[comp.sys.mac.programmer] mouse down in grow box

zaccone@shire.cs.psu.edu (10/06/89)

The Macintosh Programming Primer contains a program called the Event
Tutor.  Here is how the program handles a mouse down event in the grow
box.  The code makes sense to me, except that I don't understand the
purpose of the GetPort and SetPort function calls.  I've tried taking
them out to convince myself that they are necessary, but I still don't
understand why they are needed.  Can someone explain this to a Mac
programming novice?


case inGrow:
    windSize = GrowWindow( whichWindow, gTheEvent.where, &gSizeRect );
    if (windSize != 0 ){
        GetPort( &oldPort );
        SetPort( whichWindow );
        EraseRect( &whichWindow->portRect );
        SizeWindow( whichWindow, LoWord( windSize ), HiWord( windSize ),
                    NORMAL_UPDATES );
        InvalRect( &whichWindow->portRect);
        SetPort( oldPort );
    }
    break;

Rick Zaccone
zaccone@bknlvms.bitnet
zaccone@sol.bucknell.edu