Remove `createSDLMainRunnable()` in favour of `main()` to fix multiple issues when providing custom main/runnable code (#10434)

This allows managed applications (eg. Java, C#) to override main() to their liking.

android-project/app/src/main/java/org/libsdl/app/SDLActivity.java

@@ -247,12 +247,19 @@ public class SDLActivity extends Activity implements View.OnSystemUiVisibilityCh
     }
 
     /**
-     * This method creates a Runnable which invokes SDL_main. The default implementation
-     * uses the getMainSharedObject() and getMainFunction() methods to invoke native
-     * code from the specified shared library.
+     * The application entry point, called on a dedicated thread (SDLThread).
+     * The default implementation uses the getMainSharedObject() and getMainFunction() methods
+     * to invoke native code from the specified shared library.
+     * It can be overridden by derived classes.
      */
-    protected Runnable createSDLMainRunnable() {
-        return new SDLMain();
+    protected void main() {
+        String library = SDLActivity.mSingleton.getMainSharedObject();
+        String function = SDLActivity.mSingleton.getMainFunction();
+        String[] arguments = SDLActivity.mSingleton.getArguments();
+
+        Log.v("SDL", "Running main function " + function + " from library " + library);
+        SDLActivity.nativeRunMain(library, function, arguments);
+        Log.v("SDL", "Finished main function");
     }
 
     /**
@@ -838,7 +845,7 @@ public class SDLActivity extends Activity implements View.OnSystemUiVisibilityCh
                     // Start up the C app thread and enable sensor input for the first time
                     // FIXME: Why aren't we enabling sensor input at start?
 
-                    mSDLThread = new Thread(SDLActivity.mSingleton.createSDLMainRunnable(), "SDLThread");
+                    mSDLThread = new Thread(new SDLMain(), "SDLThread");
                     mSurface.enableSensor(Sensor.TYPE_ACCELEROMETER, true);
                     mSDLThread.start();
 
@@ -1032,6 +1039,8 @@ public class SDLActivity extends Activity implements View.OnSystemUiVisibilityCh
     // C functions we call
     public static native String nativeGetVersion();
     public static native int nativeSetupJNI();
+    public static native void nativeInitMainThread();
+    public static native void nativeCleanupMainThread();
     public static native int nativeRunMain(String library, String function, Object arguments);
     public static native void nativeLowMemory();
     public static native void nativeSendQuit();
@@ -2102,10 +2111,7 @@ public class SDLActivity extends Activity implements View.OnSystemUiVisibilityCh
 class SDLMain implements Runnable {
     @Override
     public void run() {
-        // Runs SDL_main()
-        String library = SDLActivity.mSingleton.getMainSharedObject();
-        String function = SDLActivity.mSingleton.getMainFunction();
-        String[] arguments = SDLActivity.mSingleton.getArguments();
+        // Runs SDLActivity.main()
 
         try {
             android.os.Process.setThreadPriority(android.os.Process.THREAD_PRIORITY_DISPLAY);
@@ -2113,11 +2119,9 @@ class SDLMain implements Runnable {
             Log.v("SDL", "modify thread properties failed " + e.toString());
         }
 
-        Log.v("SDL", "Running main function " + function + " from library " + library);
-
-        SDLActivity.nativeRunMain(library, function, arguments);
-
-        Log.v("SDL", "Finished main function");
+        SDLActivity.nativeInitMainThread();
+        SDLActivity.mSingleton.main();
+        SDLActivity.nativeCleanupMainThread();
 
         if (SDLActivity.mSingleton != null && !SDLActivity.mSingleton.isFinishing()) {
             // Let's finish the Activity

src/core/android/SDL_android.c

@@ -64,6 +64,12 @@ JNIEXPORT jstring JNICALL SDL_JAVA_INTERFACE(nativeGetVersion)(
 JNIEXPORT void JNICALL SDL_JAVA_INTERFACE(nativeSetupJNI)(
     JNIEnv *env, jclass cls);
 
+JNIEXPORT void JNICALL SDL_JAVA_INTERFACE(nativeInitSDLThread)(
+    JNIEnv *env, jclass cls);
+
+JNIEXPORT void JNICALL SDL_JAVA_INTERFACE(nativeCleanupSDLThread)(
+    JNIEnv *env, jclass cls);
+
 JNIEXPORT int JNICALL SDL_JAVA_INTERFACE(nativeRunMain)(
     JNIEnv *env, jclass cls,
     jstring library, jstring function, jobject array);
@@ -188,6 +194,8 @@ JNIEXPORT void JNICALL SDL_JAVA_INTERFACE(onNativeFileDialog)(
 static JNINativeMethod SDLActivity_tab[] = {
     { "nativeGetVersion", "()Ljava/lang/String;", SDL_JAVA_INTERFACE(nativeGetVersion) },
     { "nativeSetupJNI", "()I", SDL_JAVA_INTERFACE(nativeSetupJNI) },
+    { "nativeInitSDLThread", "()V", SDL_JAVA_INTERFACE(nativeInitSDLThread) },
+    { "nativeCleanupSDLThread", "()V", SDL_JAVA_INTERFACE(nativeCleanupSDLThread) },
     { "nativeRunMain", "(Ljava/lang/String;Ljava/lang/String;Ljava/lang/Object;)I", SDL_JAVA_INTERFACE(nativeRunMain) },
     { "onNativeDropFile", "(Ljava/lang/String;)V", SDL_JAVA_INTERFACE(onNativeDropFile) },
     { "nativeSetScreenResolution", "(IIIIFF)V", SDL_JAVA_INTERFACE(nativeSetScreenResolution) },
@@ -764,14 +772,10 @@ JNIEXPORT jboolean JNICALL SDL_JAVA_INTERFACE(nativeAllowRecreateActivity)(
     return SDL_AtomicGet(&bAllowRecreateActivity);
 }
 
-/* Start up the SDL app */
-JNIEXPORT int JNICALL SDL_JAVA_INTERFACE(nativeRunMain)(JNIEnv *env, jclass cls, jstring library, jstring function, jobject array)
+JNIEXPORT void JNICALL SDL_JAVA_INTERFACE(nativeInitSDLThread)(
+    JNIEnv *env, jclass jcls)
 {
-    int status = -1;
-    const char *library_file;
-    void *library_handle;
-
-    __android_log_print(ANDROID_LOG_VERBOSE, "SDL", "nativeRunMain() %d time", run_count);
+    __android_log_print(ANDROID_LOG_VERBOSE, "SDL", "nativeInitSDLThread() %d time", run_count);
     if (run_count == 1) {
         SDL_AddHintCallback(SDL_HINT_ANDROID_ALLOW_RECREATE_ACTIVITY, SDL_AllowRecreateActivityChanged, NULL);
     }
@@ -779,6 +783,22 @@ JNIEXPORT int JNICALL SDL_JAVA_INTERFACE(nativeRunMain)(JNIEnv *env, jclass cls,
 
     /* Save JNIEnv of SDLThread */
     Android_JNI_SetEnv(env);
+}
+
+JNIEXPORT void JNICALL SDL_JAVA_INTERFACE(nativeCleanupSDLThread)(
+    JNIEnv *env, jclass jcls)
+{
+    /* This is a Java thread, it doesn't need to be Detached from the JVM.
+     * Set to mThreadKey value to NULL not to call pthread_create destructor 'Android_JNI_ThreadDestroyed' */
+    Android_JNI_SetEnv(NULL);
+}
+
+/* Start up the SDL app */
+JNIEXPORT int JNICALL SDL_JAVA_INTERFACE(nativeRunMain)(JNIEnv *env, jclass cls, jstring library, jstring function, jobject array)
+{
+    int status = -1;
+    const char *library_file;
+    void *library_handle;
 
     library_file = (*env)->GetStringUTFChars(env, library, NULL);
     library_handle = dlopen(library_file, RTLD_GLOBAL);
@@ -853,10 +873,6 @@ JNIEXPORT int JNICALL SDL_JAVA_INTERFACE(nativeRunMain)(JNIEnv *env, jclass cls,
     }
     (*env)->ReleaseStringUTFChars(env, library, library_file);
 
-    /* This is a Java thread, it doesn't need to be Detached from the JVM.
-     * Set to mThreadKey value to NULL not to call pthread_create destructor 'Android_JNI_ThreadDestroyed' */
-    Android_JNI_SetEnv(NULL);
-
     /* Do not issue an exit or the whole application will terminate instead of just the SDL thread */
     /* exit(status); */