Vertical text from left to right with NSTextView

In the WebVTT video subtitle format, subtitles can be horizontal, vertical growing left, or vertical growing right. The natural text direction of NSTextView is horizontal; with setLayoutOrientation(_:) I get vertical text growing left. How can I get vertical text growing right? The documentation says that with setLayoutOrientation(_:) the text view's bounds are rotated by 90° clockwise, but manually rotating them by -90° with boundsRotation = -90 just rotates everything, including the text which should have the same orientation as before, just expanding in the opposite direction.