QPoint Class Reference

Member Function Documentation

QPoint::QPoint ()

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

See also isNull().

QPoint::QPoint ( int x, int y )

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

See also setX() and setY().

bool QPoint::isNull () const

Returns true if both the x and y coordinates are set to 0, otherwise returns false.

int QPoint::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. For example:

 QPoint oldPosition;

 MyWidget::mouseMoveEvent(QMouseEvent *event)
 {
     QPoint point = event->pos() - oldPosition;
     if (point.manhattanLength() > 3)
         // the mouse has moved more than 3 pixels since the oldPosition
 }

This is a useful, and quick to calculate, approximation to the true length:

 double trueLength = sqrt(pow(x(), 2) + pow(y(), 2));

The tradition of "Manhattan length" arises because such distances apply to travelers who can only travel on a rectangular grid, like the streets of Manhattan.

int & QPoint::rx ()

Returns a reference to the x coordinate of this point.

Using a reference makes it possible to directly manipulate x. For example:

 QPoint p(1, 2);
 p.rx()--;   // p becomes (0, 2)

See also x() and setX().

int & QPoint::ry ()

Returns a reference to the y coordinate of this point.

Using a reference makes it possible to directly manipulate y. For example:

 QPoint p(1, 2);
 p.ry()++;   // p becomes (1, 3)

See also y() and setY().

void QPoint::setX ( int x )

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

See also x() and setY().

void QPoint::setY ( int y )

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

See also y() and setX().

int QPoint::x () const

Returns the x coordinate of this point.

See also setX() and rx().

int QPoint::y () const

Returns the y coordinate of this point.

See also setY() and ry().

QPoint & QPoint::operator*= ( qreal factor )

Multiplies this point's coordinates by the given factor, and returns a reference to this point. For example:

 QPoint p(-1, 4);
 p *= 2.5;    // p becomes (-3, 10)

Note that the result is rounded to the nearest integer as points are held as integers. Use QPointF for floating point accuracy.

See also operator/=().

QPoint & QPoint::operator+= ( const QPoint & point )

Adds the given point to this point and returns a reference to this point. For example:

 QPoint p( 3, 7);
 QPoint q(-1, 4);
 p += q;    // p becomes (2, 11)

See also operator-=().

QPoint & QPoint::operator-= ( const QPoint & point )

Subtracts the given point from this point and returns a reference to this point. For example:

 QPoint p( 3, 7);
 QPoint q(-1, 4);
 p -= q;    // p becomes (4, 3)

See also operator+=().

QPoint & QPoint::operator/= ( qreal divisor )

This is an overloaded function.

Divides both x and y by the given divisor, and returns a reference to this point. For example:

 QPoint p(-3, 10);
 p /= 2.5;           // p becomes (-1, 4)

Note that the result is rounded to the nearest integer as points are held as integers. Use QPointF for floating point accuracy.

See also operator*=().