# QVector2D Class

The QVector2D class represents a vector or vertex in 2D space. More...

Header: | #include <QVector2D> |

Since: | Qt 4.6 |

## Public Functions

QVector2D() | |

QVector2D(qreal xpos, qreal ypos) | |

QVector2D(const QPoint & point) | |

QVector2D(const QPointF & point) | |

QVector2D(const QVector3D & vector) | |

QVector2D(const QVector4D & vector) | |

bool | isNull() const |

qreal | length() const |

qreal | lengthSquared() const |

void | normalize() |

QVector2D | normalized() const |

void | setX(qreal x) |

void | setY(qreal y) |

QPoint | toPoint() const |

QPointF | toPointF() const |

QVector3D | toVector3D() const |

QVector4D | toVector4D() const |

qreal | x() const |

qreal | y() const |

operator QVariant() const | |

QVector2D & | operator*=(qreal factor) |

QVector2D & | operator*=(const QVector2D & vector) |

QVector2D & | operator+=(const QVector2D & vector) |

QVector2D & | operator-=(const QVector2D & vector) |

QVector2D & | operator/=(qreal divisor) |

## Static Public Members

qreal | dotProduct(const QVector2D & v1, const QVector2D & v2) |

## Related Non-Members

bool | qFuzzyCompare(const QVector2D & v1, const QVector2D & v2) |

bool | operator!=(const QVector2D & v1, const QVector2D & v2) |

const QVector2D | operator*(qreal factor, const QVector2D & vector) |

const QVector2D | operator*(const QVector2D & vector, qreal factor) |

const QVector2D | operator*(const QVector2D & v1, const QVector2D & v2) |

const QVector2D | operator+(const QVector2D & v1, const QVector2D & v2) |

const QVector2D | operator-(const QVector2D & v1, const QVector2D & v2) |

const QVector2D | operator-(const QVector2D & vector) |

const QVector2D | operator/(const QVector2D & vector, qreal divisor) |

QDataStream & | operator<<(QDataStream & stream, const QVector2D & vector) |

bool | operator==(const QVector2D & v1, const QVector2D & v2) |

QDataStream & | operator>>(QDataStream & stream, QVector2D & vector) |

## Detailed Description

The QVector2D class represents a vector or vertex in 2D space.

The QVector2D class can also be used to represent vertices in 2D space. We therefore do not need to provide a separate vertex class.

**Note:** By design values in the QVector2D instance are stored as `float`

. This means that on platforms where the `qreal`

arguments to QVector2D functions are represented by `double`

values, it is possible to lose precision.

**See also **QVector3D, QVector4D, and QQuaternion.

## Member Function Documentation

### QVector2D::QVector2D()

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

### QVector2D::QVector2D(qreal* xpos*, qreal* ypos*)

Constructs a vector with coordinates (*xpos*, *ypos*).

### QVector2D::QVector2D(const QPoint &* point*)

Constructs a vector with x and y coordinates from a 2D *point*.

### QVector2D::QVector2D(const QPointF &* point*)

Constructs a vector with x and y coordinates from a 2D *point*.

### QVector2D::QVector2D(const QVector3D &* vector*)

Constructs a vector with x and y coordinates from a 3D *vector*. The z coordinate of *vector* is dropped.

**See also **toVector3D().

### QVector2D::QVector2D(const QVector4D &* vector*)

Constructs a vector with x and y coordinates from a 3D *vector*. The z and w coordinates of *vector* are dropped.

**See also **toVector4D().

`[static] `

qreal QVector2D::dotProduct(const QVector2D &* v1*, const QVector2D &* v2*)

Returns the dot product of *v1* and *v2*.

### bool QVector2D::isNull() const

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

### qreal QVector2D::length() const

Returns the length of the vector from the origin.

**See also **lengthSquared() and normalized().

### qreal QVector2D::lengthSquared() const

Returns the squared length of the vector from the origin. This is equivalent to the dot product of the vector with itself.

**See also **length() and dotProduct().

### void QVector2D::normalize()

Normalizes the currect vector in place. Nothing happens if this vector is a null vector or the length of the vector is very close to 1.

**See also **length() and normalized().

### QVector2D QVector2D::normalized() const

Returns the normalized unit vector form of this vector.

If this vector is null, then a null vector is returned. If the length of the vector is very close to 1, then the vector will be returned as-is. Otherwise the normalized form of the vector of length 1 will be returned.

**See also **length() and normalize().

### void QVector2D::setX(qreal* x*)

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

### void QVector2D::setY(qreal* y*)

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

### QPoint QVector2D::toPoint() const

Returns the QPoint form of this 2D vector.

**See also **toPointF() and toVector3D().

### QPointF QVector2D::toPointF() const

Returns the QPointF form of this 2D vector.

**See also **toPoint() and toVector3D().

### QVector3D QVector2D::toVector3D() const

Returns the 3D form of this 2D vector, with the z coordinate set to zero.

**See also **toVector4D() and toPoint().

### QVector4D QVector2D::toVector4D() const

Returns the 4D form of this 2D vector, with the z and w coordinates set to zero.

**See also **toVector3D() and toPoint().

### qreal QVector2D::x() const

Returns the x coordinate of this point.

### qreal QVector2D::y() const

Returns the y coordinate of this point.

### QVector2D::operator QVariant() const

Returns the 2D vector as a QVariant.

### QVector2D & QVector2D::operator*=(qreal* factor*)

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

**See also **operator/=().

### QVector2D & QVector2D::operator*=(const QVector2D &* vector*)

Multiplies the components of this vector by the corresponding components in *vector*.

### QVector2D & QVector2D::operator+=(const QVector2D &* vector*)

Adds the given *vector* to this vector and returns a reference to this vector.

**See also **operator-=().

### QVector2D & QVector2D::operator-=(const QVector2D &* vector*)

Subtracts the given *vector* from this vector and returns a reference to this vector.

**See also **operator+=().

### QVector2D & QVector2D::operator/=(qreal* divisor*)

Divides this vector's coordinates by the given *divisor*, and returns a reference to this vector.

**See also **operator*=().

## Related Non-Members

### bool qFuzzyCompare(const QVector2D &* v1*, const QVector2D &* v2*)

Returns true if *v1* and *v2* are equal, allowing for a small fuzziness factor for floating-point comparisons; false otherwise.

### bool operator!=(const QVector2D &* v1*, const QVector2D &* v2*)

Returns true if *v1* is not equal to *v2*; otherwise returns false. This operator uses an exact floating-point comparison.

### const QVector2D operator*(qreal* factor*, const QVector2D &* vector*)

Returns a copy of the given *vector*, multiplied by the given *factor*.

**See also **QVector2D::operator*=().

### const QVector2D operator*(const QVector2D &* vector*, qreal* factor*)

Returns a copy of the given *vector*, multiplied by the given *factor*.

**See also **QVector2D::operator*=().

### const QVector2D operator*(const QVector2D &* v1*, const QVector2D &* v2*)

Multiplies the components of *v1* by the corresponding components in *v2*.

### const QVector2D operator+(const QVector2D &* v1*, const QVector2D &* v2*)

Returns a QVector2D object that is the sum of the given vectors, *v1* and *v2*; each component is added separately.

**See also **QVector2D::operator+=().

### const QVector2D operator-(const QVector2D &* v1*, const QVector2D &* v2*)

Returns a QVector2D object that is formed by subtracting *v2* from *v1*; each component is subtracted separately.

**See also **QVector2D::operator-=().

### const QVector2D operator-(const QVector2D &* vector*)

This is an overloaded function.

Returns a QVector2D object that is formed by changing the sign of the components of the given *vector*.

Equivalent to `QVector2D(0,0) - vector`

.

### const QVector2D operator/(const QVector2D &* vector*, qreal* divisor*)

Returns the QVector2D object formed by dividing all three components of the given *vector* by the given *divisor*.

**See also **QVector2D::operator/=().

### QDataStream & operator<<(QDataStream &* stream*, const QVector2D &* vector*)

Writes the given *vector* to the given *stream* and returns a reference to the stream.

**See also **Serializing Qt Data Types.

### bool operator==(const QVector2D &* v1*, const QVector2D &* v2*)

Returns true if *v1* is equal to *v2*; otherwise returns false. This operator uses an exact floating-point comparison.

### QDataStream & operator>>(QDataStream &* stream*, QVector2D &* vector*)

Reads a 2D vector from the given *stream* into the given *vector* and returns a reference to the stream.

**See also **Serializing Qt Data Types.

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