- Qt 6.8
- Qt Core
- C++ Classes
- QPoint
- Qt 6.8.1 Reference Documentation

# QPoint Class

The QPoint class defines a point in the plane using integer precision. More...

Header: | `#include <QPoint>`
CMake: | `find_package(Qt6 REQUIRED COMPONENTS Core)` `target_link_libraries(mytarget PRIVATE Qt6::Core)`
qmake: | `QT += core`

- List of all members, including inherited members
- QPoint is part of Painting Classes.

This class is equality-comparable.

This class is equality-comparable with QPointF.

Note: All functions in this class are reentrant.

## Public Functions

| QPoint()
| QPoint(int xpos, int ypos)
bool | isNull() const
int | manhattanLength() const
int & | rx()
int & | ry()
void | setX(int x)
void | setY(int y)
CGPoint | toCGPoint() const
`(since 6.4)` QPointF | toPointF() const
QPoint | transposed() const
int | x() const
int | y() const
QPoint & | operator*=(double factor)
QPoint & | operator*=(float factor)
QPoint & | operator*=(int factor)
QPoint & | operator+=(const QPoint &point)
QPoint & | operator-=(const QPoint &point)
QPoint & | operator/=(qreal divisor)

## Static Public Members

int | dotProduct(const QPoint &p1, const QPoint &p2)

## Related Non-Members

bool | operator!=(const QPoint &lhs, const QPoint &rhs)
QPoint | operator*(const QPoint &point, double factor)
QPoint | operator*(const QPoint &point, float factor)
QPoint | operator*(const QPoint &point, int factor)
QPoint | operator*(double factor, const QPoint &point)
QPoint | operator*(float factor, const QPoint &point)
QPoint | operator*(int factor, const QPoint &point)
QPoint | operator+(const QPoint &point)
QPoint | operator+(const QPoint &p1, const QPoint &p2)
QPoint | operator-(const QPoint &p1, const QPoint &p2)
QPoint | operator-(const QPoint &point)
QPoint | operator/(const QPoint &point, qreal divisor)
QDataStream & | operator<<(QDataStream &stream, const QPoint &point)
bool | operator==(const QPoint &lhs, const QPoint &rhs)
QDataStream & | operator>>(QDataStream &stream, QPoint &point)

## Detailed Description

A point is specified by a x coordinate and an y coordinate which can be accessed using the x() and y() functions. The isNull() function returns `true` if both x and y are set to 0. The coordinates can be set (or altered) using the setX() and setY() functions, or alternatively the rx() and ry() functions which return references to the coordinates (allowing direct manipulation).

Given a point p, the following statements are all equivalent:

     QPoint p;

     p.setX(p.x() + 1);
     p += QPoint(1, 0);
     p.rx()++;

A QPoint object can also be used as a vector: Addition and subtraction are defined as for vectors (each component is added separately). A QPoint object can also be divided or multiplied by an `int` or a `qreal`.

In addition, the QPoint class provides the manhattanLength() function which gives an inexpensive approximation of the length of the QPoint object interpreted as a vector. Finally, QPoint objects can be streamed as well as compared.

See also QPointF and QPolygon.

## Member Function Documentation

### `[constexpr noexcept]` QPoint::QPoint()

Constructs a null point, i.e. with coordinates (0, 0)

See also isNull().

### `[constexpr noexcept]` QPoint::QPoint(int xpos, int ypos)

Constructs a point with the given coordinates (xpos, ypos).

See also setX() and setY().

### `[static constexpr]` int QPoint::dotProduct(const QPoint &p1, const QPoint &p2)

     QPoint p( 3, 7);
     QPoint q(-1, 4);
     int dotProduct = QPoint::dotProduct(p, q);   // dotProduct becomes 25

Returns the dot product of p1 and p2.

### `[constexpr noexcept]` bool QPoint::isNull() const

Returns `true` if both the x and y coordinates are set to 0, otherwise returns `false`.

### `[constexpr]` int QPoint::manhattanLength() const

Returns the sum of the absolute values of x() and y(), traditionally known as the "Manhattan length" of the vector from the origin to the point. For example:

     QPoint oldPosition;

     MyWidget::mouseMoveEvent(QMouseEvent *event)
     {
         QPoint point = event->pos() - oldPosition;
         if (point.manhattanLength() > 3)
             // the mouse has moved more than 3 pixels since the oldPosition
     }

This is a useful, and quick to calculate, approximation to the true length:

     double trueLength = std::sqrt(std::pow(x(), 2) + std::pow(y(), 2));

The tradition of "Manhattan length" arises because such distances apply to travelers who can only travel on a rectangular grid, like the streets of Manhattan.

### `[constexpr noexcept]` int &QPoint::rx()

Returns a reference to the x coordinate of this point.

Using a reference makes it possible to directly manipulate x. For example:

     QPoint p(1, 2);
     p.rx()--;   // p becomes (0, 2)

See also x() and setX().

### `[constexpr noexcept]` int &QPoint::ry()

Returns a reference to the y coordinate of this point.

Using a reference makes it possible to directly manipulate y. For example:

     QPoint p(1, 2);
     p.ry()++;   // p becomes (1, 3)

See also y() and setY().

### `[constexpr noexcept]` void QPoint::setX(int x)

Sets the x coordinate of this point to the given x coordinate.

See also x() and setY().

### `[constexpr noexcept]` void QPoint::setY(int y)

Sets the y coordinate of this point to the given y coordinate.

See also y() and setX().

### `[noexcept]` CGPoint QPoint::toCGPoint() const

Creates a CGPoint from a QPoint.

See also QPointF::fromCGPoint().

### `[constexpr noexcept, since 6.4]` QPointF QPoint::toPointF() const

Returns this point as a point with floating point accuracy.

This function was introduced in Qt 6.4.

See also QPointF::toPoint().

### `[constexpr noexcept]` QPoint QPoint::transposed() const

Returns a point with x and y coordinates exchanged:

     QPoint{1, 2}.transposed() // {2, 1}

See also x(), y(), setX(), and setY().

### `[constexpr noexcept]` int QPoint::x() const

Returns the x coordinate of this point.

See also setX() and rx().

### `[constexpr noexcept]` int QPoint::y() const

Returns the y coordinate of this point.

See also setY() and ry().

### `[constexpr]` QPoint &QPoint::operator*=(double factor)

Multiplies this point's coordinates by the given factor, and returns a reference to this point. For example:

     QPoint p(-1, 4);
     p *= 2.5;    // p becomes (-3, 10)

Note that the result is rounded to the nearest integer as points are held as integers. Use QPointF for floating point accuracy.

See also operator/=().

### `[constexpr]` QPoint &QPoint::operator*=(float factor)

Multiplies this point's coordinates by the given factor, and returns a reference to this point.

Note that the result is rounded to the nearest integer as points are held as integers. Use QPointF for floating point accuracy.

See also operator/=().

### `[constexpr]` QPoint &QPoint::operator*=(int factor)

Multiplies this point's coordinates by the given factor, and returns a reference to this point.

See also operator/=().

### `[constexpr]` QPoint &QPoint::operator+=(const QPoint &point)

Adds the given point to this point and returns a reference to this point. For example:

     QPoint p( 3, 7);
     QPoint q(-1, 4);
     p += q;    // p becomes (2, 11)

See also operator-=().

### `[constexpr]` QPoint &QPoint::operator-=(const QPoint &point)

Subtracts the given point from this point and returns a reference to this point. For example:

     QPoint p( 3, 7);
     QPoint q(-1, 4);
     p -= q;    // p becomes (4, 3)

See also operator+=().

### `[constexpr]` QPoint &QPoint::operator/=(qreal divisor)

This is an overloaded function.

Divides both x and y by the given divisor, and returns a reference to this point. For example:

     QPoint p(-3, 10);
     p /= 2.5;           // p becomes (-1, 4)

Note that the result is rounded to the nearest integer as points are held as integers. Use QPointF for floating point accuracy.

See also operator*=().

## Related Non-Members

### `[constexpr noexcept]` bool operator!=(const QPoint &lhs, const QPoint &rhs)

Returns `true` if lhs and rhs are not equal; otherwise returns `false`.

### `[constexpr]` QPoint operator*(const QPoint &point, double factor)

Returns a copy of the given point multiplied by the given factor.

Note that the result is rounded to the nearest integer as points are held as integers. Use QPointF for floating point accuracy.

See also QPoint::operator*=().

### `[constexpr]` QPoint operator*(const QPoint &point, float factor)

Returns a copy of the given point multiplied by the given factor.

Note that the result is rounded to the nearest integer as points are held as integers. Use QPointF for floating point accuracy.

See also QPoint::operator*=().

### `[constexpr noexcept]` QPoint operator*(const QPoint &point, int factor)

Returns a copy of the given point multiplied by the given factor.

See also QPoint::operator*=().

### `[constexpr]` QPoint operator*(double factor, const QPoint &point)

This is an overloaded function.

Returns a copy of the given point multiplied by the given factor.

Note that the result is rounded to the nearest integer as points are held as integers. Use QPointF for floating point accuracy.

See also QPoint::operator*=().

### `[constexpr]` QPoint operator*(float factor, const QPoint &point)

This is an overloaded function.

Returns a copy of the given point multiplied by the given factor.

Note that the result is rounded to the nearest integer as points are held as integers. Use QPointF for floating point accuracy.

See also QPoint::operator*=().

### `[constexpr noexcept]` QPoint operator*(int factor, const QPoint &point)

This is an overloaded function.

Returns a copy of the given point multiplied by the given factor.

See also QPoint::operator*=().

### `[constexpr noexcept]` QPoint operator+(const QPoint &point)

Returns point unmodified.

### `[constexpr noexcept]` QPoint operator+(const QPoint &p1, const QPoint &p2)

Returns a QPoint object that is the sum of the given points, p1 and p2; each component is added separately.

See also QPoint::operator+=().

### `[constexpr noexcept]` QPoint operator-(const QPoint &p1, const QPoint &p2)

Returns a QPoint object that is formed by subtracting p2 from p1; each component is subtracted separately.

See also QPoint::operator-=().

### `[constexpr noexcept]` QPoint operator-(const QPoint &point)

This is an overloaded function.

Returns a QPoint object that is formed by changing the sign of both components of the given point.

Equivalent to `QPoint(0,0) - point`.

### `[constexpr]` QPoint operator/(const QPoint &point, qreal divisor)

Returns the QPoint formed by dividing both components of the given point by the given divisor.

Note that the result is rounded to the nearest integer as points are held as integers. Use QPointF for floating point accuracy.

See also QPoint::operator/=().

### QDataStream &operator<<(QDataStream &stream, const QPoint &point)

Writes the given point to the given stream and returns a reference to the stream.

See also Serializing Qt Data Types.

### `[constexpr noexcept]` bool operator==(const QPoint &lhs, const QPoint &rhs)

Returns `true` if lhs and rhs are equal; otherwise returns `false`.

### QDataStream &operator>>(QDataStream &stream, QPoint &point)

Reads a point from the given stream into the given point and returns a reference to the stream.

See also Serializing Qt Data Types.