Technical information

CHAPTER 3
The PC Interface Driver
Passing Messages 51
Removing a Message Handler 3
Message handlers can be called until they are removed. Before your program terminates,
you must remove the handler so that the PC Interface driver will not call it after you
are gone.
On the Mac OS 3
To remove a message handler on the Mac OS, your program makes an appropriate
control call to the PC Interface driver and passes it a pointer to the handler.
Parameter block
→ ioCompletion long Pointer to the completion routine
← ioResult word
→ ioRefNum word
→ csCode word Equals rsRemoveMsgHandler
→ csParam+0 long Pointer to MsgRecElem
On the PC 3
To remove a message handler on the PC, your program makes a call to INT 5Fh with
AH = 3 and with a pointer to the MsgRecElem record in registers ES:BX.