Android: Isolate game execution process

The launcher and GameActivity previously ran in the same process. Native
globals and library state therefore survived after returning to the
launcher, leaking static data from one game to the next game.

Run GameActivity in a private :game process and terminate it after SDL
shutdown completes, so every game starts with fresh native state. Keep
the launcher in the main process and refresh its game list from disk
when it resumes.

android/app/src/main/AndroidManifest.xml

@@ -78,6 +78,7 @@
 
         <activity android:name=".GameActivity"
             android:label="@string/app_name"
+            android:process=":game"
             android:alwaysRetainTaskState="true"
             android:configChanges="layoutDirection|locale|orientation|uiMode|screenLayout|screenSize|smallestScreenSize|keyboard|keyboardHidden|navigation"
             android:theme="@style/AppTheme"

android/app/src/main/java/io/github/kichikuou/xsystem35/GameActivity.kt

@@ -20,6 +20,7 @@ package io.github.kichikuou.xsystem35
 import android.app.AlertDialog
 import android.media.MediaPlayer
 import android.os.Bundle
+import android.os.Process
 import android.text.InputType
 import android.util.Log
 import android.widget.EditText
@@ -56,6 +57,18 @@ class GameActivity : SDLActivity() {
         midi.onActivityResume()
     }
 
+    override fun onDestroy() {
+        try {
+            super.onDestroy()
+        } finally {
+            try {
+                midi.release()
+            } finally {
+                Process.killProcess(Process.myPid())
+            }
+        }
+    }
+
     override fun getLibraries(): Array<String> {
         return arrayOf("SDL2", "xsystem35")
     }
@@ -75,7 +88,6 @@ class GameActivity : SDLActivity() {
                 return
         }
         File(gameRoot, Launcher.TITLE_FILE).writeText(str)
-        Launcher.updateGameList()
     }
 
     private fun textInputDialog(msg: String, oldVal: String, maxLen: Int, result: Array<String?>) {
@@ -154,11 +166,21 @@ class GameActivity : SDLActivity() {
 }
 
 private class MidiPlayer {
+    private enum class State {
+        STOPPED,
+        PLAYING,
+        PAUSED,
+        RELEASED,
+    }
+
     private val player = MediaPlayer()
-    private var playing = false
-    private var playerPaused = false
+    private var state = State.STOPPED
 
     fun start(path: String, loop: Boolean) {
+        if (state == State.RELEASED) {
+            return
+        }
+        state = State.STOPPED
         try {
             player.apply {
                 reset()
@@ -167,7 +189,7 @@ private class MidiPlayer {
                 prepare()
                 start()
             }
-            playing = true
+            state = State.PLAYING
         } catch (e: IOException) {
             Log.e("midiStart", "Cannot play midi", e)
             player.reset()
@@ -175,27 +197,41 @@ private class MidiPlayer {
     }
 
     fun stop() {
-        if (playing && player.isPlaying) {
-            player.stop()
-            playing = false
+        when (state) {
+            State.PLAYING, State.PAUSED -> {
+                player.stop()
+                state = State.STOPPED
+            }
+            State.STOPPED, State.RELEASED -> Unit
         }
     }
 
     fun currentPosition(): Int {
-        return if (playing) player.currentPosition else 0
+        return when (state) {
+            State.PLAYING, State.PAUSED -> player.currentPosition
+            State.STOPPED, State.RELEASED -> 0
+        }
     }
 
     fun onActivityStop() {
-        if (playing && player.isPlaying) {
+        if (state == State.PLAYING && player.isPlaying) {
             player.pause()
-            playerPaused = true
+            state = State.PAUSED
         }
     }
 
     fun onActivityResume() {
-        if (playerPaused) {
+        if (state == State.PAUSED) {
             player.start()
-            playerPaused = false
+            state = State.PLAYING
         }
     }
+
+    fun release() {
+        if (state == State.RELEASED) {
+            return
+        }
+        state = State.RELEASED
+        player.release()
+    }
 }

android/app/src/main/java/io/github/kichikuou/xsystem35/Launcher.kt

@@ -60,9 +60,6 @@ class Launcher private constructor(rootDir: File) {
             return gLauncher!!
         }
 
-        fun updateGameList() {
-            gLauncher?.updateGameList()
-        }
     }
 
     private val store = GameStore(rootDir)
@@ -160,7 +157,7 @@ class Launcher private constructor(rootDir: File) {
         observer?.onGameListChange()
     }
 
-    private fun updateGameList() {
+    fun refreshGameList() {
         store.updateGameList()
         observer?.onGameListChange()
     }

android/app/src/main/java/io/github/kichikuou/xsystem35/LauncherActivity.kt

@@ -68,6 +68,11 @@ class LauncherActivity : Activity(), LauncherObserver {
         super.onDestroy()
     }
 
+    override fun onResume() {
+        super.onResume()
+        launcher.refreshGameList()
+    }
+
     private fun onListItemClick(position: Int) {
         startGame(launcher.games[position].path, null)
     }