fix(ui): give rx_snr real presence semantics end to end (#6523)

Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>

core/ui/src/commonMain/kotlin/org/meshtastic/core/ui/component/BuildNodeDescription.kt

@@ -37,7 +37,6 @@ import org.meshtastic.proto.Config.LoRaConfig.ModemPreset
 
 private const val MILLIS_PER_SECOND = 1000L
 private const val MAX_BATTERY_PERCENT = 100
-private const val SNR_UNSET_THRESHOLD = 100f
 
 /** Pre-resolved localized strings for TalkBack node descriptions. */
 @Immutable
@@ -82,8 +81,7 @@ internal fun buildNodeDescription(
     hopsAway: Int,
     batteryLevel: Int?,
     distance: String?,
-    snr: Float,
-    rssi: Int,
+    snr: Float?,
     viaMqtt: Boolean,
     strings: NodeDescriptionStrings,
     lastHeardIsRelative: Boolean = true,
@@ -122,7 +120,9 @@ internal fun buildNodeDescription(
         append(", ")
         append(strings.distanceAway.replace("%s", it))
     }
-    if (hopsAway == 0 && !viaMqtt && snr < SNR_UNSET_THRESHOLD && rssi < 0) {
+    // Rated from SNR alone: RSSI cannot indicate demodulability without the noise floor, and the old `rssi < 0` gate
+    // suppressed the announcement for a genuine 0 dBm reading.
+    if (hopsAway == 0 && !viaMqtt && snr != null) {
         val quality = determineSignalQuality(snr, modemPreset)
         append(", ")
         append(strings.signal.replace("%s", quality.name.lowercase()))

core/ui/src/commonMain/kotlin/org/meshtastic/core/ui/component/LoraSignalIndicator.kt

@@ -20,11 +20,7 @@ package org.meshtastic.core.ui.component
 
 import androidx.compose.foundation.layout.Arrangement
 import androidx.compose.foundation.layout.Column
-import androidx.compose.foundation.layout.ExperimentalLayoutApi
-import androidx.compose.foundation.layout.FlowRow
-import androidx.compose.foundation.layout.Row
 import androidx.compose.foundation.layout.fillMaxSize
-import androidx.compose.foundation.layout.fillMaxWidth
 import androidx.compose.foundation.layout.padding
 import androidx.compose.foundation.layout.size
 import androidx.compose.material3.Icon
@@ -56,6 +52,7 @@ import org.meshtastic.core.resources.rssi
 import org.meshtastic.core.resources.signal
 import org.meshtastic.core.resources.signal_quality
 import org.meshtastic.core.resources.snr
+import org.meshtastic.core.resources.unknown
 import org.meshtastic.core.ui.theme.StatusColors.StatusGreen
 import org.meshtastic.core.ui.theme.StatusColors.StatusOrange
 import org.meshtastic.core.ui.theme.StatusColors.StatusRed
@@ -88,60 +85,22 @@ enum class Quality(
     GOOD(Res.string.good, Res.drawable.ic_signal_cellular_4_bar, { colorScheme.StatusGreen }),
 }
 
-/**
- * Displays the `snr` and `rssi` color coded based on the signal quality, along with a human readable description and
- * related icon.
- */
-@OptIn(ExperimentalLayoutApi::class)
-@Composable
-fun NodeSignalQuality(
-    snr: Float,
-    rssi: Int?,
-    modifier: Modifier = Modifier,
-    modemPreset: ModemPreset? = LocalModemPreset.current,
-) {
-    val quality = determineSignalQuality(snr, modemPreset)
-    FlowRow(
-        modifier = modifier,
-        itemVerticalAlignment = Alignment.CenterVertically,
-        horizontalArrangement = Arrangement.SpaceBetween,
-    ) {
-        Snr(snr, modemPreset = modemPreset)
-        Rssi(rssi)
-        Text(
-            text = "${stringResource(Res.string.signal)} ${stringResource(quality.nameRes)}",
-            style = MaterialTheme.typography.labelSmall,
-            maxLines = 1,
-        )
-        Icon(
-            modifier = Modifier.size(SIZE_ICON_DP.dp),
-            imageVector = vectorResource(quality.icon),
-            contentDescription = stringResource(Res.string.signal_quality),
-            tint = quality.color(),
-        )
-    }
-}
-
 private const val SIZE_ICON_DP = 16
 
-/** Displays the `snr` and `rssi` with color depending on the values respectively. */
-@Composable
-fun SnrAndRssi(snr: Float, rssi: Int?, modemPreset: ModemPreset? = LocalModemPreset.current) {
-    Row(modifier = Modifier.fillMaxWidth(), horizontalArrangement = Arrangement.SpaceBetween) {
-        Snr(snr, modemPreset = modemPreset)
-        Rssi(rssi)
-    }
-}
-
-/** Displays a human readable description and icon representing the signal quality. */
+/**
+ * Displays a human readable description and icon representing the signal quality.
+ *
+ * A null [snr] means the packet carried no measurement, which is rendered as "Unknown" in a neutral tint. It must not
+ * fall through to [Quality.NONE] — that band means "measured, and too weak to demodulate", a different claim.
+ */
 @Composable
 fun LoraSignalIndicator(
-    snr: Float,
+    snr: Float?,
     modifier: Modifier = Modifier,
     modemPreset: ModemPreset? = LocalModemPreset.current,
     contentColor: Color = MaterialTheme.colorScheme.onSurface,
 ) {
-    val quality = determineSignalQuality(snr, modemPreset)
+    val quality = snr?.let { determineSignalQuality(it, modemPreset) }
     Column(
         verticalArrangement = Arrangement.Center,
         horizontalAlignment = Alignment.CenterHorizontally,
@@ -149,20 +108,22 @@ fun LoraSignalIndicator(
     ) {
         Icon(
             modifier = Modifier.size(SIZE_ICON_DP.dp),
-            imageVector = vectorResource(quality.icon),
+            imageVector = vectorResource(quality?.icon ?: Res.drawable.ic_signal_cellular_alt),
             contentDescription = stringResource(Res.string.signal_quality),
-            tint = quality.color(),
+            tint = quality?.color?.invoke() ?: MaterialTheme.colorScheme.onSurfaceVariant,
         )
         Text(
-            text = "${stringResource(Res.string.signal)} ${stringResource(quality.nameRes)}",
+            text = "${stringResource(Res.string.signal)} " + stringResource(quality?.nameRes ?: Res.string.unknown),
             style = MaterialTheme.typography.labelSmall,
             color = contentColor,
         )
     }
 }
 
+/** Renders nothing when [snr] is absent — 0 dB is a real reading, so it must not stand in for "no reading". */
 @Composable
-fun Snr(snr: Float, modifier: Modifier = Modifier, modemPreset: ModemPreset? = LocalModemPreset.current) {
+fun Snr(snr: Float?, modifier: Modifier = Modifier, modemPreset: ModemPreset? = LocalModemPreset.current) {
+    if (snr == null) return
     val color: Color = determineSignalQuality(snr, modemPreset).color.invoke()
 
     Text(

core/ui/src/commonMain/kotlin/org/meshtastic/core/ui/component/NodeItem.kt

@@ -145,8 +145,7 @@ fun NodeItem(
                 hopsAway = thatNode.hopsAway,
                 batteryLevel = thatNode.batteryLevel,
                 distance = distance,
-                snr = thatNode.snr,
-                rssi = thatNode.rssi,
+                snr = thatNode.snrOrNull,
                 viaMqtt = thatNode.viaMqtt,
                 strings = a11yStrings,
                 modemPreset = modemPreset,
@@ -312,9 +311,9 @@ private fun NodeSignalRow(thatNode: Node, isThisNode: Boolean, contentColor: Col
                 if (thatNode.hopsAway > 0) {
                     add { HopsInfo(hops = thatNode.hopsAway, contentColor = contentColor) }
                 } else if (thatNode.hopsAway == 0 && !thatNode.viaMqtt) {
-                    val showSnr = thatNode.snr < 100f
-                    val showRssi = thatNode.rssi < 0
-                    if (showSnr || showRssi) {
+                    val snr = thatNode.snrOrNull
+                    val rssi = thatNode.rssiOrNull
+                    if (snr != null || rssi != null) {
                         signalChip = {
                             // Full-width row: SNR left, RSSI center, quality right.
                             Row(
@@ -322,10 +321,10 @@ private fun NodeSignalRow(thatNode: Node, isThisNode: Boolean, contentColor: Col
                                 verticalAlignment = Alignment.CenterVertically,
                                 horizontalArrangement = Arrangement.SpaceBetween,
                             ) {
-                                if (showSnr) Snr(thatNode.snr)
-                                if (showRssi) Rssi(thatNode.rssi)
-                                if (showSnr && showRssi) {
-                                    val quality = determineSignalQuality(thatNode.snr, LocalModemPreset.current)
+                                Snr(snr)
+                                Rssi(rssi)
+                                if (snr != null) {
+                                    val quality = determineSignalQuality(snr, LocalModemPreset.current)
                                     IconInfo(
                                         icon = vectorResource(quality.icon),
                                         contentDescription = stringResource(Res.string.signal_quality),

core/ui/src/commonMain/kotlin/org/meshtastic/core/ui/component/NodeItemCompact.kt

@@ -155,8 +155,7 @@ fun NodeItemCompact(
                 hopsAway = thatNode.hopsAway,
                 batteryLevel = thatNode.batteryLevel,
                 distance = distance,
-                snr = thatNode.snr,
-                rssi = thatNode.rssi,
+                snr = thatNode.snrOrNull,
                 viaMqtt = thatNode.viaMqtt,
                 strings = a11yStrings,
                 lastHeardIsRelative = lastHeardIsRelative,
@@ -350,10 +349,10 @@ private fun CompactHealthRow(
             )
         }
 
-        // Signal quality
-        val hasDirectSignal = thatNode.hopsAway == 0 && thatNode.snr < 100f && !thatNode.viaMqtt && thatNode.rssi < 0
-        if (showSignal && hasDirectSignal) {
-            val quality = determineSignalQuality(thatNode.snr, LocalModemPreset.current)
+        // Signal quality, rated from SNR alone — RSSI is not part of the rating (#5446), so it must not gate it.
+        val directSnr = thatNode.snrOrNull?.takeIf { thatNode.hopsAway == 0 && !thatNode.viaMqtt }
+        if (showSignal && directSnr != null) {
+            val quality = determineSignalQuality(directSnr, LocalModemPreset.current)
             add(
                 @Composable {
                     IconInfo(

core/ui/src/commonMain/kotlin/org/meshtastic/core/ui/component/SignalInfo.kt

@@ -42,17 +42,21 @@ import org.meshtastic.core.ui.component.preview.NodePreviewParameterProvider
 import org.meshtastic.core.ui.theme.AppTheme
 import org.meshtastic.core.ui.util.LocalModemPreset
 
-const val MAX_VALID_SNR = 100F
-const val MAX_VALID_RSSI = 0
-
+/**
+ * Renders the node's signal quality, or nothing when it has no SNR reading to rate.
+ *
+ * Presence comes from [Node.snrOrNull]/[Node.rssiOrNull], not from threshold comparisons: the previous `rssi < 0` gate
+ * hid the whole row for a genuine 0 dBm reading, and `snr < 100f` would have hidden any reading at or above 100 dB.
+ */
 @Composable
 fun SignalInfo(
     modifier: Modifier = Modifier,
     node: Node,
     @Suppress("UNUSED_PARAMETER") contentColor: Color = MaterialTheme.colorScheme.onSurface,
 ) {
-    if (node.snr < MAX_VALID_SNR && node.rssi < MAX_VALID_RSSI) {
-        val quality = determineSignalQuality(node.snr, LocalModemPreset.current)
+    val snr = node.snrOrNull
+    if (snr != null) {
+        val quality = determineSignalQuality(snr, LocalModemPreset.current)
         val signalColor = quality.color.invoke()
         Row(
             modifier = modifier,
@@ -67,9 +71,8 @@ fun SignalInfo(
             )
             Text(
                 text =
-                "${MetricFormatter.snr(
-                    node.snr,
-                )} · ${MetricFormatter.rssi(node.rssi)} · ${stringResource(quality.nameRes)}",
+                "${MetricFormatter.snr(snr)} · ${MetricFormatter.rssi(node.rssiOrNull)} · " +
+                    stringResource(quality.nameRes),
                 style =
                 MaterialTheme.typography.labelSmall.copy(
                     fontWeight = FontWeight.Bold,

core/ui/src/commonTest/kotlin/org/meshtastic/core/ui/component/BuildNodeDescriptionTest.kt

@@ -48,8 +48,7 @@ class BuildNodeDescriptionTest {
         hopsAway: Int = 0,
         batteryLevel: Int? = null,
         distance: String? = null,
-        snr: Float = Float.MAX_VALUE,
-        rssi: Int = 0,
+        snr: Float? = null,
         viaMqtt: Boolean = false,
         lastHeardIsRelative: Boolean = true,
     ): String = buildNodeDescription(
@@ -62,7 +61,6 @@ class BuildNodeDescriptionTest {
         batteryLevel = batteryLevel,
         distance = distance,
         snr = snr,
-        rssi = rssi,
         viaMqtt = viaMqtt,
         strings = testStrings,
         lastHeardIsRelative = lastHeardIsRelative,
@@ -157,32 +155,33 @@ class BuildNodeDescriptionTest {
     // ---- Signal ----
 
     @Test
-    fun signal_hidden_when_snr_is_max_float() {
-        val result = describe(snr = Float.MAX_VALUE, rssi = -100, hopsAway = 0, viaMqtt = false)
+    fun signal_hidden_when_snr_is_absent() {
+        val result = describe(snr = null, hopsAway = 0, viaMqtt = false)
         assertFalse(result.contains("signal"))
     }
 
     @Test
     fun signal_hidden_when_via_mqtt() {
-        val result = describe(snr = -5f, rssi = -100, hopsAway = 0, viaMqtt = true)
+        val result = describe(snr = -5f, hopsAway = 0, viaMqtt = true)
         assertFalse(result.contains("signal"))
     }
 
     @Test
     fun signal_hidden_when_hops_greater_than_zero() {
-        val result = describe(snr = -5f, rssi = -100, hopsAway = 1, viaMqtt = false)
+        val result = describe(snr = -5f, hopsAway = 1, viaMqtt = false)
         assertFalse(result.contains("signal"))
     }
 
     @Test
-    fun signal_hidden_when_rssi_not_negative() {
-        val result = describe(snr = -5f, rssi = 0, hopsAway = 0, viaMqtt = false)
-        assertFalse(result.contains("signal"))
+    fun signal_shown_for_a_zero_snr_reading() {
+        // 0 dB is a real, strong reading. It was previously announced only when RSSI happened to be negative.
+        val result = describe(snr = 0f, hopsAway = 0, viaMqtt = false)
+        assertContains(result, "signal")
     }
 
     @Test
     fun signal_shown_when_direct_and_valid_values() {
-        val result = describe(snr = -5f, rssi = -100, hopsAway = 0, viaMqtt = false)
+        val result = describe(snr = -5f, hopsAway = 0, viaMqtt = false)
         assertContains(result, "signal")
     }
 }

core/ui/src/commonTest/kotlin/org/meshtastic/core/ui/component/LoraSignalIndicatorTest.kt

@@ -77,6 +77,22 @@ class LoraSignalIndicatorTest {
         assertEquals(Quality.NONE, determineSignalQuality(snr = -30f, modemPreset = preset)) // < limit-7.5
     }
 
+    @Test
+    fun `a zero SNR reading is rated rather than treated as missing`() {
+        // 0 dB sits well above every preset's demod floor, so it is an excellent signal — not an absent one. If a
+        // presence check ever folds zero into "unknown", this is the reading that disappears.
+        assertEquals(Quality.GOOD, determineSignalQuality(snr = 0f, modemPreset = ModemPreset.LONG_FAST))
+        assertEquals(Quality.GOOD, determineSignalQuality(snr = 0f, modemPreset = ModemPreset.SHORT_FAST))
+    }
+
+    @Test
+    fun `absent SNR is not a quality band`() {
+        // Quality has no member for "no measurement": callers must pass a non-null SNR, and the composables render
+        // absence as Unknown rather than mapping it onto NONE (which asserts a measured, undemodulable signal).
+        assertEquals(4, Quality.entries.size)
+        assertEquals(listOf(Quality.NONE, Quality.BAD, Quality.FAIR, Quality.GOOD), Quality.entries.toList())
+    }
+
     @Test
     fun `RSSI does not influence the rating`() {
         // Identical SNR + preset always yields the same verdict regardless of any RSSI (RSSI is display-only now).

core/ui/src/commonTest/kotlin/org/meshtastic/core/ui/component/LoraSignalIndicatorUiTest.kt

@@ -34,6 +34,29 @@ class LoraSignalIndicatorUiTest {
         onNodeWithText("Signal strength -70 dBm").assertIsDisplayed()
     }
 
+    @Test
+    fun snrRendersAZeroReading() = runComposeUiTest {
+        // 0 dB is a measurement and must be shown, not suppressed as "no reading".
+        setContent { AppTheme { Snr(snr = 0f) } }
+
+        onNodeWithText("SNR 0.00 dB").assertIsDisplayed()
+    }
+
+    @Test
+    fun snrRendersNothingWhenAbsent() = runComposeUiTest {
+        setContent { AppTheme { Snr(snr = null) } }
+
+        onNodeWithText("SNR 0.00 dB").assertDoesNotExist()
+    }
+
+    @Test
+    fun loraSignalIndicatorShowsUnknownWhenSnrIsAbsent() = runComposeUiTest {
+        // Absence must not render as "Signal None" — that band means a measured, undemodulable signal.
+        setContent { AppTheme { LoraSignalIndicator(snr = null) } }
+
+        onNodeWithText("Signal Unknown").assertIsDisplayed()
+    }
+
     @Test
     fun batteryUsesCallerProvidedUnknownLabel() = runComposeUiTest {
         setContent { AppTheme { MaterialBatteryInfo(level = null, unknownLabel = "Unavailable") } }