Class AndroidThread

android/src/main/cpp/GodotModule.cpp:55–167

const static char CMD_EXIT = 2;

class AndroidThread {
	std::thread thread;
	std::mutex mutex;
	std::condition_variable started;
	std::queue<std::function<void()>> tasks;
	ALooper *looper = nullptr;
	int function_queue_fd = -1;
	bool quit = false;

public:
	AndroidThread() :
			thread(&AndroidThread::run, this) {
		std::unique_lock<std::mutex> lock(mutex);
		started.wait(lock, [this]() {
			return function_queue_fd >= 0;
		});
	}

	static int looper_callback(int fd, int events, void *data) {
		char cmd;
		AndroidThread *self = (AndroidThread *)data;
		ssize_t res = read(fd, &cmd, sizeof(cmd));
		if (res < 0) {
			LOGE("Unable to read looper event from pipe: %d", errno);
			return 1;
		}
		if (res == 0) {
			LOGE("End of file event should not happen.");
			return 1;
		}
		if (res != sizeof(cmd)) {
			LOGE("Unable to read command fully from pipe");
			return 1;
		}

		switch (cmd) {
			case CMD_FUNCTION: {
				std::function<void()> task;
				{
					std::lock_guard<std::mutex> lock(self->mutex);
					if (self->tasks.empty()) {
						LOGW("Empty queue when processing CMD_FUNCTION");
						break;
					}
					task = std::move(self->tasks.front());
					self->tasks.pop();
				}
				task();
			} break;
			case CMD_EXIT: {
				self->quit = true;
			} break;
			default: {
				LOGE("Unknown command: %d", cmd);
			}
		}

		return 1;