Modernize Thread

- Based on C++11's `thread` and `thread_local`
- No more need to allocate-deallocate or check for null
- No pointer anymore, just a member variable
- Platform-specific implementations no longer needed (except for the few cases of non-portable functions)
- Simpler for `NO_THREADS`
- Thread ids are now the same across platforms (main is 1; others follow)

9 files changed, 26 insertions, 38 deletions

diff --git a/modules/cvtt/image_compress_cvtt.cpp b/modules/cvtt/image_compress_cvtt.cpp
index 6661dbbb0b..43faa52218 100644
--- a/modules/cvtt/image_compress_cvtt.cpp
+++ b/modules/cvtt/image_compress_cvtt.cpp
@@ -267,12 +267,13 @@ void image_compress_cvtt(Image *p_image, float p_lossy_quality, Image::UsedChann
 		job_queue.num_tasks = static_cast<uint32_t>(tasks.size());
 
 		for (int i = 0; i < num_job_threads; i++) {
-			threads_wb[i] = Thread::create(_digest_job_queue, &job_queue);
+			threads_wb[i] = memnew(Thread);
+			threads_wb[i]->start(_digest_job_queue, &job_queue);
 		}
 		_digest_job_queue(&job_queue);
 
 		for (int i = 0; i < num_job_threads; i++) {
-			Thread::wait_to_finish(threads_wb[i]);
+			threads_wb[i]->wait_to_finish();
 			memdelete(threads_wb[i]);
 		}
 	}
diff --git a/modules/gdnative/android/android_gdn.cpp b/modules/gdnative/android/android_gdn.cpp
index a48e51a390..fe3b3e7e12 100644
--- a/modules/gdnative/android/android_gdn.cpp
+++ b/modules/gdnative/android/android_gdn.cpp
@@ -48,7 +48,7 @@ extern "C" {
 
 JNIEnv *GDAPI godot_android_get_env() {
 #ifdef __ANDROID__
-	return ThreadAndroid::get_env();
+	return get_jni_env();
 #else
 	return nullptr;
 #endif
diff --git a/modules/gdscript/language_server/gdscript_language_server.cpp b/modules/gdscript/language_server/gdscript_language_server.cpp
index aac9cb7fd7..12ed56a568 100644
--- a/modules/gdscript/language_server/gdscript_language_server.cpp
+++ b/modules/gdscript/language_server/gdscript_language_server.cpp
@@ -36,7 +36,6 @@
 #include "editor/editor_node.h"
 
 GDScriptLanguageServer::GDScriptLanguageServer() {
-	thread = nullptr;
 	thread_running = false;
 	started = false;
 
@@ -87,9 +86,8 @@ void GDScriptLanguageServer::start() {
 	if (protocol.start(port, IP_Address("127.0.0.1")) == OK) {
 		EditorNode::get_log()->add_message("--- GDScript language server started ---", EditorLog::MSG_TYPE_EDITOR);
 		if (use_thread) {
-			ERR_FAIL_COND(thread != nullptr);
 			thread_running = true;
-			thread = Thread::create(GDScriptLanguageServer::thread_main, this);
+			thread.start(GDScriptLanguageServer::thread_main, this);
 		}
 		set_process_internal(!use_thread);
 		started = true;
@@ -98,11 +96,9 @@ void GDScriptLanguageServer::start() {
 
 void GDScriptLanguageServer::stop() {
 	if (use_thread) {
-		ERR_FAIL_COND(nullptr == thread);
+		ERR_FAIL_COND(!thread.is_started());
 		thread_running = false;
-		Thread::wait_to_finish(thread);
-		memdelete(thread);
-		thread = nullptr;
+		thread.wait_to_finish();
 	}
 	protocol.stop();
 	started = false;
diff --git a/modules/gdscript/language_server/gdscript_language_server.h b/modules/gdscript/language_server/gdscript_language_server.h
index 218f42199e..7b7837a463 100644
--- a/modules/gdscript/language_server/gdscript_language_server.h
+++ b/modules/gdscript/language_server/gdscript_language_server.h
@@ -40,7 +40,7 @@ class GDScriptLanguageServer : public EditorPlugin {
 
 	GDScriptLanguageProtocol protocol;
 
-	Thread *thread;
+	Thread thread;
 	bool thread_running;
 	bool started;
 	bool use_thread;
diff --git a/modules/mono/mono_gd/support/android_support.cpp b/modules/mono/mono_gd/support/android_support.cpp
index 59e1385e7e..cba29d63cd 100644
--- a/modules/mono/mono_gd/support/android_support.cpp
+++ b/modules/mono/mono_gd/support/android_support.cpp
@@ -109,7 +109,7 @@ bool jni_exception_check(JNIEnv *p_env) {
 String app_native_lib_dir_cache;
 
 String determine_app_native_lib_dir() {
-	JNIEnv *env = ThreadAndroid::get_env();
+	JNIEnv *env = get_jni_env();
 
 	ScopedLocalRef<jclass> activityThreadClass(env, env->FindClass("android/app/ActivityThread"));
 	jmethodID currentActivityThread = env->GetStaticMethodID(activityThreadClass, "currentActivityThread", "()Landroid/app/ActivityThread;");
@@ -253,7 +253,7 @@ int32_t get_build_version_sdk_int() {
 	// android.os.Build.VERSION.SDK_INT
 
 	if (build_version_sdk_int == 0) {
-		JNIEnv *env = ThreadAndroid::get_env();
+		JNIEnv *env = get_jni_env();
 
 		jclass versionClass = env->FindClass("android/os/Build$VERSION");
 		ERR_FAIL_NULL_V(versionClass, 0);
@@ -281,7 +281,7 @@ MonoBoolean _gd_mono_init_cert_store() {
 	//	return false;
 	// }
 
-	JNIEnv *env = ThreadAndroid::get_env();
+	JNIEnv *env = get_jni_env();
 
 	ScopedLocalRef<jclass> keyStoreClass(env, env->FindClass("java/security/KeyStore"));
 
@@ -322,7 +322,7 @@ MonoArray *_gd_mono_android_cert_store_lookup(MonoString *p_alias) {
 		return nullptr;
 	}
 
-	JNIEnv *env = ThreadAndroid::get_env();
+	JNIEnv *env = get_jni_env();
 
 	ScopedLocalRef<jstring> js_alias(env, env->NewStringUTF(alias_utf8));
 	mono_free(alias_utf8);
@@ -380,7 +380,7 @@ void cleanup() {
 	if (godot_dl_handle)
 		gd_mono_android_dlclose(godot_dl_handle, nullptr);
 
-	JNIEnv *env = ThreadAndroid::get_env();
+	JNIEnv *env = get_jni_env();
 
 	if (certStore) {
 		env->DeleteGlobalRef(certStore);
@@ -437,7 +437,7 @@ GD_PINVOKE_EXPORT mono_bool _monodroid_get_network_interface_up_state(const char
 
 	*r_is_up = 0;
 
-	JNIEnv *env = ThreadAndroid::get_env();
+	JNIEnv *env = get_jni_env();
 
 	jclass networkInterfaceClass = env->FindClass("java/net/NetworkInterface");
 	ERR_FAIL_NULL_V(networkInterfaceClass, 0);
@@ -469,7 +469,7 @@ GD_PINVOKE_EXPORT mono_bool _monodroid_get_network_interface_supports_multicast(
 
 	*r_supports_multicast = 0;
 
-	JNIEnv *env = ThreadAndroid::get_env();
+	JNIEnv *env = get_jni_env();
 
 	jclass networkInterfaceClass = env->FindClass("java/net/NetworkInterface");
 	ERR_FAIL_NULL_V(networkInterfaceClass, 0);
@@ -507,7 +507,7 @@ static void interop_get_active_network_dns_servers(char **r_dns_servers, int *dn
 	CRASH_COND(get_build_version_sdk_int() < 23);
 #endif
 
-	JNIEnv *env = ThreadAndroid::get_env();
+	JNIEnv *env = get_jni_env();
 
 	GodotJavaWrapper *godot_java = ((OS_Android *)OS::get_singleton())->get_godot_java();
 	jobject activity = godot_java->get_activity();
@@ -648,7 +648,7 @@ GD_PINVOKE_EXPORT const char *_monodroid_timezone_get_default_id() {
 	//
 	// TimeZone.getDefault().getID()
 
-	JNIEnv *env = ThreadAndroid::get_env();
+	JNIEnv *env = get_jni_env();
 
 	ScopedLocalRef<jclass> timeZoneClass(env, env->FindClass("java/util/TimeZone"));
 	ERR_FAIL_NULL_V(timeZoneClass, nullptr);
diff --git a/modules/opensimplex/noise_texture.cpp b/modules/opensimplex/noise_texture.cpp
index 1d75e46747..30a0ca3464 100644
--- a/modules/opensimplex/noise_texture.cpp
+++ b/modules/opensimplex/noise_texture.cpp
@@ -34,7 +34,6 @@
 
 NoiseTexture::NoiseTexture() {
 	update_queued = false;
-	noise_thread = nullptr;
 	regen_queued = false;
 	first_time = true;
 
@@ -52,10 +51,7 @@ NoiseTexture::~NoiseTexture() {
 	if (texture.is_valid()) {
 		RS::get_singleton()->free(texture);
 	}
-	if (noise_thread) {
-		Thread::wait_to_finish(noise_thread);
-		memdelete(noise_thread);
-	}
+	noise_thread.wait_to_finish();
 }
 
 void NoiseTexture::_bind_methods() {
@@ -109,11 +105,9 @@ void NoiseTexture::_set_texture_data(const Ref<Image> &p_image) {
 
 void NoiseTexture::_thread_done(const Ref<Image> &p_image) {
 	_set_texture_data(p_image);
-	Thread::wait_to_finish(noise_thread);
-	memdelete(noise_thread);
-	noise_thread = nullptr;
+	noise_thread.wait_to_finish();
 	if (regen_queued) {
-		noise_thread = Thread::create(_thread_function, this);
+		noise_thread.start(_thread_function, this);
 		regen_queued = false;
 	}
 }
@@ -165,8 +159,8 @@ void NoiseTexture::_update_texture() {
 	use_thread = false;
 #endif
 	if (use_thread) {
-		if (!noise_thread) {
-			noise_thread = Thread::create(_thread_function, this);
+		if (!noise_thread.is_started()) {
+			noise_thread.start(_thread_function, this);
 			regen_queued = false;
 		} else {
 			regen_queued = true;
diff --git a/modules/opensimplex/noise_texture.h b/modules/opensimplex/noise_texture.h
index 9f6e2cbf43..170275bd2e 100644
--- a/modules/opensimplex/noise_texture.h
+++ b/modules/opensimplex/noise_texture.h
@@ -45,7 +45,7 @@ class NoiseTexture : public Texture2D {
 private:
 	Ref<Image> data;
 
-	Thread *noise_thread;
+	Thread noise_thread;
 
 	bool first_time;
 	bool update_queued;
diff --git a/modules/theora/video_stream_theora.cpp b/modules/theora/video_stream_theora.cpp
index 243265769e..1026d58b85 100644
--- a/modules/theora/video_stream_theora.cpp
+++ b/modules/theora/video_stream_theora.cpp
@@ -140,9 +140,7 @@ void VideoStreamPlaybackTheora::clear() {
 #ifdef THEORA_USE_THREAD_STREAMING
 	thread_exit = true;
 	thread_sem->post(); //just in case
-	Thread::wait_to_finish(thread);
-	memdelete(thread);
-	thread = nullptr;
+	thread.wait_to_finish();
 	ring_buffer.clear();
 #endif
 
@@ -181,7 +179,7 @@ void VideoStreamPlaybackTheora::set_file(const String &p_file) {
 	int read = file->get_buffer(read_buffer.ptr(), to_read);
 	ring_buffer.write(read_buffer.ptr(), read);
 
-	thread = Thread::create(_streaming_thread, this);
+	thread.start(_streaming_thread, this);
 
 #endif
 
@@ -669,7 +667,6 @@ VideoStreamPlaybackTheora::VideoStreamPlaybackTheora() {
 	ring_buffer.resize(rb_power);
 	read_buffer.resize(RB_SIZE_KB * 1024);
 	thread_sem = Semaphore::create();
-	thread = nullptr;
 	thread_exit = false;
 	thread_eof = false;
 
diff --git a/modules/theora/video_stream_theora.h b/modules/theora/video_stream_theora.h
index d2036b5cb4..c315d682da 100644
--- a/modules/theora/video_stream_theora.h
+++ b/modules/theora/video_stream_theora.h
@@ -112,7 +112,7 @@ class VideoStreamPlaybackTheora : public VideoStreamPlayback {
 	Vector<uint8_t> read_buffer;
 	bool thread_eof;
 	Semaphore *thread_sem;
-	Thread *thread;
+	Thread thread;
 	volatile bool thread_exit;
 
 	static void _streaming_thread(void *ud);