Sending Messages to the ATQ

Sending Messages to the ATQ Communications for special circumstances

Whereas it is unlikely that opening The .MPP Driver will adversely affect

another program, an application program should never be allowed to close

The .MPP Driver, because another program might be using it. Under

certain very specific circumstances, however, the system might close

PATalkClosePrep function to send a permission-to-close transition to each

routine in the AppleTalk Transition Queue. This transition indicates that the

system intends to close The .MPP Driver so that each routine in the queue

has the opportunity to deny permission to do so.

When the operating system calls the PATalkClosePrep function, any

routine in the AppleTalk Transition Queue that wishes to deny permission to

close The .MPP Driver may return a pointer to a high-level language

string. The high-level language string should be the name of the application

that placed the entry in the queue. If any routine in the AppleTalk Transition

Queue denies permission to close The .MPP Driver, the PATalkClosePrep

function returns the result code closeErr.

If any routine denies the requested permission to close The .MPP Driver,

the AppleTalk Manager sends a cancel-close transition to every routine in

the AppleTalk Transition Queue that previously received the

permission-to-close transition. The caller of the PATalkClosePrep function

may display a dialog box informing the user that another application program is

using The .MPP Driver and showing the name (if any) returned by the

AppleTalk Transition Queue routine. The dialog box gives the user the option of

canceling the request to close AppleTalk or of closing AppleTalk anyway.

If the user chooses to close AppleTalk despite the fact that an application is

using it, the system calls the MPPClose function. AppleTalk then calls each

application in the AppleTalk Transition Queue, this time informing each one

that AppleTalk is about to close. In this case, your AppleTalk Transition Queue

routine must prepare for the imminent closing of AppleTalk; it cannot deny

permission to the MPPClose function.

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