Line Class Reference

Represents a 2D line segment between two Point endpoints. More...

#include <line.h>

Classes
class	List
	A list of Line objects with spatial query helpers. More...

Public Member Functions
	Line ()
	Default constructor — creates a zero-length line at the origin.
	Line (const QPoint &p1, const QPoint &p2)
	Construct a line from two integer points.
	Line (const QPointF &p1, const QPointF &p2)
	Construct a line from two floating-point points.
	Line (const QPointF &origin, double bearing, double distance)
	Construct a line from an origin point, bearing, and distance.
	Line (const QPointF &origin, Geo::Direction direction, double distance)
	Construct a line from an origin point, cardinal direction, and distance.
	Line (const QLineF &other)
	Construct from a QLineF.
	Line (const QLine &other)
	Construct from a QLine.
bool	operator== (const Line &other) const
	Equality comparison — endpoints must match exactly.
bool	operator!= (const Line &other) const
	Inequality comparison.
Point	p1 () const
	Return the start point.
void	setP1 (const Point &value)
	Set the start point.
Point	p2 () const
	Return the end point.
void	setP2 (const Point &value)
	Set the end point.
Point	midpoint () const
	Return the midpoint of this line.
double	length () const
	Return the length (Euclidean distance between endpoints).
double	slope () const
	Return the slope (rise/run), or infinity for vertical lines.
double	intercept () const
	Return the Y-intercept of the line's equation.
bool	isVertical () const
	Test whether this line is exactly vertical.
bool	isHorizontal () const
	Test whether this line is exactly horizontal.
double	bearing () const
	Return the compass bearing from p1 to p2, in degrees.
Angle	angle () const
	Return the angle of this line as an Angle object.
double	distanceTo (const QPointF &to) const
	Return the perpendicular distance from this line to a point.
Point	closestPointTo (const QPointF &point) const
	Return the point on this line closest to the given point.
Point	closestPointTo (const QPointF &point, double &distance) const
	Return the closest point and output the distance.
Point	furthestPointFrom (const QPointF &point) const
	Return the endpoint furthest from the given point.
Point	topMostPoint () const
	Return the endpoint with the smallest Y coordinate.
Point	bottomMostPoint () const
	Return the endpoint with the largest Y coordinate.
Point	leftMostPoint () const
	Return the endpoint with the smallest X coordinate.
Point	rightMostPoint () const
	Return the endpoint with the largest X coordinate.
bool	hasXBetween (double x1, double x2) const
	Test whether the line spans an X range.
bool	crossesX (double x) const
	Test whether the line crosses a specific X coordinate.
bool	hasYBetween (double y1, double y2) const
	Test whether the line spans a Y range.
bool	crossesY (double y) const
	Test whether the line crosses a specific Y coordinate.
bool	intersects (const Line &other) const
	Test whether this line intersects another.
bool	intersects (const Line &other, Point &intersection) const
	Test whether this line intersects another and output the intersection point.
bool	intersects (const Circle &other) const
	Test whether this line intersects a circle.
bool	intersects (const QRectF &other) const
	Test whether this line intersects a rectangle.
Point	intersection (const Line &other) const
	Compute the intersection point with another line.
bool	isLeftOf (const Line &other) const
	Test whether this line is entirely to the left of other.
bool	isRightOf (const Line &other) const
	Test whether this line is entirely to the right of other.
bool	isAbove (const Line &other) const
	Test whether this line is entirely above other.
bool	isBelow (const Line &other) const
	Test whether this line is entirely below other.
bool	isPerpendicular () const
	Test whether this line is perpendicular (horizontal or vertical).
bool	sharesAxisWith (const Line &other) const
	Test whether this line shares an axis with other (both horizontal or both vertical).
bool	sharesEndpointWith (const Line &other, double maxDistance=0) const
	Test whether this line shares an endpoint with other within a tolerance.
bool	sharesSameEndpoints (const Line &other) const
	Test whether this line has exactly the same two endpoints as other.
bool	isEndpoint (const QPointF &point, int precision=0) const
	Test whether a point is an endpoint of this line.
bool	containsPoint (const QPointF &point) const
	Test whether a point lies on this line segment.
Line &	shorten (double howMuch)
	Shorten this line by removing length from the far end.
Line &	extend (double howMuch)
	Extend this line by adding length at the far end.
Line &	grow (double howMuch)
	Grow this line symmetrically by adding length at both ends.
Geo::Direction	direction () const
	Return the cardinal direction of this line.
double	minX () const
	Return the minimum X coordinate of the two endpoints.
double	maxX () const
	Return the maximum X coordinate of the two endpoints.
double	minY () const
	Return the minimum Y coordinate of the two endpoints.
double	maxY () const
	Return the maximum Y coordinate of the two endpoints.
Point::List	points () const
	Return a list containing both endpoints.
Line &	round ()
	Round both endpoints to integer coordinates in place.
Rectangle	makeRectangle (int expandedWidth) const
	Create a rectangle of the given width centred on this line.
Line &	move (double bearing, double distance)
	Move this line by bearing and distance.
Line &	move (Geo::Direction direction, double distance)
	Move this line in a cardinal direction by a distance.
Line &	moveDelta (double dx, double dy)
	Translate this line by a (dx, dy) delta.
Line &	rotate (const Point &centroid, double angle)
	Rotate this line around a centroid by an angle.
QLine	toQLine () const
	Convert to a QLine (integer endpoints).
QLineF	toQLineF () const
	Convert to a QLineF (floating-point endpoints).
QString	toString () const
	Format this line as a human-readable string.
bool	isValid () const
	Test whether this line has non-zero length.

Static Public Member Functions
static Line	fromString (const QString &value)
	Parse a Line from a string produced by toString().
static List	verticalLines (const QRectF &rect)
	Return vertical lines along the left and right edges of a rectangle.
static List	horizontalLines (const QRectF &rect)
	Return horizontal lines along the top and bottom edges of a rectangle.

Detailed Description

Represents a 2D line segment between two Point endpoints.

Provides length, slope, bearing, midpoint, intersection, containment, and spatial relationship queries as well as movement and rotation transforms.

Definition at line 27 of file line.h.

Constructor & Destructor Documentation

Line() [1/7]

Line::Line ( )

inline

Default constructor — creates a zero-length line at the origin.

Definition at line 31 of file line.h.

Line() [2/7]

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

inline

Construct a line from two integer points.

Parameters

p1	Start point
p2	End point

Definition at line 38 of file line.h.

Line() [3/7]

Line::Line ( const QPointF &  p1, const QPointF &  p2  )

inline

Construct a line from two floating-point points.

Parameters

p1	Start point
p2	End point

Definition at line 46 of file line.h.

Line() [4/7]

Line::Line	(	const QPointF &	origin,
		double	bearing,
		double	distance
	)

Construct a line from an origin point, bearing, and distance.

Parameters

origin	Start point
bearing	Compass bearing in degrees
distance	Length of the line

Line() [5/7]

Line::Line	(	const QPointF &	origin,
		Geo::Direction	direction,
		double	distance
	)

Construct a line from an origin point, cardinal direction, and distance.

Parameters

origin	Start point
direction	Cardinal direction of travel
distance	Length of the line

Line() [6/7]

Line::Line ( const QLineF &  other )

inline

Construct from a QLineF.

Parameters

other

Source QLineF to copy endpoints from

Definition at line 69 of file line.h.

Line() [7/7]

Line::Line ( const QLine &  other )

inline

Construct from a QLine.

Parameters

other

Source QLine to copy endpoints from

Definition at line 76 of file line.h.

Member Function Documentation

angle()

Angle Line::angle

(

)

const

Return the angle of this line as an Angle object.

Returns

Angle of the line

bearing()

double Line::bearing

(

)

const

Return the compass bearing from p1 to p2, in degrees.

Returns

Bearing in degrees

bottomMostPoint()

Point Line::bottomMostPoint

(

)

const

Return the endpoint with the largest Y coordinate.

Returns

Bottom-most Point

closestPointTo() [1/2]

Point Line::closestPointTo

(

const QPointF &

point

)

const

Return the point on this line closest to the given point.

Parameters

point

Reference point

Returns

Closest Point on this line segment

closestPointTo() [2/2]

Point Line::closestPointTo	(	const QPointF &	point,
		double &	distance
	)		const

Return the closest point and output the distance.

Parameters

point	Reference point
distance	Output set to the distance

Returns

Closest Point on this line segment

containsPoint()

bool Line::containsPoint

(

const QPointF &

point

)

const

Test whether a point lies on this line segment.

Parameters

point

Point to test

Returns

true if point lies on the segment

crossesX()

bool Line::crossesX

(

double

x

)

const

Test whether the line crosses a specific X coordinate.

Parameters

x	X coordinate to test

Returns

true if the line crosses x

crossesY()

bool Line::crossesY

(

double

y

)

const

Test whether the line crosses a specific Y coordinate.

Parameters

y	Y coordinate to test

Returns

true if the line crosses y

direction()

Geo::Direction Line::direction

(

)

const

Return the cardinal direction of this line.

Returns

Cardinal direction

distanceTo()

double Line::distanceTo

(

const QPointF &

to

)

const

Return the perpendicular distance from this line to a point.

Parameters

to	Point to measure distance from

Returns

Perpendicular distance

extend()

Line & Line::extend

(

double

howMuch

)

Extend this line by adding length at the far end.

Parameters

howMuch

Amount to add

Returns

Reference to this line

fromString()

static Line Line::fromString ( const QString &  value )

static

Parse a Line from a string produced by toString().

Parameters

value

String representation

Returns

Parsed Line

furthestPointFrom()

Point Line::furthestPointFrom

(

const QPointF &

point

)

const

Return the endpoint furthest from the given point.

Parameters

point

Reference point

Returns

The furthest of p1 and p2

grow()

Line & Line::grow

(

double

howMuch

)

Grow this line symmetrically by adding length at both ends.

Parameters

howMuch

Amount to add at each end

Returns

Reference to this line

hasXBetween()

bool Line::hasXBetween	(	double	x1,
		double	x2
	)		const

Test whether the line spans an X range.

Parameters

x1	First X boundary
x2	Second X boundary

Returns

true if any part of the line falls between x1 and x2

hasYBetween()

bool Line::hasYBetween	(	double	y1,
		double	y2
	)		const

Test whether the line spans a Y range.

Parameters

y1	First Y boundary
y2	Second Y boundary

Returns

true if any part of the line falls between y1 and y2

horizontalLines()

static List Line::horizontalLines ( const QRectF &  rect )

static

Return horizontal lines along the top and bottom edges of a rectangle.

Parameters

rect	Rectangle to extract edges from

Returns

List of horizontal edge lines

intercept()

double Line::intercept

(

)

const

Return the Y-intercept of the line's equation.

Returns

Y-intercept

intersection()

Point Line::intersection

(

const Line &

other

)

const

Compute the intersection point with another line.

Parameters

other

Line to intersect with

Returns

Intersection point (may be invalid if lines are parallel)

intersects() [1/4]

bool Line::intersects

(

const Circle &

other

)

const

Test whether this line intersects a circle.

Parameters

other

Circle to test against

Returns

true if the line intersects or is tangent to the circle

intersects() [2/4]

bool Line::intersects

(

const Line &

other

)

const

Test whether this line intersects another.

Parameters

other

Line to test against

Returns

true if the segments intersect

intersects() [3/4]

bool Line::intersects	(	const Line &	other,
		Point &	intersection
	)		const

Test whether this line intersects another and output the intersection point.

Parameters

other	Line to test against
intersection	Output set to the intersection point

Returns

true if the segments intersect

intersects() [4/4]

bool Line::intersects

(

const QRectF &

other

)

const

Test whether this line intersects a rectangle.

Parameters

other

Rectangle to test against

Returns

true if the line intersects the rectangle boundary

isAbove()

bool Line::isAbove

(

const Line &

other

)

const

Test whether this line is entirely above other.

Parameters

other

Line to compare against

Returns

true if this line is entirely above

isBelow()

bool Line::isBelow

(

const Line &

other

)

const

Test whether this line is entirely below other.

Parameters

other

Line to compare against

Returns

true if this line is entirely below

isEndpoint()

bool Line::isEndpoint	(	const QPointF &	point,
		int	precision = 0
	)		const

Test whether a point is an endpoint of this line.

Parameters

point	Point to test
precision	Decimal places for comparison (0 = integer)

Returns

true if point matches p1 or p2 within precision

isHorizontal()

bool Line::isHorizontal

(

)

const

Test whether this line is exactly horizontal.

Returns

true if horizontal

isLeftOf()

bool Line::isLeftOf

(

const Line &

other

)

const

Test whether this line is entirely to the left of other.

Parameters

other

Line to compare against

Returns

true if this line is entirely to the left

isPerpendicular()

bool Line::isPerpendicular

(

)

const

Test whether this line is perpendicular (horizontal or vertical).

Returns

true if the line is horizontal or vertical

isRightOf()

bool Line::isRightOf

(

const Line &

other

)

const

Test whether this line is entirely to the right of other.

Parameters

other

Line to compare against

Returns

true if this line is entirely to the right

isValid()

bool Line::isValid ( ) const

inline

Test whether this line has non-zero length.

Returns

true if length() != 0

Definition at line 573 of file line.h.

isVertical()

bool Line::isVertical

(

)

const

Test whether this line is exactly vertical.

Returns

true if vertical

leftMostPoint()

Point Line::leftMostPoint

(

)

const

Return the endpoint with the smallest X coordinate.

Returns

Left-most Point

length()

double Line::length

(

)

const

Return the length (Euclidean distance between endpoints).

Returns

Length of the line

makeRectangle()

Rectangle Line::makeRectangle

(

int

expandedWidth

)

const

Create a rectangle of the given width centred on this line.

Parameters

expandedWidth

Width of the resulting rectangle

Returns

Rectangle enclosing the line

maxX()

double Line::maxX

(

)

const

Return the maximum X coordinate of the two endpoints.

Returns

Maximum X value

maxY()

double Line::maxY

(

)

const

Return the maximum Y coordinate of the two endpoints.

Returns

Maximum Y value

midpoint()

Point Line::midpoint

(

)

const

Return the midpoint of this line.

Returns

Midpoint

minX()

double Line::minX

(

)

const

Return the minimum X coordinate of the two endpoints.

Returns

Minimum X value

minY()

double Line::minY

(

)

const

Return the minimum Y coordinate of the two endpoints.

Returns

Minimum Y value

move() [1/2]

Line & Line::move	(	double	bearing,
		double	distance
	)

Move this line by bearing and distance.

Parameters

bearing	Direction of movement in degrees
distance	Distance to move

Returns

Reference to this line

move() [2/2]

Line & Line::move	(	Geo::Direction	direction,
		double	distance
	)

Move this line in a cardinal direction by a distance.

Parameters

direction	Cardinal direction
distance	Distance to move

Returns

Reference to this line

moveDelta()

Line & Line::moveDelta	(	double	dx,
		double	dy
	)

Translate this line by a (dx, dy) delta.

Parameters

dx	Horizontal displacement
dy	Vertical displacement

Returns

Reference to this line

operator!=()

bool Line::operator!= ( const Line &  other ) const

inline

Inequality comparison.

Parameters

other

Line to compare against

Returns

true if the lines differ

Definition at line 90 of file line.h.

operator==()

bool Line::operator== ( const Line &  other ) const

inline

Equality comparison — endpoints must match exactly.

Parameters

other

Line to compare against

Returns

true if both endpoints match

Definition at line 84 of file line.h.

p1()

Point Line::p1 ( ) const

inline

Return the start point.

Returns

Start Point

Definition at line 103 of file line.h.

p2()

Point Line::p2 ( ) const

inline

Return the end point.

Returns

End Point

Definition at line 115 of file line.h.

points()

Point::List Line::points

(

)

const

Return a list containing both endpoints.

Returns

Point::List with p1 and p2

rightMostPoint()

Point Line::rightMostPoint

(

)

const

Return the endpoint with the largest X coordinate.

Returns

Right-most Point

rotate()

Line & Line::rotate	(	const Point &	centroid,
		double	angle
	)

Rotate this line around a centroid by an angle.

Parameters

centroid	Centre of rotation
angle	Rotation angle in degrees

Returns

Reference to this line

round()

Line & Line::round

(

)

Round both endpoints to integer coordinates in place.

Returns

Reference to this line

setP1()

void Line::setP1 ( const Point &  value )

inline

Set the start point.

Parameters

value

New start point

Definition at line 109 of file line.h.

setP2()

void Line::setP2 ( const Point &  value )

inline

Set the end point.

Parameters

value

New end point

Definition at line 121 of file line.h.

sharesAxisWith()

bool Line::sharesAxisWith

(

const Line &

other

)

const

Test whether this line shares an axis with other (both horizontal or both vertical).

Parameters

other

Line to compare against

Returns

true if both lines share the same axis

sharesEndpointWith()

bool Line::sharesEndpointWith	(	const Line &	other,
		double	maxDistance = 0
	)		const

Test whether this line shares an endpoint with other within a tolerance.

Parameters

other	Line to compare
maxDistance	Maximum endpoint distance to consider shared (default 0 = exact)

Returns

true if any endpoint pair is within maxDistance of each other

sharesSameEndpoints()

bool Line::sharesSameEndpoints

(

const Line &

other

)

const

Test whether this line has exactly the same two endpoints as other.

Parameters

other

Line to compare against

Returns

true if both endpoints match in either order

shorten()

Line & Line::shorten

(

double

howMuch

)

Shorten this line by removing length from the far end.

Parameters

howMuch

Amount to remove

Returns

Reference to this line

slope()

double Line::slope

(

)

const

Return the slope (rise/run), or infinity for vertical lines.

Returns

Slope value

topMostPoint()

Point Line::topMostPoint

(

)

const

Return the endpoint with the smallest Y coordinate.

Returns

Top-most Point

toQLine()

QLine Line::toQLine

(

)

const

Convert to a QLine (integer endpoints).

Returns

QLine equivalent

toQLineF()

QLineF Line::toQLineF

(

)

const

Convert to a QLineF (floating-point endpoints).

Returns

QLineF equivalent

toString()

QString Line::toString

(

)

const

Format this line as a human-readable string.

Returns

String representation

verticalLines()

static List Line::verticalLines ( const QRectF &  rect )

static

Return vertical lines along the left and right edges of a rectangle.

Parameters

rect	Rectangle to extract edges from

Returns

List of vertical edge lines

---

The documentation for this class was generated from the following file:

• include/Kanoop/geometry/line.h