Mouse wheel event structure (event.wheel.*)
Defined in SDL_events.h
typedef struct SDL_MouseWheelEvent
{
Uint32 type; /**< SDL_MOUSEWHEEL */
Uint32 timestamp; /**< In milliseconds, populated using SDL_GetTicks() */
Uint32 windowID; /**< The window with mouse focus, if any */
Uint32 which; /**< The mouse instance id, or SDL_TOUCH_MOUSEID */
Sint32 x; /**< The amount scrolled horizontally, positive to the right and negative to the left */
Sint32 y; /**< The amount scrolled vertically, positive away from the user and negative toward the user */
Uint32 direction; /**< Set to one of the SDL_MOUSEWHEEL_* defines. When FLIPPED the values in X and Y will be opposite. Multiply by -1 to change them back */
float preciseX; /**< The amount scrolled horizontally, positive to the right and negative to the left, with float precision (added in 2.0.18) */
float preciseY; /**< The amount scrolled vertically, positive away from the user and negative toward the user, with float precision (added in 2.0.18) */
Sint32 mouseX; /**< X coordinate, relative to window (added in 2.26.0) */
Sint32 mouseY; /**< Y coordinate, relative to window (added in 2.26.0) */
} SDL_MouseWheelEvent;