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# QLineF Class Reference
[QtCore module]

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

### Types

- enum IntersectType { NoIntersection, BoundedIntersection, UnboundedIntersection }

### Methods

- __init__ (self, QLine line)
- __init__ (self)
- __init__ (self, QPointF apt1, QPointF apt2)
- __init__ (self, float x1pos, float y1pos, float x2pos, float y2pos)
- __init__ (self, QLineF other)
- float angle (self, QLineF l)
- float dx (self)
- float dy (self)
- IntersectType intersect (self, QLineF l, QPointF intersectionPoint)
- bool isNull (self)
- float length (self)
- QLineF normalVector (self)
- QPointF p1 (self)
- QPointF p2 (self)
- QPointF pointAt (self, float t)
- setLength (self, float len)
- QLine toLine (self)
- translate (self, QPointF point)
- translate (self, float adx, float ady)
- QLineF unitVector (self)
- float x1 (self)
- float x2 (self)
- float y1 (self)
- float y2 (self)

### Special Methods

- QLineF __mul__ (self, QMatrix m)
- QLineF __mul__ (self, QTransform m)
- bool __eq__ (self, QLineF d)
- bool __ne__ (self, QLineF d)
- int __nonzero__ (self)

## Detailed Description

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

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. 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 angle() 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.

See also QLine, QPolygonF, and QRectF.

## Type Documentation

### QLineF.IntersectType

Describes the intersection between two lines.

QLineF.UnboundedIntersection | QLineF.BoundedIntersection

Constant | Value | Description
--- | --- | ---
`QLineF.NoIntersection` | `0` | Indicates that the lines do not intersect; i.e. they are parallel.
`QLineF.UnboundedIntersection` | `2` | The two lines intersect, but not within the range defined by their lengths. This will be the case if the lines are not parallel.
`QLineF.BoundedIntersection` | `1` | The two lines intersect with each other within the start and end points of each line.

See also intersect().

## Method Documentation

### QLineF.__init__ (self, QLine line)

Constructs a null line.

### QLineF.__init__ (self)

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

### QLineF.__init__ (self, QPointF apt1, QPointF apt2)

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

### QLineF.__init__ (self, float x1pos, float y1pos, float x2pos, float y2pos)

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

See also toLine().

### QLineF.__init__ (self, QLineF other)

### float QLineF.angle (self, QLineF l)

Returns the angle (in degrees) between this line and 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 origo (see QLineF.UnboundedIntersection).

When the lines are parallel, this function returns 0 if they have the same direction; otherwise it returns 180.

See also intersect().

### float QLineF.dx (self)

Returns the horizontal component of the line's vector.

See also dy() and pointAt().

### float QLineF.dy (self)

Returns the vertical component of the line's vector.

See also dx() and pointAt().

### IntersectType QLineF.intersect (self, QLineF l, QPointF 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.

### bool QLineF.isNull (self)

Returns true if the line is not set up with valid start and end point; otherwise returns false.

### float QLineF.length (self)

Returns the length of the line.

See also setLength().

### QLineF QLineF.normalVector (self)

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

See also unitVector().

### QPointF QLineF.p1 (self)

Returns the line's start point.

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

### QPointF QLineF.p2 (self)

Returns the line's end point.

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

### QPointF QLineF.pointAt (self, float t)

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

See also dx() and dy().

### QLineF.setLength (self, float len)

Sets the length of the line to the given length. If the line is a null line, the length will remain zero regardless of the length specified.

See also length() and isNull().

### QLine QLineF.toLine (self)

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().

### QLineF.translate (self, QPointF point)

Translates this line by the given offset.

### QLineF.translate (self, float adx, float ady)

This is an overloaded member function, provided for convenience.

Translates this line the distance specified by dx and dy.

### QLineF QLineF.unitVector (self)

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().

### float QLineF.x1 (self)

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

See also p1().

### float QLineF.x2 (self)

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

See also p2().

### float QLineF.y1 (self)

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

See also p1().

### float QLineF.y2 (self)

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

See also p2().

### QLineF __mul__ (self, QMatrix m)

This method is only available if the QtGui module is imported.

### QLineF __mul__ (self, QTransform m)

This method is only available if the QtGui module is imported.

### bool QLineF.__eq__ (self, QLineF d)

### bool QLineF.__ne__ (self, QLineF d)

### int QLineF.__nonzero__ (self)