feat: restore portable layout on shutdown and before suspend

Add WriteConfig/Prepare backend methods (real for Hyprland, no-op for
Sway), -apply/-prepare/-no-reload CLI flags, ExecStartPre cleanup and
suspend systemd hooks so a stale docked config can never leave the
built-in display disabled after resume.

Makefile

@@ -28,6 +28,13 @@ systemd-install:
 	systemctl --user daemon-reload
 	systemctl --user enable --now monitor-lets-go
 
+# Install a system-sleep hook (requires root). This writes the portable
+# monitor config to disk before suspend so the compositor never loads a
+# stale docked config on resume. Without this hook, the daemon's polling
+# mechanism catches the change within seconds after resume.
+system-sleep-install:
+	sudo $(INSTALL) -Dm755 contrib/monitor-lets-go-system-sleep /usr/lib/systemd/system-sleep/monitor-lets-go
+
 systemd-status:
 	systemctl --user status monitor-lets-go
 

cmd/monitor-lets-go/main.go

@@ -32,10 +32,18 @@ import (
 	"monitor-lets-go/internal/hook"
 )
 
-var configPath string
+var (
+	configPath string
+	prepare    bool
+	applyMode  string
+	noReload   bool
+)
 
 func init() {
 	flag.StringVar(&configPath, "config", defaultConfigPath(), "path to YAML configuration file")
+	flag.BoolVar(&prepare, "prepare", false, "remove disabled monitors from config file and exit")
+	flag.StringVar(&applyMode, "apply", "", "apply a mode (portable/docked) and exit")
+	flag.BoolVar(&noReload, "no-reload", false, "when used with --apply, write config without reloading the compositor")
 }
 
 func main() {
@@ -45,12 +53,103 @@ func main() {
 		Level: slog.LevelInfo,
 	}))
 
-	if err := run(logger); err != nil && !errors.Is(err, context.Canceled) {
+	switch {
-		logger.Error("fatal", "error", err)
+	case prepare:
-		os.Exit(1)
+		os.Exit(runPrepare(logger))
+	case applyMode != "":
+		os.Exit(runApply(logger, applyMode))
+	default:
+		if err := run(logger); err != nil && !errors.Is(err, context.Canceled) {
+			logger.Error("fatal", "error", err)
+			os.Exit(1)
+		}
 	}
 }
 
+// runPrepare removes disabled entries from the monitor config file.
+// Useful as ExecStartPre in systemd or before starting the compositor.
+func runPrepare(logger *slog.Logger) int {
+	cfg, err := config.Load(configPath)
+	if err != nil {
+		logger.Error("load config", "error", err)
+		return 1
+	}
+
+	b, err := resolveBackend(cfg.Backend, cfg.EffectiveBackendConfig(), logger)
+	if err != nil {
+		logger.Error("resolve backend", "error", err)
+		return 1
+	}
+	defer b.Close()
+
+	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+	defer cancel()
+
+	if err := b.Prepare(ctx); err != nil {
+		logger.Error("prepare failed", "error", err)
+		return 1
+	}
+	logger.Info("prepare: cleaned disabled monitors from config")
+	return 0
+}
+
+// runApply applies a single mode (portable/docked) and exits.
+// When --no-reload is set, writes the config file without reloading
+// the compositor (useful in suspend hooks).
+func runApply(logger *slog.Logger, mode string) int {
+	cfg, err := config.Load(configPath)
+	if err != nil {
+		logger.Error("load config", "error", err)
+		return 1
+	}
+
+	b, err := resolveBackend(cfg.Backend, cfg.EffectiveBackendConfig(), logger)
+	if err != nil {
+		logger.Error("resolve backend", "error", err)
+		return 1
+	}
+	defer b.Close()
+
+	modeCfg, ok := cfg.Modes[mode]
+	if !ok {
+		keys := make([]string, 0, len(cfg.Modes))
+		for k := range cfg.Modes {
+			keys = append(keys, k)
+		}
+		logger.Error("unknown mode", "mode", mode, "available", keys)
+		return 1
+	}
+
+	monitors := make([]backend.MonitorConfig, len(modeCfg.Monitors))
+	for i, e := range modeCfg.Monitors {
+		monitors[i] = backend.MonitorConfig{
+			Name:     e.Name,
+			Enabled:  e.Enabled,
+			Mode:     e.Mode,
+			Position: e.Position,
+			Scale:    e.Scale,
+		}
+	}
+
+	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+	defer cancel()
+
+	if noReload {
+		if err := b.WriteConfig(ctx, monitors); err != nil {
+			logger.Error("write config failed", "mode", mode, "error", err)
+			return 1
+		}
+		logger.Info("config written to disk", "mode", mode)
+	} else {
+		if err := b.ApplyLayout(ctx, monitors); err != nil {
+			logger.Error("apply layout failed", "mode", mode, "error", err)
+			return 1
+		}
+		logger.Info("layout applied", "mode", mode)
+	}
+	return 0
+}
+
 func run(logger *slog.Logger) error {
 	// Load and validate configuration.
 	cfg, err := config.Load(configPath)
@@ -79,10 +178,13 @@ func run(logger *slog.Logger) error {
 	)
 	defer stop()
 
-	// Start systemd watchdog pings if running under systemd with Type=notify.
+	// Start systemd watchdog pings (WATCHDOG=1, STOPPING=1).
 	go systemdWatchdog(ctx, logger)
 
-	return d.Run(ctx)
+	// Run the daemon. READY=1 is sent after the initial state is applied.
+	return d.Run(ctx, func() {
+		notifySystemd(os.Getenv("NOTIFY_SOCKET"), "READY=1")
+	})
 }
 
 // resolveBackend returns the first available backend. When backendName is
@@ -139,8 +241,9 @@ func defaultConfigPath() string {
 
 // systemdWatchdog sends periodic WATCHDOG=1 notifications so systemd's
 // WatchdogSec can detect a hung daemon and restart it. Also sends
-// READY=1 on startup and STOPPING=1 on shutdown.
+// STOPPING=1 on shutdown.
 //
+// READY=1 is now sent by Run() after the initial state is applied.
 // This is a no-op if NOTIFY_SOCKET is not set.
 func systemdWatchdog(ctx context.Context, logger *slog.Logger) {
 	socketPath := os.Getenv("NOTIFY_SOCKET")
@@ -148,9 +251,6 @@ func systemdWatchdog(ctx context.Context, logger *slog.Logger) {
 		return
 	}
 
-	// Notify systemd that the daemon is ready.
-	notifySystemd(socketPath, "READY=1")
-
 	// WatchdogSec=30, so ping at half the interval.
 	ticker := time.NewTicker(15 * time.Second)
 	defer ticker.Stop()

contrib/monitor-lets-go-suspend.service

@@ -0,0 +1,20 @@
+[Unit]
+Description=monitor-lets-go -- restore portable layout before suspend
+Documentation=https://github.com/mat/monitor-lets-go
+
+# Run before the system enters sleep. The ExecStop action writes a portable
+# monitor config so that on resume the compositor never loads a stale docked
+# config that would leave the built-in display disabled.
+Before=sleep.target
+
+[Service]
+# RemainAfterExit: ExecStop runs when the service is stopped (before sleep).
+# This is the standard pattern for systemd suspend hooks.
+Type=oneshot
+RemainAfterExit=yes
+
+ExecStart=/bin/true
+ExecStop=%h/.local/bin/monitor-lets-go -config %h/.config/monitor-lets-go/config.yaml -apply portable -no-reload
+
+[Install]
+WantedBy=sleep.target

contrib/monitor-lets-go-system-sleep

@@ -0,0 +1,28 @@
+#!/bin/bash
+# system-sleep hook for monitor-lets-go
+# Install to /usr/lib/systemd/system-sleep/monitor-lets-go
+#
+# Writes the portable monitor config before suspend so the compositor
+# never loads a stale docked config on resume (prevents black screen).
+#
+# Requires: sudo (passwordless for the user's own commands)
+
+case $1/$2 in
+  pre/*)
+    USER_NAME="$(logname 2>/dev/null || echo "${SUDO_USER:-$USER}")"
+    USER_UID="$(id -u "$USER_NAME" 2>/dev/null || echo 1000)"
+
+    # Extract HYPRLAND_INSTANCE_SIGNATURE from the user's systemd session
+    HYPR_ENV="$(systemctl --user -M "${USER_UID}@" show-environment 2>/dev/null)"
+    HYPR_INSTANCE="$(echo "$HYPR_ENV" | grep HYPRLAND_INSTANCE_SIGNATURE | cut -d= -f2)"
+
+    if [ -n "$HYPR_INSTANCE" ] && [ -n "$USER_NAME" ]; then
+      XDG_RUNTIME_DIR="/run/user/$USER_UID" \
+      HYPRLAND_INSTANCE_SIGNATURE="$HYPR_INSTANCE" \
+      sudo -u "$USER_NAME" \
+        /home/mat/.local/bin/monitor-lets-go \
+          -config /home/mat/.config/monitor-lets-go/config.yaml \
+          -apply portable -no-reload
+    fi
+    ;;
+esac

contrib/monitor-lets-go.service

@@ -16,6 +16,11 @@ Requires=graphical-session.target
 Type=notify
 WatchdogSec=30
 
+# Remove disabled entries from the monitor config before starting.
+# Prevents black screen if a stale docked config disables the built-in
+# display (e.g. after undocking while suspended).
+ExecStartPre=%h/.local/bin/monitor-lets-go -config %h/.config/monitor-lets-go/config.yaml -prepare
+
 ExecStart=%h/.local/bin/monitor-lets-go -config %h/.config/monitor-lets-go/config.yaml
 
 # Fast restart on failure: if the daemon crashes during docked mode,

internal/backend/hyprland.go

@@ -133,6 +133,88 @@ func (h *hyprlandBackend) ApplyLayout(ctx context.Context, monitors []MonitorCon
 	return nil
 }
 
+// WriteConfig writes the monitor configuration to disk without calling
+// hyprctl reload. This is used during shutdown when the compositor may
+// not be available. Resolves monitor names with a short timeout; falls
+// back to plain-name-only entries if resolution fails.
+func (h *hyprlandBackend) WriteConfig(ctx context.Context, monitors []MonitorConfig) error {
+	resolveCtx, cancel := context.WithTimeout(ctx, 3*time.Second)
+	defer cancel()
+
+	resolved, err := resolveMonitorNames(resolveCtx, monitors, h.GetMonitors, h.logger)
+	if err != nil {
+		h.logger.Warn("cannot resolve monitor names for WriteConfig — using plain names only",
+			"error", err)
+		var plain []MonitorConfig
+		for _, m := range monitors {
+			if !strings.HasPrefix(m.Name, "desc:") && !strings.HasPrefix(m.Name, "size:") {
+				plain = append(plain, m)
+			}
+		}
+		if len(plain) == 0 {
+			plain = []MonitorConfig{
+				{Name: "eDP-1", Enabled: true, Mode: "preferred", Position: "auto", Scale: 1.0},
+			}
+		}
+		resolved = plain
+	}
+
+	content := h.generateConf(resolved)
+	destPath, err := h.resolveOutputPath()
+	if err != nil {
+		return fmt.Errorf("resolve output path: %w", err)
+	}
+	if err := atomicWrite(destPath, []byte(content)); err != nil {
+		return fmt.Errorf("write monitor config: %w", err)
+	}
+	h.logger.Info("config written to disk", "path", destPath, "monitors", len(resolved))
+	return nil
+}
+
+// Prepare removes all monitor=...,disabled lines from the monitors.conf
+// file. This prevents the "no active displays" issue when Hyprland starts
+// with a stale config. If the resulting file would be empty (or doesn't
+// exist), a generic built-in entry is written as a fallback.
+func (h *hyprlandBackend) Prepare(ctx context.Context) error {
+	destPath, err := h.resolveOutputPath()
+	if err != nil {
+		return fmt.Errorf("resolve output path: %w", err)
+	}
+
+	data, err := os.ReadFile(destPath)
+	if err != nil {
+		if os.IsNotExist(err) {
+			h.logger.Debug("prepare: no config file to clean")
+			return nil
+		}
+		return fmt.Errorf("read %s: %w", destPath, err)
+	}
+
+	lines := strings.Split(string(data), "\n")
+	var cleaned []string
+	for _, line := range lines {
+		trimmed := strings.TrimSpace(line)
+		if trimmed == "" {
+			continue
+		}
+		if strings.HasPrefix(trimmed, "monitor=") && strings.HasSuffix(trimmed, ",disabled") {
+			continue
+		}
+		cleaned = append(cleaned, line)
+	}
+
+	content := strings.Join(cleaned, "\n")
+	if strings.TrimSpace(content) == "" {
+		content = "monitor=eDP-1,preferred,auto,1\n"
+	}
+
+	if err := atomicWrite(destPath, []byte(content)); err != nil {
+		return fmt.Errorf("write cleaned config: %w", err)
+	}
+	h.logger.Info("prepare: cleaned disabled entries from config", "path", destPath)
+	return nil
+}
+
 // Events connects to the socket2 unix socket and emits parsed hotplug events.
 // On connection loss it attempts reconnection with exponential backoff.
 func (h *hyprlandBackend) Events(ctx context.Context) (<-chan Event, <-chan error) {

internal/backend/interface.go

@@ -96,6 +96,18 @@ type Backend interface {
 	// are enabled is ever visible.
 	ApplyLayout(ctx context.Context, monitors []MonitorConfig) error
 
+	// WriteConfig persists the monitor configuration to disk without
+	// reloading the compositor. Used during shutdown (SIGTERM) when
+	// the compositor may not be available. For backends that don't
+	// use a config file (e.g. Sway), this is a no-op.
+	WriteConfig(ctx context.Context, monitors []MonitorConfig) error
+
+	// Prepare ensures the monitor config file has no disabled entries.
+	// This prevents the "no active displays" issue when the compositor
+	// starts with a stale config. For backends that don't use a config
+	// file (e.g. Sway), this is a no-op.
+	Prepare(ctx context.Context) error
+
 	// Events returns a channel of hotplug events and a channel of errors.
 	// The caller must read from both channels. When ctx is cancelled,
 	// the backend closes both channels and stops listening.

internal/backend/sway.go

@@ -554,4 +554,16 @@ func (s *swayBackend) Close() error {
 	return nil
 }
 
+// ---------------------------------------------------------------------------
+// WriteConfig / Prepare (no-ops for Sway — no persistent config file)
+// ---------------------------------------------------------------------------
+
+func (s *swayBackend) WriteConfig(ctx context.Context, monitors []MonitorConfig) error {
+	return nil
+}
+
+func (s *swayBackend) Prepare(ctx context.Context) error {
+	return nil
+}
+
 

internal/daemon/daemon.go

@@ -45,11 +45,15 @@ func New(b backend.Backend, cfg *config.Config, hr *hook.Runner, logger *slog.Lo
 }
 
 // Run starts the daemon's event loop. It blocks until ctx is cancelled.
-func (d *Daemon) Run(ctx context.Context) error {
+// onReady is called after the initial state is applied (may be nil).
+func (d *Daemon) Run(ctx context.Context, onReady func()) error {
 	d.logger.Info("daemon starting", "backend", d.backend.Name())
 
 	// Phase 1: determine and apply the initial state.
 	d.applyInitialState(ctx)
+	if onReady != nil {
+		onReady()
+	}
 
 	// Phase 2: subscribe to compositor events.
 	events, _ := d.backend.Events(ctx)
@@ -105,10 +109,21 @@ func (d *Daemon) Run(ctx context.Context) error {
 // applyInitialState determines the current hardware state and applies the
 // matching layout. This is the failsafe: if the daemon crashed while docked,
 // a restart will detect that externals are gone and re-enable the built-in.
+//
+// Before determining state, it runs Prepare() to remove disabled entries
+// from the monitor config file, preventing a black screen when loading a
+// stale docked config (e.g. after undocking while suspended).
 func (d *Daemon) applyInitialState(ctx context.Context) {
 	ctx, cancel := context.WithTimeout(ctx, 10*time.Second)
 	defer cancel()
 
+	// Step 1: safe fallback — remove disabled entries so at least one
+	// monitor is active even if state detection or layout application fail.
+	if err := d.backend.Prepare(ctx); err != nil {
+		d.logger.Error("safe fallback (prepare) failed", "error", err)
+	}
+
+	// Step 2: determine state and apply the correct layout.
 	monitors, err := d.getMonitorsWithRetry(ctx)
 	if err != nil {
 		d.logger.Error("cannot get monitors on startup", "error", err)
@@ -281,7 +296,10 @@ func (d *Daemon) getMonitorsWithRetry(ctx context.Context) ([]backend.MonitorInf
 	return nil, fmt.Errorf("after %d retries: %w", maxRetries, lastErr)
 }
 
-// onShutdown applies the portable layout before exit if configured.
+// onShutdown writes the portable monitor config before exit if configured.
+// It writes directly to disk without calling hyprctl reload because the
+// compositor may already be unavailable during shutdown. The config file
+// will be read next time the compositor starts.
 func (d *Daemon) onShutdown(ctx context.Context) {
 	if d.config.RestoreOnExit == nil || !*d.config.RestoreOnExit {
 		return
@@ -290,12 +308,30 @@ func (d *Daemon) onShutdown(ctx context.Context) {
 		return // already portable
 	}
 
-	d.logger.Info("shutdown: restoring portable layout")
+	d.logger.Info("shutdown: writing portable config")
-	ctx, cancel := context.WithTimeout(ctx, 10*time.Second)
+
+	mode, ok := d.config.Modes["portable"]
+	if !ok {
+		d.logger.Error("shutdown restore: no portable mode in config")
+		return
+	}
+
+	monitors := make([]backend.MonitorConfig, len(mode.Monitors))
+	for i, e := range mode.Monitors {
+		monitors[i] = backend.MonitorConfig{
+			Name:     e.Name,
+			Enabled:  e.Enabled,
+			Mode:     e.Mode,
+			Position: e.Position,
+			Scale:    e.Scale,
+		}
+	}
+
+	ctx, cancel := context.WithTimeout(ctx, 5*time.Second)
 	defer cancel()
 
-	if err := d.applyState(ctx, backend.StatePortable); err != nil {
+	if err := d.backend.WriteConfig(ctx, monitors); err != nil {
-		d.logger.Error("shutdown restore failed", "error", err)
+		d.logger.Error("shutdown write config failed", "error", err)
 	}
 }