QuickTime 4 Reference

Generating Tween Media Values

Your tween component must process kTweenerDoTweenSelect requests from the Component Manager. Listing 22 shows a function, TweenDoTween, for processing this request. It takes short-integer values and performs the necessary interpolation.

Listing 22 Function that generates tween media values



 
pascal ComponentResult TweenDoTween (

                                         TweenerComponent tc,

                                         TweenRecord *tr)

{

    short       *data;

    short       tFrom, tTo, tValue;



    QTGetAtomDataPtr(tr->container, tr->dataAtom, nil, (Ptr *)&data);



    tFrom = data[0];

    tTo = data[1];

    tValue = tFrom + FixMul(tTo - tFrom, tr->percent);



    (tr->dataProc)((struct TweenRecord *)tr, &tValue,

        sizeof(tValue), 1, nil, nil, nil, nil);



    return noErr;

}