MessageQueue: integrate with glib main loop

Adds a special treatment for the main Looper to not block in java code,
but instead return to glib managed thread loop. Timeouts in the mainloop
are now handled using g_timeout_add_full().

Also defer Activity construction, so that every thing is set up properly
when the constructor runs.

src/api-impl-jni/android_os_MessageQueue.c

@@ -5,6 +5,10 @@
 #include <stdint.h>
 #include <stdlib.h>
 
+#include <glib.h>
+
+#include "generated_headers/android_os_MessageQueue.h"
+
 /* TODO put these in a header */
 typedef void ALooper;
 ALooper * ALooper_prepare(void);
@@ -15,14 +19,30 @@ int ALooper_pollOnce(int timeoutMillis, int* outFd, int* outEvents, void** outDa
 struct native_message_queue {
 	ALooper *looper;
 	bool in_callback;
+	bool is_main_thread;
 };
 
+static GThread *main_thread_id;
+
+void prepare_main_looper(JNIEnv* env) {
+	main_thread_id = g_thread_self();
+
+	jclass class = (*env)->FindClass(env, "android/os/Looper");
+	(*env)->CallStaticVoidMethod(env, class, _STATIC_METHOD(class, "prepareMainLooper", "()V"));
+	if((*env)->ExceptionCheck(env))
+		(*env)->ExceptionDescribe(env);
+	(*env)->CallStaticVoidMethod(env, class, _STATIC_METHOD(class, "loop", "()V"));
+	if((*env)->ExceptionCheck(env))
+		(*env)->ExceptionDescribe(env);
+}
+
 JNIEXPORT jlong JNICALL Java_android_os_MessageQueue_nativeInit(JNIEnv *env, jclass this)
 {
 	struct native_message_queue *message_queue = malloc(sizeof(struct native_message_queue));
 
 	message_queue->in_callback = false;
 	message_queue->looper = ALooper_prepare();
+	message_queue->is_main_thread = g_thread_self() == main_thread_id;
 
 	return _INTPTR(message_queue);
 }
@@ -34,10 +54,37 @@ JNIEXPORT void JNICALL Java_android_os_MessageQueue_nativeDestroy(JNIEnv *env, j
 	free(message_queue);
 }
 
-JNIEXPORT void JNICALL Java_android_os_MessageQueue_nativePollOnce(JNIEnv *env, jclass this, jlong ptr, jint timeout_millis)
+/**
+ * callback to execute java handlers on glib managed thread loops
+ */
+static gboolean glib_context_callback(gpointer user_data) {
+	JavaVM *jvm = user_data;
+	JNIEnv *env;
+	(*jvm)->GetEnv(jvm, (void**)&env, JNI_VERSION_1_6);
+
+	jclass class = (*env)->FindClass(env, "android/os/Looper");
+	(*env)->CallStaticVoidMethod(env, class, _STATIC_METHOD(class, "loop", "()V"));
+	if((*env)->ExceptionCheck(env))
+		(*env)->ExceptionDescribe(env);
+
+	return FALSE;  // cancel timer
+}
+
+JNIEXPORT jboolean JNICALL Java_android_os_MessageQueue_nativePollOnce(JNIEnv *env, jclass this, jlong ptr, jint timeout_millis)
 {
 	struct native_message_queue *message_queue = _PTR(ptr);
 
+	if (message_queue->is_main_thread) {  // thread loop is managed by glib
+		JavaVM *jvm;
+		(*env)->GetJavaVM(env, &jvm);
+		if (timeout_millis) {
+			g_timeout_add_full(0, timeout_millis, glib_context_callback, jvm, NULL);
+			return true;  // indicate that java side should return to block in glib managed loop
+		} else {
+			return false;
+		}
+	}
+
 //	printf("Java_android_os_MessageQueue_nativePollOnce: entry (timeout: %d)\n", timeout_millis);
 	message_queue->in_callback = true;
 	ALooper_pollOnce(timeout_millis, NULL, NULL, NULL);
@@ -45,12 +92,20 @@ JNIEXPORT void JNICALL Java_android_os_MessageQueue_nativePollOnce(JNIEnv *env,
 //	printf("Java_android_os_MessageQueue_nativePollOnce: exit\n");
 
 	/* TODO: what's with the exception stuff */
+	return false;
 }
 
 JNIEXPORT void JNICALL Java_android_os_MessageQueue_nativeWake(JNIEnv *env, jclass this, jlong ptr)
 {
 	struct native_message_queue *message_queue = _PTR(ptr);
 
+	if (message_queue->is_main_thread) {  // thread loop is managed by glib
+		JavaVM *jvm;
+		(*env)->GetJavaVM(env, &jvm);
+		g_idle_add_full(0, glib_context_callback, jvm, NULL);
+		return;
+	}
+
 	ALooper_wake(message_queue->looper);
 }
 

src/api-impl-jni/generated_headers/android_os_MessageQueue.h

@@ -26,9 +26,9 @@ JNIEXPORT void JNICALL Java_android_os_MessageQueue_nativeDestroy
 /*
  * Class:     android_os_MessageQueue
  * Method:    nativePollOnce
- * Signature: (JI)V
+ * Signature: (JI)Z
  */
-JNIEXPORT void JNICALL Java_android_os_MessageQueue_nativePollOnce
+JNIEXPORT jboolean JNICALL Java_android_os_MessageQueue_nativePollOnce
   (JNIEnv *, jclass, jlong, jint);
 
 /*

src/api-impl-jni/util.c

@@ -39,15 +39,11 @@ void _gdb_get_java_stack_trace(void)
 	(*env)->ExceptionDescribe(env);
 }
 
-void set_up_handle_cache(JNIEnv *env, char *apk_main_activity_class)
+void set_up_handle_cache(JNIEnv *env)
 {
 	(*env)->GetJavaVM(env, &jvm);
 
 	handle_cache.apk_main_activity.class = _REF((*env)->FindClass(env, "android/app/Activity"));
-	if((*env)->ExceptionCheck(env))
-		(*env)->ExceptionDescribe(env);
-	jmethodID createMainActivity = _STATIC_METHOD(handle_cache.apk_main_activity.class, "createMainActivity", "(Ljava/lang/String;)Landroid/app/Activity;");
-	handle_cache.apk_main_activity.object = _REF((*env)->CallStaticObjectMethod(env, handle_cache.apk_main_activity.class, createMainActivity, _JSTRING(apk_main_activity_class)));
 	if((*env)->ExceptionCheck(env))
 		(*env)->ExceptionDescribe(env);
 	handle_cache.apk_main_activity.onCreate = _METHOD(handle_cache.apk_main_activity.class, "onCreate", "(Landroid/os/Bundle;)V");
@@ -55,7 +51,6 @@ void set_up_handle_cache(JNIEnv *env, char *apk_main_activity_class)
 	handle_cache.apk_main_activity.onWindowFocusChanged = _METHOD(handle_cache.apk_main_activity.class, "onWindowFocusChanged", "(Z)V");
 	handle_cache.apk_main_activity.onResume = _METHOD(handle_cache.apk_main_activity.class, "onResume", "()V");
 	handle_cache.apk_main_activity.onDestroy = _METHOD(handle_cache.apk_main_activity.class, "onDestroy", "()V");
-	handle_cache.apk_main_activity.set_window = _METHOD((*env)->FindClass(env, "android/app/Activity"), "set_window", "(J)V");
 
 	handle_cache.attribute_set.class = _REF((*env)->FindClass(env, "android/util/AttributeSet"));
 	if((*env)->ExceptionCheck(env))

src/api-impl-jni/util.h

@@ -14,7 +14,6 @@ struct handle_cache {
 		jmethodID onResume;
 		jmethodID onWindowFocusChanged;
 		jmethodID onDestroy;
-		jmethodID set_window;
 	} apk_main_activity;
 	struct {
 		jclass class;
@@ -81,7 +80,9 @@ extern struct handle_cache handle_cache;
 
 const char * attribute_set_get_string(JNIEnv *env, jobject attrs, char *attribute, char *schema);
 int attribute_set_get_int(JNIEnv *env, jobject attrs, char *attribute, char *schema, int default_value);
-void set_up_handle_cache(JNIEnv *env, char *apk_main_activity_class);
+void set_up_handle_cache(JNIEnv *env);
 void extract_from_apk(const char *path, const char *target);
 
+void prepare_main_looper(JNIEnv* env);
+
 #endif

src/api-impl/android/app/Activity.java

@@ -36,7 +36,7 @@ public class Activity extends Context {
 	 * @param className  class name of activity or null
 	 * @return  instance of main activity class
 	 */
-	private static Activity createMainActivity(String className) throws ClassNotFoundException, NoSuchMethodException, SecurityException, InstantiationException, IllegalAccessException, IllegalArgumentException, InvocationTargetException, IOException {
+	private static Activity createMainActivity(String className, long native_window) throws ClassNotFoundException, NoSuchMethodException, SecurityException, InstantiationException, IllegalAccessException, IllegalArgumentException, InvocationTargetException, IOException {
 		if (className == null) {
 			InputStream inStream = ClassLoader.getSystemClassLoader().getResourceAsStream("AndroidManifest.xml");
 			AndroidManifestBlock block = AndroidManifestBlock.load(inStream);
@@ -49,11 +49,9 @@ public class Activity extends Context {
 		}
 		Class<? extends Activity> cls = Class.forName(className).asSubclass(Activity.class);
 		Constructor<? extends Activity> constructor = cls.getConstructor();
-		return constructor.newInstance();
-	}
-
-	protected void set_window(long native_window) {
-		window.native_window = native_window;
+		Activity activity = constructor.newInstance();
+		activity.window.native_window = native_window;
+		return activity;
 	}
 
 	public Activity() {
@@ -104,12 +102,6 @@ public class Activity extends Context {
 	protected void onCreate(Bundle savedInstanceState) {
 		System.out.println("- onCreate - yay!");
 
-		/* TODO: this probably belongs elsewhere, but this is our entry point for better or worse */
-		Looper looper = Looper.myLooper();
-		if(looper == null) {
-			Looper.prepareMainLooper();
-		}
-
 		return;
 	}
 

src/api-impl/android/os/MessageQueue.java

@@ -50,7 +50,7 @@ public final class MessageQueue {
 
 	private native static long nativeInit();
 	private native static void nativeDestroy(long ptr);
-	private native static void nativePollOnce(long ptr, int timeoutMillis);
+	private native static boolean nativePollOnce(long ptr, int timeoutMillis);
 	private native static void nativeWake(long ptr);
 	private native static boolean nativeIsIdling(long ptr);
 
@@ -134,7 +134,9 @@ public final class MessageQueue {
 
 			// We can assume mPtr != 0 because the loop is obviously still running.
 			// The looper will not call this method after the loop quits.
-			nativePollOnce(mPtr, nextPollTimeoutMillis);
+			if (nativePollOnce(mPtr, nextPollTimeoutMillis)) {
+				return null;  // thread is managed by glib, so return instead of blocking
+			}
 
 			synchronized (this) {
 				// Try to retrieve the next message.  Return if found.

src/main-executable/main.c

@@ -315,7 +315,7 @@ static void open(GtkApplication *app, GFile** files, gint nfiles, const gchar* h
 
 	free(app_lib_dir);
 
-	set_up_handle_cache(env, d->apk_main_activity_class);
+	set_up_handle_cache(env);
 
 	jclass display_class = (*env)->FindClass(env, "android/view/Display");
 	_SET_STATIC_INT_FIELD(display_class, "window_width", d->window_width);
@@ -329,9 +329,6 @@ static void open(GtkApplication *app, GFile** files, gint nfiles, const gchar* h
 	FIXME__HEIGHT = d->window_height;
 
 	window = gtk_application_window_new(app);
-	(*env)->CallVoidMethod(env, handle_cache.apk_main_activity.object, handle_cache.apk_main_activity.set_window, _INTPTR(window));
-	if((*env)->ExceptionCheck(env))
-		(*env)->ExceptionDescribe(env);
 
 	gtk_window_set_title(GTK_WINDOW(window), "com.example.demo_application");
 	gtk_window_set_default_size(GTK_WINDOW(window), d->window_width, d->window_height);
@@ -364,6 +361,15 @@ static void open(GtkApplication *app, GFile** files, gint nfiles, const gchar* h
 	/* extract native libraries from apk*/
 	extract_from_apk("lib/" NATIVE_ARCH "/", "lib/");
 
+	prepare_main_looper(env);
+
+	// construct main Activity
+	handle_cache.apk_main_activity.object = _REF((*env)->CallStaticObjectMethod(env, handle_cache.apk_main_activity.class,
+		_STATIC_METHOD(handle_cache.apk_main_activity.class, "createMainActivity", "(Ljava/lang/String;J)Landroid/app/Activity;"),
+		_JSTRING(d->apk_main_activity_class), _INTPTR(window)));
+	if((*env)->ExceptionCheck(env))
+		(*env)->ExceptionDescribe(env);
+
 	/* -- run the main activity's onCreate -- */
 
 	(*env)->CallVoidMethod(env, handle_cache.apk_main_activity.object, handle_cache.apk_main_activity.onCreate, NULL);