Convert SDL_MULTIGESTURE dDist into pixels

Hi all,

Is there a way to convert dDist from mgesture into pixels? How can I achive that?

dDist is a normalized distance, from what I understand. But normalized between what values?
Does the direction and number of fingers influence it?
And what is the padding in the struct bellow?

typedef struct SDL_MultiGestureEvent
    Uint32 type;        /**< ::SDL_MULTIGESTURE */
    Uint32 timestamp;   /**< In milliseconds, populated using SDL_GetTicks() */
    SDL_TouchID touchId; /**< The touch device id */
    float dTheta;
    float dDist;
    float x;
    float y;
    Uint16 numFingers;
    Uint16 padding;
} SDL_MultiGestureEvent;

I already saw something on the lazy foo tutorials, but I’m not convinced of what it is there. I think it is true if you only move on X axys and all fingers on the same Y position, which is not always true.

Thank you