- Qt 5.15
- Qt Core
- C++ Classes
- QWinEventNotifier
- Qt 5.15.18 Reference Documentation

# QWinEventNotifier Class

The QWinEventNotifier class provides support for the Windows Wait functions. More...

Header: | #include <QWinEventNotifier>
qmake: | QT += core
Since: | Qt 5.0
Inherits: | QObject

This class was introduced in Qt 5.0.

- List of all members, including inherited members

## Public Functions

| QWinEventNotifier(HANDLE hEvent, QObject *parent = nullptr)
| QWinEventNotifier(QObject *parent = nullptr)
virtual | ~QWinEventNotifier()
HANDLE | handle() const
bool | isEnabled() const
void | setHandle(HANDLE hEvent)

## Public Slots

void | setEnabled(bool enable)

## Reimplemented Protected Functions

virtual bool | event(QEvent *e) override

## Detailed Description

The QWinEventNotifier class makes it possible to use the wait functions on windows in a asynchronous manner. With this class, you can register a HANDLE to an event and get notification when that event becomes signalled. The state of the event is not modified in the process so if it is a manual reset event you will need to reset it after the notification.

Once you have created a event object using Windows API such as CreateEvent() or OpenEvent(), you can create an event notifier to monitor the event handle. If the event notifier is enabled, it will emit the activated() signal whenever the corresponding event object is signalled.

The setEnabled() function allows you to disable as well as enable the event notifier. It is generally advisable to explicitly enable or disable the event notifier. A disabled notifier does nothing when the event object is signalled (the same effect as not creating the event notifier). Use the isEnabled() function to determine the notifier's current status.

Finally, you can use the setHandle() function to register a new event object, and the handle() function to retrieve the event handle.

Further information: Although the class is called QWinEventNotifier, it can be used for certain other objects which are so-called synchronization objects, such as Processes, Threads, Waitable timers.

Warning: This class is only available on Windows.

## Member Function Documentation

### QWinEventNotifier::QWinEventNotifier(HANDLE hEvent, QObject *parent = nullptr)

Constructs an event notifier with the given parent. It enables the notifier, and watches for the event hEvent.

The notifier is enabled by default, i.e. it emits the activated() signal whenever the corresponding event is signalled. However, it is generally advisable to explicitly enable or disable the event notifier.

See also setEnabled() and isEnabled().

### QWinEventNotifier::QWinEventNotifier(QObject *parent = nullptr)

Constructs an event notifier with the given parent.

### `[slot]` void QWinEventNotifier::setEnabled(bool enable)

If enable is true, the notifier is enabled; otherwise the notifier is disabled.

See also isEnabled() and activated().

### `[virtual]` QWinEventNotifier::~QWinEventNotifier()

Destroys this notifier.

### `[override virtual protected]` bool QWinEventNotifier::event(QEvent *e)

Reimplements: QObject::event(QEvent *e).

### HANDLE QWinEventNotifier::handle() const

Returns the HANDLE that has been registered in the notifier.

See also setHandle().

### bool QWinEventNotifier::isEnabled() const

Returns `true` if the notifier is enabled; otherwise returns `false`.

See also setEnabled().

### void QWinEventNotifier::setHandle(HANDLE hEvent)

Register the HANDLE hEvent. The old HANDLE will be automatically unregistered.

Note: The notifier will be disabled as a side effect and needs to be re-enabled.

See also handle() and setEnabled().