Depending on the hardware, you may get motion events when the pen is not
touching a tablet, for tracking a pen even when it isn't drawing. You
should listen for SDL_EVENT_PEN_DOWN and SDL_EVENT_PEN_UP events, or check
pen_state & SDL_PEN_INPUT_DOWN to decide if a pen is "drawing" when
dealing with pen motion.
Pressure-sensitive pen motion event structure (event.pmotion.*)
Depending on the hardware, you may get motion events when the pen is not touching a tablet, for tracking a pen even when it isn't drawing. You should listen for SDL_EVENT_PEN_DOWN and SDL_EVENT_PEN_UP events, or check pen_state & SDL_PEN_INPUT_DOWN to decide if a pen is "drawing" when dealing with pen motion.
\since This struct is available since SDL 3.2.0.