feat(android): mic uplink + connect-screen redesign

Microphone uplink (client → host's virtual mic, 0xCB) and a cleaner connect screen.

Mic (Rust-heavy, mirrors the audio playback path in reverse):
- crates/punktfunk-android/src/mic.rs: AAudio LowLatency **input** → realtime callback hands
  captured f32 to a channel → a worker thread Opus-encodes 20 ms stereo frames (48 kHz, VOIP,
  64 kbps) and calls NativeClient::send_mic. MicCapture owns the stream + encode thread (RAII stop).
- session.rs: SessionHandle gains a `mic` slot; nativeStartMic/nativeStopMic JNI (mirror of audio);
  stopped in Drop. NativeBridge: the two externs.
- Settings: a `micEnabled` flag + a Microphone toggle in SettingsScreen that requests RECORD_AUDIO
  (denied → stays off). StreamScreen starts the mic only if enabled AND the permission is held.

Connect-screen redesign:
- One scrollable Column (was a fixed centered layout that could clip with the new tab bar);
  host rows render via forEach (no nested LazyColumn). Colored section labels ("Saved hosts",
  "Discovered on the network", "Connect manually"), full-width host cards / fields / Connect button,
  a header + subtitle, and a muted footer.

Verified live (emulator pf_phone -> home-worker-2): toggling mic requests RECORD_AUDIO; with it
granted, a session sends mic frames (client "mic: sent=250 … peak=0.439" — real audio) and the host
logs "client datagram stream ended … mic=276". Redesigned screen confirmed via screenshots.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

clients/android/app/src/main/kotlin/io/unom/punktfunk/MainActivity.kt

@@ -1,5 +1,7 @@
 package io.unom.punktfunk
 
+import android.Manifest
+import android.content.pm.PackageManager
 import android.os.Build
 import android.os.Bundle
 import android.view.InputDevice
@@ -15,26 +17,23 @@ import androidx.activity.enableEdgeToEdge
 import androidx.compose.foundation.clickable
 import androidx.compose.foundation.gestures.awaitEachGesture
 import androidx.compose.foundation.gestures.awaitFirstDown
-import androidx.compose.foundation.layout.Arrangement
 import androidx.compose.foundation.layout.Box
 import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.Row
 import androidx.compose.foundation.layout.Spacer
 import androidx.compose.foundation.layout.fillMaxSize
 import androidx.compose.foundation.layout.fillMaxWidth
 import androidx.compose.foundation.layout.height
-import androidx.compose.foundation.layout.heightIn
-import androidx.compose.foundation.layout.Row
 import androidx.compose.foundation.layout.padding
-import androidx.compose.foundation.lazy.LazyColumn
-import androidx.compose.foundation.lazy.items
+import androidx.compose.foundation.rememberScrollState
 import androidx.compose.foundation.text.KeyboardOptions
+import androidx.compose.foundation.verticalScroll
 import androidx.compose.material3.AlertDialog
 import androidx.compose.material3.Button
 import androidx.compose.material3.Card
 import androidx.compose.material.icons.Icons
 import androidx.compose.material.icons.filled.Home
 import androidx.compose.material.icons.filled.Settings
-import androidx.compose.material3.HorizontalDivider
 import androidx.compose.material3.Icon
 import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.NavigationBar
@@ -62,6 +61,7 @@ import androidx.compose.ui.platform.LocalContext
 import androidx.compose.ui.text.input.KeyboardType
 import androidx.compose.ui.unit.dp
 import androidx.compose.ui.viewinterop.AndroidView
+import androidx.core.content.ContextCompat
 import io.unom.punktfunk.kit.Gamepad
 import io.unom.punktfunk.kit.GamepadFeedback
 import io.unom.punktfunk.kit.Keymap
@@ -178,7 +178,7 @@ private fun App() {
 
     if (streamHandle != 0L) {
         // Immersive: the stream takes the whole screen, no bottom bar.
-        StreamScreen(streamHandle, onDisconnect = { streamHandle = 0L })
+        StreamScreen(streamHandle, micEnabled = settings.micEnabled, onDisconnect = { streamHandle = 0L })
     } else {
         Scaffold(
             bottomBar = {
@@ -309,61 +309,59 @@ private fun ConnectScreen(settings: Settings, onConnected: (Long) -> Unit) {
     }
 
     Column(
-        modifier = Modifier.fillMaxSize().padding(24.dp),
+        modifier = Modifier
+            .fillMaxSize()
+            .verticalScroll(rememberScrollState())
+            .padding(horizontal = 24.dp, vertical = 16.dp),
         horizontalAlignment = Alignment.CenterHorizontally,
-        verticalArrangement = Arrangement.Center,
     ) {
-        Text("punktfunk", style = MaterialTheme.typography.headlineMedium)
-        Text("Android client", style = MaterialTheme.typography.bodyMedium)
-        Spacer(Modifier.height(24.dp))
+        Text("punktfunk", style = MaterialTheme.typography.headlineLarge)
+        Text(
+            "stream a remote desktop",
+            style = MaterialTheme.typography.bodyMedium,
+            color = MaterialTheme.colorScheme.onSurfaceVariant,
+        )
+        Spacer(Modifier.height(28.dp))
 
         if (savedHosts.isNotEmpty()) {
-            Text("Saved hosts", style = MaterialTheme.typography.labelLarge)
-            Spacer(Modifier.height(8.dp))
-            LazyColumn(modifier = Modifier.fillMaxWidth().heightIn(max = 220.dp)) {
-                items(savedHosts, key = { "${it.address}:${it.port}" }) { kh ->
-                    SavedHostRow(
-                        kh,
-                        enabled = !connecting,
-                        onConnect = {
-                            host = kh.address
-                            port = kh.port.toString()
-                            connect(kh.address, kh.port)
-                        },
-                        onForget = {
-                            knownHostStore.remove(kh.address, kh.port)
-                            savedHosts = knownHostStore.all()
-                        },
-                    )
-                }
+            SectionLabel("Saved hosts")
+            savedHosts.forEach { kh ->
+                SavedHostRow(
+                    kh,
+                    enabled = !connecting,
+                    onConnect = {
+                        host = kh.address
+                        port = kh.port.toString()
+                        connect(kh.address, kh.port)
+                    },
+                    onForget = {
+                        knownHostStore.remove(kh.address, kh.port)
+                        savedHosts = knownHostStore.all()
+                    },
+                )
             }
-            Spacer(Modifier.height(16.dp))
-            HorizontalDivider()
-            Spacer(Modifier.height(16.dp))
+            Spacer(Modifier.height(20.dp))
         }
 
         if (discovered.isNotEmpty()) {
-            Text("Discovered hosts", style = MaterialTheme.typography.labelLarge)
-            Spacer(Modifier.height(8.dp))
-            LazyColumn(modifier = Modifier.fillMaxWidth().heightIn(max = 220.dp)) {
-                items(discovered, key = { it.key }) { dh ->
-                    DiscoveredHostRow(dh, enabled = !connecting) {
-                        host = dh.host
-                        port = dh.port.toString()
-                        connect(dh.host, dh.port, dh)
-                    }
+            SectionLabel("Discovered on the network")
+            discovered.forEach { dh ->
+                DiscoveredHostRow(dh, enabled = !connecting) {
+                    host = dh.host
+                    port = dh.port.toString()
+                    connect(dh.host, dh.port, dh)
                 }
             }
-            Spacer(Modifier.height(16.dp))
-            HorizontalDivider()
-            Spacer(Modifier.height(16.dp))
+            Spacer(Modifier.height(20.dp))
         }
 
+        SectionLabel("Connect manually")
         OutlinedTextField(
             value = host,
             onValueChange = { host = it },
             label = { Text("Host") },
             singleLine = true,
+            modifier = Modifier.fillMaxWidth(),
         )
         Spacer(Modifier.height(8.dp))
         OutlinedTextField(
@@ -372,18 +370,28 @@ private fun ConnectScreen(settings: Settings, onConnected: (Long) -> Unit) {
             label = { Text("Port") },
             singleLine = true,
             keyboardOptions = KeyboardOptions(keyboardType = KeyboardType.Number),
+            modifier = Modifier.fillMaxWidth(),
         )
         Spacer(Modifier.height(16.dp))
         Button(
             enabled = !connecting && host.isNotBlank() && port.isNotBlank(),
             onClick = { connect(host.trim(), port.toInt()) },
+            modifier = Modifier.fillMaxWidth(),
         ) { Text(if (connecting) "Connecting…" else "Connect  ($w×$h@$hz)") }
         status?.let {
             Spacer(Modifier.height(12.dp))
-            Text(it, style = MaterialTheme.typography.bodySmall)
+            Text(
+                it,
+                style = MaterialTheme.typography.bodySmall,
+                color = MaterialTheme.colorScheme.error,
+            )
         }
-        Spacer(Modifier.height(24.dp))
-        Text("core ABI v$abi", style = MaterialTheme.typography.labelSmall)
+        Spacer(Modifier.height(28.dp))
+        Text(
+            "core ABI v$abi",
+            style = MaterialTheme.typography.labelSmall,
+            color = MaterialTheme.colorScheme.onSurfaceVariant,
+        )
     }
 
     pendingTrust?.let { pt ->
@@ -499,6 +507,17 @@ private fun ConnectScreen(settings: Settings, onConnected: (Long) -> Unit) {
     }
 }
 
+/** Left-aligned section header above each block of the connect screen. */
+@Composable
+private fun SectionLabel(text: String) {
+    Text(
+        text,
+        style = MaterialTheme.typography.titleSmall,
+        color = MaterialTheme.colorScheme.primary,
+        modifier = Modifier.fillMaxWidth().padding(bottom = 8.dp),
+    )
+}
+
 @Composable
 private fun DiscoveredHostRow(dh: DiscoveredHost, enabled: Boolean, onTap: () -> Unit) {
     Card(
@@ -547,10 +566,15 @@ private fun SavedHostRow(
 }
 
 @Composable
-private fun StreamScreen(handle: Long, onDisconnect: () -> Unit) {
+private fun StreamScreen(handle: Long, micEnabled: Boolean, onDisconnect: () -> Unit) {
     val context = LocalContext.current
     val activity = context as? MainActivity
     val window = activity?.window
+    // Start mic only if the user enabled it AND granted RECORD_AUDIO (else the AAudio input fails).
+    val micWanted = micEnabled && ContextCompat.checkSelfPermission(
+        context,
+        Manifest.permission.RECORD_AUDIO,
+    ) == PackageManager.PERMISSION_GRANTED
 
     DisposableEffect(handle) {
         window?.addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON)
@@ -564,7 +588,8 @@ private fun StreamScreen(handle: Long, onDisconnect: () -> Unit) {
             activity?.axisMapper = null
             activity?.streamHandle = 0L
             window?.clearFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON)
-            // Leaving the stream: stop the audio + decode threads and tear down the session.
+            // Leaving the stream: stop the mic + audio + decode threads and tear down the session.
+            NativeBridge.nativeStopMic(handle)
             NativeBridge.nativeStopAudio(handle)
             NativeBridge.nativeStopVideo(handle)
             NativeBridge.nativeClose(handle)
@@ -582,11 +607,13 @@ private fun StreamScreen(handle: Long, onDisconnect: () -> Unit) {
                         override fun surfaceCreated(holder: SurfaceHolder) {
                             NativeBridge.nativeStartVideo(handle, holder.surface)
                             NativeBridge.nativeStartAudio(handle)
+                            if (micWanted) NativeBridge.nativeStartMic(handle)
                         }
 
                         override fun surfaceChanged(holder: SurfaceHolder, format: Int, width: Int, height: Int) {}
 
                         override fun surfaceDestroyed(holder: SurfaceHolder) {
+                            NativeBridge.nativeStopMic(handle)
                             NativeBridge.nativeStopAudio(handle)
                             NativeBridge.nativeStopVideo(handle)
                         }

clients/android/app/src/main/kotlin/io/unom/punktfunk/Settings.kt

@@ -15,6 +15,7 @@ data class Settings(
     val bitrateKbps: Int = 0,
     val compositor: Int = 0,
     val gamepad: Int = 0,
+    val micEnabled: Boolean = false,
 )
 
 /** Loads/saves [Settings] in the app-private `punktfunk_settings` prefs. */
@@ -29,6 +30,7 @@ class SettingsStore(context: Context) {
         bitrateKbps = prefs.getInt(K_BITRATE, 0),
         compositor = prefs.getInt(K_COMPOSITOR, 0),
         gamepad = prefs.getInt(K_GAMEPAD, 0),
+        micEnabled = prefs.getBoolean(K_MIC, false),
     )
 
     fun save(s: Settings) {
@@ -39,6 +41,7 @@ class SettingsStore(context: Context) {
             .putInt(K_BITRATE, s.bitrateKbps)
             .putInt(K_COMPOSITOR, s.compositor)
             .putInt(K_GAMEPAD, s.gamepad)
+            .putBoolean(K_MIC, s.micEnabled)
             .apply()
     }
 
@@ -49,6 +52,7 @@ class SettingsStore(context: Context) {
         const val K_BITRATE = "bitrate_kbps"
         const val K_COMPOSITOR = "compositor"
         const val K_GAMEPAD = "gamepad"
+        const val K_MIC = "mic_enabled"
     }
 }
 

clients/android/app/src/main/kotlin/io/unom/punktfunk/SettingsScreen.kt

@@ -1,8 +1,13 @@
 package io.unom.punktfunk
 
+import android.Manifest
+import android.content.pm.PackageManager
 import androidx.activity.compose.BackHandler
+import androidx.activity.compose.rememberLauncherForActivityResult
+import androidx.activity.result.contract.ActivityResultContracts
 import androidx.compose.foundation.layout.Arrangement
 import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.Row
 import androidx.compose.foundation.layout.Spacer
 import androidx.compose.foundation.layout.fillMaxSize
 import androidx.compose.foundation.layout.fillMaxWidth
@@ -17,6 +22,7 @@ import androidx.compose.material3.ExposedDropdownMenuAnchorType
 import androidx.compose.material3.ExposedDropdownMenuDefaults
 import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.OutlinedTextField
+import androidx.compose.material3.Switch
 import androidx.compose.material3.Text
 import androidx.compose.material3.TextButton
 import androidx.compose.runtime.Composable
@@ -24,9 +30,11 @@ import androidx.compose.runtime.getValue
 import androidx.compose.runtime.mutableStateOf
 import androidx.compose.runtime.remember
 import androidx.compose.runtime.setValue
+import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.platform.LocalContext
 import androidx.compose.ui.unit.dp
+import androidx.core.content.ContextCompat
 
 /**
  * Stream settings. Edits are persisted immediately via [onChange]; [onBack] returns to the connect
@@ -82,6 +90,31 @@ fun SettingsScreen(initial: Settings, onChange: (Settings) -> Unit, onBack: () -
             selected = s.gamepad,
         ) { g -> update(s.copy(gamepad = g)) }
 
+        // Mic uplink — turning it on requests RECORD_AUDIO; if denied, the toggle stays off.
+        val micLauncher = rememberLauncherForActivityResult(
+            ActivityResultContracts.RequestPermission(),
+        ) { granted -> update(s.copy(micEnabled = granted)) }
+        Row(modifier = Modifier.fillMaxWidth(), verticalAlignment = Alignment.CenterVertically) {
+            Column(Modifier.weight(1f)) {
+                Text("Microphone", style = MaterialTheme.typography.bodyLarge)
+                Text(
+                    "Send your mic to the host's virtual microphone",
+                    style = MaterialTheme.typography.bodySmall,
+                )
+            }
+            Switch(
+                checked = s.micEnabled,
+                onCheckedChange = { on ->
+                    when {
+                        !on -> update(s.copy(micEnabled = false))
+                        ContextCompat.checkSelfPermission(context, Manifest.permission.RECORD_AUDIO) ==
+                            PackageManager.PERMISSION_GRANTED -> update(s.copy(micEnabled = true))
+                        else -> micLauncher.launch(Manifest.permission.RECORD_AUDIO)
+                    }
+                },
+            )
+        }
+
         Spacer(Modifier.height(8.dp))
         TextButton(onClick = onBack) { Text("Done") }
     }

clients/android/kit/src/main/kotlin/io/unom/punktfunk/kit/NativeBridge.kt

@@ -84,6 +84,16 @@ object NativeBridge {
     /** Stop + join the audio thread and close AAudio, without closing the session. No-op on `0`. */
     external fun nativeStopAudio(handle: Long)
 
+    /**
+     * Start mic uplink: AAudio input → Opus (48 kHz stereo, 20 ms) → host (`send_mic` / 0xCB), all in
+     * Rust. No-op if already running. The caller MUST hold RECORD_AUDIO; otherwise the AAudio input
+     * stream fails to open and the rest of the session keeps streaming.
+     */
+    external fun nativeStartMic(handle: Long)
+
+    /** Stop + join the mic thread and close the AAudio input stream. No-op on `0`. */
+    external fun nativeStopMic(handle: Long)
+
     // ---- Input: Kotlin captures, Rust forwards to the host (send_input) ----
 
     /** Relative mouse move; dx/dy are device-pixel deltas (screen +y down). */