fix: close stale Quest XR sessions before reentry

app/src/main/java/com/droiddeck/launcher/QuestXrActivity.kt

@@ -2,9 +2,12 @@ package com.droiddeck.launcher
 
 import android.app.NativeActivity
 import android.os.Bundle
+import android.os.SystemClock
 import android.util.Log
+import android.widget.Toast
 import com.droiddeck.launcher.gpu.SteamVr
 import com.droiddeck.launcher.session.SessionService
+import com.droiddeck.launcher.session.SessionState
 import com.droiddeck.launcher.wayland.CompositorHost
 import com.droiddeck.launcher.wayland.WaylandCompositor
 
@@ -12,7 +15,9 @@ class QuestXrActivity : NativeActivity() {
     private var steamVrStarted = false
     @Volatile private var closing = false
     @Volatile private var steamVrStatus = SteamVr.Status.UNAVAILABLE
+    private var sessionId: String? = null
     override fun onCreate(savedInstanceState: Bundle?) {
+        sessionId = SessionState.sessionId
         SessionService.setXrActivityVisible(this, true)
         super.onCreate(savedInstanceState)
     }
@@ -36,16 +41,59 @@ class QuestXrActivity : NativeActivity() {
         if (!steamVrStarted) {
             steamVrStarted = true
             Thread({
-                if (!SteamVr.run(this, "start")) Log.e("DroidDeckXR", "SteamVR start failed")
-                while (!closing) {
-                    steamVrStatus = SteamVr.status(this)
-                    Thread.sleep(1000)
+                try {
+                    val started = synchronized(steamVrLock) {
+                        if (closing || !sessionAlive()) false else {
+                            steamVrOwner = this
+                            SteamVr.run(this, "start")
+                        }
+                    }
+                    if (!started) {
+                        leaveXr("SteamVR start failed", true)
+                        return@Thread
+                    }
+                    val startupDeadline = SystemClock.elapsedRealtime() + 30_000
+                    var lastRunning: Long? = null
+                    while (!closing) {
+                        if (!sessionAlive()) {
+                            leaveXr("Steam session ended", false)
+                            break
+                        }
+                        steamVrStatus = SteamVr.status(this)
+                        val now = SystemClock.elapsedRealtime()
+                        if (steamVrStatus == SteamVr.Status.RUNNING) lastRunning = now
+                        val deadline = lastRunning?.plus(5_000) ?: startupDeadline
+                        if (steamVrStatus != SteamVr.Status.RUNNING && now >= deadline) {
+                            leaveXr("SteamVR stopped or did not finish starting", true)
+                            break
+                        }
+                        Thread.sleep(1000)
+                    }
+                } finally {
+                    synchronized(steamVrLock) {
+                        // A retiring activity must not stop a replacement's SteamVR session.
+                        if (steamVrOwner === this) {
+                            if (sessionAlive()) SteamVr.run(this, "stop")
+                            steamVrOwner = null
+                        }
+                    }
                 }
-                SteamVr.run(this, "stop")
             }, "quest-steamvr-start").start()
         }
     }
 
+    private fun sessionAlive() = SessionState.running && !SessionState.stopRequested &&
+        sessionId != null && SessionState.sessionId == sessionId
+
+    private fun leaveXr(reason: String, failed: Boolean) {
+        Log.w("DroidDeckXR", reason)
+        closing = true
+        runOnUiThread {
+            if (failed) Toast.makeText(this, R.string.cardboard_steamvr_failed, Toast.LENGTH_LONG).show()
+            finish()
+        }
+    }
+
     fun onXrFrame(frameTimeNanos: Long) {
         WaylandCompositor.nativeVsync(frameTimeNanos)
     }
@@ -62,4 +110,9 @@ class QuestXrActivity : NativeActivity() {
         SessionService.setXrActivityVisible(this, false)
         super.onStop()
     }
+
+    companion object {
+        private val steamVrLock = Any()
+        private var steamVrOwner: QuestXrActivity? = null
+    }
 }

docs/quest.md

@@ -81,6 +81,10 @@ The panel compositor detaches before OpenXR starts displaying guest frames.
 Session suspension accounts for the immersive activity while the panel is hidden.
 Closing the immersive activity stops SteamVR. The panel remains available for
 returning to the normal Steam session.
+The immersive activity belongs to the Steam session that opened it. Ending that
+session closes XR; a failed startup or stopped SteamVR also returns to the panel
+with an error instead of leaving a black scene. Enter SteamVR can then start a
+fresh connection.
 
 With Steam already running, `python3 tools/test_quest_xr.py --serial SERIAL`
 launches the immersive activity and verifies advancing owned images, tracked