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# QPolygonF Class Reference
[QtGui module]

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

    #include <QPolygonF>

Inherits QVector<QPointF>.

Note: All the functions in this class are reentrant.

- List of all members, including inherited members

### 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 isClosed () const
- QPolygon toPolygon () const
- void translate ( const QPointF & offset )
- void translate ( qreal dx, qreal dy )

- 62 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::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().

### 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.

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

This is an overloaded member function, provided for convenience.

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

## Related Non-Members

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

This is an overloaded member function, provided for convenience.

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

See also Format of the QDataStream Operators.

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

This is an overloaded member function, provided for convenience.

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

See also Format of the QDataStream Operators.