) { st.openEvent(ev) })
+		if haveDay {
+			line("ink", day.Format("Monday 2 January 2006"))
+			y += 3
+		}
+	}
+
+	line("ink", hdrs["summary"])
+	if st, en := hdrs["start"], hdrs["end"]; st != "" {
+		when := clock(st) + " - " + clock(en)
+		if !haveDay {
+			when = st
+		}
+		if hdrs["rrule"] != "" {
+			when += "   (repeats)"
+		}
+		line("ink", when)
+	}
+
+	det := uuidDir(e.file, hdrs["event"])
+	if loc := strings.TrimSpace(field(det, "location")); loc != "" {
+		line("ink", "at "+loc)
+	}
+	if org := strings.TrimSpace(field(det, "organizer")); org != "" {
+		line("ink", "organizer: "+org)
+	}
+	if att := attendees(det); len(att) > 0 {
+		y += 3
+		line("ink", fmt.Sprintf("%d attendees", len(att)))
+		for _, a := range att {
+			line("ink", "  "+a)
+		}
+	}
+
+	if strings.TrimSpace(body) == "" {
+		body = field(det, "description")
+	}
+	if strings.TrimSpace(body) != "" {
+		y += 3
+		for _, w := range wrap(s, body, r.Dx()-pad*2) {
+			line("ink", w)
+		}
+	}
+}
+
+// uuidDir resolves the "event:" cross-link, which is relative to the day
+// directory the event file sits in.
+func uuidDir(eventFile, link string) string {
+	if link == "" {
+		return ""
+	}
+	return path.Clean(path.Join(path.Dir(eventFile), link))
+}
+
+// field reads one file out of the event's uuid directory.
+func field(dir, name string) string {
+	if dir == "" {
+		return ""
+	}
+	b, err := os.ReadFile(path.Join(dir, name))
+	if err != nil {
+		return ""
+	}
+	return string(b)
+}
+
+// attendees renders the tab-separated STATUS/name/email rows compactly, with
+// the status as a leading mark so a long list still scans.
+func attendees(dir string) []string {
+	raw := field(dir, "attendees")
+	if strings.TrimSpace(raw) == "" {
+		return nil
+	}
+	mark := map[string]string{
+		"ACCEPTED":     "+",
+		"DECLINED":     "-",
+		"TENTATIVE":    "~",
+		"NEEDS-ACTION": "?",
+	}
+	var out []string
+	for _, ln := range strings.Split(strings.TrimRight(raw, "\n"), "\n") {
+		f := strings.Split(ln, "\t")
+		if len(f) == 0 || strings.TrimSpace(ln) == "" {
+			continue
+		}
+		st := strings.TrimSpace(f[0])
+		m, ok := mark[st]
+		if !ok {
+			m = "."
+		}
+		who := st
+		if len(f) > 1 && strings.TrimSpace(f[1]) != "" {
+			who = strings.TrimSpace(f[1])
+		} else if len(f) > 2 {
+			who = strings.TrimSpace(f[2])
+		}
+		out = append(out, m+" "+who)
+	}
+	return out
+}
+
+// clock pulls HH:MM out of an RFC3339 timestamp without parsing it; the
+// filesystem already guarantees the shape.
+// dayOf returns the date part of a start header as a time, so the event
+// panel can say which day it is on and offer a way back to that day.
+func dayOf(ts string) (time.Time, bool) {
+	if len(ts) < 10 {
+		return time.Time{}, false
+	}
+	t, err := time.ParseInLocation("2006-01-02", ts[:10], time.Local)
+	if err != nil {
+		return time.Time{}, false
+	}
+	return t, true
+}
+
+func clock(ts string) string {
+	if i := strings.IndexByte(ts, 'T'); i >= 0 && len(ts) >= i+6 {
+		return ts[i+1 : i+6]
+	}
+	return ts
+}
+
+// readEvent splits the header block from the body.
+func readEvent(file string) (map[string]string, string) {
+	h := map[string]string{}
+	b, err := os.ReadFile(file)
+	if err != nil {
+		return h, ""
+	}
+	txt := string(b)
+	i := strings.Index(txt, "\n\n")
+	head, body := txt, ""
+	if i >= 0 {
+		head, body = txt[:i], txt[i+2:]
+	}
+	for _, ln := range strings.Split(head, "\n") {
+		if k, v, ok := strings.Cut(ln, ":"); ok {
+			h[strings.TrimSpace(k)] = strings.TrimSpace(v)
+		}
+	}
+	return h, body
+}
+
+// wrap breaks text to fit w pixels, keeping existing line breaks.
+func wrap(s *state, text string, w int32) []string {
+	var out []string
+	for _, para := range strings.Split(text, "\n") {
+		if strings.TrimSpace(para) == "" {
+			out = append(out, "")
+			continue
+		}
+		cur := ""
+		for _, word := range strings.Fields(para) {
+			try := word
+			if cur != "" {
+				try = cur + " " + word
+			}
+			if s.f.Width(try) <= w {
+				cur = try
+				continue
+			}
+			if cur != "" {
+				out = append(out, cur)
+			}
+			cur = word
+		}
+		if cur != "" {
+			out = append(out, cur)
+		}
+	}
+	return out
+}
diff --git a/pim/cmd/cal9/menu.go b/pim/cmd/cal9/menu.go
new file mode 100644
index 0000000..4443b00
--- /dev/null
+++ b/pim/cmd/cal9/menu.go
@@ -0,0 +1,267 @@
+package main
+
+import (
+	"fmt"
+	"time"
+	"os"
+	"os/exec"
+	"regexp"
+	"strings"
+
+	"9front/gui/draw"
+)
+
+// A button-3 menu, the way page and vdir do it: press 3, drag, release on an
+// item. acme's plumb-on-3 is the outlier on this system, so plumbing lives
+// in here as an item rather than owning the button.
+type menuItem struct {
+	label string
+	do    func(*state)
+}
+
+func (s *state) menu(at draw.Point, mc *draw.Mousectl) {
+	items := s.menuItems()
+	if len(items) == 0 {
+		return
+	}
+
+	lh := int32(s.f.Height) + 4
+	var w int32
+	for _, it := range items {
+		if x := s.f.Width(it.label) + 20; x > w {
+			w = x
+		}
+	}
+	h := lh*int32(len(items)) + 4
+	win := s.win.Rect()
+	r := draw.Rect(at.X, at.Y, at.X+w, at.Y+h)
+	// Keep it on screen.
+	if r.Max.X > win.Max.X {
+		r = r.Add(draw.Point{X: win.Max.X - r.Max.X})
+	}
+	if r.Max.Y > win.Max.Y {
+		r = r.Add(draw.Point{Y: win.Max.Y - r.Max.Y})
+	}
+
+	sel := -1
+	paint := func() {
+		s.fill(r, "tag")
+		s.fill(draw.Rect(r.Min.X, r.Min.Y, r.Max.X, r.Min.Y+1), "border")
+		s.fill(draw.Rect(r.Min.X, r.Max.Y-1, r.Max.X, r.Max.Y), "border")
+		s.fill(draw.Rect(r.Min.X, r.Min.Y, r.Min.X+1, r.Max.Y), "border")
+		s.fill(draw.Rect(r.Max.X-1, r.Min.Y, r.Max.X, r.Max.Y), "border")
+		for i, it := range items {
+			ir := draw.Rect(r.Min.X+1, r.Min.Y+2+int32(i)*lh, r.Max.X-1, r.Min.Y+2+int32(i+1)*lh)
+			if i == sel {
+				s.fill(ir, "today")
+			}
+			s.text(draw.Point{X: ir.Min.X + 8, Y: ir.Min.Y + 2}, "ink", it.label)
+		}
+		s.d.Flush()
+	}
+	itemAt := func(p draw.Point) int {
+		if p.X < r.Min.X || p.X >= r.Max.X {
+			return -1
+		}
+		i := int((p.Y - r.Min.Y - 2) / lh)
+		if i < 0 || i >= len(items) || p.Y < r.Min.Y+2 {
+			return -1
+		}
+		return i
+	}
+	paint()
+
+	// Track until button 3 comes back up.
+	for m := range mc.C {
+		if n := itemAt(m.Point); n != sel {
+			sel = n
+			paint()
+		}
+		if m.Buttons&4 == 0 {
+			if sel >= 0 {
+				items[sel].do(s)
+			} else {
+				s.redraw()
+			}
+			return
+		}
+	}
+}
+
+func (s *state) menuItems() []menuItem {
+	items := []menuItem{}
+	if s.sel != nil {
+		items = append(items, menuItem{"Plumb", func(st *state) {
+			if err := st.plumb(st.sel); err != nil {
+				fmt.Fprintf(os.Stderr, "cal: plumb: %v\n", err)
+			}
+			st.redraw()
+		}})
+		items = append(items, menuItem{"Open event", func(st *state) {
+			st.openEvent(st.sel)
+		}})
+		items = append(items, menuItem{"Close event", func(st *state) {
+			st.sel = nil
+			st.redraw()
+		}})
+	}
+	if s.sel == nil && !s.pick.IsZero() {
+		items = append(items, menuItem{"Close day", func(st *state) {
+			st.pick = time.Time{}
+			st.redraw()
+		}})
+	}
+	// one toggle per calendar, so a crowded work calendar can be put
+	// aside without unmounting anything
+	for _, c := range s.cals {
+		c := c
+		mark := "[ ] "
+		if s.on[c] {
+			mark = "[x] "
+		}
+		items = append(items, menuItem{mark + c, func(st *state) {
+			st.on[c] = !st.on[c]
+			st.load()
+			st.redraw()
+		}})
+	}
+	// A second view of the calendar is a second cal, in its own window.
+	items = append(items, menuItem{"Open " + strings.ToLower(viewName[s.view]),
+		func(st *state) { st.openCal(st.view, st.at) }})
+	if !s.pick.IsZero() && s.view != vDay {
+		d := s.pick
+		items = append(items, menuItem{"Open " + d.Format("2 Jan"),
+			func(st *state) { st.openCal(vDay, d) }})
+	}
+	items = append(items,
+		menuItem{"Today", func(st *state) {
+			st.at = now()
+			st.top = 8 * 60
+			st.load()
+			st.redraw()
+		}},
+		// rio has no iconify, so "compact" is a resize request: shrink the
+		// window and the small-window view takes over by itself.
+		menuItem{"Compact", func(st *state) {
+			r := st.win.Rect()
+			st.wctl(fmt.Sprintf("resize -r %d %d %d %d",
+				r.Min.X, r.Min.Y, r.Min.X+320, r.Min.Y+72))
+		}},
+		menuItem{"Restore", func(st *state) {
+			r := st.win.Rect()
+			st.wctl(fmt.Sprintf("resize -r %d %d %d %d",
+				r.Min.X, r.Min.Y, r.Min.X+820, r.Min.Y+620))
+		}},
+		menuItem{"Move", func(st *state) { st.track(st.mc, false) }},
+		menuItem{"Resize", func(st *state) { st.track(st.mc, true) }},
+		menuItem{"Hide", func(st *state) { st.wctl("hide") }},
+		menuItem{"Exit", func(st *state) { st.quit = true }},
+	)
+	return items
+}
+
+// wctl asks rio to do something to our window. Errors are worth showing:
+// outside rio there is no wctl and the menu items simply do nothing.
+func (s *state) wctl(cmd string) {
+	f, err := os.OpenFile("/dev/wctl", os.O_WRONLY, 0)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "cal: wctl: %v\n", err)
+		return
+	}
+	defer f.Close()
+	if _, err := f.WriteString(cmd); err != nil {
+		fmt.Fprintf(os.Stderr, "cal: wctl %q: %v\n", cmd, err)
+	}
+}
+
+var urlRe = regexp.MustCompile(`https?://[^\s<>"]+`)
+
+// plumb sends the event's join link to the plumber, falling back to the
+// event file itself, which lands in acme.
+func (s *state) plumb(e *event) error {
+	data := e.file
+	if body, err := os.ReadFile(e.file); err == nil {
+		if m := urlRe.Find(body); m != nil {
+			data = strings.TrimRight(string(m), ".,)")
+		}
+	}
+	return exec.Command("/bin/plumb", data).Run()
+}
+
+// track implements Move and Resize ourselves. rio's wctl has no "let the
+// user sweep" verb -- only move/resize with an explicit rectangle -- so we
+// follow the pointer and write a new rect as it goes, and rio does the
+// actual work. Any button press drops the window where it is.
+//
+// rio hands out a new image whenever the window's screen rect changes, so
+// this loop has to service resize events as well as motion, or every write
+// would be drawing into a stale image.
+func (s *state) track(mc *draw.Mousectl, resize bool) {
+	r := s.win.Rect()
+	w, h := r.Dx(), r.Dy()
+	grab := draw.Point{} // pointer offset within the window, for Move
+	first := true
+	last := r
+
+	for {
+		select {
+		case m, ok := <-mc.C:
+			if !ok {
+				return
+			}
+			if first {
+				grab = draw.Point{X: m.X - r.Min.X, Y: m.Y - r.Min.Y}
+				first = false
+				continue
+			}
+			if m.Buttons != 0 { // any press drops it
+				s.redraw()
+				return
+			}
+			var nr draw.Rectangle
+			if resize {
+				nr = draw.Rect(r.Min.X, r.Min.Y, m.X, m.Y)
+				if nr.Dx() < 120 {
+					nr.Max.X = nr.Min.X + 120
+				}
+				if nr.Dy() < 60 {
+					nr.Max.Y = nr.Min.Y + 60
+				}
+			} else {
+				min := draw.Point{X: m.X - grab.X, Y: m.Y - grab.Y}
+				nr = draw.Rect(min.X, min.Y, min.X+w, min.Y+h)
+			}
+			// Only bother rio when it would actually change something.
+			if abs(nr.Min.X-last.Min.X)+abs(nr.Min.Y-last.Min.Y)+
+				abs(nr.Max.X-last.Max.X)+abs(nr.Max.Y-last.Max.Y) < 4 {
+				continue
+			}
+			last = nr
+			verb := "move"
+			if resize {
+				verb = "resize"
+			}
+			s.wctl(fmt.Sprintf("%s -r %d %d %d %d", verb,
+				nr.Min.X, nr.Min.Y, nr.Max.X, nr.Max.Y))
+
+		case <-mc.Resize:
+			win, err := s.d.Reattach("/dev", s.win)
+			if err != nil {
+				return
+			}
+			s.win = win
+			r = s.win.Rect()
+			if !resize {
+				w, h = r.Dx(), r.Dy()
+			}
+			s.redraw()
+		}
+	}
+}
+
+func abs(n int32) int32 {
+	if n < 0 {
+		return -n
+	}
+	return n
+}
diff --git a/pim/cmd/icalfs/config.go b/pim/cmd/icalfs/config.go
new file mode 100644
index 0000000..b081743
--- /dev/null
+++ b/pim/cmd/icalfs/config.go
@@ -0,0 +1,137 @@
+package main
+
+import (
+	"pim/lib/cal"
+
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+	"sync"
+	"time"
+)
+
+// A Cal is one calendar the server keeps current.
+//
+// The config is per-user, in ndb's attribute-pair syntax, one calendar
+// per line:
+//
+//	cal=work me=you@work.example
+//	cal=home me=you@home.example,alias@home.example
+//
+// In iTIP your identity is the mailto: in your own ATTENDEE line -- there
+// is no separate field for it -- so a calendar has to be told whose it
+// is before anything can reply on its behalf. Aliases are listed because
+// you may be invited at one address and send from another.
+//
+// Fetching is not this server's business. A subscribed calendar is a
+// file somebody else wrote; see pim/fetch(1).
+//
+// It lives in $home/lib/pim by default. The urls of private calendars
+// are secrets, which is the other reason they belong in a file rather
+// than in argv where ps(1) would show them.
+type Cal struct {
+	Name    string
+	Refresh time.Duration // how often to re-stat, if the config says
+	File    string
+	Me      []string // the addresses that count as you on this calendar
+
+	mu   sync.Mutex
+	last time.Time
+	err  string
+}
+
+func (c *Cal) status() (time.Time, string) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	return c.last, c.err
+}
+
+func (c *Cal) note(t time.Time, err error) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	c.last = t
+	if err != nil {
+		c.err = err.Error()
+	} else {
+		c.err = ""
+	}
+}
+
+// readConfig parses the calendar list. Blank lines and lines beginning
+// with # are ignored; everything else is a tuple of attr=value pairs.
+func readConfig(path, dir string) ([]*Cal, error) {
+	b, err := os.ReadFile(path)
+	if err != nil {
+		return nil, err
+	}
+	var cals []*Cal
+	for n, line := range strings.Split(string(b), "\n") {
+		line = strings.TrimSpace(line)
+		if line == "" || strings.HasPrefix(line, "#") {
+			continue
+		}
+		c := &Cal{Refresh: 15 * time.Minute}
+		for _, f := range strings.Fields(line) {
+			k, v, ok := strings.Cut(f, "=")
+			if !ok {
+				return nil, fmt.Errorf("%s:%d: %q is not attr=value", path, n+1, f)
+			}
+			v = strings.Trim(v, `"'`)
+			switch k {
+			case "cal":
+				c.Name = v
+			case "url":
+				// fetching moved out; the url belongs to the script
+				// that writes the file
+				cal.Warnf("%s:%d: url= is ignored, see pim/fetch", path, n+1)
+			case "me":
+				for _, a := range strings.Split(v, ",") {
+					if a = strings.TrimSpace(a); a != "" {
+						c.Me = append(c.Me, a)
+					}
+				}
+			case "refresh":
+				d, err := time.ParseDuration(v)
+				if err != nil || d <= 0 {
+					return nil, fmt.Errorf("%s:%d: bad refresh %q", path, n+1, v)
+				}
+				c.Refresh = d
+			default:
+				return nil, fmt.Errorf("%s:%d: unknown attribute %q", path, n+1, k)
+			}
+		}
+		if c.Name == "" {
+			return nil, fmt.Errorf("%s:%d: no cal= name", path, n+1)
+		}
+		c.File = filepath.Join(dir, c.Name+".ics")
+		cals = append(cals, c)
+	}
+	if len(cals) == 0 {
+		return nil, fmt.Errorf("%s: no calendars", path)
+	}
+	return cals, nil
+}
+
+// pick selects one calendar by name. A server serves exactly one; the
+// config lists them all so that whatever starts them has a single place
+// to read.
+func pick(cals []*Cal, name string) (*Cal, error) {
+	if name == "" {
+		if len(cals) == 1 {
+			return cals[0], nil
+		}
+		var names []string
+		for _, c := range cals {
+			names = append(names, c.Name)
+		}
+		return nil, fmt.Errorf("which calendar? -N one of: %s",
+			strings.Join(names, " "))
+	}
+	for _, c := range cals {
+		if c.Name == name {
+			return c, nil
+		}
+	}
+	return nil, fmt.Errorf("no calendar named %q", name)
+}
diff --git a/pim/cmd/icalfs/main.go b/pim/cmd/icalfs/main.go
new file mode 100644
index 0000000..c155252
--- /dev/null
+++ b/pim/cmd/icalfs/main.go
@@ -0,0 +1,222 @@
+// ical/fs serves a directory of .ics files as a 9p file system.
+//
+// It does not fetch anything. A subscribed calendar is a file somebody
+// else wrote -- pim/fetch(1), a svc entry, an editor -- which is why a
+// local calendar and a subscribed one are the same thing here. Writing
+// a file and poking ctl is the whole interface for keeping it current.
+//
+// It is one backend behind pim/lib/cal, which owns the tree. Files on
+// disk are read-only as far as scheduling goes: there is nowhere to PUT
+// and no METHOD:REQUEST to reply to, so this backend reports "read" and
+// nothing above it has to guess.
+package main
+
+import (
+	"flag"
+	"fmt"
+	"os"
+	"path/filepath"
+	"sort"
+	"strings"
+	"sync"
+	"time"
+
+	"pim/lib/cal"
+)
+
+func fatal(format string, a ...interface{}) {
+	cal.Warnf(format, a...)
+	os.Exit(1)
+}
+
+// backend reads a directory of .ics files.
+type backend struct {
+	c    *Cal // nil when serving -d alone
+	dir  string
+	poll time.Duration
+
+	mu   sync.Mutex
+	evs  []*cal.Event
+	sig  string // what the directory looked like when last loaded
+	last time.Time
+	err  string
+}
+
+func (b *backend) Name() string {
+	if b.c != nil {
+		return b.c.Name
+	}
+	return "calendar"
+}
+
+// A published feed can only be read. See pim/doc/design.md.
+func (b *backend) Caps() string { return "read" }
+
+// Refresh is how often to re-stat the directory. Whoever writes the
+// files should poke ctl instead; this only catches a hand edit.
+func (b *backend) Refresh() time.Duration { return b.poll }
+
+func (b *backend) Status() (time.Time, string) {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+	return b.last, b.err
+}
+
+func (b *backend) Describe() string {
+	s := fmt.Sprintf("dir %s\n", b.dir)
+	if b.c != nil && len(b.c.Me) > 0 {
+		s += "me " + joinComma(b.c.Me) + "\n"
+	}
+	return s
+}
+
+// Sync reloads if the directory has changed. Name, size and mtime are
+// enough to notice: a rewrite that keeps all three identical is a
+// rewrite of identical content.
+func (b *backend) Sync() (bool, error) {
+	sig, err := dirsig(b.dir)
+	b.note(time.Now(), err)
+	if err != nil {
+		return false, err
+	}
+	b.mu.Lock()
+	same := sig == b.sig && b.evs != nil
+	b.mu.Unlock()
+	if same {
+		return false, nil
+	}
+	evs, err := cal.LoadDir(b.dir)
+	if err != nil {
+		return false, err
+	}
+	b.mu.Lock()
+	b.evs, b.sig = evs, sig
+	b.mu.Unlock()
+	return true, nil
+}
+
+// dirsig summarises every .ics in dir.
+func dirsig(dir string) (string, error) {
+	names, err := filepath.Glob(filepath.Join(dir, "*.ics"))
+	if err != nil {
+		return "", err
+	}
+	sort.Strings(names)
+	var b strings.Builder
+	for _, n := range names {
+		fi, err := os.Stat(n)
+		if err != nil {
+			continue
+		}
+		fmt.Fprintf(&b, "%s:%d:%d\n", n, fi.Size(), fi.ModTime().UnixNano())
+	}
+	return b.String(), nil
+}
+
+func (b *backend) Events() ([]*cal.Event, error) {
+	b.mu.Lock()
+	evs := b.evs
+	b.mu.Unlock()
+	if evs != nil {
+		return evs, nil
+	}
+	evs, err := cal.LoadDir(b.dir)
+	if err != nil {
+		return nil, err
+	}
+	b.mu.Lock()
+	b.evs = evs
+	b.mu.Unlock()
+	return evs, nil
+}
+
+func (b *backend) note(t time.Time, err error) {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+	b.last = t
+	if err != nil {
+		b.err = err.Error()
+	} else {
+		b.err = ""
+	}
+}
+
+func joinComma(a []string) string {
+	s := ""
+	for i, x := range a {
+		if i > 0 {
+			s += ","
+		}
+		s += x
+	}
+	return s
+}
+
+func main() {
+	cal.Argv0 = "ical/fs"
+	var (
+		dir   = flag.String("d", ".", "directory of .ics files")
+		name  = flag.String("s", "", "service name to post in /srv (default ical.$user.$pid)")
+		days  = flag.Int("w", 400, "expansion window in days")
+		dry   = flag.Bool("n", false, "load and report, do not serve")
+		conf  = flag.String("c", "", "calendar config (default $home/lib/pim)")
+		which = flag.String("N", "", "which calendar in the config to serve")
+		poll  = flag.Duration("r", 0, "re-stat the directory this often (0: only on ctl refresh)")
+	)
+	flag.Usage = func() {
+		fmt.Fprintf(os.Stderr,
+			"usage: ical/fs [-n] [-c config] [-N name] [-d dir] [-s srv] [-w days] [-r poll]\n")
+		os.Exit(2)
+	}
+	flag.Parse()
+
+	user := os.Getenv("user")
+	if user == "" {
+		user = "glenda"
+	}
+	if *name == "" {
+		// as rio(1) and plumb(1) name theirs, so several may run at once
+		*name = fmt.Sprintf("ical.%s.%d", user, os.Getpid())
+	}
+
+	path := *conf
+	if path == "" {
+		path = filepath.Join(os.Getenv("home"), "lib", "pim")
+		if _, err := os.Stat(path); err != nil {
+			path = "" // no config is fine: -d alone works
+		}
+	}
+
+	// One server serves one calendar; several calendars means several
+	// servers, each mounted at its own name under /mnt/pim/calendars.
+	be := &backend{dir: *dir, poll: *poll}
+	if *which != "" {
+		// a name even without a config: -o still wants to be called
+		// something other than "calendar" under calendars/
+		be.c = &Cal{Name: *which}
+	}
+	if path != "" {
+		cals, err := readConfig(path, *dir)
+		if err != nil {
+			fatal("%v", err)
+		}
+		if be.c, err = pick(cals, *which); err != nil {
+			fatal("%v", err)
+		}
+	}
+
+	s := cal.New(be, cal.Config{
+		User: user, Srv: *name, Conf: path,
+		Window: time.Duration(*days) * 24 * time.Hour,
+	})
+
+	if *dry {
+		if err := s.Report(); err != nil {
+			fatal("%v", err)
+		}
+		return
+	}
+	if err := s.Serve(); err != nil {
+		fatal("%v", err)
+	}
+}