Pinch event structure (event.pinch.*)
Defined in <SDL3/SDL_events.h>
typedef struct SDL_PinchFingerEvent
{
SDL_EventType type; /**< ::SDL_EVENT_PINCH_BEGIN or ::SDL_EVENT_PINCH_UPDATE or ::SDL_EVENT_PINCH_END */
Uint32 reserved;
Uint64 timestamp; /**< In nanoseconds, populated using SDL_GetTicksNS() */
float scale; /**< The scale change since the last SDL_EVENT_PINCH_UPDATE. Scale < 1 is "zoom out". Scale > 1 is "zoom in". */
SDL_WindowID windowID; /**< The window underneath the finger, if any */
float span_x; /**< On mobile devices, the average X distance between each of the pointers forming the pinch in window coordinates. Otherwise, -1. */
float span_y; /**< On mobile devices, the average Y distance between each of the pointers forming the pinch in window coordinates. Otherwise, -1. */
float focus_x; /**< On mobile devices, the X coordinate of the current gesture's focal point in window coordinates. Otherwise, -1. */
float focus_y; /**< On mobile devices, the Y coordinate of the current gesture's focal point in window coordinates. Otherwise, -1. */
} SDL_PinchFingerEvent;span_(x/y) and focus_(x/y) are only available for pinch gestures on mobile devices