test: fix the CI hang in the Compose rendering tests (#157)

* test: print all threads when a test times out

The rare CI hang in SelectedStationMessageUiVisualRenderingTest blocks on a
monitor in SnapshotStateObserver.observeReads (line 643 is the monitorenter
of observedScopeMapsLock in Compose 1.8.2). The timed-out thread's stack
shows where it waits but not which thread holds the lock. With the thread
dump enabled, JUnit prints every thread to the test's standard output, which
ends up in the XML report of the test-results artifact.

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

* 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

@@ -55,6 +55,7 @@ class CompactControlsVisualRenderingTest(@param:TempDir private val tempDir: Pat
         }
         val filters = StationFilterState()
 
+        return onEventThread {
             val scene = ImageComposeScene(width = 1366, height = 380, density = Density(scale)) {
                 Kst4ContestTheme(darkMode = darkMode, baseFontSizeSp = 12f) {
                     Surface(
@@ -90,12 +91,13 @@ class CompactControlsVisualRenderingTest(@param:TempDir private val tempDir: Pat
                     }
                 }
             }
-        return try {
+            try {
                 scene.render().encodeToData()!!.bytes
             } finally {
                 scene.close()
             }
         }
+    }
 
     private class RenderActions(private val preferences: ChatPreferences) : ChatInputActions {
         override fun panelSelection(): ChatMember? = null

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

@@ -84,6 +84,7 @@ class SelectedStationMessageUiVisualRenderingTest {
             replaceRows(listOf(message(member("DL1ABC", 2), member("DL2XYZ", 2), "pse sked")))
         }
 
+        return onEventThread {
             val scene = ImageComposeScene(width = 1366, height = windowHeight, density = Density(scale)) {
                 Kst4ContestTheme(darkMode = darkMode, baseFontSizeSp = 12f) {
                     Surface(
@@ -111,12 +112,13 @@ class SelectedStationMessageUiVisualRenderingTest {
                 }
             }
 
-        return try {
+            try {
                 scene.render().encodeToData()!!.bytes
             } finally {
                 scene.close()
             }
         }
+    }
 
     private fun messageTable() = DataTableState(
         columns = listOf(

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

@@ -87,6 +87,7 @@ class StationWorkspaceVisualRenderingTest {
             RowKeys.byReference<ChatMessage>(),
         )
 
+        return onEventThread {
             val scene = ImageComposeScene(
                 width = 1366,
                 height = scenario.height,
@@ -139,12 +140,13 @@ class StationWorkspaceVisualRenderingTest {
                 }
             }
 
-        return try {
+            try {
                 scene.render().encodeToData()!!.bytes
             } finally {
                 scene.close()
             }
         }
+    }
 
     private fun member(callSign: String, category: Int) = ChatMember().apply {
         this.callSign = callSign

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

@@ -32,6 +32,7 @@ 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
+        onEventThread {
             val scene = ImageComposeScene(width = 360, height = 500, density = Density(1f)) {
                 TopPriorityCandidatesWindow.CandidateListForTest(twoCandidates) {
                     picked = it.displayCallSign
@@ -44,6 +45,7 @@ class TopPriorityCandidatesWindowTest {
             } finally {
                 scene.close()
             }
+        }
         return picked
     }
 
@@ -78,6 +80,7 @@ class TopPriorityCandidatesWindowTest {
     @Test
     fun `the list renders with candidates and without`() {
         listOf(emptyList(), twoCandidates).forEach { ranking ->
+            onEventThread {
                 val scene = ImageComposeScene(width = 360, height = 500, density = Density(1f)) {
                     TopPriorityCandidatesWindow.CandidateListForTest(ranking) { }
                 }
@@ -88,6 +91,7 @@ class TopPriorityCandidatesWindowTest {
                 }
             }
         }
+    }
 
     /**
      * A double click picks the candidate under it, and picks the right one.

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
@@ -71,6 +72,7 @@ class ComposeStationMapDrawingTest {
         workedGrossFields: Set<String> = emptySet(),
         darkMode: Boolean = true,
     ): BufferedImage {
+        return onEventThread {
             val scene = ImageComposeScene(canvasWidth, canvasHeight, Density(1f)) {
                 ComposeStationMap(
                     markers = markers,
@@ -89,11 +91,12 @@ class ComposeStationMapDrawingTest {
                 )
             }
             try {
-            return ImageIO.read(ByteArrayInputStream(scene.render().encodeToData()!!.bytes))
+                ImageIO.read(ByteArrayInputStream(scene.render().encodeToData()!!.bytes))
             } finally {
                 scene.close()
             }
         }
+    }
 
     private fun countColour(image: BufferedImage, rgb: Int): Int {
         var count = 0

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
@@ -33,6 +34,7 @@ class ComposeStationMapLayoutTest {
     )
 
     private fun renderAt(widthPx: Int, heightPx: Int, zoom: Float) {
+        onEventThread {
             val scene = ImageComposeScene(
                 width = widthPx,
                 height = heightPx,
@@ -59,6 +61,7 @@ class ComposeStationMapLayoutTest {
                 scene.close()
             }
         }
+    }
 
     @Test
     fun `renders at a normal window size and integer zoom`() = renderAt(900, 600, 6f)

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
 
@@ -25,6 +26,7 @@ class PathAnalysisDetailsLayoutTest {
     private val narrowWidthPx = 120
 
     private fun renderAt(widthPx: Int, result: PathAnalysisResult?) {
+        onEventThread {
             val scene = ImageComposeScene(
                 width = widthPx,
                 height = 600,
@@ -42,6 +44,7 @@ class PathAnalysisDetailsLayoutTest {
                 scene.close()
             }
         }
+    }
 
     @Test
     fun `renders when the column is narrower than the assessment label`() {

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
@@ -31,6 +32,7 @@ class PathAnalysisDetailsWidthTest {
     private val assessmentBackground = 0x33383E
 
     private fun render(paneWidthPx: Int, heightPx: Int = 600): BufferedImage {
+        return onEventThread {
             val scene = ImageComposeScene(width = paneWidthPx, height = heightPx, density = Density(1f)) {
                 PathAnalysisDetails(
                     result = PathAnalysisResult.loading("JO50JP", "JN24JB", "F5JMI"),
@@ -40,11 +42,12 @@ class PathAnalysisDetailsWidthTest {
             }
             try {
                 val png = scene.render().encodeToData()!!.bytes
-            return ImageIO.read(ByteArrayInputStream(png))
+                ImageIO.read(ByteArrayInputStream(png))
             } finally {
                 scene.close()
             }
         }
+    }
 
     /** The smallest x at which the assessment background appears, or -1 when it does not. */
     private fun assessmentLeftEdge(image: BufferedImage): Int {

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
 
 /**
@@ -18,6 +19,7 @@ import org.junit.jupiter.api.Test
 class PathProfileChartLayoutTest {
 
     private fun renderAt(widthPx: Int, heightPx: Int) {
+        onEventThread {
             val scene = ImageComposeScene(
                 width = widthPx,
                 height = heightPx,
@@ -31,6 +33,7 @@ class PathProfileChartLayoutTest {
                 scene.close()
             }
         }
+    }
 
     @Test
     fun `renders at the height the window gives it`() = renderAt(800, 210)

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
@@ -88,6 +89,7 @@ class StationMapBodyLayoutTest {
     }
 
     private fun renderAt(widthPx: Int, heightPx: Int, pathAnalysisVisible: Boolean = true) {
+        onEventThread {
             val scene = ImageComposeScene(width = widthPx, height = heightPx, density = Density(1f)) {
                 Body(pathAnalysisVisible)
             }
@@ -97,6 +99,7 @@ class StationMapBodyLayoutTest {
                 scene.close()
             }
         }
+    }
 
     @Test
     fun `renders at the window's minimum size`() = renderAt(900, 600)

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 {