Data Type(IM: QC)

Inside Macintosh: QuickTime Components /: Chapter 11 - Clock Components / Clock Components Reference

Data Type
The clock component data structure is a private data structure. Programs that use your clock component never change the contents of this data structure directly. Your clock component provides functions that allow programs to use this data structure.
The callback header structure specifies the callback function for an operation. Your application can obtain callback function identifiers by calling its clock component's ClockNewCallBack function (described on page 11-9).
The QTCallBackHeader data type defines the callback header structure.
struct QTCallBackHeader {
      long     callBackFlags;    /* flags used by clock
                                    component to communicate
                                    scheduling data about
                                    callback to Movie Toolbox */
      long     reserved1;        /* reserved for use by Apple */
      char     qtPrivate[40];    /* reserved for use by Apple */
};
Field descriptions

callBackFlags
Contains flags that your component can use to communicate scheduling information about the callback event to the Movie Toolbox. This scheduling information tells the Movie Toolbox what time base events your clock component needs to know about in order to support the callback event. The following flags are defined (all other flags must be
set to 0):
               enum {
                  qtcbNeedsRateChanges = 1,  /* clock needs to
                                                know about rate
                                                changes */
                  qtcbNeedsTimeChanges = 2   /* clock needs to
                                                know about time
                                                changes */
                  qtcbNeedsStartStopChanges  
                                       = 4   /* clock needs to 
                                                know about time
                                                base changes */
               };
qtcbNeedsRateChanges
Indicates that your clock component needs to know about rate changes. If you set this flag to 1, the Movie Toolbox calls your ClockRateChanged function (described on page 11-14) whenever the rate of the callback event's time base changes.
qtcbNeedsTimeChanges
Indicates that your clock component needs to know about time changes. If you set this flag to 1, the Movie Toolbox calls your ClockTimeChanged function (described on page 11-13) whenever a program changes the time value of the time base, or when the time value changes by an amount that is different from the time base's rate.
qtcbNeedsStartStopChanges
Indicates that your clock component needs to know
about the time base's start and stop changes. If you
set this flag to 1, the Movie Toolbox calls your ClockStartStopChanged function (described on page 11-14) whenever a program changes the start or stop time of the time base.
reserved1
Reserved for use by Apple.
qtPrivate
Reserved for use by Apple.