full scope implementation

Package.swift

@@ -20,7 +20,15 @@ let package = Package(
 			dependencies: [
 				.product(name: "ArgumentParser", package: "swift-argument-parser"),
 				.product(name: "TOML", package: "swift-toml"),
-			]
+			],
+			resources: [
+				.process("config.toml"),
+				.process("Themes/voltage.toml"),
+				// .process("Themes/catppuccin-mocha.toml"),
+				.process("Themes/dracula.toml"),
+				// .process("Themes/gruvbox.toml"),
+				// .process("Themes/tokyo-night.toml"),
+			],
 		),
 		.testTarget(
 			name: "phbarTests",

Sources/phbar/AppDelegate.swift

@@ -4,20 +4,35 @@ import AppKit
 final class AppDelegate: NSObject, NSApplicationDelegate {
 	var barController: PHController!
 	var window: BarWindow!
+	private var observers: [IPCObserver] = []
 
-	init(screen: NSScreen, blocks: [PHBlock]) {
+	init(config: PHConfig, screen: NSScreen, theme: PHTheme, blocks: [PHBlock], debug: Bool = false) {
 		super.init()
 
-		self.barController = PHController(screen: screen, blocks: blocks)
+		self.barController = PHController(config: config, screen: screen, theme: theme, blocks: blocks)
+		barController.debug = debug
 	}
 
 	func applicationDidFinishLaunching(_ notification: Notification) {
 		window = BarWindow(controller: barController)
 		window.orderFront(nil)
 		barController.startAutoRefresh()
+
+		// Listen for refresh notifications from `phbar refresh`.
+		let token = IPC.observe(.refresh) { [weak self] _ in
+			Task { @MainActor in
+				self?.refresh()
+			}
+		}
+		observers.append(token)
+	}
+
+	func refresh() {
+		barController.refresh()
 	}
 
 	func applicationWillTerminate(_ notification: Notification) {
 		barController.stopAutoRefresh()
+		observers.removeAll()
 	}
 }

Sources/phbar/CLI/cli+refresh.swift

@@ -0,0 +1,14 @@
+import ArgumentParser
+
+extension phbar {
+	struct refresh: ParsableCommand {
+		static let configuration = CommandConfiguration(
+			commandName: "refresh",
+			abstract: "Refresh the running status bar."
+		)
+
+		mutating func run() throws {
+			IPC.post(.refresh)
+		}
+	}
+}

Sources/phbar/CLI/cli+start.swift

@@ -9,8 +9,13 @@ extension phbar {
 			abstract: "Start the status bar."
 		)
 
+		@Flag(name: .long, help: "Display visual guides to help align elements.")
+		var debug: Bool = false
+
 		mutating func run() throws {
+			let config = try PHConfig.load()
 			let screen = try targetScreen(monitor: 0)
+			let theme = try PHTheme.load("voltage")
 
 			// NOTE: Make sure NSApp.run() runs in the main thread
 			dispatchPrecondition(condition: .onQueue(.main))
@@ -18,7 +23,7 @@ extension phbar {
 			try MainActor.assumeIsolated {
 				let blocks = try PHBlock.load()
 
-				let delegate = AppDelegate(screen: screen, blocks: blocks)
+				let delegate = AppDelegate(config: config, screen: screen, theme: theme, blocks: blocks, debug: debug)
 				let app = NSApplication.shared
 				app.setActivationPolicy(.accessory)
 				app.delegate = delegate

Sources/phbar/Controllers/PHController.swift

@@ -2,16 +2,55 @@ import SwiftUI
 
 @MainActor
 final class PHController: ObservableObject {
+	let config: PHConfig
 	let screen: NSScreen
+	let theme: PHTheme
+	var debug: Bool = false {
+		didSet {
+			for block in blocks {
+				block.debug = debug
+			}
+		}
+	}
 	@Published var blocks: [PHBlock]
 
-	init(screen: NSScreen, blocks: [PHBlock]) {
+	var arrangedBlocks: [PHBlock] {
-		self.screen = screen
+		blocks.filter { $0.centered != true }
-		self.blocks = blocks
 	}
 
-	// MARK: - Refresh
+	var centeredBlocks: [PHBlock] {
+		blocks.filter { $0.centered == true }
+	}
 
+	init(config: PHConfig, screen: NSScreen, theme: PHTheme, blocks: [PHBlock]) {
+		self.config = config
+		self.screen = screen
+		self.theme = theme
+		self.blocks = blocks
+
+		for block in blocks {
+			block.style = style(for: block)
+		}
+	}
+}
+
+// Style
+
+extension PHController {
+	func style(for block: PHBlock) -> PHTheme.Style {
+		guard let style = theme.styles.first(where: { $0.name == block.styleName }) else {
+			guard let defaultStyle = theme.styles.first(where: { $0.name == "default" }) else {
+				return PHTheme.Style.default
+			}
+			return defaultStyle
+		}
+		return style
+	}
+}
+
+// Refresh
+
+extension PHController {
 	/// Start auto-refresh for every block.
 	func startAutoRefresh() {
 		for block in blocks {

Sources/phbar/Events/PHEvent.swift

@@ -0,0 +1,36 @@
+import Foundation
+
+/// A subscribable system event.
+///
+/// Declared as a `String`-backed enum so it decodes straight from the TOML
+/// config (e.g. `events = ["volume", "network"]`) while staying typo-proof: an
+/// unknown value fails to load instead of silently doing nothing.
+///
+/// To add a new event: add a case here, conform a `PHEventSource` to it in
+/// `PHEventRegistry.defaultFactory`, and ship the source under `Events/Sources/`.
+enum PHEvent: String, CaseIterable, Sendable {
+	/// System output volume or default output device changes (CoreAudio).
+	case volume
+	/// Network reachability / interface changes (Network framework).
+	case network
+	/// Light/Dark appearance changes (DistributedNotificationCenter).
+	case appearance
+	/// Power source changes — AC plug/unplug, battery updates (IOKit).
+	case power
+	/// Music Player Daemon state changes — playback, playlist, etc. (MPD `idle`).
+	case mpd
+}
+
+extension PHEvent: Decodable {
+	init(from decoder: Decoder) throws {
+		let container = try decoder.singleValueContainer()
+		let raw = try container.decode(String.self)
+		guard let value = Self(rawValue: raw) else {
+			throw DecodingError.dataCorrupted(.init(
+				codingPath: decoder.codingPath,
+				debugDescription: "unknown event '\(raw)'; valid events: \(PHEvent.allCases.map(\.rawValue).joined(separator: ", "))"
+			))
+		}
+		self = value
+	}
+}

Sources/phbar/Events/PHEventRegistry.swift

@@ -0,0 +1,92 @@
+import Foundation
+
+/// Lazily-activated, ref-counted broker for system events.
+///
+/// Blocks never talk to `CoreAudio` / `Network` / `IOKit` directly. Instead they
+/// `subscribe(_:)` to a `PHEvent` and receive a main-actor callback whenever it
+/// fires. The registry keeps exactly one `PHEventSource` alive per event for as
+/// long as at least one subscriber exists, so an event that no block cares about
+/// costs nothing.
+///
+/// The shared instance is used app-wide; tests inject a registry built with a
+/// custom `factory` (typically returning a fake source).
+@MainActor
+final class PHEventRegistry {
+	static let shared = PHEventRegistry()
+
+	private struct Slot {
+		let source: any PHEventSource
+		var subscribers: [UUID: @MainActor () -> Void] = [:]
+	}
+
+	private var slots: [PHEvent: Slot] = [:]
+	private let factory: @MainActor @Sendable (PHEvent) -> any PHEventSource
+
+	init(factory: @escaping @MainActor @Sendable (PHEvent) -> any PHEventSource = PHEventRegistry.defaultFactory) {
+		self.factory = factory
+	}
+
+	/// Subscribe to `event`.
+	///
+	/// - Parameters:
+	///   - handler: Invoked on the main actor every time the event fires.
+	/// - Returns: A cancellable. The underlying listener is started on the first
+	///   subscriber and stopped once the last one cancels.
+	@discardableResult
+	func subscribe(_ event: PHEvent, handler: @escaping @MainActor () -> Void) -> PHEventSubscription {
+		if slots[event] == nil {
+			slots[event] = Slot(source: factory(event))
+		}
+
+		let id = UUID()
+		let wasEmpty = slots[event]?.subscribers.isEmpty ?? true
+		slots[event]?.subscribers[id] = handler
+
+		if wasEmpty {
+			slots[event]?.source.start { [weak self] in
+				self?.broadcast(event)
+			}
+		}
+
+		return PHEventSubscription { [weak self] in
+			guard let self else { return }
+			Task { @MainActor in self.unsubscribe(event, id: id) }
+		}
+	}
+
+	/// Number of active subscribers for `event` (handy for tests/debugging).
+	func subscriberCount(for event: PHEvent) -> Int {
+		slots[event]?.subscribers.count ?? 0
+	}
+
+	/// Forward one firing to every current subscriber. Called on the main actor.
+	private func broadcast(_ event: PHEvent) {
+		guard let slot = slots[event] else { return }
+		for handler in slot.subscribers.values {
+			handler()
+		}
+	}
+
+	/// Remove one subscriber, stopping and dropping the source when none remain.
+	private func unsubscribe(_ event: PHEvent, id: UUID) {
+		guard var slot = slots[event] else { return }
+		slot.subscribers[id] = nil
+		if slot.subscribers.isEmpty {
+			slot.source.stop()
+			slots[event] = nil
+		} else {
+			slots[event] = slot
+		}
+	}
+
+	/// Maps each event to its concrete adapter.
+	static func defaultFactory(_ event: PHEvent) -> any PHEventSource {
+		switch event {
+		case .volume: return VolumeEventSource()
+		case .network: return NetworkEventSource()
+		case .appearance: return AppearanceEventSource()
+		case .power: return PowerEventSource()
+		case .mpd: return MPDEventSource()
+		}
+	}
+}

Sources/phbar/Events/PHEventSource.swift

@@ -0,0 +1,20 @@
+import Foundation
+
+/// A single adapter that observes one kind of system event.
+///
+/// The registry owns source lifecycles: a source is `start`ed on its first
+/// subscriber and `stop`ped when the last one cancels. Conformers are
+/// `@MainActor` for their mutable state, but the `notify` closure they are
+/// handed is `@MainActor`-isolated and `Sendable`, so an adapter that receives
+/// callbacks on a background queue (CoreAudio, Network) must hop to the main
+/// actor before calling it.
+@MainActor
+protocol PHEventSource: AnyObject {
+	/// Begin observing. `notify` must be retained for as long as the source is
+	/// started and is invoked on the main actor for every state change.
+	/// Idempotent: calling `start` while already started is a no-op.
+	func start(notify: @escaping @MainActor @Sendable () -> Void)
+
+	/// Stop observing and release system resources. Idempotent.
+	func stop()
+}

Sources/phbar/Events/PHEventSubscription.swift

@@ -0,0 +1,25 @@
+import Foundation
+
+/// A cancellable handle returned by `PHEventRegistry.subscribe(_:)`.
+///
+/// Cancel it (e.g. in `PHBlock.stopAutoRefresh`) to decrement the event's
+/// subscriber count; the registry tears the underlying listener down when the
+/// last subscriber for an event cancels. `cancel` is safe to call from any
+/// context and from `deinit`; the actual unregistration is performed on the
+/// main actor.
+final class PHEventSubscription: @unchecked Sendable {
+	private var cancellation: (@Sendable () -> Void)?
+
+	init(_ cancellation: @escaping @Sendable () -> Void) {
+		self.cancellation = cancellation
+	}
+
+	/// Stop the subscription. Safe to call more than once.
+	func cancel() {
+		let cancellation = cancellation
+		self.cancellation = nil
+		cancellation?()
+	}
+
+	deinit { cancellation?() }
+}

Sources/phbar/Events/Sources/AppearanceEventSource.swift

@@ -0,0 +1,34 @@
+import Foundation
+
+/// Fires when the system appearance switches between Light and Dark mode.
+///
+/// `AppleInterfaceThemeChangedNotification` is a distributed notification posted
+/// system-wide, so it reaches the bar even when it isn't frontmost.
+@MainActor
+final class AppearanceEventSource: PHEventSource {
+	static let notificationName = Notification.Name("AppleInterfaceThemeChangedNotification")
+
+	private var observer: NSObjectProtocol?
+	private var started = false
+
+	func start(notify: @escaping @MainActor @Sendable () -> Void) {
+		guard !started else { return }
+		started = true
+		observer = DistributedNotificationCenter.default().addObserver(
+			forName: Self.notificationName,
+			object: nil,
+			queue: .main
+		) { _ in
+			Task { @MainActor in notify() }
+		}
+	}
+
+	func stop() {
+		guard started else { return }
+		started = false
+		if let observer {
+			DistributedNotificationCenter.default().removeObserver(observer)
+		}
+		observer = nil
+	}
+}

Sources/phbar/Events/Sources/MPDEventSource.swift

@@ -0,0 +1,182 @@
+import Foundation
+import Network
+
+/// Fires whenever the Music Player Daemon (MPD) state changes — playback
+/// start/stop/seek, playlist edits, volume, options, etc.
+///
+/// Connects to MPD's TCP socket (default `127.0.0.1:6600`) and issues the
+/// `idle` command, which blocks server-side until a subsystem changes. When MPD
+/// replies with `changed: …` lines terminated by `OK`, the source fires `notify`
+/// and re-enters idle. The specifics of *what* changed are intentionally
+/// ignored: blocks only need to know that the music state changed so they can
+/// recompute. If the connection drops or MPD is unreachable, the source
+/// reconnects after a short delay for as long as it is started.
+@MainActor
+final class MPDEventSource: PHEventSource {
+	/// Seconds to wait before retrying a failed/dropped connection.
+	static let reconnectDelay: Duration = .seconds(1)
+	/// The `idle` command, newline-terminated, as sent over the wire.
+	static let idleCommand = Data("idle\n".utf8)
+
+	private let host: NWEndpoint.Host
+	private let port: NWEndpoint.Port
+	private let queue = DispatchQueue(label: "phbar.mpd", qos: .utility)
+
+	private var started = false
+	/// Bumped on every `start`/`stop` so a reconnect scheduled by a torn-down
+	/// generation bails out instead of racing a fresh `start`.
+	private var generation = 0
+	private var connection: NWConnection?
+	private var notify: (@MainActor @Sendable () -> Void)?
+	/// Accumulates partial lines across `receive` callbacks (TCP is a stream).
+	private var buffer = Data()
+
+	init(host: String = "127.0.0.1", port: UInt16 = 6600) {
+		self.host = NWEndpoint.Host(host)
+		self.port = NWEndpoint.Port(rawValue: port) ?? .any
+	}
+
+	func start(notify: @escaping @MainActor @Sendable () -> Void) {
+		guard !started else { return }
+		started = true
+		self.notify = notify
+		buffer.removeAll()
+		openConnection()
+	}
+
+	func stop() {
+		guard started else { return }
+		started = false
+		generation += 1
+		connection?.cancel()
+		connection = nil
+		notify = nil
+		buffer.removeAll()
+	}
+
+	// MARK: - Connection lifecycle
+
+	private func openConnection() {
+		guard started else { return }
+		let connection = NWConnection(host: host, port: port, using: .tcp)
+		connection.stateUpdateHandler = { [weak self] state in
+			Task { @MainActor [weak self] in
+				self?.handle(state: state, connection: connection)
+			}
+		}
+		connection.start(queue: queue)
+		self.connection = connection
+	}
+
+	private func handle(state: NWConnection.State, connection: NWConnection) {
+		// Only react for the currently-active connection; an old connection
+		// winding down after a reconnect must not trigger another one.
+		guard self.connection === connection else { return }
+		switch state {
+		case .ready:
+			beginReadLoop(on: connection)
+		case .failed, .cancelled:
+			self.connection = nil
+			buffer.removeAll()
+			if started {
+				scheduleReconnect()
+			}
+		default:
+			break
+		}
+	}
+
+	/// Drop the current connection; the state handler drives the reconnect.
+	private func fail(connection: NWConnection) {
+		guard self.connection === connection else { return }
+		connection.cancel()
+	}
+
+	private func scheduleReconnect() {
+		let gen = generation
+		Task { [weak self] in
+			try? await Task.sleep(for: Self.reconnectDelay)
+			guard let self, self.started, self.generation == gen, !Task.isCancelled else { return }
+			self.openConnection()
+		}
+	}
+
+	// MARK: - MPD idle protocol
+
+	/// Reads lines from `connection` until it fails or closes. `onLine` runs on
+	/// the main actor for each complete line.
+	private func readLines(
+		on connection: NWConnection,
+		_ onLine: @escaping @MainActor (String) -> Void
+	) {
+		connection.receive(minimumIncompleteLength: 1, maximumLength: 65536) { [weak self] content, _, isComplete, error in
+			Task { @MainActor [weak self] in
+				guard let self, self.started else { return }
+				if error != nil || isComplete {
+					self.fail(connection: connection)
+					return
+				}
+				if let content, !content.isEmpty {
+					self.buffer.append(content)
+				}
+				while let line = self.buffer.popLine() {
+					onLine(line)
+				}
+				self.readLines(on: connection, onLine)
+			}
+		}
+	}
+
+	/// The MPD greeting (e.g. `OK MPD 0.23.5`) arrives first; once it's consumed
+	/// the source enters the idle loop, re-sending `idle` after every `OK`.
+	private func beginReadLoop(on connection: NWConnection) {
+		var consumedGreeting = false
+		readLines(on: connection) { [weak self] line in
+			guard let self, self.started else { return }
+			if !consumedGreeting {
+				consumedGreeting = true
+				self.sendIdle(on: connection)
+				return
+			}
+			// `OK` ends an idle response — fire and re-arm. `changed: …` and
+			// `ACK …` lines are ignored; only the fact of a change matters.
+			if line == "OK" {
+				self.fire()
+				self.sendIdle(on: connection)
+			}
+		}
+	}
+
+	private func sendIdle(on connection: NWConnection) {
+		guard started else { return }
+		connection.send(content: Self.idleCommand, completion: .contentProcessed { [weak self] error in
+			Task { @MainActor [weak self] in
+				guard let self, self.started else { return }
+				if error != nil {
+					self.fail(connection: connection)
+				}
+			}
+		})
+	}
+
+	private func fire() {
+		notify?()
+	}
+}
+
+// MARK: - Line buffering
+
+private extension Data {
+	/// Removes and returns the first `\n`-terminated line (without the
+	/// terminator and any trailing `\r`), or `nil` if no complete line is buffered.
+	mutating func popLine() -> String? {
+		guard let newline = firstIndex(of: UInt8(ascii: "\n")) else { return nil }
+		var line = self[startIndex..<newline]
+		if line.last == UInt8(ascii: "\r") {
+			line = line.dropLast()
+		}
+		let string = String(data: line, encoding: .utf8) ?? ""
+		removeSubrange(startIndex...newline)
+		return string
+	}
+}

Sources/phbar/Events/Sources/NetworkEventSource.swift

@@ -0,0 +1,30 @@
+import Foundation
+import Network
+
+/// Fires whenever the system's network path changes (Wi-Fi up/down, interface
+/// switch, reachability). Uses `NWPathMonitor`, which needs no special
+/// permissions — unlike reading the SSID via CoreWLAN.
+@MainActor
+final class NetworkEventSource: PHEventSource {
+	private var monitor: NWPathMonitor?
+	private var started = false
+
+	func start(notify: @escaping @MainActor @Sendable () -> Void) {
+		guard !started else { return }
+		started = true
+
+		let monitor = NWPathMonitor()
+		monitor.pathUpdateHandler = { _ in
+			Task { @MainActor in notify() }
+		}
+		monitor.start(queue: .global(qos: .utility))
+		self.monitor = monitor
+	}
+
+	func stop() {
+		guard started else { return }
+		started = false
+		monitor?.cancel()
+		monitor = nil
+	}
+}

Sources/phbar/Events/Sources/PowerEventSource.swift

@@ -0,0 +1,53 @@
+import Foundation
+import IOKit.ps
+
+/// Fires when the power source changes — AC adapter plugged/unplugged, battery
+/// level/charging state updates — via IOKit's power-source run-loop source.
+@MainActor
+final class PowerEventSource: PHEventSource {
+	/// Holds the notify closure so the C callback can reach it without capturing.
+	fileprivate final class ContextBox: @unchecked Sendable {
+		let notify: @MainActor @Sendable () -> Void
+		init(notify: @escaping @MainActor @Sendable () -> Void) { self.notify = notify }
+	}
+
+	private var runLoopSource: CFRunLoopSource?
+	private var contextBox: ContextBox?
+	private var started = false
+
+	func start(notify: @escaping @MainActor @Sendable () -> Void) {
+		guard !started else { return }
+		started = true
+
+		let box = ContextBox(notify: notify)
+		contextBox = box
+
+		let source = IOPSNotificationCreateRunLoopSource(
+			phbarPowerSourceChanged,
+			Unmanaged.passUnretained(box).toOpaque()
+		).takeRetainedValue()
+		CFRunLoopAddSource(CFRunLoopGetMain(), source, .defaultMode)
+		runLoopSource = source
+	}
+
+	func stop() {
+		guard started else { return }
+		started = false
+		if let runLoopSource {
+			CFRunLoopRemoveSource(CFRunLoopGetMain(), runLoopSource, .defaultMode)
+		}
+		runLoopSource = nil
+		contextBox = nil
+	}
+}
+
+// MARK: - IOKit callback
+//
+// `IOPowerSourceCallbackType` is a C function pointer. The source is added to
+// the main run loop, so this runs on the main thread — safe to assume MainActor.
+
+private func phbarPowerSourceChanged(_ context: UnsafeMutableRawPointer?) {
+	guard let context else { return }
+	let box = Unmanaged<PowerEventSource.ContextBox>.fromOpaque(context).takeUnretainedValue()
+	MainActor.assumeIsolated { box.notify() }
+}

Sources/phbar/Events/Sources/VolumeEventSource.swift

@@ -0,0 +1,197 @@
+import AudioToolbox
+import CoreAudio
+import Foundation
+
+/// Read access to the system output volume with change notifications.
+///
+/// Wraps the public CoreAudio HAL so callers can ignore C callbacks and property
+/// addresses. This tracks the virtual master output volume (the value the macOS
+/// volume slider controls) and re-attaches when the default device changes.
+enum SystemAudioVolume {
+	/// Current default output volume in `0...1`, or `0` if unavailable.
+	static var current: Float {
+		guard let device = defaultDevice else { return 0 }
+		return volume(of: device)
+	}
+
+	/// The system's default output device, if any.
+	static var defaultDevice: AudioDeviceID? {
+		var address = AudioObjectPropertyAddress(
+			mSelector: kAudioHardwarePropertyDefaultOutputDevice,
+			mScope: kAudioObjectPropertyScopeGlobal,
+			mElement: kAudioObjectPropertyElementMain
+		)
+		var device = AudioDeviceID(0)
+		var size = UInt32(MemoryLayout<AudioDeviceID>.size)
+		let status = AudioObjectGetPropertyData(AudioObjectID(kAudioObjectSystemObject), &address, 0, nil, &size, &device)
+		return status == noErr ? device : nil
+	}
+
+	/// Virtual master volume `[0, 1]` for a given output device.
+	static func volume(of device: AudioDeviceID) -> Float {
+		var address = AudioObjectPropertyAddress(
+			mSelector: kAudioHardwareServiceDeviceProperty_VirtualMainVolume,
+			mScope: kAudioDevicePropertyScopeOutput,
+			mElement: kAudioObjectPropertyElementMain
+		)
+		var value = Float32(0)
+		var size = UInt32(MemoryLayout<Float32>.size)
+		let status = AudioObjectGetPropertyData(device, &address, 0, nil, &size, &value)
+		return status == noErr ? Float(value) : 0
+	}
+
+	/// Observe volume changes on the current default device. The handler is
+	/// invoked immediately with the current value, then whenever the volume or
+	/// the default device changes. Keep the returned `Listener` alive.
+	static func observe(_ handler: @escaping @Sendable (Float) -> Void) -> Listener {
+		let listener = Listener(handler: handler)
+		listener.activate()
+		return listener
+	}
+
+	// MARK: - Listener
+
+	/// A self-contained listener that re-attaches when the default device changes.
+	/// Not `@MainActor`: CoreAudio delivers callbacks on its own thread.
+	final class Listener {
+		private let handler: @Sendable (Float) -> Void
+		private let lock = NSLock()
+		private var observedDevice: AudioDeviceID?
+		private var systemListenerInstalled = false
+
+		init(handler: @escaping @Sendable (Float) -> Void) {
+			self.handler = handler
+		}
+
+		func activate() {
+			installSystemListener()
+			attach(to: SystemAudioVolume.defaultDevice)
+		}
+
+		private func installSystemListener() {
+			lock.lock()
+			defer { lock.unlock() }
+			guard !systemListenerInstalled else { return }
+			systemListenerInstalled = true
+			var address = Self.defaultDeviceAddress
+			AudioObjectAddPropertyListener(
+				AudioObjectID(kAudioObjectSystemObject), &address, phbarDefaultDeviceChanged,
+				Unmanaged.passUnretained(self).toOpaque()
+			)
+		}
+
+		private func attach(to device: AudioDeviceID?) {
+			lock.lock()
+			let previous = observedDevice
+			observedDevice = device
+			lock.unlock()
+
+			if let previous {
+				var address = Self.volumeAddress
+				AudioObjectRemovePropertyListener(
+					previous, &address, phbarVolumeChanged,
+					Unmanaged.passUnretained(self).toOpaque()
+				)
+			}
+
+			guard let device else { return }
+			var address = Self.volumeAddress
+			AudioObjectAddPropertyListener(
+				device, &address, phbarVolumeChanged,
+				Unmanaged.passUnretained(self).toOpaque()
+			)
+			// Emit current value once on attach.
+			handler(SystemAudioVolume.volume(of: device))
+		}
+
+		/// Called from the CoreAudio thread when the volume property fires.
+		fileprivate func fire(for device: AudioDeviceID) {
+			handler(SystemAudioVolume.volume(of: device))
+		}
+
+		/// Called from the CoreAudio thread when the default device changes.
+		fileprivate func reattach() {
+			attach(to: SystemAudioVolume.defaultDevice)
+		}
+
+		deinit {
+			let context = Unmanaged.passUnretained(self).toOpaque()
+			if systemListenerInstalled {
+				var address = Self.defaultDeviceAddress
+				AudioObjectRemovePropertyListener(AudioObjectID(kAudioObjectSystemObject), &address, phbarDefaultDeviceChanged, context)
+			}
+			if let device = observedDevice {
+				var address = Self.volumeAddress
+				AudioObjectRemovePropertyListener(device, &address, phbarVolumeChanged, context)
+			}
+		}
+
+		static var defaultDeviceAddress: AudioObjectPropertyAddress {
+			AudioObjectPropertyAddress(
+				mSelector: kAudioHardwarePropertyDefaultOutputDevice,
+				mScope: kAudioObjectPropertyScopeGlobal,
+				mElement: kAudioObjectPropertyElementMain
+			)
+		}
+
+		static var volumeAddress: AudioObjectPropertyAddress {
+			AudioObjectPropertyAddress(
+			mSelector: kAudioHardwareServiceDeviceProperty_VirtualMainVolume,
+				mScope: kAudioDevicePropertyScopeOutput,
+				mElement: kAudioObjectPropertyElementMain
+			)
+		}
+	}
+}
+
+// MARK: - CoreAudio callbacks
+//
+// `AudioObjectPropertyListenerProc` is a C function pointer, so these must be
+// non-capturing top-level functions. They recover `self` via the client data
+// pointer passed alongside the listener.
+
+private func phbarVolumeChanged(
+	_ objectID: AudioObjectID,
+	_ count: UInt32,
+	_ addresses: UnsafePointer<AudioObjectPropertyAddress>,
+	_ clientData: UnsafeMutableRawPointer?
+) -> OSStatus {
+	guard let clientData else { return noErr }
+	let listener = Unmanaged<SystemAudioVolume.Listener>.fromOpaque(clientData).takeUnretainedValue()
+	listener.fire(for: objectID)
+	return noErr
+}
+
+private func phbarDefaultDeviceChanged(
+	_ objectID: AudioObjectID,
+	_ count: UInt32,
+	_ addresses: UnsafePointer<AudioObjectPropertyAddress>,
+	_ clientData: UnsafeMutableRawPointer?
+) -> OSStatus {
+	guard let clientData else { return noErr }
+	let listener = Unmanaged<SystemAudioVolume.Listener>.fromOpaque(clientData).takeUnretainedValue()
+	listener.reattach()
+	return noErr
+}
+
+// MARK: - PHEventSource
+
+@MainActor
+final class VolumeEventSource: PHEventSource {
+	private var listener: SystemAudioVolume.Listener?
+	private var started = false
+
+	func start(notify: @escaping @MainActor @Sendable () -> Void) {
+		guard !started else { return }
+		started = true
+		listener = SystemAudioVolume.observe { _ in
+			Task { @MainActor in notify() }
+		}
+	}
+
+	func stop() {
+		guard started else { return }
+		started = false
+		listener = nil
+	}
+}

Sources/phbar/Extensions/Color+Extensions.swift

@@ -0,0 +1,17 @@
+import SwiftUI
+
+extension SwiftUI.Color {
+	init(hex: String, opacity: Double?) {
+		let scanner = Scanner(string: hex)
+		_ = scanner.scanString("#")
+
+		var rgb: UInt64 = 0
+		scanner.scanHexInt64(&rgb)
+
+		let red = Double((rgb >> 16) & 0xFF) / 255.0
+		let green = Double((rgb >> 8) & 0xFF) / 255.0
+		let blue = Double(rgb & 0xFF) / 255.0
+
+		self.init(red: red, green: green, blue: blue, opacity: opacity ?? 1.0)
+	}
+}

Sources/phbar/IPC/IPC.swift

@@ -0,0 +1,167 @@
+import Foundation
+
+// MARK: - Notification Name
+
+/// A type-safe identifier for cross-process notifications.
+///
+/// Names should be reverse-DNS strings (e.g. `"com.paninihouse.phbar.refresh"`)
+/// to avoid collisions with other applications using distributed notifications.
+struct IPCNotificationName: Hashable, RawRepresentable, ExpressibleByStringLiteral {
+	let rawValue: String
+
+	init(rawValue: String) { self.rawValue = rawValue }
+	init(_ rawValue: String) { self.rawValue = rawValue }
+	init(stringLiteral value: String) { self.rawValue = value }
+
+	/// The Foundation name used by the underlying distributed center.
+	fileprivate var nsName: Notification.Name { Notification.Name(rawValue) }
+}
+
+// MARK: - Notification
+
+/// A received cross-process notification with its optional payload.
+struct IPCNotification {
+	let name: IPCNotificationName
+	let userInfo: [String: Any]?
+
+	init(name: IPCNotificationName, userInfo: [String: Any]? = nil) {
+		self.name = name
+		self.userInfo = userInfo
+	}
+
+	/// Decode a Codable value from the notification's `userInfo` payload.
+	///
+	/// Returns `nil` if `userInfo` is missing or cannot be decoded as `type`.
+	func decode<T: Decodable>(_ type: T.Type) -> T? {
+		guard let userInfo,
+		      JSONSerialization.isValidJSONObject(userInfo),
+		      let data = try? JSONSerialization.data(withJSONObject: userInfo) else {
+			return nil
+		}
+		return try? JSONDecoder().decode(type, from: data)
+	}
+}
+
+// MARK: - Notification Center
+
+/// A thin layer over `DistributedNotificationCenter` for sending lightweight
+/// cross-process signals between the `phbar` daemon and short-lived CLI commands.
+///
+/// Distributed notifications are delivered best-effort to processes running under
+/// the same user. They are ideal for idempotent signals (e.g. "refresh"); do not
+/// rely on them for critical, ordered, or large data transfer.
+///
+/// ## Usage
+/// ```swift
+/// // Post a bare signal
+/// IPC.post(.refresh)
+///
+/// // Post with a Codable payload
+/// IPC.post(.updateItem, payload: Item(title: "Hello", count: 3))
+///
+/// // Observe (token must be retained)
+/// let token = IPC.observe(.refresh) { notification in
+///     // ...
+/// }
+///
+/// // Observe a typed payload
+/// let token = IPC.observe(.updateItem, as: Item.self) { item in
+///     // ...
+/// }
+/// ```
+enum IPC {
+	/// The shared distributed notification center (one per user session).
+	static var center: DistributedNotificationCenter { .default() }
+
+	/// Post a signal with an optional property-list payload.
+	///
+	/// `userInfo` must contain only property-list types (`String`, `Number`,
+	/// `Date`, `Data`, `Array`, `Dictionary`); other values are dropped during
+	/// cross-process delivery.
+	static func post(_ name: IPCNotificationName, userInfo: [String: Any]? = nil) {
+		center.postNotificationName(
+			name.nsName,
+			object: nil,
+			userInfo: userInfo as [AnyHashable: Any]?,
+			deliverImmediately: true
+		)
+	}
+
+	/// Post a signal carrying a Codable payload.
+	///
+	/// The payload is JSON-encoded into the notification's `userInfo`.
+	/// Returns `false` if encoding fails.
+	@discardableResult
+	static func post<T: Encodable>(_ name: IPCNotificationName, payload: T) -> Bool {
+		guard let data = try? JSONEncoder().encode(payload),
+		      let dict = try? JSONSerialization.jsonObject(with: data) as? [String: Any] else {
+			return false
+		}
+		post(name, userInfo: dict)
+		return true
+	}
+
+	/// Observe a signal.
+	///
+	/// The handler is invoked on the main thread (distributed notifications are
+	/// delivered to the receiving process's main run loop).
+	///
+	/// - Returns: A token that must be retained while observing. Releasing it
+	///   automatically unregisters the observer.
+	static func observe(
+		_ name: IPCNotificationName,
+		handler: @escaping (IPCNotification) -> Void
+	) -> IPCObserver {
+		IPCObserver(center: center, name: name.nsName, handler: handler)
+	}
+
+	/// Observe a signal and decode its Codable payload.
+	///
+	/// `handler` is called only when the payload decodes successfully; malformed
+	/// or missing payloads are silently ignored.
+	static func observe<T: Decodable>(
+		_ name: IPCNotificationName,
+		as type: T.Type,
+		handler: @escaping (T) -> Void
+	) -> IPCObserver {
+		observe(name) { notification in
+			guard let payload: T = notification.decode(type) else { return }
+			handler(payload)
+		}
+	}
+}
+
+// MARK: - Observer
+
+/// An observation token for a distributed notification.
+///
+/// Wraps the target/selector API of `DistributedNotificationCenter` so callers
+/// can register a Swift closure. The notification center dispatches the selector
+/// to this object; releasing the token removes the observer in `deinit`.
+final class IPCObserver: NSObject {
+	private let center: DistributedNotificationCenter
+	private let name: Notification.Name
+	private let handler: (IPCNotification) -> Void
+
+	fileprivate init(
+		center: DistributedNotificationCenter,
+		name: Notification.Name,
+		handler: @escaping (IPCNotification) -> Void
+	) {
+		self.center = center
+		self.name = name
+		self.handler = handler
+		super.init()
+		center.addObserver(self, selector: #selector(handle(_:)), name: name, object: nil)
+	}
+
+	@objc private func handle(_ notification: Notification) {
+		let name = IPCNotificationName(notification.name.rawValue)
+		let userInfo = notification.userInfo as? [String: Any]
+		handler(IPCNotification(name: name, userInfo: userInfo))
+	}
+
+	deinit {
+		center.removeObserver(self, name: name, object: nil)
+	}
+}

Sources/phbar/IPC/PHBar+Notifications.swift

@@ -0,0 +1,8 @@
+import Foundation
+
+// MARK: - PHBar Notification Names
+
+extension IPCNotificationName {
+	/// Sent by `phbar refresh` to request the running status bar to update.
+	static let refresh = IPCNotificationName("com.paninihouse.phbar.refresh")
+}

Sources/phbar/Models/Gesture/PHGesture.swift

@@ -0,0 +1,6 @@
+enum PHGesture: String {
+	case leftMouseDown = "left_mouse_down"
+	case rightMouseDown = "right_mouse_down"
+	case otherMouseDown = "other_mouse_down"
+	case scrollWheel = "scroll_wheel"
+}

Sources/phbar/Models/Gesture/PHGestureEvent.swift

@@ -0,0 +1,24 @@
+import AppKit
+
+struct PHGestureEvent {
+	static let typeKey = "GESTURE"
+	static let infoKey = "GESTURE_INFO"
+
+	let type: PHGesture
+	let data: String?
+
+	static func from(_ event: NSEvent) -> PHGestureEvent? {
+		switch event.type {
+		case .leftMouseDown:
+			return .init(type: .leftMouseDown, data: nil)
+		case .rightMouseDown:
+			return .init(type: .rightMouseDown, data: nil)
+		case .otherMouseDown:
+			return .init(type: .otherMouseDown, data: String(event.buttonNumber))
+		case .scrollWheel:
+			return .init(type: .scrollWheel, data: "\(event.scrollingDeltaX) \(event.scrollingDeltaY)")
+		default:
+			return nil
+		}
+	}
+}

Sources/phbar/Models/PHBlock.swift

@@ -8,75 +8,162 @@ final class PHBlock: ObservableObject, Decodable, Identifiable {
 	let id = UUID()
 	let command: String
 	let name: String?
-	let style: String?
+	let styleName: String?
+	@Published var style: PHTheme.Style = .default
 	let refresh: Double?
+	let centered: Bool?
+	var debug: Bool = false
 
-	@Published private(set) var label = ""
+	var visible: Bool {
+		label != nil && !label!.isEmpty
+	}
 
-	/// The repeating refresh task, if any.
+	/// System events that should trigger a refresh (e.g. `["volume", "network"]`).
-	private var refreshTask: Task<Void, Never>?
+	/// `nil` when omitted from config.
+	let events: [PHEvent]?
+
+	/// Event source registry used to subscribe to system events. Defaults to the
+	/// shared instance; inject a custom one for testing.
+	var registry: PHEventRegistry = .shared
+
+	@Published private(set) var label: String?
+
+	/// The repeating interval task, if any.
+	private var intervalTask: Task<Void, Never>?
+
+	/// Active event subscriptions, torn down in `stopAutoRefresh`.
+	private var subscriptions: [PHEventSubscription] = []
+
+	/// Guards against stacking concurrent updates during rapid event bursts
+	/// (e.g. dragging the volume slider fires many events in quick succession).
+	private var updateScheduled = false
 
 	private enum CodingKeys: String, CodingKey {
-		case command, name, style, refresh
+		case command, name
+		case styleName = "style"
+		case refresh, events, centered
 	}
 
 	deinit {
-		refreshTask?.cancel()
+		intervalTask?.cancel()
+		subscriptions.forEach { $0.cancel() }
+	}
+}
+
+// Kind
+
+extension PHBlock {
+	enum Kind: String {
+		case text, space
 	}
 
-	// MARK: - Refresh
+	var kind: Kind {
+		if command.starts(with: "_space") { return .space }
+		return .text
+	}
+}
 
+// Refresh
+
+extension PHBlock {
 	/// Start keeping the label up to date.
 	///
-	/// The label is always recomputed immediately. When `refresh` is set to a
+	/// Three independent triggers drive refreshes, and any combination works:
-	/// positive number of seconds, it is then recomputed on that interval until
+	///
-	/// `stopAutoRefresh()` is called. With no interval set, only the initial
+	/// 1. **Interval** — when `refresh` is a positive number of seconds, the
-	/// computation runs and later updates must be triggered manually via
+	///    label is recomputed on that interval.
-	/// `update()`.
+	/// 2. **Events** — each name in `events` subscribes to a system event source
+	///    (volume, network, appearance, power). Sources are activated lazily by
+	///    the registry: a listener runs only while at least one block subscribes
+	///    to it, so unused events cost nothing.
+	/// 3. **Manual** — `update()`, `PHController.refresh()`, or `phbar refresh`.
+	///
+	/// The label is always recomputed once immediately on start, then again on
+	/// any of the triggers above until `stopAutoRefresh()` is called.
 	func startAutoRefresh() {
 		stopAutoRefresh()
 
-		guard let interval = refresh, interval > 0 else {
+		// Immediate refresh so the bar isn't blank until the first trigger fires.
-			// No interval: compute once, rely on manual updates afterwards.
+		scheduleUpdate()
-			Task { await update() }
-			return
-		}
 
-		let milliseconds = Int(interval * 1000)
+		// 1. Periodic refresh.
-		refreshTask = Task { [weak self] in
+		if let interval = refresh, interval > 0 {
-			while !Task.isCancelled {
+			let milliseconds = Int(interval * 1000)
-				await self?.update()
+			intervalTask = Task { [weak self] in
-				try? await Task.sleep(for: .milliseconds(milliseconds))
+				while !Task.isCancelled {
+					try? await Task.sleep(for: .milliseconds(milliseconds))
+					if Task.isCancelled { break }
+					await self?.update()
+				}
 			}
 		}
+
+		// 2. Event-driven refresh. The registry lazily activates each underlying
+		//    system listener only while at least one block subscribes to it.
+		for event in (events ?? []) {
+			let subscription = registry.subscribe(event) { [weak self] in
+				self?.scheduleUpdate()
+			}
+			subscriptions.append(subscription)
+		}
 	}
 
-	/// Cancel the repeating auto-refresh, if any.
+	/// Cancel the interval task and all event subscriptions.
 	func stopAutoRefresh() {
-		refreshTask?.cancel()
+		intervalTask?.cancel()
-		refreshTask = nil
+		intervalTask = nil
+		subscriptions.forEach { $0.cancel() }
+		subscriptions.removeAll()
 	}
 
-	/// Recompute the label from `command`. Used by auto-refresh and manual updates.
+	/// Recompute the label from `command`. Used by the interval loop, event
+	/// handlers, and manual updates.
 	func update() async {
 		label = await compute()
 	}
 
+	/// Request an update on the main actor, coalescing rapid bursts into a single
+	/// recomputation.
+	private func scheduleUpdate() {
+		guard !updateScheduled else { return }
+		updateScheduled = true
+		Task { [weak self] in
+			defer { self?.updateScheduled = false }
+			await self?.update()
+		}
+	}
+
+	func handleGesture(_ event: PHGestureEvent) {
+		Task { label = await compute(with: event) }
+	}
+
 	/// Runs the provided command and returns its stdout.
 	///
 	/// Runs off the main actor so it can be awaited safely from SwiftUI views
 	/// without blocking the UI.
 	///
 	/// - Returns: A non-optional String to use as the block label.
-	func compute() async -> String {
+	func compute(with gestureEvent: PHGestureEvent? = nil) async -> String? {
+		guard kind == .text else { return nil }
+
 		let command = command
-		return await Task.detached(priority: .userInitiated) {
+
+		let lines: [Substring]? = await Task.detached(priority: .userInitiated) {
 			let process = Process()
+			process.currentDirectoryURL = Self.configFile.deletingLastPathComponent()
 			process.executableURL = URL(fileURLWithPath: "/bin/bash")
 			process.arguments = ["-c", command]
 
 			// Inherit the parent's environment (includes $PATH, etc.)
 			process.environment = ProcessInfo.processInfo.environment
+			if let gestureEvent {
+				let type = gestureEvent.type.rawValue
+				process.environment?.updateValue(type, forKey: PHGestureEvent.typeKey)
+
+				if let data = gestureEvent.data {
+					process.environment?.updateValue(data, forKey: PHGestureEvent.infoKey)
+				}
+			}
 
 			// Capture stdout via a pipe (otherwise standardOutput is always nil).
 			let pipe = Pipe()
@@ -86,12 +173,18 @@ final class PHBlock: ObservableObject, Decodable, Identifiable {
 				try process.run()
 				process.waitUntilExit()
 				let data = pipe.fileHandleForReading.readDataToEndOfFile()
-				return String(data: data, encoding: .utf8) ?? ""
+				let string = String(data: data, encoding: .utf8)
+				guard let lines = string?.split(whereSeparator: \.isNewline) else { return nil }
+				return lines
 			} catch {
 				// Silently ignore failures
-				return ""
+				return nil
 			}
 		}.value
+
+		guard let lines else { return nil }
+		if self.debug { for line in lines { print(line) } }
+		return lines.last?.description
 	}
 }
 
@@ -106,15 +199,15 @@ extension PHBlock {
 		}
 	}
 
+	private nonisolated static var configFile: URL {
+		FileManager.default.homeDirectoryForCurrentUser.appending(path: ".config/phbar/blocks.toml")
+	}
+
 	/// Load blocks from the default path (~/.config/phbar/blocks.toml).
 	/// If the file doesn't exist or fails to parse, defaults are used (non-fatal).
 	static func load() throws -> [PHBlock] {
-		let url = FileManager.default.homeDirectoryForCurrentUser.appending(
+		if FileManager.default.fileExists(atPath: Self.configFile.relativePath) {
-			path: ".config/phbar/blocks.toml"
+			return try load(from: Self.configFile)
-		)
-
-		if FileManager.default.fileExists(atPath: url.relativePath) {
-			return try load(from: url)
 		} else {
 			throw phbar.Error("Failed to load blocks file")
 		}

Sources/phbar/Models/PHConfig.swift

@@ -0,0 +1,3 @@
+struct PHConfig: Decodable {
+	let text: Text
+}

Sources/phbar/Models/PHConfig/PHConfig+Loading.swift

@@ -0,0 +1,49 @@
+import Foundation
+import TOML
+
+extension PHConfig {
+	/// Load configuration from the default path (~/.config/pmenu/config.toml).
+	/// If the file doesn't exist or fails to parse, defaults are used (non-fatal).
+	static func load() throws -> PHConfig {
+		let url = FileManager.default.homeDirectoryForCurrentUser.appending(
+			path: ".config/phbar/config.toml")
+
+		if FileManager.default.fileExists(atPath: url.relativePath) {
+			return try load(from: url)
+		} else {
+			guard
+				let defaultConfig = Bundle.module.url(
+					forResource: "config",
+					withExtension: "toml"
+				)?.resolvingSymlinksInPath()
+			else {
+				throw phbar.Error("Failed to load config file")
+			}
+			return try load(from: defaultConfig)
+		}
+	}
+
+	/// Decode configuration from a file at URL.
+	/// If the file doesn't exist or fails to parse, the execution is interrupted.
+	static func load(from url: URL) throws -> PHConfig {
+		guard let data = try? Data(contentsOf: url),
+			let contents = String(data: data, encoding: .utf8)
+		else {
+			throw phbar.Error("Failed to load config file")
+		}
+
+		return try load(from: contents)
+	}
+
+	/// Decode configuration from a TOML string.
+	/// If the content fails to parse, the execution is interrupted.
+	static func load(from contents: String) throws -> PHConfig {
+		do {
+			let decoder = TOMLDecoder()
+			let configFile = try decoder.decode(PHConfig.self, from: contents)
+			return configFile
+		} catch {
+			throw phbar.Error("Failed to parse config file", underlyingError: error)
+		}
+	}
+}

Sources/phbar/Models/PHConfig/PHConfig+Text.swift

@@ -0,0 +1,162 @@
+import AppKit
+import SwiftUI
+
+extension PHConfig {
+	struct Text: Decodable {
+		let fontFamily: String
+		let size: Double
+		let weight: Weight
+		let style: Style
+		let offset: Double?
+
+		enum CodingKeys: String, CodingKey {
+			case fontFamily = "font"
+			case size, weight, style, offset
+		}
+	}
+}
+
+// Font
+
+extension PHConfig.Text {
+	/// Construct an `NSFont` from the typeface settings.
+	///
+	/// Falls back to the system font if parsing fails.
+	var nsFont: NSFont {
+		if let systemDesign {
+			let baseFont = NSFont.systemFont(ofSize: size, weight: weight.nsWeight)
+			let descriptor =
+				baseFont.fontDescriptor.withDesign(systemDesign)
+				?? baseFont.fontDescriptor
+
+			return NSFont(descriptor: descriptor, size: size)
+				?? baseFont
+		} else {
+			let descriptor = NSFontDescriptor.init(fontAttributes: [
+				.family: fontFamily,
+				.traits: [
+					NSFontDescriptor.TraitKey.weight: weight.nsWeight
+				],
+			])
+
+			return NSFont(descriptor: descriptor, size: size)
+				?? NSFont(name: fontFamily, size: size)
+				?? NSFont.systemFont(ofSize: size, weight: weight.nsWeight)
+		}
+	}
+
+	/// Construct a `Font` from the typeface settings.
+	///
+	/// Falls back to the system font if parsing fails.
+	var font: Font {
+		if let design {
+			return Font.system(size: size, weight: weight.uiWeight, design: design)
+		} else {
+			return Font.custom(fontFamily, fixedSize: size).weight(weight.uiWeight)
+		}
+	}
+}
+
+// Design
+
+extension PHConfig.Text {
+	var design: SwiftUI.Font.Design? {
+		switch fontFamily {
+		case "sans":
+			return .default
+		case "monospace":
+			return .monospaced
+		case "serif":
+			return .serif
+		default:
+			return nil
+		}
+	}
+
+	var systemDesign: NSFontDescriptor.SystemDesign? {
+		switch fontFamily {
+		case "sans":
+			return .default
+		case "monospace":
+			return .monospaced
+		case "serif":
+			return .serif
+		default:
+			return nil
+		}
+	}
+}
+
+// Weight
+
+extension PHConfig.Text {
+	enum Weight: String, Decodable {
+		case thin
+		case ultraLight = "ultralight"
+		case light
+		case regular
+		case medium
+		case semiBold = "semibold"
+		case bold
+		case heavy
+		case black
+
+		var uiWeight: SwiftUI.Font.Weight {
+			switch self {
+			case .thin:
+				return .thin
+			case .ultraLight:
+				return .ultraLight
+			case .light:
+				return .light
+			case .regular:
+				return .regular
+			case .medium:
+				return .medium
+			case .semiBold:
+				return .semibold
+			case .bold:
+				return .bold
+			case .heavy:
+				return .heavy
+			case .black:
+				return .black
+			}
+		}
+
+		var nsWeight: NSFont.Weight {
+			switch self {
+			case .thin:
+				return .thin
+			case .ultraLight:
+				return .ultraLight
+			case .light:
+				return .light
+			case .regular:
+				return .regular
+			case .medium:
+				return .medium
+			case .semiBold:
+				return .semibold
+			case .bold:
+				return .bold
+			case .heavy:
+				return .heavy
+			case .black:
+				return .black
+			}
+		}
+	}
+}
+
+// Style
+
+extension PHConfig.Text {
+	enum Style: String, Decodable {
+		case normal, italic
+	}
+
+	var italic: Bool {
+		style == .italic
+	}
+}

Sources/phbar/Models/PHTheme.swift

@@ -0,0 +1,53 @@
+struct PHTheme: Decodable {
+	static let `default` = "dracula"
+
+	static let bundled = [
+		"voltage",
+		"catppuccin-mocha",
+		"dracula",
+		"gruvbox",
+		"tokyo-night",
+	]
+
+	let window: Window
+	let styles: [Style]
+
+	enum CodingKeys: String, CodingKey {
+		case window
+		case styles = "style"
+	}
+}
+
+// Window
+
+extension PHTheme {
+	struct Window: Decodable {
+		let hasShadow: Bool
+		let blur: Double
+
+		enum CodingKeys: String, CodingKey {
+			case hasShadow = "shadow"
+			case blur
+		}
+	}
+}
+
+// Style
+
+extension PHTheme {
+	struct Style: Decodable {
+		let name: String
+		let foreground: PHTheme.Color
+		let background: PHTheme.Color
+		let padding: PHTheme.Padding
+
+		static let `default`: Self = {
+			Style(
+				name: "_default",
+				foreground: .init(color: "#000000", alpha: nil),
+				background: .init(color: "#ffffff", alpha: nil),
+				padding: .init(leading: 10, trailing: 10)
+			)
+		}()
+	}
+}

Sources/phbar/Models/PHTheme/PHTheme+Color.swift

@@ -0,0 +1,27 @@
+import SwiftUI
+
+extension PHTheme {
+	struct Color: Decodable, ShapeStyle {
+		typealias Resolved = SwiftUI.Color
+
+		let color: String
+		let alpha: Double?
+
+		var uiColor: SwiftUI.Color {
+			SwiftUI.Color(hex: color, opacity: alpha)
+		}
+
+		var nsColor: NSColor? {
+			guard let cgColor else { return nil }
+			return NSColor(cgColor: cgColor)
+		}
+
+		var cgColor: CGColor? {
+			uiColor.cgColor
+		}
+
+		func resolve(in environment: EnvironmentValues) -> SwiftUI.Color {
+			uiColor
+		}
+	}
+}

Sources/phbar/Models/PHTheme/PHTheme+Loading.swift

@@ -0,0 +1,58 @@
+import Foundation
+import TOML
+
+extension PHTheme {
+	/// Load theme from the default path (~/.config/phbar/theme.toml).
+	/// If the file doesn't exist or fails to parse, defaults are used (non-fatal).
+	static func load(_ theme: String?) throws -> PHTheme {
+		let theme = theme ?? Self.default
+		let url = FileManager.default.homeDirectoryForCurrentUser.appending(
+			path: ".config/phbar/themes/\(theme).toml"
+		)
+
+		if FileManager.default.fileExists(atPath: url.relativePath) {
+			return try load(from: url)
+		} else {
+			return try load(bundled: theme)
+		}
+	}
+
+	/// Load a bundled theme.
+	/// If the theme doesn't exist or fails to parse, the execution is interrupted.
+	static func load(bundled theme: String) throws -> PHTheme {
+		guard
+			let defaultConfig = Bundle.module.url(
+				forResource: theme,
+				withExtension: "toml"
+			)?.resolvingSymlinksInPath()
+		else {
+			throw phbar.Error("Failed to load theme file")
+		}
+		return try load(from: defaultConfig)
+	}
+
+	/// Load theme from a file at URL.
+	/// If the file doesn't exist or fails to parse, the execution is interrupted.
+	static func load(from url: URL) throws -> PHTheme {
+		do {
+			let data = try Data(contentsOf: url)
+			guard let contents = String(data: data, encoding: .utf8), !contents.isEmpty else {
+				throw phbar.Error("the file is empty")
+			}
+			return try load(from: contents)
+		} catch {
+			throw phbar.Error("Failed to load theme file", underlyingError: error)
+		}
+	}
+
+	/// Load theme from a TOML string.
+	/// If the content fails to parse, the execution is interrupted.
+	static func load(from contents: String) throws -> PHTheme {
+		do {
+			let decoder = TOMLDecoder()
+			return try decoder.decode(PHTheme.self, from: contents)
+		} catch {
+			throw phbar.Error("Failed to parse theme file", underlyingError: error)
+		}
+	}
+}

Sources/phbar/Models/PHTheme/PHTheme+Padding.swift

@@ -0,0 +1,12 @@
+extension PHTheme {
+	struct Padding: Decodable {
+		let leading: Double
+		let trailing: Double
+
+		var total: Double { leading + trailing }
+
+		static var zero: Padding {
+			Self.init(leading: 0, trailing: 0)
+		}
+	}
+}

Sources/phbar/Themes/dracula.toml

@@ -0,0 +1,19 @@
+# phbar theme file ~ Dracula
+#
+# Place at ~/.config/phbar/themes/dracula.toml
+
+[window]
+shadow = false
+blur   = 10.0
+
+[[style]]
+name = "default"
+foreground = { color = "#f8f8f2" }
+background = { color = "#000000", alpha = 0.5 }
+padding    = { leading = 0.0, trailing = 0.0 }
+
+[[style]]
+name = "tinted"
+foreground = { color = "#282a36" }
+background = { color = "#bd93f9" }
+padding    = { leading = 10.0, trailing = 10.0 }

Sources/phbar/Themes/voltage.toml

@@ -0,0 +1,25 @@
+# phbar theme file ~ Voltage
+#
+# Place at ~/.config/phbar/themes/voltage.toml
+
+[window]
+shadow = false
+blur   = 0.0
+
+[[style]]
+name = "default"
+foreground = { color = "#aed3f3" }
+background = { color = "#010408", alpha = 0.825 }
+padding    = { leading = 0.0, trailing = 0.0 }
+
+[[style]]
+name = "floating"
+foreground = { color = "#aed3f3" }
+background = { color = "#000000", alpha = 0 }
+padding    = { leading = 0.0, trailing = 0.0 }
+
+[[style]]
+name = "tinted"
+foreground = { color = "#aed3f3" }
+background = { color = "#0f304a" }
+padding    = { leading = 12.0, trailing = 12.0 }

Sources/phbar/Views/BarView.swift

@@ -8,14 +8,31 @@ struct BarView: View {
 	}
 
 	var body: some View {
-		HStack(alignment: .center, spacing: 0) {
+		ZStack {
-			ForEach(bar.blocks) { block in
+			HStack(alignment: .center, spacing: 0) {
-				TextBlock(block: block)
+				ForEach(bar.arrangedBlocks) { block in
+					switch block.kind {
+					case .text:
+						TextBlock(block: block)
+					case .space:
+						SpaceBlock(block: block)
+					}
+				}
 			}
 
-			SpaceBlock()
+			HStack(alignment: .center, spacing: 0) {
+				ForEach(bar.centeredBlocks) { block in
+					switch block.kind {
+					case .text:
+						TextBlock(block: block)
+					case .space:
+						SpaceBlock(block: block)
+					}
+				}
+			}
 		}
-		.font(.custom("Comic Code", size: 14))
+		.font(bar.config.text.font)
+		.italic(bar.config.text.italic)
 		.frame(height: 30)
 		.ignoresSafeArea()
 		.environmentObject(bar)

Sources/phbar/Views/BarWindow.swift

@@ -3,6 +3,8 @@ import SwiftUI
 
 final class BarWindow: NSPanel {
 	let barController: PHController
+
+	var backgroundView: BarWindowBackground!
 	var barView: NSHostingView<BarView>!
 
 	init(controller: PHController) {
@@ -20,9 +22,6 @@ final class BarWindow: NSPanel {
 		self.isFloatingPanel = true
 		self.level = .floating
 		self.animationBehavior = .utilityWindow
-		self.isOpaque = false
-		self.backgroundColor = .clear
-		// self.hasShadow = pmenu.config.window.shadow
 		self.collectionBehavior = [.canJoinAllSpaces, .fullScreenAuxiliary, .stationary]
 		self.acceptsMouseMovedEvents = false
 		self.isMovable = false
@@ -33,11 +32,16 @@ final class BarWindow: NSPanel {
 		self.isRestorable = false
 		self.displaysWhenScreenProfileChanges = true
 
+		self.backgroundView = BarWindowBackground(controller: barController)
+		backgroundView.autoresizingMask = [.width, .height]
+		backgroundView.frame = self.contentView?.bounds ?? .zero
+
 		self.barView = NSHostingView(rootView: BarView(controller: barController))
 		barView.autoresizingMask = [.width, .height]
-		barView.frame = self.contentView?.bounds ?? .zero
+		barView.frame = contentView?.bounds ?? .zero
+		self.backgroundView.addSubview(barView)
 
-		self.contentView = barView
+		self.contentView = self.backgroundView
 	}
 }
 

Sources/phbar/Views/Blocks/SpaceBlock.swift

@@ -1,8 +1,17 @@
 import SwiftUI
 
 struct SpaceBlock: View {
+	@ObservedObject var block: PHBlock
+
+	var width: CGFloat? {
+		guard let arg = block.command.split(separator: " ").last else { return nil }
+		guard let width = Double(arg) else { return nil }
+		return CGFloat(width)
+	}
+
 	var body: some View {
 		Rectangle()
-			.fill(.blue)
+			.fill(block.style.background)
+			.frame(width: width)
 	}
 }

Sources/phbar/Views/Blocks/TextBlock.swift

@@ -1,16 +1,49 @@
 import SwiftUI
 
 struct TextBlock: View {
+	@EnvironmentObject private var bar: PHController
 	@ObservedObject var block: PHBlock
 
-	var body: some View {
+	@State var hovering = false
-		ZStack {
-			Rectangle()
-				.fill(.red)
 
-			Text(block.label)
+	private var adjustOffset: CGAffineTransform {
-				.foregroundColor(.white)
+		guard let offset = bar.config.text.offset else { return .init() }
+		return .init(translationX: 0, y: offset)
+	}
+
+	var body: some View {
+		if let label = block.label, !label.isEmpty {
+			ZStack(alignment: .center) {
+				RoundedRectangle(cornerRadius: 0)
+					.fill(block.style.background)
+
+				Group {
+					Text(label)
+						.foregroundStyle(block.style.foreground)
+						.transformEffect(adjustOffset)
+						.border(bar.debug ? .blue : .clear)
+				}
+				.padding(.leading, block.style.padding.leading)
+				.padding(.trailing, block.style.padding.trailing)
+			}
+			.fixedSize(horizontal: true, vertical: false)
+			.border(bar.debug ? .red : .clear)
+			.onHover { hovering = $0 }
+			.onAppear {
+				NSEvent.addLocalMonitorForEvents(matching: [
+					.leftMouseDown,
+					.rightMouseDown,
+					.otherMouseDown,
+					.scrollWheel,
+				]) { event in
+					if hovering, let gestureEvent = PHGestureEvent.from(event) {
+						block.handleGesture(gestureEvent)
+					}
+					return event
+				}
+			}
+		} else {
+			EmptyView()
 		}
-		.fixedSize(horizontal: true, vertical: false)
 	}
 }

Sources/phbar/Views/Window/BarWindowBackground.swift

@@ -0,0 +1,108 @@
+import AppKit
+
+final class BarWindowBackground: NSView {
+	var hasShadow: Bool {
+		didSet { configureShadow() }
+	}
+
+	var blur: CGFloat {
+		didSet { configureBlur() }
+	}
+
+	init(controller: PHController) {
+		self.hasShadow = controller.theme.window.hasShadow
+		self.blur = controller.theme.window.blur
+		super.init(frame: .zero)
+		setup()
+	}
+
+	@available(*, unavailable)
+	required init?(coder: NSCoder) {
+		fatalError("init(coder:) has not been implemented")
+	}
+
+	private func setup() {
+		wantsLayer = true
+		configureShadow()
+		configureBlur()
+	}
+
+	// Blur is applied to the *window*, not the layer, so we need a window
+	// to exist first. Re-apply whenever the view moves to a (possibly new) window.
+	override func viewDidMoveToWindow() {
+		super.viewDidMoveToWindow()
+		configureShadow()
+		configureBlur()
+	}
+
+	private func configureShadow() {
+		guard let window else { return }
+		window.hasShadow = hasShadow
+	}
+
+	private func configureBlur() {
+		guard let window else { return }
+		// Window must be non-opaque for the desktop/other windows behind it
+		// to be visible at all, let alone blurred.
+		window.isOpaque = false
+		// Near-zero (not fully .clear) alpha keeps the window eligible for
+		// compositor blur on some macOS versions; fully transparent windows
+		// are sometimes excluded from the blur pass. This mirrors Kitty's
+		// approach (NSColor(white: 0, alpha: 0.001) vs .clear).
+		if blur > 0 {
+			window.backgroundColor = NSColor(white: 0, alpha: 0.001)
+		} else {
+			window.backgroundColor = .clear
+		}
+
+		let radius = Int32(clamping: Int(blur.rounded()))
+		let applied = CGSPrivate.applyBlur(to: window, radius: radius)
+		if !applied {
+			// Private symbols unavailable/renamed on this macOS version.
+			// Fails silently rather than crashing; falls back to no blur.
+			#if DEBUG
+				print("BackgroundView: failed to apply private window blur (radius: \(radius))")
+			#endif
+		}
+	}
+}
+
+// HACK: - Private CoreGraphics Services blur API
+// This mirrors what Kitty terminal does on macOS: dlopen/dlsym the private
+// CGSSetWindowBackgroundBlurRadius symbol at runtime rather than linking
+// against it directly. This is UNDOCUMENTED, PRIVATE API:
+//   - Works reliably in practice (Kitty ships it to a huge user base)
+//   - Can break on future macOS updates with no notice
+//   - Will get an app rejected from the Mac App Store
+private enum CGSPrivate {
+	typealias ConnectionFn = @convention(c) () -> UnsafeMutableRawPointer?
+	typealias BlurFn = @convention(c) (UnsafeMutableRawPointer?, Int, Int32) -> OSStatus
+
+	static let getConnection: ConnectionFn? = {
+		guard
+			let handle = dlopen(
+				"/System/Library/Frameworks/CoreGraphics.framework/CoreGraphics", RTLD_NOW),
+			let sym = dlsym(handle, "CGSDefaultConnectionForThread")
+		else { return nil }
+		return unsafeBitCast(sym, to: ConnectionFn.self)
+	}()
+
+	static let setBlurRadius: BlurFn? = {
+		guard
+			let handle = dlopen(
+				"/System/Library/Frameworks/CoreGraphics.framework/CoreGraphics", RTLD_NOW),
+			let sym = dlsym(handle, "CGSSetWindowBackgroundBlurRadius")
+		else { return nil }
+		return unsafeBitCast(sym, to: BlurFn.self)
+	}()
+
+	/// Returns true if the private symbols were resolved and the call was issued.
+	@MainActor
+	@discardableResult
+	static func applyBlur(to window: NSWindow, radius: Int32) -> Bool {
+		guard let getConnection, let setBlurRadius else { return false }
+		let connection = getConnection()
+		let status = setBlurRadius(connection, window.windowNumber, radius)
+		return status == noErr
+	}
+}

Sources/phbar/config.toml

@@ -0,0 +1,6 @@
+[text]
+font   = "Comic Code"
+size   = 14
+weight = "regular"
+style  = "normal"
+offset = -0.5

Tests/phbarTests/phbarTests.swift

@@ -1,9 +1,431 @@
+import AppKit
+import Foundation
 import Testing
 
 @testable import phbar
 
-@Test func example() async throws {
+// MARK: - Payload Types for Testing
-	// Write your test here and use APIs like `#expect(...)` to check expected conditions.
+
-	// Swift Testing Documentation
+private struct TestPayload: Codable, Equatable {
-	// https://developer.apple.com/documentation/testing
+	let message: String
+	let count: Int
 }
+
+// MARK: - Notification Name Tests
+
+@Test func notificationNameIsHashable() async throws {
+	let a = IPCNotificationName("com.example.test")
+	let b = IPCNotificationName("com.example.test")
+	let c = IPCNotificationName("com.example.other")
+
+	#expect(a == b)
+	#expect(a != c)
+	#expect(a.hashValue == b.hashValue)
+}
+
+@Test func notificationNameIsExpressibleByStringLiteral() async throws {
+	let name: IPCNotificationName = "com.example.test"
+	#expect(name.rawValue == "com.example.test")
+}
+
+@Test func notificationNameRawRepresentable() async throws {
+	let name = IPCNotificationName(rawValue: "com.example.test")
+	#expect(name.rawValue == "com.example.test")
+}
+
+// MARK: - Payload Decoding Tests
+
+@Test func decodePayloadFromNotification() async throws {
+	let payload = TestPayload(message: "hello", count: 42)
+	let userInfo: [String: Any] = ["message": "hello", "count": 42]
+	let notification = IPCNotification(name: .refresh, userInfo: userInfo)
+
+	let decoded: TestPayload? = notification.decode(TestPayload.self)
+	#expect(decoded == payload)
+}
+
+@Test func decodePayloadReturnsNilForMissingUserInfo() async throws {
+	let notification = IPCNotification(name: .refresh, userInfo: nil)
+	let decoded: TestPayload? = notification.decode(TestPayload.self)
+	#expect(decoded == nil)
+}
+
+@Test func decodePayloadReturnsNilForInvalidData() async throws {
+	let userInfo: [String: Any] = ["wrong": "data"]
+	let notification = IPCNotification(name: .refresh, userInfo: userInfo)
+	let decoded: TestPayload? = notification.decode(TestPayload.self)
+	#expect(decoded == nil)
+}
+
+// MARK: - Posting Tests
+
+@Test func postWithoutPayloadDoesNotCrash() async throws {
+	IPC.post(.refresh)
+}
+
+@Test func postWithUserInfoDoesNotCrash() async throws {
+	IPC.post(.refresh, userInfo: ["key": "value"])
+}
+
+@Test func postWithEncodablePayloadDoesNotCrash() async throws {
+	let payload = TestPayload(message: "test", count: 1)
+	let result = IPC.post(.refresh, payload: payload)
+	#expect(result == true)
+}
+
+// MARK: - Observer Tests
+
+@Test func observerCleansUpOnDeinit() async throws {
+	// Verify that creating and releasing an observer doesn't crash.
+	// The token removes itself from the distributed center on deinit.
+	let token = IPC.observe(.refresh) { _ in }
+	withExtendedLifetime(token) {}
+}
+
+// MARK: - Refresh Command Config
+
+@Test func refreshCommandConfigurationIsCorrect() async throws {
+	let config = phbar.refresh.configuration
+	#expect(config.commandName == "refresh")
+	#expect(config.abstract == "Refresh the running status bar.")
+}
+
+// MARK: - PHBlock Loading & Compute
+
+@MainActor
+@Test func loadBlocksFromTOML() throws {
+	let toml = """
+	[[block]]
+	command = "echo hello"
+	name = "greeting"
+	refresh = 5.0
+
+	[[block]]
+	command = "echo world"
+	"""
+
+	let blocks = try PHBlock.load(from: toml)
+
+	#expect(blocks.count == 2)
+	#expect(blocks[0].command == "echo hello")
+	#expect(blocks[0].name == "greeting")
+	#expect(blocks[0].refresh == 5.0)
+	#expect(blocks[0].label == "")
+	#expect(blocks[1].name == nil)
+	#expect(blocks[1].refresh == nil)
+}
+
+@MainActor
+@Test func loadBlocksRejectsInvalidTOML() {
+	#expect(throws: (any Error).self) {
+		try PHBlock.load(from: "not = valid = toml = =")
+	}
+}
+
+@MainActor
+@Test func computeReturnsCommandStdout() async throws {
+	let blocks = try PHBlock.load(from: """
+	[[block]]
+	command = "printf panini"
+	""")
+
+	let output = await blocks[0].compute()
+
+	#expect(output == "panini")
+}
+
+// MARK: - PHBlock Refresh
+
+@MainActor
+@Test func updateSetsLabel() async throws {
+	let block = try PHBlock.load(from: """
+	[[block]]
+	command = "printf panini"
+	""")[0]
+
+	#expect(block.label == "")
+
+	await block.update()
+
+	#expect(block.label == "panini")
+}
+
+@MainActor
+@Test func startAutoRefreshWithoutIntervalComputesOnce() async throws {
+	let block = try PHBlock.load(from: """
+	[[block]]
+	command = "printf hi"
+	""")[0]
+
+	block.startAutoRefresh()
+
+	// Allow the one-shot update task to run.
+	try await Task.sleep(for: .milliseconds(100))
+
+	#expect(block.label == "hi")
+
+	block.stopAutoRefresh()
+}
+
+@MainActor
+@Test func startAutoRefreshRepeatsAtInterval() async throws {
+	// A counter file lets us observe how many times the command ran.
+	let counter = FileManager.default.temporaryDirectory
+		.appending(path: "phbar_test_\(UUID().uuidString)")
+	defer { try? FileManager.default.removeItem(at: counter) }
+
+	let path = counter.path
+	let toml = """
+	[[block]]
+	command = "n=$(cat \(path) 2>/dev/null || echo 0); n=$((n+1)); echo $n > \(path); echo $n"
+	refresh = 0.05
+	"""
+
+	let block = try PHBlock.load(from: toml)[0]
+
+	block.startAutoRefresh()
+
+	try await Task.sleep(for: .milliseconds(250))
+
+	block.stopAutoRefresh()
+
+	let count = Int(block.label.trimmingCharacters(in: .whitespacesAndNewlines)) ?? 0
+
+	// At ~20Hz over 250ms the command should have run more than once.
+	#expect(count >= 2)
+}
+
+// MARK: - PHEvent
+
+@MainActor
+@Test func eventDecodesFromKnownStrings() throws {
+	let toml = """
+	[[block]]
+	command = "echo hi"
+	events = ["volume", "network", "appearance", "power", "mpd"]
+	"""
+
+	let blocks = try PHBlock.load(from: toml)
+
+	#expect(blocks[0].events == [.volume, .network, .appearance, .power, .mpd])
+}
+
+@MainActor
+@Test func eventRejectsUnknownString() {
+	#expect(throws: (any Error).self) {
+		try PHBlock.load(from: """
+		[[block]]
+		command = "echo hi"
+		events = ["totally_made_up"]
+		""")
+	}
+}
+
+@MainActor
+@Test func eventsOptionalWhenOmitted() throws {
+	let blocks = try PHBlock.load(from: """
+	[[block]]
+	command = "echo hi"
+	""")
+
+	#expect(blocks[0].events == nil)
+}
+
+@MainActor
+@Test func defaultFactoryReturnsMPDSource() {
+	let source = PHEventRegistry.defaultFactory(.mpd)
+	#expect(source is MPDEventSource)
+}
+
+@MainActor
+@Test func mpdSourceIsIdempotentStartStop() {
+	// With MPD absent the source keeps trying to connect; ensure start/stop are
+	// safe and idempotent without a running daemon.
+	let source = MPDEventSource(host: "127.0.0.1", port: 1)
+	source.start(notify: {})
+	source.start(notify: {})  // second start is a no-op
+	source.stop()
+	source.stop()  // second stop is a no-op
+}
+
+// MARK: - PHEventRegistry
+
+/// A no-op source that records its lifecycle and can be fired on demand.
+@MainActor
+private final class FakeEventSource: PHEventSource {
+	private(set) var startCount = 0
+	private(set) var stopCount = 0
+	private var notify: (@MainActor @Sendable () -> Void)?
+
+	func start(notify: @escaping @MainActor @Sendable () -> Void) {
+		startCount += 1
+		self.notify = notify
+	}
+
+	func stop() {
+		stopCount += 1
+		notify = nil
+	}
+
+	func fire() { notify?() }
+}
+
+@MainActor
+@Test func registryActivatesSourceLazilyAndRefcounts() async throws {
+	let fake = FakeEventSource()
+	let registry = PHEventRegistry(factory: { _ in fake })
+
+	#expect(fake.startCount == 0)
+	#expect(fake.stopCount == 0)
+
+	var fired = 0
+	let s1 = registry.subscribe(.volume) { fired += 1 }
+	#expect(fake.startCount == 1)
+	#expect(registry.subscriberCount(for: .volume) == 1)
+
+	// A second subscriber must reuse the already-running source.
+	let s2 = registry.subscribe(.volume) { fired += 1 }
+	#expect(fake.startCount == 1)
+	#expect(registry.subscriberCount(for: .volume) == 2)
+
+	// One firing fans out to both subscribers.
+	fake.fire()
+	#expect(fired == 2)
+
+	// Cancelling one keeps the source alive for the other.
+	s1.cancel()
+	try await Task.sleep(for: .milliseconds(20))
+	#expect(fake.stopCount == 0)
+	#expect(registry.subscriberCount(for: .volume) == 1)
+
+	fake.fire()
+	#expect(fired == 3)
+
+	// Cancelling the last subscriber tears the source down.
+	s2.cancel()
+	try await Task.sleep(for: .milliseconds(20))
+	#expect(fake.stopCount == 1)
+	#expect(registry.subscriberCount(for: .volume) == 0)
+}
+
+@MainActor
+@Test func registryStartsSeparateSourcePerEvent() async throws {
+	let volumeFake = FakeEventSource()
+	let networkFake = FakeEventSource()
+	let factory: @MainActor @Sendable (PHEvent) -> any PHEventSource = { event in
+		switch event {
+		case .volume: return volumeFake
+		default: return networkFake
+		}
+	}
+	let registry = PHEventRegistry(factory: factory)
+
+	let v = registry.subscribe(.volume) {}
+	let n = registry.subscribe(.network) {}
+
+	#expect(volumeFake.startCount == 1)
+	#expect(networkFake.startCount == 1)
+	#expect(registry.subscriberCount(for: .volume) == 1)
+	#expect(registry.subscriberCount(for: .network) == 1)
+
+	v.cancel()
+	n.cancel()
+}
+
+// MARK: - PHBlock + Events
+
+@MainActor
+@Test func blockRefreshesOnEvent() async throws {
+	let counter = FileManager.default.temporaryDirectory
+		.appending(path: "phbar_evt_\(UUID().uuidString)")
+	defer { try? FileManager.default.removeItem(at: counter) }
+	let path = counter.path
+
+	let fake = FakeEventSource()
+	let registry = PHEventRegistry(factory: { _ in fake })
+
+	let block = try PHBlock.load(from: """
+	[[block]]
+	command = "n=$(cat \(path) 2>/dev/null || echo 0); n=$((n+1)); echo $n > \(path); echo $n"
+	events = ["volume"]
+	""")[0]
+	block.registry = registry
+
+	block.startAutoRefresh()
+	try await Task.sleep(for: .milliseconds(100))
+
+	#expect(block.label.trimmingCharacters(in: .whitespacesAndNewlines) == "1")
+	#expect(fake.startCount == 1)
+
+	// Firing the event triggers a second refresh.
+	fake.fire()
+	try await Task.sleep(for: .milliseconds(100))
+
+	#expect(block.label.trimmingCharacters(in: .whitespacesAndNewlines) == "2")
+
+	// Stopping cancels the subscription and tears the source down.
+	block.stopAutoRefresh()
+	try await Task.sleep(for: .milliseconds(20))
+
+	#expect(fake.stopCount == 1)
+}
+
+@MainActor
+@Test func blockCombinesIntervalAndEvents() async throws {
+	let counter = FileManager.default.temporaryDirectory
+		.appending(path: "phbar_combo_\(UUID().uuidString)")
+	defer { try? FileManager.default.removeItem(at: counter) }
+	let path = counter.path
+
+	let fake = FakeEventSource()
+	let registry = PHEventRegistry(factory: { _ in fake })
+
+	let block = try PHBlock.load(from: """
+	[[block]]
+	command = "n=$(cat \(path) 2>/dev/null || echo 0); n=$((n+1)); echo $n > \(path); echo $n"
+	refresh = 0.2
+	events = ["volume"]
+	""")[0]
+	block.registry = registry
+
+	block.startAutoRefresh()
+	try await Task.sleep(for: .milliseconds(50))
+
+	let afterInitial = Int(block.label.trimmingCharacters(in: .whitespacesAndNewlines)) ?? 0
+	#expect(afterInitial == 1)
+	#expect(fake.startCount == 1)
+
+	// Both an event and the interval can drive updates independently.
+	fake.fire()
+	try await Task.sleep(for: .milliseconds(50))
+
+	let afterEvent = Int(block.label.trimmingCharacters(in: .whitespacesAndNewlines)) ?? 0
+	#expect(afterEvent >= 2)
+
+	block.stopAutoRefresh()
+}
+
+// MARK: - PHController
+
+@MainActor
+@Test func controllerRefreshUpdatesAllBlocks() async throws {
+	let screen = try #require(NSScreen.main)
+	let blocks = try PHBlock.load(from: """
+	[[block]]
+	command = "printf a"
+
+	[[block]]
+	command = "printf b"
+	""")
+
+	let controller = PHController(screen: screen, blocks: blocks)
+
+	controller.refresh()
+
+	// Allow the per-block update tasks to run.
+	try await Task.sleep(for: .milliseconds(100))
+
+	#expect(blocks[0].label == "a")
+	#expect(blocks[1].label == "b")
+}
+