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

# QPointF Class

The QPointF class defines a point in the plane using floating point precision. More...

Header: | #include <QPointF>
qmake: | QT += core

- List of all members, including inherited members

Note: All functions in this class are reentrant.

## Public Functions

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

## Static Public Members

qreal | dotProduct(const QPointF &p1, const QPointF &p2)
QPointF | fromCGPoint(CGPoint point)

## Related Non-Members

bool | operator!=(const QPointF &p1, const QPointF &p2)
const QPointF | operator*(const QPointF &point, qreal factor)
const QPointF | operator*(qreal factor, const QPointF &point)
const QPointF | operator+(const QPointF &p1, const QPointF &p2)
const QPointF | operator+(const QPointF &point)
const QPointF | operator-(const QPointF &p1, const QPointF &p2)
const QPointF | operator-(const QPointF &point)
const QPointF | operator/(const QPointF &point, qreal divisor)
QDataStream & | operator<<(QDataStream &stream, const QPointF &point)
bool | operator==(const QPointF &p1, const QPointF &p2)
QDataStream & | operator>>(QDataStream &stream, QPointF &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 coordinates of the point are specified using floating point numbers for accuracy. The isNull() function returns `true` if both x and y are set to 0.0. 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:

     QPointF p;

     p.setX(p.x() + 1.0);
     p += QPointF(1.0, 0.0);
     p.rx()++;

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

In addition, the QPointF class provides a constructor converting a QPoint object into a QPointF object, and a corresponding toPoint() function which returns a QPoint copy of this point. Finally, QPointF objects can be streamed as well as compared.

See also QPoint and QPolygonF.

## Member Function Documentation

### QPointF::QPointF(qreal xpos, qreal ypos)

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

See also setX() and setY().

### QPointF::QPointF(const QPoint &point)

Constructs a copy of the given point.

See also toPoint().

### QPointF::QPointF()

Constructs a null point, i.e. with coordinates (0.0, 0.0)

See also isNull().

### `[static]` qreal QPointF::dotProduct(const QPointF &p1, const QPointF &p2)

     QPointF p( 3.1, 7.1);
     QPointF q(-1.0, 4.1);
     int lengthSquared = QPointF::dotProduct(p, q);   // lengthSquared becomes 26.01

Returns the dot product of p1 and p2.

This function was introduced in Qt 5.1.

### `[static]` QPointF QPointF::fromCGPoint(CGPoint point)

Creates a QRectF from CGPoint point.

This function was introduced in Qt 5.8.

See also toCGPoint().

### bool QPointF::isNull() const

Returns `true` if both the x and y coordinates are set to 0.0 (ignoring the sign); otherwise returns `false`.

### qreal QPointF::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.

This function was introduced in Qt 4.6.

See also QPoint::manhattanLength().

### qreal &QPointF::rx()

Returns a reference to the x coordinate of this point.

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

      QPointF p(1.1, 2.5);
      p.rx()--;   // p becomes (0.1, 2.5)

See also x() and setX().

### qreal &QPointF::ry()

Returns a reference to the y coordinate of this point.

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

     QPointF p(1.1, 2.5);
     p.ry()++;   // p becomes (1.1, 3.5)

See also y() and setY().

### void QPointF::setX(qreal x)

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

See also x() and setY().

### void QPointF::setY(qreal y)

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

See also y() and setX().

### CGPoint QPointF::toCGPoint() const

Creates a CGPoint from a QPointF.

This function was introduced in Qt 5.8.

See also fromCGPoint().

### QPoint QPointF::toPoint() const

Rounds the coordinates of this point to the nearest integer, and returns a QPoint object with the rounded coordinates.

See also QPointF().

### QPointF QPointF::transposed() const

Returns a point with x and y coordinates exchanged:

     QPointF{1.0, 2.0}.transposed() // {2.0, 1.0}

This function was introduced in Qt 5.14.

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

### qreal QPointF::x() const

Returns the x coordinate of this point.

See also setX() and rx().

### qreal QPointF::y() const

Returns the y coordinate of this point.

See also setY() and ry().

### QPointF &QPointF::operator*=(qreal factor)

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

     QPointF p(-1.1, 4.1);
     p *= 2.5;    // p becomes (-2.75, 10.25)

See also operator/=().

### QPointF &QPointF::operator+=(const QPointF &point)

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

     QPointF p( 3.1, 7.1);
     QPointF q(-1.0, 4.1);
     p += q;    // p becomes (2.1, 11.2)

See also operator-=().

### QPointF &QPointF::operator-=(const QPointF &point)

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

     QPointF p( 3.1, 7.1);
     QPointF q(-1.0, 4.1);
     p -= q;    // p becomes (4.1, 3.0)

See also operator+=().

### QPointF &QPointF::operator/=(qreal divisor)

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

     QPointF p(-2.75, 10.25);
     p /= 2.5;           // p becomes (-1.1, 4.1)

See also operator*=().

## Related Non-Members

### bool operator!=(const QPointF &p1, const QPointF &p2)

Returns `true` if p1 is sufficiently different from p2; otherwise returns `false`.

Warning: This function does not check for strict inequality; instead, it uses a fuzzy comparison to compare the points' coordinates.

See also qFuzzyCompare.

### const QPointF operator*(const QPointF &point, qreal factor)

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

See also QPointF::operator*=().

### const QPointF operator*(qreal factor, const QPointF &point)

This is an overloaded function.

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

### const QPointF operator+(const QPointF &p1, const QPointF &p2)

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

See also QPointF::operator+=().

### const QPointF operator+(const QPointF &point)

Returns point unmodified.

This function was introduced in Qt 5.0.

### const QPointF operator-(const QPointF &p1, const QPointF &p2)

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

See also QPointF::operator-=().

### const QPointF operator-(const QPointF &point)

This is an overloaded function.

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

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

### const QPointF operator/(const QPointF &point, qreal divisor)

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

See also QPointF::operator/=().

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

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

See also Serializing Qt Data Types.

### bool operator==(const QPointF &p1, const QPointF &p2)

Returns `true` if p1 is approximately equal to p2; otherwise returns `false`.

Warning: This function does not check for strict equality; instead, it uses a fuzzy comparison to compare the points' coordinates.

See also qFuzzyCompare.

### QDataStream &operator>>(QDataStream &stream, QPointF &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.