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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.

### Public Functions

• 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.

## Member Function Documentation

### QPolygonF::QPolygonF ()

Constructs a polygon with no points.

### QPolygonF::QPolygonF ( int size )

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

### 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.

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

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

### 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.

### bool QPolygonF::containsPoint ( const QPointF & point, Qt::FillRulefillRule ) 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.

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.

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

Returns a polygon which is r subtracted from this polygon.

This function was introduced in Qt 4.3.

### QPolygon QPolygonF::toPolygon () const

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

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

Translate all points in the polygon by the given offset.

### void QPolygonF::translate ( qrealdx, qrealdy )

This is an overloaded member function, provided for convenience.

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

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

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

This function was introduced in Qt 4.3.

## 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.