QuickTime 4 Reference

Creating a Single Tween Container

To create a single tween container, do the following:

Create a QT atom container.
Insert a kTweenEntry atom into the QT atom container for the tween. A kTweenEntry atom contains the atoms that define the tween.
Insert a kTweenType atom that specifies the tween type into the kTweenEntry atom.
Insert a kTweenData atom that contains the data for the tween into the kTweenEntry atom .

Listing 6 shows how to create a single kTweenTypeLong tween container that a component could use to interpolate two long integers.

Listing 6 Creating a single kTweenTypeLong tween container



 
QTAtomContainer container = nil;

long tweenDataLong[2];

QTAtomType tweenType;

QTAtom tweenAtom;



tweenDataLong[0] = EndianU32_NtoB(512);

tweenDataLong[1] = EndianU32_NtoB(0);



// create a new atom container

QTNewAtomContainer (&container);

// create the parent tween entry atom

tweenType = kTweenTypeLong;

QTInsertChild (container, kParentAtomIsContainer, kTweenEntry, 1, 0, 0,

                nil, &tweenAtom);

// add two child atoms to the tween entry atom --

// * the type atom, kTweenType

QTInsertChild (container, tweenAtom, kTweenType, 1, 0,

                sizeof(tweenType), &tweenType, nil);

// * the data atom, kTweenData

QTInsertChild (container, tweenAtom, kTweenData, 1, 0, 

                sizeof(long) * 2, tweenDataLong, nil);