SDL_WindowEvent.3type - Man Page

#include <SDL3/SDL_events.h>

typedef struct SDL_WindowEvent
{
    SDL_EventType type; /**< SDL_EVENT_WINDOW_* */
    Uint32 reserved;
    Uint64 timestamp;   /**< In nanoseconds, populated using SDL_GetTicksNS() */
    SDL_WindowID windowID; /**< The associated window */
    Sint32 data1;       /**< event dependent data */
    Sint32 data2;       /**< event dependent data */
} SDL_WindowEvent;

This struct is available since SDL 3.2.0.