QLineF Class

The QLineF class provides a two-dimensional vector using floating point precision. More...

Header: #include <QLineF>
qmake: QT += core

Public Types

enum IntersectType { NoIntersection, UnboundedIntersection, BoundedIntersection }

Public Functions

qreal angle() const
qreal length() const
void setAngle(qreal angle)
QLineF unitVector() const

Static Public Members

QLineF fromPolar(qreal length, qreal angle)
QDataStream &operator<<(QDataStream &stream, const QLineF &line)
QDataStream &operator>>(QDataStream &stream, QLineF &line)

Detailed Description

A QLineF describes a finite length line (or line segment) on a two-dimensional surface. QLineF defines the start and end points of the line using floating point accuracy for coordinates. Use the toLine() function to retrieve an integer based copy of this line.

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, respectively.

The line's length can be retrieved using the length() function, and altered using the setLength() function. Similarly, angle() and setAngle() are respectively used for retrieving and altering the angle of the line. Use the isNull() function to determine whether the QLineF represents a valid line or a null line.

The intersect() function determines the IntersectType for this line and a given line, while the angleTo() function returns the angle between the lines. In addition, the unitVector() function returns a line that has the same starting point as this line, but with a length of only 1, while the normalVector() function returns a line that is perpendicular to this line with the same starting point and length.

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

Constraints

QLine is limited to the minimum and maximum values for the int type. Operations on a QLine that could potentially result in values outside this range will result in undefined behavior.

See also QLine, QPolygonF, and QRectF.

Member Type Documentation

enum QLineF::IntersectType

Describes the intersection between two lines.

QLineF::UnboundedIntersectionQLineF::BoundedIntersection
ConstantValueDescription
QLineF::NoIntersection0Indicates that the lines do not intersect; i.e. they are parallel.
QLineF::UnboundedIntersection2The two lines intersect, but not within the range defined by their lengths. This will be the case if the lines are not parallel. intersect() will also return this value if the intersect point is within the start and end point of only one of the lines.
QLineF::BoundedIntersection1The two lines intersect with each other within the start and end points of each line.

See also intersect().

Member Function Documentation

qreal QLineF::angle() const

Returns the angle of the line in degrees.

The return value will be in the range of values from 0.0 up to but not including 360.0. The angles are measured counter-clockwise from a point on the x-axis to the right of the origin (x > 0).

This function was introduced in Qt 4.4.

See also setAngle().

[static] QLineF QLineF::fromPolar(qreal length, qreal angle)

Returns a QLineF with the given length and angle.

The first point of the line will be on the origin.

Positive values for the angles mean counter-clockwise while negative values mean the clockwise direction. Zero degrees is at the 3 o'clock position.

This function was introduced in Qt 4.4.

qreal QLineF::length() const

Returns the length of the line.

See also setLength().

void QLineF::setAngle(qreal angle)

Sets the angle of the line to the given angle (in degrees). This will change the position of the second point of the line such that the line has the given angle.

Positive values for the angles mean counter-clockwise while negative values mean the clockwise direction. Zero degrees is at the 3 o'clock position.

This function was introduced in Qt 4.4.

See also angle().

QLineF QLineF::unitVector() const

Returns the unit vector for this line, i.e a line starting at the same point as this line with a length of 1.0.

See also normalVector().

Related Non-Members

QDataStream &QLineF::operator<<(QDataStream &stream, const QLineF &line)

Writes the given line to the given stream and returns a reference to the stream.

See also Serializing Qt Data Types.

QDataStream &QLineF::operator>>(QDataStream &stream, QLineF &line)

Reads a line from the given stream into the given line and returns a reference to the stream.

See also Serializing Qt Data Types.