Carry the power draw to the bar over the bus, not through a file (hq ADR 0260)

Modules talk over the bus. The power module's bundle puts each fresh reading of its own
sampler in its state draw, keyed by the machine; the bar's block shows that state, which
the bar's bundle watches under the read the mesh grants it. A new catalogue check refuses
a module naming another module's path under /run or /var/lib.

modules/i3status-rust/README.md

@@ -41,6 +41,14 @@ contributes it to `node-bar` as data that says what it shows, and this module re
 - **Where it applies:** a contribution may name a capability the machine must report. The `power`
   module's battery block names `battery` and its power-draw block names `power-meter`, so the laptop's
   bar gets both and a desktop only the power draw.
+- **A value from the bus:** a block that `shows: state` names another module's state, such as
+  `power.draw`. The mesh grants this module the read, because a module on its machine offers it; the
+  manifest names no other module. This module's bundle watches it and leaves the value's text in the
+  account's runtime directory (`i3status-rust/values/`), and the block runs `~/.local/bin/i3status-value`,
+  which prints it, or nothing when it is more than 30 s old, so the block hides. No file of another
+  module is read: modules talk over the bus.
+- **The battery** is i3status-rust's own battery block, which reads the kernel's power-supply class
+  itself: the bar reading the machine, not another module.
 
 Still left out:
 

modules/i3status-rust/cmd/i3status-rust-tools/blocks_test.go

@@ -5,6 +5,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"os"
+	"path/filepath"
 	"strings"
 	"testing"
 	"text/template"
@@ -33,7 +34,7 @@ func blockTemplate(t *testing.T) *template.Template {
 
 func render(t *testing.T, tmpl *template.Template, piece string) string {
 	t.Helper()
-	view := map[string]any{"module": "power"}
+	view := map[string]any{"module": "power", "machine": "laptop"}
 	if err := json.Unmarshal([]byte(piece), &view); err != nil {
 		t.Fatal(err)
 	}
@@ -96,3 +97,24 @@ func TestTheMemoryIsWhatProgramsHoldNotTheCache(t *testing.T) {
 		t.Fatal("the memory block counts the cache as used")
 	}
 }
+
+func TestAContributedStateIsACustomBlockReadingThisMachinesValue(t *testing.T) {
+	tmpl := blockTemplate(t)
+	got := render(t, tmpl, `{"bar":"bottom","place":"status","shows":"state","options":{"state":"power.draw"}}`)
+	want := "[[block]]\nblock = \"custom\"\ncommand = \"~/.local/bin/i3status-value power.draw laptop\"\ninterval = 5\nhide_when_empty = true\n\n"
+	if got != want {
+		t.Fatalf("%q, want %q", got, want)
+	}
+	got = render(t, tmpl, `{"bar":"bottom","place":"status","shows":"state","options":{"state":"power.draw","key":"desk"}}`)
+	if !strings.Contains(got, "i3status-value power.draw desk") {
+		t.Fatalf("%q", got)
+	}
+	// And the bundle finds what it rendered.
+	f := filepath.Join(t.TempDir(), "bottom-bar.toml")
+	if err := os.WriteFile(f, []byte(got), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	if w := wantedIn([]string{f}); len(w) != 1 || w[0] != (Wanted{"power.draw", "desk"}) {
+		t.Fatalf("%v", w)
+	}
+}

modules/i3status-rust/cmd/i3status-rust-tools/main.go

@@ -11,6 +11,8 @@ import (
 )
 
 func main() {
+	// The values other modules keep on the bus for their blocks (novox/hq ADR 0260).
+	go FollowValues()
 	if err := stdio.Serve("", tools()); err != nil {
 		fmt.Fprintln(os.Stderr, err)
 		os.Exit(1)

modules/i3status-rust/cmd/i3status-rust-tools/manifest_test.go

@@ -33,6 +33,7 @@ func TestItOwnsItsFilesAsWrittenInTheModule(t *testing.T) {
 	for id, src := range map[string]string{
 		"top-bar": "files/top-bar.toml", "bottom-bar": "files/bottom-bar.toml", "icons": "files/icons/custom-icons.toml",
 		"updates": "files/bin/i3status-updates", "watchdog": "files/bin/i3bar-watchdog",
+		"value": "files/bin/i3status-value",
 	} {
 		m.sameAsSource(t, id, src)
 	}

modules/i3status-rust/cmd/i3status-rust-tools/values.go

@@ -0,0 +1,118 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+	"path/filepath"
+	"regexp"
+	"sort"
+	"strconv"
+	"time"
+
+	stdio "git.novox.be/novox/mesh-sdk/go"
+)
+
+// The values other modules keep on the bus for a block they contributed (novox/hq ADR 0260).
+//
+// A block that `shows` a state is rendered as a custom block running `i3status-value <state> <key>`.
+// i3status-rs cannot reach the bus, and this bundle can: the node's runtime launched it, and the mesh
+// granted this module a read of every state the modules on its machine offer the bar. So it watches each
+// state its bars name and leaves the value's text in this module's own directory, where the block's
+// command reads it. No file of another module is read, and nothing but the bus passes between them.
+
+// valueCall is how a bar names a value: the command the template renders.
+var valueCall = regexp.MustCompile(`i3status-value ([a-z0-9][a-z0-9-]*\.[a-z0-9][a-z0-9-]*) ([^\s"]+)`)
+
+// Wanted is one state and key a bar shows.
+type Wanted struct{ State, Key string }
+
+func (w Wanted) file() string { return w.State + "@" + w.Key }
+
+// wantedIn is every value the bars' files name, each once, in order.
+func wantedIn(files []string) []Wanted {
+	seen := map[Wanted]bool{}
+	for _, f := range files {
+		raw, err := os.ReadFile(f)
+		if err != nil {
+			continue
+		}
+		for _, m := range valueCall.FindAllStringSubmatch(string(raw), -1) {
+			seen[Wanted{State: m[1], Key: m[2]}] = true
+		}
+	}
+	out := make([]Wanted, 0, len(seen))
+	for w := range seen {
+		out = append(out, w)
+	}
+	sort.Slice(out, func(i, j int) bool { return out[i].file() < out[j].file() })
+	return out
+}
+
+// valuesDir is where the values are left: the account's runtime directory, gone at logout.
+func valuesDir() string {
+	return filepath.Join(runUserDir, strconv.Itoa(os.Getuid()), "i3status-rust", "values")
+}
+
+// keep writes one change of a value to its file: the value's `text`, or no file once it is deleted.
+func keep(dir string, w Wanted, c stdio.StateChange) error {
+	path := filepath.Join(dir, w.file())
+	if c.Op == "delete" || c.Op == "purge" {
+		if err := os.Remove(path); err != nil && !os.IsNotExist(err) {
+			return err
+		}
+		return nil
+	}
+	var v struct {
+		Text string `json:"text"`
+	}
+	if err := json.Unmarshal(c.Value, &v); err != nil {
+		return fmt.Errorf("%s's value for %s has no text: %w", w.State, w.Key, err)
+	}
+	if err := os.MkdirAll(dir, 0o700); err != nil {
+		return err
+	}
+	tmp := path + ".new"
+	if err := os.WriteFile(tmp, []byte(v.Text+"\n"), 0o600); err != nil {
+		return err
+	}
+	return os.Rename(tmp, path)
+}
+
+// Watcher is a function that watches one key of one state; the SDK's in the bundle, a fake in a test.
+type Watcher func(state, key string, handle func(stdio.StateChange) error) error
+
+// followValues watches every value the bars name, starting the ones not yet watched each time it is
+// called; one the runtime refuses — a read not granted yet — is tried again the next time.
+func followValues(files []string, dir string, watching map[Wanted]bool, watch Watcher) []string {
+	var said []string
+	for _, w := range wantedIn(files) {
+		if watching[w] {
+			continue
+		}
+		w := w
+		err := watch(w.State, w.Key, func(c stdio.StateChange) error { return keep(dir, w, c) })
+		if err != nil {
+			said = append(said, fmt.Sprintf("cannot watch %s %s: %v", w.State, w.Key, err))
+			continue
+		}
+		watching[w] = true
+	}
+	return said
+}
+
+// FollowValues runs followValues every half minute for as long as the bundle runs, so a block a push
+// adds is followed without a restart.
+func FollowValues() {
+	watching := map[Wanted]bool{}
+	watch := func(state, key string, handle func(stdio.StateChange) error) error {
+		return stdio.State(state).Watch(key, handle)
+	}
+	for {
+		files, _ := filepath.Glob(filepath.Join(configDir(), "*.toml"))
+		for _, s := range followValues(files, valuesDir(), watching, watch) {
+			fmt.Fprintln(os.Stderr, "i3status-rust:", s)
+		}
+		time.Sleep(30 * time.Second)
+	}
+}

modules/i3status-rust/cmd/i3status-rust-tools/values_test.go

@@ -0,0 +1,92 @@
+package main
+
+import (
+	"errors"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strings"
+	"testing"
+	"time"
+
+	stdio "git.novox.be/novox/mesh-sdk/go"
+)
+
+// Defends novox/hq ADR 0260: a value another module keeps reaches the bar over the bus, through this
+// module's own bundle and directory, and an old one is not shown as if it were now.
+
+func TestAValueIsKeptAsItsTextAndGoneWhenDeleted(t *testing.T) {
+	dir := t.TempDir()
+	w := Wanted{"power.draw", "laptop"}
+	if err := keep(dir, w, stdio.StateChange{Op: "put", Value: []byte(`{"text":"18.2 W machine","watts":18.2}`)}); err != nil {
+		t.Fatal(err)
+	}
+	b, err := os.ReadFile(filepath.Join(dir, "power.draw@laptop"))
+	if err != nil || string(b) != "18.2 W machine\n" {
+		t.Fatalf("%q %v", b, err)
+	}
+	if err := keep(dir, w, stdio.StateChange{Op: "delete"}); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := os.Stat(filepath.Join(dir, "power.draw@laptop")); !os.IsNotExist(err) {
+		t.Fatal("a deleted value is still shown")
+	}
+	if err := keep(dir, w, stdio.StateChange{Op: "put", Value: []byte(`"no text"`)}); err == nil {
+		t.Fatal("a value with no text was kept")
+	}
+}
+
+func TestARefusedWatchIsTriedAgainAndAWatchedOneIsNot(t *testing.T) {
+	bar := filepath.Join(t.TempDir(), "bottom-bar.toml")
+	if err := os.WriteFile(bar, []byte(`command = "~/.local/bin/i3status-value power.draw laptop"`+"\n"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	watching := map[Wanted]bool{}
+	calls := 0
+	refuse := func(string, string, func(stdio.StateChange) error) error { calls++; return errors.New("not granted") }
+	if said := followValues([]string{bar}, t.TempDir(), watching, refuse); len(said) != 1 || !strings.Contains(said[0], "not granted") {
+		t.Fatalf("%v", said)
+	}
+	accept := func(state, key string, _ func(stdio.StateChange) error) error {
+		calls++
+		if state != "power.draw" || key != "laptop" {
+			t.Fatalf("watched %s %s", state, key)
+		}
+		return nil
+	}
+	followValues([]string{bar}, t.TempDir(), watching, accept)
+	followValues([]string{bar}, t.TempDir(), watching, accept)
+	if calls != 2 {
+		t.Fatalf("%d watches; once refused, once taken, then left alone", calls)
+	}
+}
+
+func TestTheBlocksCommandShowsOnlyAFreshValue(t *testing.T) {
+	runtime := t.TempDir()
+	dir := filepath.Join(runtime, "i3status-rust", "values")
+	run := func() string {
+		cmd := exec.Command("sh", "../../files/bin/i3status-value", "power.draw", "laptop")
+		cmd.Env = append(os.Environ(), "XDG_RUNTIME_DIR="+runtime)
+		out, err := cmd.Output()
+		if err != nil {
+			t.Fatal(err)
+		}
+		return strings.TrimSpace(string(out))
+	}
+	if got := run(); got != "" {
+		t.Fatalf("no value: %q", got)
+	}
+	if err := keep(dir, Wanted{"power.draw", "laptop"}, stdio.StateChange{Op: "put", Value: []byte(`{"text":"8.0 W CPU"}`)}); err != nil {
+		t.Fatal(err)
+	}
+	if got := run(); got != "8.0 W CPU" {
+		t.Fatalf("fresh: %q", got)
+	}
+	old := time.Now().Add(-31 * time.Second)
+	if err := os.Chtimes(filepath.Join(dir, "power.draw@laptop"), old, old); err != nil {
+		t.Fatal(err)
+	}
+	if got := run(); got != "" {
+		t.Fatalf("31 s old: %q", got)
+	}
+}

modules/i3status-rust/files/bin/i3status-value

@@ -0,0 +1,13 @@
+#!/bin/sh
+# i3status-value <state> <key> (module i3status-rust, novox/hq ADR 0260): one value another module keeps
+# on the bus, for a block it contributed.
+#
+# This module's own tools bundle watches the state on the bus (the mesh grants it the read) and leaves
+# the value's text in this module's own directory; this prints it. A value not refreshed for thirty
+# seconds is one its module stopped giving, and prints nothing, so the block hides rather than show an
+# old number as if it were now.
+dir="${XDG_RUNTIME_DIR:-/run/user/$(id -u)}/i3status-rust/values"
+f="$dir/$1@$2"
+if [ -r "$f" ] && [ $(( $(date +%s) - $(stat -c %Y "$f") )) -le 30 ]; then
+	head -n 1 "$f"
+fi

modules/i3status-rust/files/block.tmpl

@@ -1,5 +1,5 @@
 {{- /* A block other modules contribute, in i3status-rust's grammar (novox/hq ADR 0255). The controller
-renders one piece at a time: its fields (bar, place, order, shows, options) and module. */ -}}
+renders one piece at a time: its fields (bar, place, order, shows, options), module and machine. */ -}}
 {{- if eq .shows "battery" -}}
 [[block]]
 block = "battery"
@@ -16,5 +16,11 @@ missing_format = ""
 block = "custom"
 command = {{quote .options.command}}
 interval = {{.options.interval}}
+{{- else if eq .shows "state" -}}
+[[block]]
+block = "custom"
+command = {{quote (printf "~/.local/bin/i3status-value %s %s" .options.state (or .options.key .machine))}}
+interval = 5
+hide_when_empty = true
 {{- end}}
 

modules/i3status-rust/module.json

@@ -12,7 +12,7 @@
       "name": "node-bar",
       "scope": "node",
       "renders": {
-        "block": "{{- /* A block other modules contribute, in i3status-rust's grammar (novox/hq ADR 0255). The controller\nrenders one piece at a time: its fields (bar, place, order, shows, options) and module. */ -}}\n{{- if eq .shows \"battery\" -}}\n[[block]]\nblock = \"battery\"\n{{with .options}}{{with .device}}device = {{quote .}}\n{{end}}{{end -}}\nformat = \"$icon $percentage{ $time|}\"\ncharging_format = \"$icon $percentage{ $time|}\"\nnot_charging_format = \"$icon $percentage\"\nfull_format = \"$icon $percentage\"\nempty_format = \"$icon $percentage\"\nmissing_format = \"\"\n{{- else if eq .shows \"command\" -}}\n[[block]]\nblock = \"custom\"\ncommand = {{quote .options.command}}\ninterval = {{.options.interval}}\n{{- end}}\n\n"
+        "block": "{{- /* A block other modules contribute, in i3status-rust's grammar (novox/hq ADR 0255). The controller\nrenders one piece at a time: its fields (bar, place, order, shows, options), module and machine. */ -}}\n{{- if eq .shows \"battery\" -}}\n[[block]]\nblock = \"battery\"\n{{with .options}}{{with .device}}device = {{quote .}}\n{{end}}{{end -}}\nformat = \"$icon $percentage{ $time|}\"\ncharging_format = \"$icon $percentage{ $time|}\"\nnot_charging_format = \"$icon $percentage\"\nfull_format = \"$icon $percentage\"\nempty_format = \"$icon $percentage\"\nmissing_format = \"\"\n{{- else if eq .shows \"command\" -}}\n[[block]]\nblock = \"custom\"\ncommand = {{quote .options.command}}\ninterval = {{.options.interval}}\n{{- else if eq .shows \"state\" -}}\n[[block]]\nblock = \"custom\"\ncommand = {{quote (printf \"~/.local/bin/i3status-value %s %s\" .options.state (or .options.key .machine))}}\ninterval = 5\nhide_when_empty = true\n{{- end}}\n\n"
       }
     }
   ],
@@ -88,6 +88,14 @@
       "owner": "${machine:account}",
       "mode": "0755",
       "content": "#!/usr/bin/env bash\n# i3bar-watchdog [session-pid] (module i3status-rust, novox/hq ADR 0208): respawns a bar that died.\n#\n# i3 starts one i3bar per `bar { }` block and never restarts one that exits, and a reload does not\n# either. Changing the monitor setup reliably kills the bar that owns the tray. This brings back the\n# one missing i3bar, without restarting i3, and logs the outputs at that moment: the evidence for the\n# cause, which is i3bar's.\n#\n# Started once per session from the session's start, with the session's own pid; it ends when that\n# process does. Adopted from the predecessor's i3-bar-watchdog user unit of 2026-10-04.\nset -uo pipefail\n\nsession_pid=\"${1:-}\"\ninterval=\"${I3_BAR_WATCHDOG_INTERVAL:-5}\"\n# Two misses in a row before acting: an i3 restart tears every bar down and starts them again.\nconfirm=\"${I3_BAR_WATCHDOG_CONFIRM:-2}\"\n# Never respawn the same bar more often than this, so a bar that dies at once is not a tight loop.\ncooldown=\"${I3_BAR_WATCHDOG_COOLDOWN:-30}\"\n\nlog() { printf 'i3bar-watchdog: %s\\n' \"$*\" >&2; }\n\nfor tool in i3-msg i3bar pgrep; do\n\tcommand -v \"$tool\" >/dev/null 2>&1 || {\n\t\tlog \"$tool is missing; not watching\"\n\t\texit 1\n\t}\ndone\n\ndeclare -A missed=() fixed=()\n\nbar_ids() { i3-msg -t get_bar_config 2>/dev/null | grep -oE '\"[^\"]+\"' | tr -d '\"'; }\noutputs() { xrandr --listmonitors 2>/dev/null | tail -n +2 | awk '{print $2\" \"$3}' | tr '\\n' ' '; }\nsession_alive() { [ -z \"$session_pid\" ] || kill -0 \"$session_pid\" 2>/dev/null; }\n\nwhile session_alive; do\n\tsleep \"$interval\"\n\tsocket=\"$(i3 --get-socketpath 2>/dev/null)\"\n\t[ -n \"$socket\" ] && [ -S \"$socket\" ] || continue\n\tids=\"$(bar_ids)\"\n\t[ -n \"$ids\" ] || continue\n\twhile read -r id; do\n\t\t[ -n \"$id\" ] || continue\n\t\tif pgrep -u \"$EUID\" -f -- \"i3bar --bar_id=$id\" >/dev/null 2>&1; then\n\t\t\tmissed[$id]=0\n\t\t\tcontinue\n\t\tfi\n\t\tmissed[$id]=$((${missed[$id]:-0} + 1))\n\t\t[ \"${missed[$id]}\" -ge \"$confirm\" ] || continue\n\t\tnow=\"$(date +%s)\"\n\t\tif [ $((now - ${fixed[$id]:-0})) -lt \"$cooldown\" ]; then\n\t\t\tcontinue\n\t\tfi\n\t\tlog \"$id is gone; respawning it. Outputs now: $(outputs)\"\n\t\tnohup i3bar --bar_id=\"$id\" --socket=\"$socket\" >/dev/null 2>&1 &\n\t\tdisown 2>/dev/null || true\n\t\tfixed[$id]=\"$now\"\n\t\tsleep 2\n\t\tif pgrep -u \"$EUID\" -f -- \"i3bar --bar_id=$id\" >/dev/null 2>&1; then\n\t\t\tmissed[$id]=0\n\t\telse\n\t\t\tlog \"$id exited within 2s of respawning; check its status_command\"\n\t\tfi\n\tdone <<<\"$ids\"\ndone\n"
+    },
+    {
+      "id": "value",
+      "type": "file",
+      "path": "${machine:account-home}/.local/bin/i3status-value",
+      "owner": "${machine:account}",
+      "mode": "0755",
+      "content": "#!/bin/sh\n# i3status-value <state> <key> (module i3status-rust, novox/hq ADR 0260): one value another module keeps\n# on the bus, for a block it contributed.\n#\n# This module's own tools bundle watches the state on the bus (the mesh grants it the read) and leaves\n# the value's text in this module's own directory; this prints it. A value not refreshed for thirty\n# seconds is one its module stopped giving, and prints nothing, so the block hides rather than show an\n# old number as if it were now.\ndir=\"${XDG_RUNTIME_DIR:-/run/user/$(id -u)}/i3status-rust/values\"\nf=\"$dir/$1@$2\"\nif [ -r \"$f\" ] && [ $(( $(date +%s) - $(stat -c %Y \"$f\") )) -le 30 ]; then\n\thead -n 1 \"$f\"\nfi\n"
     }
   ],
   "build": {