SDL_MouseWheelDirection.3type - Man Page

#include <SDL3/SDL_mouse.h>

typedef enum SDL_MouseWheelDirection
{
    SDL_MOUSEWHEEL_NORMAL,    /**< The scroll direction is normal */
    SDL_MOUSEWHEEL_FLIPPED    /**< The scroll direction is flipped / natural */
} SDL_MouseWheelDirection;

This enum is available since SDL 3.2.0.