QPointingDeviceUniqueId Class | Qt GUI 5.12.9

- Qt 5.12
- Qt GUI
- C++ Classes
- QPointingDeviceUniqueId
- Qt 5.12.9 Reference Documentation

# QPointingDeviceUniqueId Class

QPointingDeviceUniqueId identifies a unique object, such as a tagged token or stylus, which is used with a pointing device. More...

Header: | #include <QPointingDeviceUniqueId>
qmake: | QT += gui
Since: | Qt 5.8

- List of all members, including inherited members

## Properties

- numericId : const qint64

## Public Functions

| QPointingDeviceUniqueId()
bool | isValid() const
qint64 | numericId() const

## Static Public Members

QPointingDeviceUniqueId | fromNumericId(qint64 id)
const QMetaObject | staticMetaObject

## Related Non-Members

uint | qHash(QPointingDeviceUniqueId key, uint seed = 0)
bool | operator!=(QPointingDeviceUniqueId lhs, QPointingDeviceUniqueId rhs)
bool | operator==(QPointingDeviceUniqueId lhs, QPointingDeviceUniqueId rhs)

## Detailed Description

QPointingDeviceUniqueId identifies a unique object, such as a tagged token or stylus, which is used with a pointing device.

QPointingDeviceUniqueIds can be compared for equality, and can be used as keys in a QHash. You get access to the numerical ID via numericId(), if the device supports such IDs. For future extensions, though, you should not use that function, but compare objects of this type using the equality operator.

This class is a thin wrapper around an integer ID. You pass it into and out of functions by value.

This type actively prevents you from holding it in a QList, because doing so would be very inefficient. Use a QVector instead, which has the same API as QList, but more efficient storage.

See also QTouchEvent::TouchPoint.

## Property Documentation

### numericId : const qint64

This property holds the numeric unique ID of the token represented by a touchpoint

If the device provides a numeric ID, isValid() returns true, and this property provides the numeric ID; otherwise it is -1.

You should not use the value of this property in portable code, but instead rely on equality to identify pointers.

Access functions:

qint64 | numericId() const

See also isValid().

## Member Function Documentation

### QPointingDeviceUniqueId::QPointingDeviceUniqueId()

Constructs an invalid unique pointer ID.

### `[static]` QPointingDeviceUniqueId QPointingDeviceUniqueId::fromNumericId(qint64 id)

Constructs a unique pointer ID from numeric ID id.

### bool QPointingDeviceUniqueId::isValid() const

Returns whether this unique pointer ID is valid, that is, it represents an actual pointer.

## Related Non-Members

### uint qHash(QPointingDeviceUniqueId key, uint seed = 0)

Returns the hash value for key, using seed to seed the calculation.

This function was introduced in Qt 5.8.

### bool operator!=(QPointingDeviceUniqueId lhs, QPointingDeviceUniqueId rhs)

Returns whether the two unique pointer IDs lhs and rhs identify different pointers (`true`) or not (`false`).

This function was introduced in Qt 5.8.

### bool operator==(QPointingDeviceUniqueId lhs, QPointingDeviceUniqueId rhs)

Returns whether the two unique pointer IDs lhs and rhs identify the same pointer (`true`) or not (`false`).

This function was introduced in Qt 5.8.