QPoint Class

  QPoint p;

  p.setX(p.x() + 1);
  p += QPoint(1, 0);
  p.rx()++;

Member Function Documentation

QPoint::QPoint()

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

See also isNull().

QPoint::QPoint(int xpos, int ypos)

Constructs a point with the given coordinates (xpos, ypos).

See also setX() and setY().

[static] int QPoint::dotProduct(const QPoint &p1, const QPoint &p2)

  QPoint p( 3, 7);
  QPoint q(-1, 4);
  int lengthSquared = QPoint::dotProduct(p, q);   // lengthSquared becomes 25

Returns the dot product of p1 and p2.

This function was introduced in Qt 5.1.

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 = std::sqrt(std::pow(x(), 2) + std::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*=(float factor)

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

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*=(double 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*=(int factor)

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

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*=().