test: render every ImageComposeScene on the AWT event thread

The rare CI hang is a lock-order deadlock in Compose Multiplatform 1.8.2,
shown by the thread dump of run 40299943329:

- the test thread renders the scene and holds the FlushCoroutineDispatcher
  runLock while LazyListState.scrollToItem measures and wants the
  SnapshotStateObserver's observedScopeMapsLock;
- the AWT event thread sends the global snapshot notifications and holds
  observedScopeMapsLock in drainChanges while a re-read derived state wakes
  the scene's snapshotFlow collector, whose dispatch wants runLock.

The application renders on the event thread, where both monitors are simply
re-entered. The tests now do the same: onEventThread builds, renders and
closes each scene there and rethrows what the block throws.

Claude-Session: https://claude.ai/code/session_01FJBfPYm6rCH4zD6T7bcC7Y

app-desktop/src/test/kotlin/kst4contest/view/compose/CompactControlsVisualRenderingTest.kt

@@ -55,45 +55,47 @@ class CompactControlsVisualRenderingTest(@param:TempDir private val tempDir: Pat
         }
         val filters = StationFilterState()
 
-        val scene = ImageComposeScene(width = 1366, height = 380, density = Density(scale)) {
-            Kst4ContestTheme(darkMode = darkMode, baseFontSizeSp = 12f) {
-                Surface(
-                    modifier = Modifier.fillMaxSize(),
-                    color = MaterialTheme.colorScheme.background,
-                ) {
-                    Column(Modifier.padding(4.dp)) {
-                        TimelineView(
-                            state = TimelineState(),
-                            onCandidateClicked = {},
-                            modifier = Modifier.fillMaxWidth(),
-                        )
-                        Spacer(Modifier.height(8.dp))
-                        StationFilterBar(
-                            filters = filters,
-                            activeBands = EnumSet.of(Band.B_144, Band.B_432, Band.B_1296),
-                            reachability = ReachabilityState(
-                                EnumSet.of(Band.B_144, Band.B_432, Band.B_1296),
-                            ),
-                            onChanged = {},
-                        )
-                        Spacer(Modifier.height(12.dp))
-                        ChatInputRow(
-                            state = chatInputState,
-                            prefs = preferences,
-                            ownQrgMain = ObservedValue(preferences.getMYQRGFirstCat()),
-                            ownQrgSecond = ObservedValue(preferences.getMYQRGSecondCat()),
-                            antennaQtf = ObservedValue(preferences.getActualQTF()),
-                            antennaQtf2 = ObservedValue(preferences.getActualQTF2()),
-                            so2rEnabled = false,
-                        )
+        return onEventThread {
+            val scene = ImageComposeScene(width = 1366, height = 380, density = Density(scale)) {
+                Kst4ContestTheme(darkMode = darkMode, baseFontSizeSp = 12f) {
+                    Surface(
+                        modifier = Modifier.fillMaxSize(),
+                        color = MaterialTheme.colorScheme.background,
+                    ) {
+                        Column(Modifier.padding(4.dp)) {
+                            TimelineView(
+                                state = TimelineState(),
+                                onCandidateClicked = {},
+                                modifier = Modifier.fillMaxWidth(),
+                            )
+                            Spacer(Modifier.height(8.dp))
+                            StationFilterBar(
+                                filters = filters,
+                                activeBands = EnumSet.of(Band.B_144, Band.B_432, Band.B_1296),
+                                reachability = ReachabilityState(
+                                    EnumSet.of(Band.B_144, Band.B_432, Band.B_1296),
+                                ),
+                                onChanged = {},
+                            )
+                            Spacer(Modifier.height(12.dp))
+                            ChatInputRow(
+                                state = chatInputState,
+                                prefs = preferences,
+                                ownQrgMain = ObservedValue(preferences.getMYQRGFirstCat()),
+                                ownQrgSecond = ObservedValue(preferences.getMYQRGSecondCat()),
+                                antennaQtf = ObservedValue(preferences.getActualQTF()),
+                                antennaQtf2 = ObservedValue(preferences.getActualQTF2()),
+                                so2rEnabled = false,
+                            )
+                        }
                     }
                 }
             }
-        }
-        return try {
-            scene.render().encodeToData()!!.bytes
-        } finally {
-            scene.close()
+            try {
+                scene.render().encodeToData()!!.bytes
+            } finally {
+                scene.close()
+            }
         }
     }
 

app-desktop/src/test/kotlin/kst4contest/view/compose/OnEventThread.kt

@@ -0,0 +1,37 @@
+package kst4contest.view.compose
+
+import java.awt.EventQueue
+import java.lang.reflect.InvocationTargetException
+
+/*
+ * An ImageComposeScene must live on the AWT event thread, the thread the application renders
+ * on. Compose Multiplatform 1.8.2 sends the global snapshot notifications there
+ * (GlobalSnapshotManager), and doing so takes two locks in the opposite order from a render
+ * on any other thread:
+ *
+ *  - the render holds the scene's FlushCoroutineDispatcher runLock while a task it runs
+ *    (here LazyListState.scrollToItem) measures and wants the SnapshotStateObserver's
+ *    observedScopeMapsLock;
+ *  - the event thread holds observedScopeMapsLock in drainChanges while a derived state it
+ *    re-reads wakes a snapshotFlow collector of that scene, whose dispatch wants runLock.
+ *
+ * Both waited forever in CI runs 40252077018, 40252089738 and 40299943329; the thread dump of
+ * the last one shows both stacks. On one thread the two monitors are simply re-entered, which
+ * is why the application never hangs this way.
+ */
+
+/**
+ * Runs [block] on the AWT event thread, waits for it and returns its result. Whatever
+ * [block] throws is rethrown here unwrapped, so a failed assertion still reads as one.
+ */
+internal fun <T> onEventThread(block: () -> T): T {
+    if (EventQueue.isDispatchThread()) return block()
+
+    var result: Result<T>? = null
+    try {
+        EventQueue.invokeAndWait { result = runCatching(block) }
+    } catch (wrapped: InvocationTargetException) {
+        throw wrapped.cause ?: wrapped
+    }
+    return result!!.getOrThrow()
+}

app-desktop/src/test/kotlin/kst4contest/view/compose/SelectedStationMessageUiVisualRenderingTest.kt

@@ -84,37 +84,39 @@ class SelectedStationMessageUiVisualRenderingTest {
             replaceRows(listOf(message(member("DL1ABC", 2), member("DL2XYZ", 2), "pse sked")))
         }
 
-        val scene = ImageComposeScene(width = 1366, height = windowHeight, density = Density(scale)) {
-            Kst4ContestTheme(darkMode = darkMode, baseFontSizeSp = 12f) {
-                Surface(
-                    modifier = Modifier.fillMaxSize(),
-                    color = MaterialTheme.colorScheme.background,
-                ) {
-                    Row(Modifier.fillMaxSize().padding(6.dp)) {
-                        MessageTabs(
-                            publicMessages = publicMessages,
-                            clusterMessages = clusterTable(),
-                            qsoOfTheOther = qsoMessages,
-                            modifier = Modifier.weight(1f),
-                        )
-                        SelectedStationPanel(
-                            state = selectedState,
-                            messages = selectedMessages,
-                            activeBands = EnumSet.of(Band.B_144, Band.B_432, Band.B_1296),
-                            openInBrowser = Consumer {},
-                            onShowOnMap = {},
-                            onShowPathInAirScout = {},
-                            modifier = Modifier.width(panelWidth).padding(start = 6.dp),
-                        )
+        return onEventThread {
+            val scene = ImageComposeScene(width = 1366, height = windowHeight, density = Density(scale)) {
+                Kst4ContestTheme(darkMode = darkMode, baseFontSizeSp = 12f) {
+                    Surface(
+                        modifier = Modifier.fillMaxSize(),
+                        color = MaterialTheme.colorScheme.background,
+                    ) {
+                        Row(Modifier.fillMaxSize().padding(6.dp)) {
+                            MessageTabs(
+                                publicMessages = publicMessages,
+                                clusterMessages = clusterTable(),
+                                qsoOfTheOther = qsoMessages,
+                                modifier = Modifier.weight(1f),
+                            )
+                            SelectedStationPanel(
+                                state = selectedState,
+                                messages = selectedMessages,
+                                activeBands = EnumSet.of(Band.B_144, Band.B_432, Band.B_1296),
+                                openInBrowser = Consumer {},
+                                onShowOnMap = {},
+                                onShowPathInAirScout = {},
+                                modifier = Modifier.width(panelWidth).padding(start = 6.dp),
+                            )
+                        }
                     }
                 }
             }
-        }
 
-        return try {
-            scene.render().encodeToData()!!.bytes
-        } finally {
-            scene.close()
+            try {
+                scene.render().encodeToData()!!.bytes
+            } finally {
+                scene.close()
+            }
         }
     }
 

app-desktop/src/test/kotlin/kst4contest/view/compose/StationWorkspaceVisualRenderingTest.kt

@@ -87,62 +87,64 @@ class StationWorkspaceVisualRenderingTest {
             RowKeys.byReference<ChatMessage>(),
         )
 
-        val scene = ImageComposeScene(
-            width = 1366,
-            height = scenario.height,
-            density = Density(scale),
-        ) {
-            Kst4ContestTheme(darkMode = darkMode, baseFontSizeSp = 12f) {
-                Surface(
-                    modifier = Modifier.fillMaxSize(),
-                    color = MaterialTheme.colorScheme.background,
-                ) {
-                    Box(Modifier.fillMaxSize()) {
-                    Column(
-                        Modifier
-                            .width(scenario.width.dp)
-                            .fillMaxHeight()
-                            .align(Alignment.TopEnd)
-                            .padding(4.dp),
+        return onEventThread {
+            val scene = ImageComposeScene(
+                width = 1366,
+                height = scenario.height,
+                density = Density(scale),
+            ) {
+                Kst4ContestTheme(darkMode = darkMode, baseFontSizeSp = 12f) {
+                    Surface(
+                        modifier = Modifier.fillMaxSize(),
+                        color = MaterialTheme.colorScheme.background,
                     ) {
-                        StationFilterBar(
-                            filters = StationFilterState(),
-                            activeBands = EnumSet.of(Band.B_144, Band.B_432),
-                            reachability = ReachabilityState(EnumSet.of(Band.B_144, Band.B_432)),
-                            onChanged = {},
-                        )
-                        DataTableView(
-                            state = stations,
-                            modifier = Modifier.weight(0.45f),
-                            emphasizeCell = { member, column ->
-                                column.id == "callsign" && newJoined.isRecent(member)
-                            },
-                        )
-                        TopPriorityBar(
-                            state = priority,
-                            newJoined = newJoined,
-                            onShowMore = {},
-                        )
-                        SelectedStationPanel(
-                            state = selected,
-                            messages = selectedMessages,
-                            activeBands = EnumSet.of(Band.B_144, Band.B_432),
-                            contentSplitter = SplitterState(2, doubleArrayOf(0.48)) {},
-                            openInBrowser = Consumer {},
-                            onShowOnMap = {},
-                            onShowPathInAirScout = {},
-                            modifier = Modifier.weight(0.55f),
-                        )
-                    }
+                        Box(Modifier.fillMaxSize()) {
+                        Column(
+                            Modifier
+                                .width(scenario.width.dp)
+                                .fillMaxHeight()
+                                .align(Alignment.TopEnd)
+                                .padding(4.dp),
+                        ) {
+                            StationFilterBar(
+                                filters = StationFilterState(),
+                                activeBands = EnumSet.of(Band.B_144, Band.B_432),
+                                reachability = ReachabilityState(EnumSet.of(Band.B_144, Band.B_432)),
+                                onChanged = {},
+                            )
+                            DataTableView(
+                                state = stations,
+                                modifier = Modifier.weight(0.45f),
+                                emphasizeCell = { member, column ->
+                                    column.id == "callsign" && newJoined.isRecent(member)
+                                },
+                            )
+                            TopPriorityBar(
+                                state = priority,
+                                newJoined = newJoined,
+                                onShowMore = {},
+                            )
+                            SelectedStationPanel(
+                                state = selected,
+                                messages = selectedMessages,
+                                activeBands = EnumSet.of(Band.B_144, Band.B_432),
+                                contentSplitter = SplitterState(2, doubleArrayOf(0.48)) {},
+                                openInBrowser = Consumer {},
+                                onShowOnMap = {},
+                                onShowPathInAirScout = {},
+                                modifier = Modifier.weight(0.55f),
+                            )
+                        }
+                        }
                     }
                 }
             }
-        }
 
-        return try {
-            scene.render().encodeToData()!!.bytes
-        } finally {
-            scene.close()
+            try {
+                scene.render().encodeToData()!!.bytes
+            } finally {
+                scene.close()
+            }
         }
     }
 

app-desktop/src/test/kotlin/kst4contest/view/compose/TopPriorityCandidatesWindowTest.kt

@@ -32,17 +32,19 @@ class TopPriorityCandidatesWindowTest {
     /** Runs [block] against a rendered list of [twoCandidates] and reports what it picked. */
     private fun picking(block: (ImageComposeScene) -> Unit): String? {
         var picked: String? = null
-        val scene = ImageComposeScene(width = 360, height = 500, density = Density(1f)) {
-            TopPriorityCandidatesWindow.CandidateListForTest(twoCandidates) {
-                picked = it.displayCallSign
+        onEventThread {
+            val scene = ImageComposeScene(width = 360, height = 500, density = Density(1f)) {
+                TopPriorityCandidatesWindow.CandidateListForTest(twoCandidates) {
+                    picked = it.displayCallSign
+                }
+            }
+            try {
+                scene.render()
+                block(scene)
+                scene.render()
+            } finally {
+                scene.close()
             }
-        }
-        try {
-            scene.render()
-            block(scene)
-            scene.render()
-        } finally {
-            scene.close()
         }
         return picked
     }
@@ -78,13 +80,15 @@ class TopPriorityCandidatesWindowTest {
     @Test
     fun `the list renders with candidates and without`() {
         listOf(emptyList(), twoCandidates).forEach { ranking ->
-            val scene = ImageComposeScene(width = 360, height = 500, density = Density(1f)) {
-                TopPriorityCandidatesWindow.CandidateListForTest(ranking) { }
-            }
-            try {
-                scene.render()
-            } finally {
-                scene.close()
+            onEventThread {
+                val scene = ImageComposeScene(width = 360, height = 500, density = Density(1f)) {
+                    TopPriorityCandidatesWindow.CandidateListForTest(ranking) { }
+                }
+                try {
+                    scene.render()
+                } finally {
+                    scene.close()
+                }
             }
         }
     }

app-desktop/src/test/kotlin/kst4contest/view/compose/map/ComposeStationMapDrawingTest.kt

@@ -4,6 +4,7 @@ import androidx.compose.foundation.layout.fillMaxSize
 import androidx.compose.ui.ImageComposeScene
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.unit.Density
+import kst4contest.view.compose.onEventThread
 import kst4contest.view.map.MapCallsignRawSnapshot
 import kst4contest.view.map.MapViewport
 import kst4contest.view.map.TileFetcher
@@ -71,27 +72,29 @@ class ComposeStationMapDrawingTest {
         workedGrossFields: Set<String> = emptySet(),
         darkMode: Boolean = true,
     ): BufferedImage {
-        val scene = ImageComposeScene(canvasWidth, canvasHeight, Density(1f)) {
-            ComposeStationMap(
-                markers = markers,
-                tileFetcher = offlineTileFetcher,
-                mapState = MapState(zoom = zoom, centerLon = 10.0, centerLat = 51.0),
-                groupingEnabled = false,
-                selectedMarkerCallsign = null,
-                ownLocator6 = ownLocator6,
-                antennaAzimuthDeg = 90.0,
-                antennaBeamWidthDeg = 0.0,
-                maxQrbKm = 0.0,
-                onMarkerClicked = null,
-                workedGrossFields = workedGrossFields,
-                darkMode = darkMode,
-                modifier = Modifier.fillMaxSize(),
-            )
-        }
-        try {
-            return ImageIO.read(ByteArrayInputStream(scene.render().encodeToData()!!.bytes))
-        } finally {
-            scene.close()
+        return onEventThread {
+            val scene = ImageComposeScene(canvasWidth, canvasHeight, Density(1f)) {
+                ComposeStationMap(
+                    markers = markers,
+                    tileFetcher = offlineTileFetcher,
+                    mapState = MapState(zoom = zoom, centerLon = 10.0, centerLat = 51.0),
+                    groupingEnabled = false,
+                    selectedMarkerCallsign = null,
+                    ownLocator6 = ownLocator6,
+                    antennaAzimuthDeg = 90.0,
+                    antennaBeamWidthDeg = 0.0,
+                    maxQrbKm = 0.0,
+                    onMarkerClicked = null,
+                    workedGrossFields = workedGrossFields,
+                    darkMode = darkMode,
+                    modifier = Modifier.fillMaxSize(),
+                )
+            }
+            try {
+                ImageIO.read(ByteArrayInputStream(scene.render().encodeToData()!!.bytes))
+            } finally {
+                scene.close()
+            }
         }
     }
 

app-desktop/src/test/kotlin/kst4contest/view/compose/map/ComposeStationMapLayoutTest.kt

@@ -4,6 +4,7 @@ import androidx.compose.foundation.layout.fillMaxSize
 import androidx.compose.ui.ImageComposeScene
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.unit.Density
+import kst4contest.view.compose.onEventThread
 import kst4contest.view.map.MapCallsignRawSnapshot
 import kst4contest.view.map.TileFetcher
 import org.junit.jupiter.api.Test
@@ -33,30 +34,32 @@ class ComposeStationMapLayoutTest {
     )
 
     private fun renderAt(widthPx: Int, heightPx: Int, zoom: Float) {
-        val scene = ImageComposeScene(
-            width = widthPx,
-            height = heightPx,
-            density = Density(1f),
-        ) {
-            ComposeStationMap(
-                markers = stations,
-                tileFetcher = TileFetcher(),
-                mapState = MapState(zoom = zoom, centerLon = 10.0, centerLat = 51.0),
-                groupingEnabled = true,
-                selectedMarkerCallsign = "F5JMI",
-                ownLocator6 = "JO50JP",
-                antennaAzimuthDeg = 229.0,
-                antennaBeamWidthDeg = 60.0,
-                maxQrbKm = 800.0,
-                onMarkerClicked = null,
-                darkMode = true,
-                modifier = Modifier.fillMaxSize(),
-            )
-        }
-        try {
-            scene.render()
-        } finally {
-            scene.close()
+        onEventThread {
+            val scene = ImageComposeScene(
+                width = widthPx,
+                height = heightPx,
+                density = Density(1f),
+            ) {
+                ComposeStationMap(
+                    markers = stations,
+                    tileFetcher = TileFetcher(),
+                    mapState = MapState(zoom = zoom, centerLon = 10.0, centerLat = 51.0),
+                    groupingEnabled = true,
+                    selectedMarkerCallsign = "F5JMI",
+                    ownLocator6 = "JO50JP",
+                    antennaAzimuthDeg = 229.0,
+                    antennaBeamWidthDeg = 60.0,
+                    maxQrbKm = 800.0,
+                    onMarkerClicked = null,
+                    darkMode = true,
+                    modifier = Modifier.fillMaxSize(),
+                )
+            }
+            try {
+                scene.render()
+            } finally {
+                scene.close()
+            }
         }
     }
 

app-desktop/src/test/kotlin/kst4contest/view/compose/map/PathAnalysisDetailsLayoutTest.kt

@@ -4,6 +4,7 @@ import androidx.compose.foundation.layout.fillMaxWidth
 import androidx.compose.ui.ImageComposeScene
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.unit.Density
+import kst4contest.view.compose.onEventThread
 import kst4contest.view.map.PathAnalysisResult
 import org.junit.jupiter.api.Test
 
@@ -25,21 +26,23 @@ class PathAnalysisDetailsLayoutTest {
     private val narrowWidthPx = 120
 
     private fun renderAt(widthPx: Int, result: PathAnalysisResult?) {
-        val scene = ImageComposeScene(
-            width = widthPx,
-            height = 600,
-            density = Density(1f),
-        ) {
-            PathAnalysisDetails(
-                result = result,
-                darkMode = true,
-                modifier = Modifier.fillMaxWidth(),
-            )
-        }
-        try {
-            scene.render()
-        } finally {
-            scene.close()
+        onEventThread {
+            val scene = ImageComposeScene(
+                width = widthPx,
+                height = 600,
+                density = Density(1f),
+            ) {
+                PathAnalysisDetails(
+                    result = result,
+                    darkMode = true,
+                    modifier = Modifier.fillMaxWidth(),
+                )
+            }
+            try {
+                scene.render()
+            } finally {
+                scene.close()
+            }
         }
     }
 

app-desktop/src/test/kotlin/kst4contest/view/compose/map/PathAnalysisDetailsWidthTest.kt

@@ -4,6 +4,7 @@ import androidx.compose.foundation.layout.fillMaxWidth
 import androidx.compose.ui.ImageComposeScene
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.unit.Density
+import kst4contest.view.compose.onEventThread
 import kst4contest.view.map.PathAnalysisResult
 import org.junit.jupiter.api.Assertions.assertTrue
 import org.junit.jupiter.api.Test
@@ -31,18 +32,20 @@ class PathAnalysisDetailsWidthTest {
     private val assessmentBackground = 0x33383E
 
     private fun render(paneWidthPx: Int, heightPx: Int = 600): BufferedImage {
-        val scene = ImageComposeScene(width = paneWidthPx, height = heightPx, density = Density(1f)) {
-            PathAnalysisDetails(
-                result = PathAnalysisResult.loading("JO50JP", "JN24JB", "F5JMI"),
-                darkMode = true,
-                modifier = Modifier.fillMaxWidth(),
-            )
-        }
-        try {
-            val png = scene.render().encodeToData()!!.bytes
-            return ImageIO.read(ByteArrayInputStream(png))
-        } finally {
-            scene.close()
+        return onEventThread {
+            val scene = ImageComposeScene(width = paneWidthPx, height = heightPx, density = Density(1f)) {
+                PathAnalysisDetails(
+                    result = PathAnalysisResult.loading("JO50JP", "JN24JB", "F5JMI"),
+                    darkMode = true,
+                    modifier = Modifier.fillMaxWidth(),
+                )
+            }
+            try {
+                val png = scene.render().encodeToData()!!.bytes
+                ImageIO.read(ByteArrayInputStream(png))
+            } finally {
+                scene.close()
+            }
         }
     }
 

app-desktop/src/test/kotlin/kst4contest/view/compose/map/PathProfileChartLayoutTest.kt

@@ -4,6 +4,7 @@ import androidx.compose.foundation.layout.fillMaxSize
 import androidx.compose.ui.ImageComposeScene
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.unit.Density
+import kst4contest.view.compose.onEventThread
 import org.junit.jupiter.api.Test
 
 /**
@@ -18,17 +19,19 @@ import org.junit.jupiter.api.Test
 class PathProfileChartLayoutTest {
 
     private fun renderAt(widthPx: Int, heightPx: Int) {
-        val scene = ImageComposeScene(
-            width = widthPx,
-            height = heightPx,
-            density = Density(1f),
-        ) {
-            PathProfileChart(modifier = Modifier.fillMaxSize(), darkMode = true)
-        }
-        try {
-            scene.render()
-        } finally {
-            scene.close()
+        onEventThread {
+            val scene = ImageComposeScene(
+                width = widthPx,
+                height = heightPx,
+                density = Density(1f),
+            ) {
+                PathProfileChart(modifier = Modifier.fillMaxSize(), darkMode = true)
+            }
+            try {
+                scene.render()
+            } finally {
+                scene.close()
+            }
         }
     }
 

app-desktop/src/test/kotlin/kst4contest/view/compose/map/StationMapBodyLayoutTest.kt

@@ -15,6 +15,7 @@ import androidx.compose.ui.unit.dp
 import kst4contest.view.compose.SplitterOrientation
 import kst4contest.view.compose.SplitterPane
 import kst4contest.view.compose.SplitterState
+import kst4contest.view.compose.onEventThread
 import kst4contest.view.map.MapCallsignRawSnapshot
 import kst4contest.view.map.PathAnalysisResult
 import kst4contest.view.map.TileFetcher
@@ -88,13 +89,15 @@ class StationMapBodyLayoutTest {
     }
 
     private fun renderAt(widthPx: Int, heightPx: Int, pathAnalysisVisible: Boolean = true) {
-        val scene = ImageComposeScene(width = widthPx, height = heightPx, density = Density(1f)) {
-            Body(pathAnalysisVisible)
-        }
-        try {
-            scene.render()
-        } finally {
-            scene.close()
+        onEventThread {
+            val scene = ImageComposeScene(width = widthPx, height = heightPx, density = Density(1f)) {
+                Body(pathAnalysisVisible)
+            }
+            try {
+                scene.render()
+            } finally {
+                scene.close()
+            }
         }
     }
 

build.gradle.kts

@@ -151,6 +151,13 @@ subprojects {
          */
         systemProperty("junit.jupiter.execution.timeout.default", "2m")
         systemProperty("junit.jupiter.execution.timeout.thread.mode.default", "SEPARATE_THREAD")
+        /*
+         * The timed-out thread's stack shows where a test waits, not who it waits for: the
+         * rare CI hang in SelectedStationMessageUiVisualRenderingTest blocks on a monitor
+         * that another thread holds. On a timeout JUnit prints all threads to the test's
+         * standard output, which lands in its XML report (the test-results artifact).
+         */
+        systemProperty("junit.jupiter.execution.timeout.threaddump.enabled", "true")
         // The default short format prints only the first frame of each cause, which for a
         // timed-out test is the line it hung in but not the call that blocked there.
         testLogging {