Qt 4.8: QPointF Class Reference

Qt Reference Documentation

# QPointF Class Reference

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

     #include <QPointF>

- List of all members, including inherited members

## Public Functions

| QPointF ()
| QPointF ( const QPoint & point )
| QPointF ( qreal x, qreal y )
bool | isNull () const
qreal | manhattanLength () const
qreal & | rx ()
qreal & | ry ()
void | setX ( qreal x )
void | setY ( qreal y )
QPoint | toPoint () 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 )

## Related Non-Members

bool | operator!= ( const QPointF & p1, const QPointF & p2 )
const QPointF | operator* ( qreal factor, const QPointF & point )
const QPointF | operator* ( const QPointF & point, qreal factor )
const QPointF | operator+ ( const QPointF & p1, const QPointF & p2 )
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

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

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 ()

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

See also isNull().

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

Constructs a copy of the given point.

See also toPoint().

### QPointF::QPointF ( qreal x, qreal y )

Constructs a point with the given coordinates (x, y).

See also setX() and setY().

### bool QPointF::isNull () const

Returns true if both the x and y coordinates are set to +0.0; otherwise returns false.

Note: Since this function treats +0.0 and -0.0 differently, points with zero-valued coordinates where either or both values have a negative sign are not defined to be null points.

### 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().

### 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().

### 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 not equal to p2; otherwise returns false.

### 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 & point, qreal factor )

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

See also QPointF::operator*=().

### 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 & 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 equal to p2; otherwise returns false.

### 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.