feat(timer): native rotation for settings, lock portrait only in timer

app/src/main/AndroidManifest.xml

@@ -22,7 +22,7 @@
         <activity
             android:name=".MainActivity"
             android:exported="true"
-            android:screenOrientation="portrait"
+            android:configChanges="orientation|screenSize|screenLayout|keyboardHidden"
             android:theme="@style/Theme.SleepTimer">
             <intent-filter>
                 <action android:name="android.intent.action.MAIN" />

app/src/main/kotlin/dev/xitee/sleeptimer/navigation/SleepTimerNavHost.kt

@@ -1,21 +1,46 @@
 package dev.xitee.sleeptimer.navigation
 
+import androidx.compose.animation.EnterTransition
+import androidx.compose.animation.ExitTransition
+import androidx.compose.animation.fadeIn
+import androidx.compose.animation.fadeOut
 import androidx.compose.runtime.Composable
+import androidx.compose.runtime.getValue
 import androidx.navigation.compose.NavHost
 import androidx.navigation.compose.composable
+import androidx.navigation.compose.currentBackStackEntryAsState
 import androidx.navigation.compose.rememberNavController
+import androidx.navigation.NavDestination.Companion.hasRoute
 import dev.xitee.sleeptimer.feature.timer.about.AboutScreen
 import dev.xitee.sleeptimer.feature.timer.settings.SettingsScreen
 import dev.xitee.sleeptimer.feature.timer.settings.ThemePickerScreen
+import dev.xitee.sleeptimer.feature.timer.timer.AppOrientationController
+import dev.xitee.sleeptimer.feature.timer.timer.DeviceOrientation
 import dev.xitee.sleeptimer.feature.timer.timer.TimerScreen
+import dev.xitee.sleeptimer.feature.timer.timer.rememberDeviceOrientation
 
 @Composable
 fun SleepTimerNavHost() {
     val navController = rememberNavController()
+    val backStackEntry by navController.currentBackStackEntryAsState()
+    val isTimer = backStackEntry?.destination?.hasRoute<TimerRoute>() ?: true
 
+    // Skip the cross-screen fade when the device is tilted: the orientation
+    // flip that accompanies Timer ↔ Settings navigation combined with a fade
+    // briefly shows Timer's counter-rotated content being rotated by the
+    // window manager, appearing upside-down. In natural portrait there is no
+    // orientation flip, so the fade is kept.
+    val deviceOrientation by rememberDeviceOrientation()
+    val animate = deviceOrientation == DeviceOrientation.PORTRAIT
+
+    AppOrientationController(orientation = deviceOrientation, lockPortrait = isTimer)
     NavHost(
         navController = navController,
         startDestination = TimerRoute,
+        enterTransition = { if (animate) fadeIn() else EnterTransition.None },
+        exitTransition = { if (animate) fadeOut() else ExitTransition.None },
+        popEnterTransition = { if (animate) fadeIn() else EnterTransition.None },
+        popExitTransition = { if (animate) fadeOut() else ExitTransition.None },
     ) {
         composable<TimerRoute> {
             TimerScreen(

feature/timer/src/main/kotlin/dev/xitee/sleeptimer/feature/timer/timer/AppOrientationController.kt

@@ -0,0 +1,37 @@
+package dev.xitee.sleeptimer.feature.timer.timer
+
+import android.app.Activity
+import android.content.Context
+import android.content.ContextWrapper
+import android.content.pm.ActivityInfo
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.LaunchedEffect
+import androidx.compose.runtime.getValue
+import androidx.compose.ui.platform.LocalContext
+
+// Owns the Activity's requestedOrientation for the whole session. Driven by the
+// caller's already-tracked DeviceOrientation so there is no disposal gap when the
+// lock is released — the pose is known at all times, avoiding Android's own sensor
+// debounce on the handoff.
+@Composable
+fun AppOrientationController(orientation: DeviceOrientation, lockPortrait: Boolean) {
+    val context = LocalContext.current
+
+    LaunchedEffect(lockPortrait, orientation) {
+        val activity = context.findActivity() ?: return@LaunchedEffect
+        activity.requestedOrientation = if (lockPortrait) {
+            ActivityInfo.SCREEN_ORIENTATION_PORTRAIT
+        } else {
+            orientation.toActivityInfoOrientation()
+        }
+    }
+}
+
+private fun Context.findActivity(): Activity? {
+    var ctx: Context? = this
+    while (ctx is ContextWrapper) {
+        if (ctx is Activity) return ctx
+        ctx = ctx.baseContext
+    }
+    return null
+}

feature/timer/src/main/kotlin/dev/xitee/sleeptimer/feature/timer/timer/DeviceOrientation.kt

@@ -1,5 +1,6 @@
 package dev.xitee.sleeptimer.feature.timer.timer
 
+import android.content.pm.ActivityInfo
 import android.view.OrientationEventListener
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.DisposableEffect
@@ -22,6 +23,13 @@ fun DeviceOrientation.counterRotationDegrees(): Float = when (this) {
     DeviceOrientation.LANDSCAPE_RIGHT -> 90f
 }
 
+fun DeviceOrientation.toActivityInfoOrientation(): Int = when (this) {
+    DeviceOrientation.PORTRAIT -> ActivityInfo.SCREEN_ORIENTATION_PORTRAIT
+    DeviceOrientation.LANDSCAPE_LEFT -> ActivityInfo.SCREEN_ORIENTATION_REVERSE_LANDSCAPE
+    DeviceOrientation.PORTRAIT_REVERSED -> ActivityInfo.SCREEN_ORIENTATION_REVERSE_PORTRAIT
+    DeviceOrientation.LANDSCAPE_RIGHT -> ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE
+}
+
 @Composable
 fun rememberDeviceOrientation(): State<DeviceOrientation> {
     val context = LocalContext.current