QPoint Class

Member Function Documentation

QPoint::QPoint(int xpos, int ypos)

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

See also setX() and setY().

QPoint::QPoint()

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

See also isNull().

[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().

CGPoint QPoint::toCGPoint() const

Creates a CGPoint from a QPoint.

This function was introduced in Qt 5.8.

See also QPointF::fromCGPoint().

QPoint QPoint::transposed() const

Returns a point with x and y coordinates exchanged:

QPoint{1, 2}.transposed() // {2, 1}

This function was introduced in Qt 5.14.

See also x(), y(), setX(), and setY().

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*=().