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Enables an application that has registered to receive notifications from Print Spooler-hosted printing components to unregister.
Syntax
HRESULT UnRegisterForPrintAsyncNotifications(
[in] HANDLE unnamedParam1
);
Parameters
[in] unnamedParam1
The registration handle to be unregistered.
Return value
| HRESULT | Severity | Meaning |
|---|---|---|
| S_OK | SUCCESS | The function completed successfully. |
| ALREADY_UNREGISTERED |
SUCCESS
ERROR |
The registration handler has already been unregistered. If this HRESULT has an ERROR severity, the calling function should handle the error condition. |
| NOT_REGISTERED | SUCCESS | The registration handler was not registered. |
The return values are COM error codes. Because this function might complete the operation successfully yet return an HRESULT other than S_OK you should use the SUCCEEDED or FAILED macro to determine the success of the call. To get the specific HRESULT that was returned by the function, use the HRESULT_CODE macro.
The following code example shows how these macros can be used to evaluate the return value.
if (SUCCEEDED(hr)) {
// Call succeeded, check HRESULT value returned
switch (HRESULT_CODE(hr)){
case S_OK:
// Some action
break;
case NOT_REGISTERED:
// Some action
break;
case ALREADY_UNREGISTERED:
// Some action
break;
default:
// Default action
break;
}
} else {
// Call failed, check HRESULT value returned
switch (HRESULT_CODE(hr)){
// This can be error and a successful return
case ALREADY_UNREGISTERED:
// Some action
break;
default:
// Default action
break;
}
}
For more information about COM error codes, see Error Handling.
See PrintAsyncNotifyError for other possible return values.
Remarks
Note This is a blocking or synchronous function and might not return immediately. How quickly this function returns depends on run-time factors such as network status, print server configuration, and printer driver implementation—factors that are difficult to predict when writing an application. Calling this function from a thread that manages interaction with the user interface could make the application appear to be unresponsive.
If the channel is bidirectional, a call to UnRegisterForPrintAsyncNotifications only prevents notifications from communication channels created after that point. To end notifications from the existing channel, the listening application must close the channel with IPrintAsyncNotifyChannel::CloseChannel.
A call to UnRegisterForPrintAsyncNotifications will decrement the reference count of the pCallback object passed to RegisterForPrintAsyncNotifications.
After this function succeeds, hRegistrationHandler is invalid and must not be used again.
Requirements
| Requirement | Value |
|---|---|
| Minimum supported client | Windows Vista [desktop apps only] |
| Minimum supported server | Windows Server 2008 [desktop apps only] |
| Target Platform | Windows |
| Header | prnasnot.h |
| Library | WinSpool.lib |
| DLL | Spoolss.dll |