QuickTime 4 Reference

Value Setting Function

The function that you call to send the interpolated value to the receiving track is defined as a universal procedure in systems that support the Macintosh Code Fragment Manager (CFM) or is defined as a data procedure for non-CFM systems:



 
typedef UniversalProcPtr TweenerDataUPP;    /* CFM */



 
typedef TweenerDataProcPtr TweenerDataUPP;  /* non-CFM */

The TweenerDataUPP function pointer specifies the function the tween component calls with the value generated by the tween operation. A tween component calls this function from its implementation of the TweenerDoTween function.



 
typedef pascal ComponentResult (*TweenerDataProcPtr)(

                     TweenRecord *tr,

                     void *tweenData,

                     long tweenDataSize,

                     long dataDescriptionSeed,

                     Handle dataDescription,

                     ICMCompletionProcRecordPtr asyncCompletionProc,

                     ProcPtr transferProc,

                     void *refCon);

tr: Contains a pointer to the tween record for the tween operation.
tweenData: Contains a pointer to the generated tween value.
tweenDataSize: Specifies the size, in bytes, of the tween value.
dataDescriptionSeed: Specifies the starting value for the calculation. Every time the content of the dataDescription handle changes, this value should be incremented.
dataDescription: Specifies a handle containing a description of the tween value passed. For basic types such as integers, the calling tween component should set this parameter to nil. For more complex types such as compressed image data, the calling tween component should set this handle to contain a description of the tween value, such as an image description.
asyncCompletionProc: Contains a pointer to a completion procedure for asynchronous operations. The calling tween component should set the value of this parameter to nil .
transferProc: Contains a pointer to a procedure to transfer the data. The calling tween component should set the value of this parameter to nil .
refCon: Contains a pointer to a reference constant. The calling tween component should set the value of this parameter to nil .

DISCUSSION

You call this function by invoking the function specified in the tween record's dataProc field.

RESULT CODES

`noErr`	0	No error
`paramErr`	-50	Invalid parameter specified