QuickTime 4 Reference

Modifying Atoms

QuickTime provides functions that you can call to modify attributes or data associated with an atom in an atom container. To modify an atom's ID, you call the function QTSetAtomID .

You use the QTSetAtomData function to update the data associated with a leaf atom in an atom container. The QTSetAtomData function replaces a leaf atom's data with new data. The code sample in Listing 10 calls QTFindChildByIndex to determine whether an atom container contains a sprite's visible property. If so, the sample calls QTSetAtomData to replace the atom's data with a new visible property.

Listing 10 Modifying an atom's data



 
QTAtom propertyAtom;



// if the atom isn't in the container, add it

if ((propertyAtom = QTFindChildByIndex (sprite, kParentAtomIsContainer,

    kSpritePropertyVisible, 1, nil)) == 0)

    FailOSErr (QTInsertChild (sprite, kParentAtomIsContainer,

        kSpritePropertyVisible, 1, 0, sizeof(short), visible, nil))



// if the atom is in the container, replace its data

else

    FailOSErr (QTSetAtomData (sprite, propertyAtom, sizeof(short),

        visible));