android: home/routing UI - poll only while visible, no idle animation

- traffic (1 s) and probe (10 s) loops run only while the Home screen is
  shown and the VPN is connected; no 1 s idle tick otherwise
- the refresh button no longer runs a second exit-IP trace
- the glow pulse is not composed at all while disconnected or with
  animations off (it redrew a transparent circle every frame)
- RTT sparkline appends each probe result once (it duplicated stale ones)
- Routing dead-host poll is lifecycle-aware

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/frontends/android/app/src/main/java/org/strongswan/android/ui/compose/HomeScreen.kt

@@ -89,6 +89,7 @@ import androidx.compose.material3.TextButton
 import androidx.compose.material3.rememberModalBottomSheetState
 import androidx.compose.material3.pulltorefresh.PullToRefreshBox
 import androidx.compose.runtime.Composable
+import androidx.compose.runtime.DisposableEffect
 import androidx.compose.runtime.LaunchedEffect
 import androidx.compose.runtime.getValue
 import androidx.compose.runtime.mutableStateListOf
@@ -104,6 +105,7 @@ import androidx.compose.ui.geometry.Offset
 import androidx.compose.ui.geometry.Size
 import androidx.compose.ui.graphics.Brush
 import androidx.compose.ui.graphics.Color
+import androidx.compose.ui.graphics.drawscope.DrawScope
 import androidx.compose.ui.graphics.graphicsLayer
 import androidx.compose.ui.graphics.vector.ImageVector
 import androidx.compose.ui.platform.LocalContext
@@ -169,15 +171,29 @@ fun HomeScreen(
 	val deadTargets by viewModel.deadTargets.collectAsStateWithLifecycle()
 	/* rolling RTT history per target, rendered as sparklines in the availability card */
 	val probeHistory = remember { mutableStateMapOf<ProbeTarget, SnapshotStateList<ProbeResult?>>() }
+	/* the map is updated one target at a time as the parallel probes finish:
+	 * only append results that are new, not every entry on every emission */
+	val lastSeen = remember { HashMap<ProbeTarget, ProbeResult>() }
+	DisposableEffect(viewModel)
+	{	/* the view model only polls traffic and probes while Home is shown */
+		viewModel.setHomeVisible(true)
+		onDispose { viewModel.setHomeVisible(false) }
+	}
 	LaunchedEffect(probes)
 	{
 		if (probes.isEmpty())
 		{
 			probeHistory.clear()
+			lastSeen.clear()
 		}
 		else
 		{
 			probes.forEach { (target, result) ->
+				if (lastSeen[target] === result)
+				{
+					return@forEach
+				}
+				lastSeen[target] = result
 				val list = probeHistory.getOrPut(target) { mutableStateListOf() }
 				list.add(result)
 				while (list.size > RTT_HISTORY)
@@ -533,30 +549,43 @@ private fun StatusGlowBackground(color: Color, active: Boolean)
 		) != 0f
 	}
 	val animated by animateColorAsState(color, label = "glow")
-	val transition = rememberInfiniteTransition(label = "pulse")
-	/* read inside the draw scope below so the pulse only invalidates drawing,
-	 * instead of recomposing this composable on every frame */
-	val pulse by transition.animateFloat(
-		initialValue = 0.30f,
-		targetValue = 0.55f,
-		animationSpec = infiniteRepeatable(tween(1600, easing = LinearEasing), RepeatMode.Reverse),
-		label = "a",
-	)
-	Canvas(Modifier.fillMaxSize())
-	{
-		val alpha = if (active) (if (animationsOn) pulse else 0.42f) else 0f
-		val cx = size.width / 2f
-		val cy = size.height * 0.16f
-		drawCircle(
-			brush = Brush.radialGradient(
-				colors = listOf(animated.copy(alpha = alpha * 0.30f), Color.Transparent),
-				center = Offset(cx, cy),
-				radius = size.minDimension * 0.62f,
-			),
-			radius = size.minDimension * 0.62f,
-			center = Offset(cx, cy),
-		)
+	if (!active)
+	{	/* nothing to draw: no canvas and, above all, no infinite transition
+		 * redrawing a transparent circle every frame while disconnected */
+		return
 	}
+	if (animationsOn)
+	{
+		val transition = rememberInfiniteTransition(label = "pulse")
+		/* read inside the draw scope below so the pulse only invalidates drawing,
+		 * instead of recomposing this composable on every frame */
+		val pulse by transition.animateFloat(
+			initialValue = 0.30f,
+			targetValue = 0.55f,
+			animationSpec = infiniteRepeatable(tween(1600, easing = LinearEasing), RepeatMode.Reverse),
+			label = "a",
+		)
+		Canvas(Modifier.fillMaxSize()) { drawGlow(animated, pulse) }
+	}
+	else
+	{
+		Canvas(Modifier.fillMaxSize()) { drawGlow(animated, 0.42f) }
+	}
+}
+
+private fun DrawScope.drawGlow(color: Color, alpha: Float)
+{
+	val center = Offset(size.width / 2f, size.height * 0.16f)
+	val radius = size.minDimension * 0.62f
+	drawCircle(
+		brush = Brush.radialGradient(
+			colors = listOf(color.copy(alpha = alpha * 0.30f), Color.Transparent),
+			center = center,
+			radius = radius,
+		),
+		radius = radius,
+		center = center,
+	)
 }
 
 @OptIn(ExperimentalMaterial3Api::class)

src/frontends/android/app/src/main/java/org/strongswan/android/ui/compose/HomeViewModel.kt

@@ -36,11 +36,16 @@ import androidx.lifecycle.viewModelScope
 import androidx.localbroadcastmanager.content.LocalBroadcastManager
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.coroutineScope
+import kotlinx.coroutines.currentCoroutineContext
 import kotlinx.coroutines.delay
 import kotlinx.coroutines.flow.MutableSharedFlow
 import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.SharedFlow
 import kotlinx.coroutines.flow.StateFlow
+import kotlinx.coroutines.flow.collectLatest
+import kotlinx.coroutines.flow.combine
+import kotlinx.coroutines.flow.distinctUntilChanged
+import kotlinx.coroutines.flow.map
 import kotlinx.coroutines.flow.update
 import kotlinx.coroutines.isActive
 import kotlinx.coroutines.launch
@@ -131,6 +136,7 @@ class HomeViewModel(app: Application) : AndroidViewModel(app), VpnStateService.V
 	private val _messages = MutableSharedFlow<Int>(extraBufferCapacity = 4)
 	val messages: SharedFlow<Int> = _messages
 
+	private val homeVisible = MutableStateFlow(false)
 	private val _ui = MutableStateFlow(HomeUiState())
 	val ui: StateFlow<HomeUiState> = _ui
 
@@ -204,46 +210,66 @@ class HomeViewModel(app: Application) : AndroidViewModel(app), VpnStateService.V
 		)
 		reloadProfiles()
 		WhiteListManager.getInstance(ctx).refreshIfStale()
-		/* poll traffic only while the app is visible, and off the main thread */
+		/* poll traffic only while the Home screen is shown (not on the other
+		 * tabs or behind another activity), the VPN is up, and off the main thread */
 		viewModelScope.launch {
 			ProcessLifecycleOwner.get().lifecycle.repeatOnLifecycle(Lifecycle.State.STARTED) {
-				while (isActive)
-				{
+				whileHomeConnected {
 					tickTraffic()
 					delay(TRAFFIC_POLL_MS)
 				}
 			}
 		}
-		/* probe availability while the app is visible and the VPN is connected */
+		/* probe availability under the same conditions */
 		viewModelScope.launch {
 			ProcessLifecycleOwner.get().lifecycle.repeatOnLifecycle(Lifecycle.State.STARTED) {
 				var lastProbeAt = 0L
-				while (isActive)
-				{
-					val connected = _ui.value.vpnState == State.CONNECTED
-					if (connected && SystemClock.elapsedRealtime() - lastProbeAt >= PROBE_INTERVAL_MS)
+				whileHomeConnected {
+					val wait = PROBE_INTERVAL_MS - (SystemClock.elapsedRealtime() - lastProbeAt)
+					if (wait > 0)
 					{
-						lastProbeAt = SystemClock.elapsedRealtime()
-						probeNow()
+						delay(wait)
 					}
-					delay(PROBE_TICK_MS)
+					lastProbeAt = SystemClock.elapsedRealtime()
+					probeNow()
 				}
 			}
 		}
 	}
 
+	/**
+	 * Runs [block] repeatedly while the Home screen is visible and the VPN is
+	 * connected; suspends without any polling otherwise.  [block] is
+	 * cancelled as soon as either condition goes away.
+	 */
+	private suspend fun whileHomeConnected(block: suspend () -> Unit)
+	{
+		combine(homeVisible, _ui.map { it.vpnState == State.CONNECTED }) { visible, connected ->
+			visible && connected
+		}.distinctUntilChanged().collectLatest { active ->
+			while (active && currentCoroutineContext().isActive)
+			{
+				block()
+			}
+		}
+	}
+
+	/** Called by the Home screen while it is (not) shown. */
+	fun setHomeVisible(visible: Boolean)
+	{
+		homeVisible.value = visible
+	}
+
 	/** Immediately reruns the availability probe round (refresh button). */
 	fun refreshProbes()
 	{
 		WhiteListManager.getInstance(getApplication()).checkNow()
 		viewModelScope.launch {
-			probeNow()
-			refreshExit(force = true)
-			refreshDeadTargets()
+			probeNow(forceExit = true)
 		}
 	}
 
-	private suspend fun probeNow()
+	private suspend fun probeNow(forceExit: Boolean = false)
 	{
 		/* direct (outside the tunnel) probes: at most once per TTL, event-driven */
 		WhiteListManager.getInstance(getApplication()).refreshIfStale()
@@ -263,7 +289,7 @@ class HomeViewModel(app: Application) : AndroidViewModel(app), VpnStateService.V
 			addAll(healthConfig.targets)
 		}
 		refreshDeadTargets()
-		viewModelScope.launch { refreshExit(force = false) }
+		viewModelScope.launch { refreshExit(force = forceExit) }
 		if (targets.isEmpty())
 		{
 			return
@@ -630,7 +656,6 @@ class HomeViewModel(app: Application) : AndroidViewModel(app), VpnStateService.V
 	companion object
 	{
 		private const val TRAFFIC_POLL_MS = 1000L
-		private const val PROBE_TICK_MS = 1000L
 		private const val PROBE_INTERVAL_MS = 10_000L
 		private const val EXIT_REFRESH_MS = 60_000L
 		private const val EXIT_TIMEOUT_MS = 5000

src/frontends/android/app/src/main/java/org/strongswan/android/ui/compose/RoutingScreen.kt

@@ -60,7 +60,10 @@ import androidx.compose.ui.semantics.heading
 import androidx.compose.ui.semantics.semantics
 import androidx.compose.ui.text.font.FontWeight
 import androidx.compose.ui.unit.dp
+import androidx.lifecycle.Lifecycle
+import androidx.lifecycle.compose.LocalLifecycleOwner
 import androidx.lifecycle.compose.collectAsStateWithLifecycle
+import androidx.lifecycle.repeatOnLifecycle
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.delay
 import kotlinx.coroutines.launch
@@ -161,21 +164,26 @@ private fun RoutingPageContent(
 		}
 	}
 
-	/* dead direct destinations the engine keeps refusing */
-	val deadTargets by produceState(initialValue = emptyList<DeadTargetUi>())
+	/* dead direct destinations the engine keeps refusing; polled only while
+	 * the screen is visible (not while the activity is stopped) */
+	val lifecycle = LocalLifecycleOwner.current.lifecycle
+	val deadTargets by produceState(initialValue = emptyList<DeadTargetUi>(), lifecycle)
 	{
-		while (true)
+		lifecycle.repeatOnLifecycle(Lifecycle.State.STARTED)
 		{
-			val raw = try
+			while (true)
 			{
-				withContext(Dispatchers.Default) { CharonVpnService.getDeadDirectTargets() }
+				val raw = try
+				{
+					withContext(Dispatchers.Default) { CharonVpnService.getDeadDirectTargets() }
+				}
+				catch (_: Throwable)
+				{
+					null
+				}
+				value = HomeViewModel.parseDeadTargets(raw)
+				delay(5_000)
 			}
-			catch (_: Throwable)
-			{
-				null
-			}
-			value = HomeViewModel.parseDeadTargets(raw)
-			delay(5_000)
 		}
 	}