Function is_main_thread

src/platforms/stub/thread_stub_stl.h:46–48

@brief Check if the current thread is the main thread

/// @brief Check if the current thread is the main thread
inline bool is_main_thread() FL_NOEXCEPT {
    return std::this_thread::get_id() == main_thread_id();  // okay std namespace
}

/// @brief Native sleep for 1ms
inline void native_sleep_1ms() FL_NOEXCEPT {