[vlc-devel] [PATCH v2 6/7] android: utils: setup Handler for SurfaceTextureListener

[Alexandre Janniaux]

SurfaceTextureListener is calling the frame callback from a Handler
object, which is by default either using the looper from the current
thread, or the main looper. Since there is no looper installed in the
vout thread, the main looper is used. However, the main looper is also
used by the windowing code whose events require the display_lock, so the
display code cannot use this looper.

Instead, we create a thread within the decoder device to attach a new
looper. For the SurfaceTexture, this is only possible since API 21 in
Android so anterior version will not be able to use any looper or
SurfaceTextureListener. It is possible to workaround this limitation by
creation the SurfaceTexture within the looper thread, but it needs
additional java wrapping code to implement the Handler behaviour in the
looper thread, so is deferred to a later patchset.
---
 modules/video_output/android/utils.c | 137 +++++++++++++++++++++++++++
 1 file changed, 137 insertions(+)

diff --git a/modules/video_output/android/utils.c b/modules/video_output/android/utils.c
index 44f3c94a77..c2e678bdb9 100644
--- a/modules/video_output/android/utils.c
+++ b/modules/video_output/android/utils.c
@@ -122,6 +122,25 @@ struct vlc_android_jfields
         jclass clazz;
         jmethodID init;
     } SurfaceTextureListener;
+    struct {
+        jclass clazz;
+        jmethodID init;
+    } Handler;
+    struct {
+        jclass clazz;
+        jmethodID prepare;
+        jmethodID quit;
+        jmethodID loop;
+        jmethodID myLooper;
+    } Looper;
+};
+
+struct vlc_android_handler_thread {
+    struct AWindowHandler *awh;
+    vlc_sem_t sem_ready;
+    jobject handler;
+    jobject looper;
+    vlc_thread_t thread;
 };
 
 struct AWindowHandler
@@ -155,6 +174,8 @@ struct AWindowHandler
         jfloatArray jtransform_mtx_array;
         jfloat *jtransform_mtx;
     } stex;
+
+    struct vlc_android_handler_thread handler;
 };
 
 #define JNI_CALL(what, obj, method, ...) \
@@ -718,6 +739,78 @@ const JNINativeMethod SurfaceTextureListener_jni_callbacks[] = {
     { "nativeOnFrameAvailable", "(Landroid/graphics/SurfaceTexture;)V",
         (void *) SurfaceTextureListener_onFrameAvailable },
 };
+
+static void *HandlerThread(void *data)
+{
+    struct vlc_android_handler_thread *handler = data;
+    JNIEnv *env = android_getEnvCommon(NULL, handler->awh->p_jvm, "AWH looper");
+    if (env == NULL)
+        return NULL;
+
+    (*env)->CallStaticVoidMethod(env,
+            handler->awh->jfields.Looper.clazz,
+            handler->awh->jfields.Looper.prepare);
+
+    jobject jlooper = (*env)->CallStaticObjectMethod(env,
+            handler->awh->jfields.Looper.clazz,
+            handler->awh->jfields.Looper.myLooper);
+    handler->looper = (*env)->NewGlobalRef(env, jlooper);
+    (*env)->DeleteLocalRef(env, jlooper);
+
+    jobject jhandler = (*env)->NewObject(env, handler->awh->jfields.Handler.clazz,
+            handler->awh->jfields.Handler.init, handler->looper);
+    handler->handler = (*env)->NewGlobalRef(env, jhandler);
+    (*env)->DeleteLocalRef(env, jhandler);
+
+    vlc_sem_post(&handler->sem_ready);
+
+    (*env)->CallStaticVoidMethod(env,
+            handler->awh->jfields.Looper.clazz,
+            handler->awh->jfields.Looper.loop);
+
+    return NULL;
+}
+
+static int CreateAndStartHandlerThread(
+        JNIEnv *env, AWindowHandler *awh,
+        struct vlc_android_handler_thread *handler)
+{
+    /* Preinit for error handling */
+    handler->looper = handler->handler = NULL;
+    handler->awh = awh;
+    vlc_sem_init(&handler->sem_ready, 0);
+
+    /* The looper is created in the target thread */
+    int ret = vlc_clone(&handler->thread, HandlerThread, handler, VLC_THREAD_PRIORITY_LOW);
+    if (ret != VLC_SUCCESS)
+        goto error;
+
+    /* Wait for handler and looper to be created or an error to happen. */
+    vlc_sem_wait(&handler->sem_ready);
+
+    if (handler->handler == NULL || handler->looper == NULL)
+        goto error;
+
+    return VLC_SUCCESS;
+
+error:
+    if (handler->handler != NULL)
+        (*env)->DeleteGlobalRef(env, handler->handler);
+    return VLC_EGENERIC;
+}
+
+static void StopAndJoinHandlerThread(
+        JNIEnv *env, AWindowHandler *awh,
+        struct vlc_android_handler_thread *handler)
+{
+    (*env)->CallVoidMethod(env, handler->looper, awh->jfields.Looper.quit);
+    // TODO check exception;
+    vlc_join(handler->thread, NULL);
+
+    (*env)->DeleteGlobalRef(env, handler->handler);
+    (*env)->DeleteGlobalRef(env, handler->looper);
+}
+
 static int
 InitJNIFields(JNIEnv *env, vlc_object_t *p_obj, jobject *jobj, AWindowHandler *awh)
 {
@@ -747,6 +840,11 @@ InitJNIFields(JNIEnv *env, vlc_object_t *p_obj, jobject *jobj, AWindowHandler *a
             env, awh->jfields.id_clazz.clazz, (str), (args)); \
     CHECK_EXCEPTION("GetMethodID("str")", critical); \
 } while( 0 )
+#define GET_STATIC_METHOD(id_clazz, id, str, args, critical) do { \
+    awh->jfields.id_clazz.id = (*env)->GetStaticMethodID(\
+            env, awh->jfields.id_clazz.clazz, (str), (args)); \
+    CHECK_EXCEPTION("GetMethodID("str")", critical); \
+} while( 0 )
 
     if (jobj)
     {
@@ -859,6 +957,21 @@ InitJNIFields(JNIEnv *env, vlc_object_t *p_obj, jobject *jobj, AWindowHandler *a
             msg_Err(p_obj, "RegisterNatives for SurfaceTextureListener failed");
             goto error;
         }
+
+        clazz = (*env)->FindClass(env, "android/os/Looper");
+        CHECK_EXCEPTION("android/os/Looper class", true);
+        awh->jfields.Looper.clazz = (*env)->NewGlobalRef(env, clazz);
+        (*env)->DeleteLocalRef(env, clazz);
+        GET_STATIC_METHOD(Looper, prepare, "prepare", "()V", true);
+        GET_STATIC_METHOD(Looper, myLooper, "myLooper", "()Landroid/os/Looper;", true);
+        GET_STATIC_METHOD(Looper, loop, "loop", "()V", true);
+        GET_METHOD(Looper, quit, "quit", "()V", true);
+
+        clazz = (*env)->FindClass(env, "android/os/Handler");
+        CHECK_EXCEPTION("android/os/Handler class", true);
+        awh->jfields.Handler.clazz = (*env)->NewGlobalRef(env, clazz);
+        (*env)->DeleteLocalRef(env, clazz);
+        GET_METHOD(Handler, init, "<init>", "(Landroid/os/Looper;)V", true);
     }
 
 #undef GET_METHOD
@@ -874,6 +987,10 @@ end:
 
 error:
     i_init_state = 0;
+    if (awh->jfields.Handler.clazz)
+        (*env)->DeleteGlobalRef(env, awh->jfields.Handler.clazz);
+    if (awh->jfields.Looper.clazz)
+        (*env)->DeleteGlobalRef(env, awh->jfields.Looper.clazz);
     if (awh->jfields.SurfaceTextureListener.clazz)
         (*env)->DeleteGlobalRef(env, awh->jfields.SurfaceTextureListener.clazz);
     if (awh->jfields.SurfaceTexture.clazz)
@@ -1004,6 +1121,13 @@ AWindowHandler_new(vlc_object_t *obj, vout_window_t *wnd, awh_events_t *p_events
         free(vout_modules);
     }
 
+#ifdef __ANDROID_API__ < 21
+    if (android_get_device_api_level() >= 21)
+#endif
+    {
+        CreateAndStartHandlerThread(p_env, p_awh, &p_awh->handler);
+    }
+
     return p_awh;
 }
 
@@ -1031,8 +1155,21 @@ AWindowHandler_destroy(AWindowHandler *p_awh)
 {
     JNIEnv *p_env = AWindowHandler_getEnv(p_awh);
 
+#ifdef __ANDROID_API__ < 21
+    if (android_get_device_api_level() >= 21)
+#endif
+    {
+        StopAndJoinHandlerThread(p_env, p_awh, &p_awh->handler);
+    }
+
     if (p_env)
     {
+        if (p_awh->jfields.Handler.clazz)
+            (*p_env)->DeleteGlobalRef(p_env, p_awh->jfields.Handler.clazz);
+
+        if (p_awh->jfields.Looper.clazz)
+            (*p_env)->DeleteGlobalRef(p_env, p_awh->jfields.Looper.clazz);
+
         if (p_awh->jfields.SurfaceTextureListener.clazz)
             (*p_env)->DeleteGlobalRef(p_env, p_awh->jfields.SurfaceTextureListener.clazz);
 
-- 
2.30.1