Carbon


OSLAdjustMarksProcPtr

Header: AEObjects.h Carbon status: Supported

Defines a pointer to a mark adjusting object callback function. Your mark adjusting function adjusts the marks made with the current mark token.

typedef OSErr(* OSLAdjustMarksProcPtr) (
    SInt32 newStart, 
    SInt32 newStop, 
    const AEDesc *markToken
);

You would declare your function like this if you were to name it MyOSLAdjustMarksCallback:

OSErr MyOSLAdjustMarksCallback (
    SInt32 newStart, 
    SInt32 newStop, 
    const AEDesc *markToken
);
Parameter descriptions
newStart

The mark count value (provided when the MyAdjustMarksCallback callback function was called to mark the object) for the first object in the new set of marked objects.

newStop

The mark count value (provided when the MyAdjustMarksCallback callback function was called to mark the object) for the last object in the new set of marked objects.

markToken

A pointer to the mark token for the marked objects. (Token is defined in AEDisposeToken.)

function result

A result code. Your adjust marks function should return noErr if it successfully adjusted the marks and errAEEventNotHandled if it could not locate the object. When the Apple Event Manager gets an error result of errAEEventNotHandled, it attempts to adjust the marks by calling the equivalent system mark-adjusting function.

DISCUSSION

When the Apple Event Manager needs to identify either a range of elements or the absolute position of an element in a group of Apple event objects that pass a test, it can use your application’s mark-adjusting function to unmark objects previously marked by a call to your marking function.

For example, suppose an object specifier record specifies “any row in the table ‘MyCustomers’ for which the City column is ‘San Francisco.’” The Apple Event Manager first uses the appropriate object accessor function to locate all the rows in the table for which the City column is “San Francisco” and calls the application’s marking function repeatedly to mark them. It then generates a random number between 1 and the number of rows it found that passed the test and calls the application’s mark-adjusting function to unmark all the rows whose mark count does not match the randomly generated number. If the randomly chosen row has a mark count value of 5, the Apple Event Manager passes the value 5 to the mark-adjusting function in both the newStart parameter and the newStop parameter, and passes the current mark token in the markToken parameter.

When the Apple Event Manager calls your MyAdjustMarks function, your application must dispose of any data structures that it created to mark the previously marked objects.

To provide a pointer to your adjust marks callback function, you create a universal procedure pointer (UPP) of type OSLAdjustMarksUPP, using the function NewOSLAdjustMarksUPP. You can do so with code like the following:

OSLAdjustMarksUPP MyAdjustMarksUPP;

MyAdjustMarksUPP = NewOSLAdjustMarksUPP (&MyAdjustMarksCallback);

You can then pass the UPP MyAdjustMarksUPP as a parameter to the AESetObjectCallbacks function or the AEInstallSpecialHandler function.

If you wish to call your adjust marks callback function directly, you can use the InvokeOSLAdjustMarksUPP function.

After you are finished with your adjust marks callback function, you can dispose of the UPP with the DisposeOSLAdjustMarksUPP function. However, if you will use the same adjust marks function in subsequent calls to the function AESetObjectCallbacks or the function AEInstallSpecialHandler, you can reuse the same UPP, rather than dispose of it and later create a new UPP.


© 2000 Apple Computer, Inc. (Last Updated 6/30/2000)