QLine Class

The QLine class provides a two-dimensional vector using integer precision. More...

Header:	#include <QLine>
CMake:	find_package(Qt6 COMPONENTS Core REQUIRED) target_link_libraries(mytarget PRIVATE Qt6::Core)
qmake:	QT += core

• List of all members, including inherited members

Public Functions

	QLine(int x1, int y1, int x2, int y2)
	QLine(const QPoint &p1, const QPoint &p2)
	QLine()
QPoint	p1() const
QPoint	p2() const
int	x1() const
int	x2() const
int	y1() const
int	y2() const
QPoint	center() const
int	dx() const
int	dy() const
bool	isNull() const
void	setP1(const QPoint &p1)
void	setP2(const QPoint &p2)
void	setLine(int x1, int y1, int x2, int y2)
void	setPoints(const QPoint &p1, const QPoint &p2)
void	translate(const QPoint &offset)
void	translate(int dx, int dy)
QLine	translated(const QPoint &offset) const
QLine	translated(int dx, int dy) const
bool	operator!=(const QLine &line) const
bool	operator==(const QLine &line) const

Related Non-Members

QDataStream &	operator<<(QDataStream &stream, const QLine &line)
QDataStream &	operator>>(QDataStream &stream, QLine &line)

Detailed Description

A QLine describes a finite length line (or a line segment) on a two-dimensional surface. The start and end points of the line are specified using integer point accuracy for coordinates. Use the QLineF constructor to retrieve a floating point copy.

The positions of the line's start and end points can be retrieved using the p1(), x1(), y1(), p2(), x2(), and y2() functions. The dx() and dy() functions return the horizontal and vertical components of the line. Use isNull() to determine whether the QLine represents a valid line or a null line.

Finally, the line can be translated a given offset using the translate() function.

See also QLineF, QPolygon, and QRect.

Member Function Documentation

QLine::QLine(int x1, int y1, int x2, int y2)

Constructs a line object that represents the line between (x1, y1) and (x2, y2).

QLine::QLine(const QPoint &p1, const QPoint &p2)

Constructs a line object that represents the line between p1 and p2.

QLine::QLine()

Constructs a null line.

QPoint QLine::p1() const

Returns the line's start point.

See also setP1(), x1(), y1(), and p2().

QPoint QLine::p2() const

Returns the line's end point.

See also setP2(), x2(), y2(), and p1().

int QLine::x1() const

Returns the x-coordinate of the line's start point.

See also p1().

int QLine::x2() const

Returns the x-coordinate of the line's end point.

See also p2().

int QLine::y1() const

Returns the y-coordinate of the line's start point.

See also p1().

int QLine::y2() const

Returns the y-coordinate of the line's end point.

See also p2().

[since 5.8] QPoint QLine::center() const

Returns the center point of this line. This is equivalent to (p1() + p2()) / 2, except it will never overflow.

This function was introduced in Qt 5.8.

int QLine::dx() const

Returns the horizontal component of the line's vector.

See also dy().

int QLine::dy() const

Returns the vertical component of the line's vector.

See also dx().

bool QLine::isNull() const

Returns true if the line does not have distinct start and end points; otherwise returns false.

void QLine::setP1(const QPoint &p1)

Sets the starting point of this line to p1.

See also setP2() and p1().

void QLine::setP2(const QPoint &p2)

Sets the end point of this line to p2.

See also setP1() and p2().

void QLine::setLine(int x1, int y1, int x2, int y2)

Sets this line to the start in x1, y1 and end in x2, y2.

See also setP1(), setP2(), p1(), and p2().

void QLine::setPoints(const QPoint &p1, const QPoint &p2)

Sets the start point of this line to p1 and the end point of this line to p2.

See also setP1(), setP2(), p1(), and p2().

void QLine::translate(const QPoint &offset)

Translates this line by the given offset.

void QLine::translate(int dx, int dy)

This is an overloaded function.

Translates this line the distance specified by dx and dy.

QLine QLine::translated(const QPoint &offset) const

Returns this line translated by the given offset.

QLine QLine::translated(int dx, int dy) const

This is an overloaded function.

Returns this line translated the distance specified by dx and dy.

bool QLine::operator!=(const QLine &line) const

Returns true if the given line is not the same as this line.

A line is different from another line if any of their start or end points differ, or the internal order of the points is different.

bool QLine::operator==(const QLine &line) const

Returns true if the given line is the same as this line.

A line is identical to another line if the start and end points are identical, and the internal order of the points is the same.