class QLineF#

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

Synopsis#

Methods#

Static functions#

Note

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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.

qline-point1

qline-coordinates2

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 intersects() function determines the IntersectionType 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 QRectF

class IntersectionType#

Describes the intersection between two lines.

qlinef-unbounded1

qlinef-bounded2

QLineF::UnboundedIntersection

QLineF::BoundedIntersection

Constant

Description

QLineF.NoIntersection

Indicates that the lines do not intersect; i.e. they are parallel.

QLineF.UnboundedIntersection

The 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.BoundedIntersection

The two lines intersect with each other within the start and end points of each line.

See also

intersects()

__init__(line)#
Parameters:

lineQLine

Construct a QLineF object from the given integer-based line.

See also

toLine() toLineF()

__init__()

Constructs a null line.

__init__(x1, y1, x2, y2)
Parameters:
  • x1 – float

  • y1 – float

  • x2 – float

  • y2 – float

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

__init__(pt1, pt2)
Parameters:

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

__reduce__()#
Return type:

object

__repr__()#
Return type:

object

angle()#
Return type:

float

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).

See also

setAngle()

angleTo(l)#
Parameters:

lQLineF

Return type:

float

Returns the angle (in degrees) from this line to the given line, taking the direction of the lines into account. If the lines do not intersect within their range, it is the intersection point of the extended lines that serves as origin (see UnboundedIntersection ).

The returned value represents the number of degrees you need to add to this line to make it have the same angle as the given line, going counter-clockwise.

See also

intersects()

center()#
Return type:

QPointF

Returns the center point of this line. This is equivalent to 0.5 * p1() + 0.5 * p2() .

dx()#
Return type:

float

Returns the horizontal component of the line’s vector.

See also

dy() pointAt()

dy()#
Return type:

float

Returns the vertical component of the line’s vector.

See also

dx() pointAt()

static fromPolar(length, angle)#
Parameters:
  • length – float

  • angle – float

Return type:

QLineF

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.

intersects(l)#
Parameters:

lQLineF

Return type:

(intersectType, intersectionPoint)

Returns a value indicating whether or not this line intersects with the given line.

The actual intersection point is extracted to intersectionPoint (if the pointer is valid). If the lines are parallel, the intersection point is undefined.

isNull()#
Return type:

bool

Returns true if the line does not have distinct start and end points; otherwise returns false. The start and end points are considered distinct if qFuzzyCompare() can distinguish them in at least one coordinate.

Note

Due to the use of fuzzy comparison, isNull() may return true for lines whose length() is not zero.

See also

qFuzzyCompare() length()

length()#
Return type:

float

Returns the length of the line.

normalVector()#
Return type:

QLineF

Returns a line that is perpendicular to this line with the same starting point and length.

../../_images/qlinef-normalvector.png

See also

unitVector()

__ne__(d)#
Parameters:

dQLineF

Return type:

bool

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

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

__mul__(m)#
Parameters:

mQTransform

Return type:

QLineF

__eq__(d)#
Parameters:

dQLineF

Return type:

bool

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.

p1()#
Return type:

QPointF

Returns the line’s start point.

See also

setP1() x1() y1() p2()

p2()#
Return type:

QPointF

Returns the line’s end point.

See also

setP2() x2() y2() p1()

pointAt(t)#
Parameters:

t – float

Return type:

QPointF

Returns the point at the position specified by finite parameter t. The function returns the line’s start point if t = 0, and its end point if t = 1.

See also

dx() dy()

setAngle(angle)#
Parameters:

angle – float

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.

See also

angle()

setLength(len)#
Parameters:

len – float

Sets the length of the line to the given finite length. QLineF will move the end point - p2() - of the line to give the line its new length, unless length() was previously zero, in which case no scaling is attempted.

setLine(x1, y1, x2, y2)#
Parameters:
  • x1 – float

  • y1 – float

  • x2 – float

  • y2 – float

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

setP1(p1)#
Parameters:

p1QPointF

Sets the starting point of this line to p1.

See also

setP2() p1()

setP2(p2)#
Parameters:

p2QPointF

Sets the end point of this line to p2.

See also

setP1() p2()

setPoints(p1, p2)#
Parameters:

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

toLine()#
Return type:

QLine

Returns an integer-based copy of this line.

Note that the returned line’s start and end points are rounded to the nearest integer.

See also

QLineF() toLineF()

toTuple()#
Return type:

object

translate(p)#
Parameters:

pQPointF

Translates this line by the given offset.

translate(dx, dy)
Parameters:
  • dx – float

  • dy – float

This is an overloaded function.

Translates this line the distance specified by dx and dy.

translated(p)#
Parameters:

pQPointF

Return type:

QLineF

Returns this line translated by the given offset.

translated(dx, dy)
Parameters:
  • dx – float

  • dy – float

Return type:

QLineF

This is an overloaded function.

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

unitVector()#
Return type:

QLineF

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, provided the line is non-null.

x1()#
Return type:

float

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

See also

p1()

x2()#
Return type:

float

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

See also

p2()

y1()#
Return type:

float

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

See also

p1()

y2()#
Return type:

float

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

See also

p2()