public int64 get_frame_time ()
Gets the time that should currently be used for animations.
Inside the processing of a frame, it’s the time used to compute the animation position of everything in a frame. Outside of a frame, it's the time of the conceptual “previous frame,” which may be either the actual previous frame time, or if that’s too old, an updated time.
a timestamp in microseconds, in the timescale of of get_monotonic_time .