Technical Q&A TB66

CloseDialog and 'ictb's

Q: I have a dialog that I create using GetNewDialog, passing in a pointer to the dStorage parameter so that I can control the memory used by the dialog. When I close the dialog, I follow the guidelines in Inside Macintosh and call CloseDialog rather than DisposeDialog. However, if my dialog has an 'ictb' resource associated with it, I find that CloseDialog fails to dispose of the Dialog Manager's copy of the 'ictb', and my application leaks. What should I do?

A: There are a number of things that you can do to solve this problem. The best solution is to simply pass nil to the dStorage parameter of GetNewDialog (and dispose of your dialog by calling DisposeDialog). This will avoid the memory leak (DisposeDialog does dispose of the Dialog Manager's copy of your 'ictb') and, as an added bonus, will make your application easier to port to Carbon. Under Carbon, it is required that you let the toolbox allocate storage for your windows and dialog by passing nil to the storage parameter of the creation routines.

Alternatively, you can replace your 'ictb' resource with the more modern 'dftb' resource, which supports most of the useful functionality of an 'ictb' and will not suffer from this bug.

The worst solution we can think of is to plug the memory leak with the following code:

static void MyCloseDialog(DialogRef dlg)
{
    AuxWinHandle auxWH;
    Handle ictbH;
 
    ictbH = nil;
    if ( GetAuxWin(dlg, &auxWH) ) {
        ictbH = (**auxWH).reserved;
    }
    CloseDialog(dlg);
    if (ictbH != nil) {
        DisposeHandle(ictbH);
    }
}

Since many applications in use today assume that CloseDialog does not dispose of the dialog's 'ictb' data, there is no plan for changing this behavior.

[Jan 18 2000]