# QPolygonF Class

The QPolygonF class provides a vector of points using floating point precision. More...

Header: | #include <QPolygonF> |

qmake: | QT += gui |

Inherits: | QVector<QPointF> |

**Note:** All functions in this class are reentrant.

## Public Functions

QPolygonF() | |

QPolygonF(int size) | |

QPolygonF(const QPolygonF & polygon) | |

QPolygonF(const QVector<QPointF> & points) | |

QPolygonF(const QRectF & rectangle) | |

QPolygonF(const QPolygon & polygon) | |

~QPolygonF() | |

QRectF | boundingRect() const |

bool | containsPoint(const QPointF & point, Qt::FillRule fillRule) const |

QPolygonF | intersected(const QPolygonF & r) const |

bool | isClosed() const |

QPolygonF | subtracted(const QPolygonF & r) const |

void | swap(QPolygonF & other) |

QPolygon | toPolygon() const |

void | translate(const QPointF & offset) |

void | translate(qreal dx, qreal dy) |

QPolygonF | translated(const QPointF & offset) const |

QPolygonF | translated(qreal dx, qreal dy) const |

QPolygonF | united(const QPolygonF & r) const |

operator QVariant() const |

- 78 public functions inherited from QVector

## Related Non-Members

QDataStream & | operator<<(QDataStream & stream, const QPolygonF & polygon) |

QDataStream & | operator>>(QDataStream & stream, QPolygonF & polygon) |

### Additional Inherited Members

- 2 static public members inherited from QVector

## Detailed Description

The QPolygonF class provides a vector of points using floating point precision.

A QPolygonF is a QVector<QPointF>. The easiest way to add points to a QPolygonF is to use its streaming operator, as illustrated below:

QPolygonF polygon; polygon << QPointF(10.4, 20.5) << QPointF(20.2, 30.2);

In addition to the functions provided by QVector, QPolygonF provides the boundingRect() and translate() functions for geometry operations. Use the QMatrix::map() function for more general transformations of QPolygonFs.

QPolygonF also provides the isClosed() function to determine whether a polygon's start and end points are the same, and the toPolygon() function returning an integer precision copy of this polygon.

The QPolygonF class is implicitly shared.

**See also **QVector, QPolygon, and QLineF.

## Member Function Documentation

### QPolygonF::QPolygonF()

Constructs a polygon with no points.

**See also **QVector::isEmpty().

### QPolygonF::QPolygonF(int* size*)

Constructs a polygon of the given *size*. Creates an empty polygon if *size* == 0.

**See also **QVector::isEmpty().

### QPolygonF::QPolygonF(const QPolygonF &* polygon*)

Constructs a copy of the given *polygon*.

### QPolygonF::QPolygonF(const QVector<QPointF> &* points*)

Constructs a polygon containing the specified *points*.

### QPolygonF::QPolygonF(const QRectF &* rectangle*)

Constructs a closed polygon from the specified *rectangle*.

The polygon contains the four vertices of the rectangle in clockwise order starting and ending with the top-left vertex.

**See also **isClosed().

### QPolygonF::QPolygonF(const QPolygon &* polygon*)

Constructs a float based polygon from the specified integer based *polygon*.

**See also **toPolygon().

### QPolygonF::~QPolygonF()

Destroys the polygon.

### QRectF QPolygonF::boundingRect() const

Returns the bounding rectangle of the polygon, or QRectF(0,0,0,0) if the polygon is empty.

**See also **QVector::isEmpty().

### bool QPolygonF::containsPoint(const QPointF &* point*, Qt::FillRule* fillRule*) const

Returns `true`

if the given *point* is inside the polygon according to the specified *fillRule*; otherwise returns `false`

.

This function was introduced in Qt 4.3.

### QPolygonF QPolygonF::intersected(const QPolygonF &* r*) const

Returns a polygon which is the intersection of this polygon and *r*.

Set operations on polygons will treat the polygons as areas. Non-closed polygons will be treated as implicitly closed.

This function was introduced in Qt 4.3.

### bool QPolygonF::isClosed() const

Returns `true`

if the polygon is closed; otherwise returns `false`

.

A polygon is said to be closed if its start point and end point are equal.

**See also **QVector::first() and QVector::last().

### QPolygonF QPolygonF::subtracted(const QPolygonF &* r*) const

Returns a polygon which is *r* subtracted from this polygon.

Set operations on polygons will treat the polygons as areas. Non-closed polygons will be treated as implicitly closed.

This function was introduced in Qt 4.3.

### void QPolygonF::swap(QPolygonF &* other*)

Swaps polygon *other* with this polygon. This operation is very fast and never fails.

This function was introduced in Qt 4.8.

### QPolygon QPolygonF::toPolygon() const

Creates and returns a QPolygon by converting each QPointF to a QPoint.

**See also **QPointF::toPoint().

### void QPolygonF::translate(const QPointF &* offset*)

Translate all points in the polygon by the given *offset*.

**See also **translated().

### void QPolygonF::translate(qreal* dx*, qreal* dy*)

This is an overloaded function.

Translates all points in the polygon by (*dx*, *dy*).

**See also **translated().

### QPolygonF QPolygonF::translated(const QPointF &* offset*) const

Returns a copy of the polygon that is translated by the given *offset*.

This function was introduced in Qt 4.6.

**See also **translate().

### QPolygonF QPolygonF::translated(qreal* dx*, qreal* dy*) const

This is an overloaded function.

Returns a copy of the polygon that is translated by (*dx*, *dy*).

This function was introduced in Qt 4.6.

**See also **translate().

### QPolygonF QPolygonF::united(const QPolygonF &* r*) const

Returns a polygon which is the union of this polygon and *r*.

Set operations on polygons will treat the polygons as areas. Non-closed polygons will be treated as implicitly closed.

This function was introduced in Qt 4.3.

**See also **intersected() and subtracted().

### QPolygonF::operator QVariant() const

Returns the polygon as a QVariant.

## Related Non-Members

### QDataStream & operator<<(QDataStream &* stream*, const QPolygonF &* polygon*)

Writes the given *polygon* to the given *stream*, and returns a reference to the stream.

**See also **Serializing Qt Data Types.

### QDataStream & operator>>(QDataStream &* stream*, QPolygonF &* polygon*)

Reads a polygon from the given *stream* into the given *polygon*, and returns a reference to the stream.

**See also **Serializing Qt Data Types.

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