QuickTime 4 Reference

Using a `kTweenTypePathXtoY` Tween Component

To use kTweenTypePathXtoY tween components, either absolute or delta, do the following:

Create a QT atom container.
Insert a kTweenEntry atom into the QT atom container for the tween.
Insert a kTweenType atom that specifies the tween type into the kTweenEntry atom.
Insert a kTweenData atom into the kTweenEntry atom.
Perform the tweening operation, using QTDoTween .

Listing 17 shows how to create both kinds of kTweenTypePathXtoY tweens.

Listing 17 Creating kTweenTypePathXtoY tweens container



 
// kTweenTypePathXtoY - normal

err = CreateSamplePathTweenContainer( container, kTweenTypePathXtoY, 3,

                                        false, duration, 0, &tweenAtom );

if ( err ) goto bail;



err = QTNewTween( &tween, container, tweenAtom, duration );

if ( err ) goto bail;



for ( tweenTime = 0; tweenTime <= duration; tweenTime++ ) {

    Fixed absoluteYvalue;

    

    err = QTDoTween( tween, tweenTime, result, nil, nil, nil );

    if ( err ) goto bail;

    

    absoluteYvalue = *(Fixed *)*result;

}

    

err = QTDisposeTween( tween );



 
// kTweenTypePathXtoY - delta

err = CreateSamplePathTweenContainer( container, kTweenTypePathXtoY, 3,

                                        true, duration, 0, &tweenAtom );

if ( err ) goto bail;



err = QTNewTween( &tween, container, tweenAtom, duration );

if ( err ) goto bail;



for ( tweenTime = 0; tweenTime <= duration; tweenTime++ ) {

    Fixed deltaYalue;

    

    err = QTDoTween( tween, tweenTime, result, nil, nil, nil );

    if ( err ) goto bail;

    

    deltaYalue = *(Fixed *)*result;

}

    

err = QTDisposeTween( tween );



bail:

    if ( container ) QTDisposeAtomContainer( container );

    if ( result ) DisposeHandle( result );

Using a kTweenTypePathXtoY Tween Component

Using a `kTweenTypePathXtoY` Tween Component