line.md
In rswipl: Embed 'SWI'-'Prolog'

class line {#class-line}

Description

Straight line segment connecting two points. A line may have a ->pen (thickness) and a ->texture (dash-pattern). A line may have ->arrows on both sides, see class joint and class arrow for attaching arrows to a line.

Bugs:

There are no provisions to display a label in a line. In the application-area of PCE, this would be a useful extension.

@see class connection

line<-first_arrow: graphical* Arrow displayed on the start-point.

@see line->first_arrow @see line->arrows
line<-second_arrow: graphical* Arrow displayed on the end-point.

@see line->second_arrow @see line->arrows

line->copy: line Copy the attributes from class graphical and the arrows. This method is used by class connection to instantiate itself from the related link.
line->end: point Inherits description from: line<-end

@see line->points
line->end_x: int Inherits description from: line<-end_x

@see line->points
line->end_y: int Inherits description from: line<-end_x

@see line->points
line->first_arrow: graphical* @see line-first_arrow @see class arrow
line->initialise: start_x=[int], start_y=[int], end_x=[int], end_y=[int], arrows=[{none,first,second,both}] Create a line from X1,Y1 to X2,Y2 with specified ->arrows. A default line has ->pen: 1 and ->texture: none.
line->orientation: {north_west,south_west,north_east,south_east} Redefined from graphical: no-op.
line->normalise Succeed without side-effect. Normalising a line could change the direction as a line is defines to go from
```
<-x, <-y towards <-x + <-width, <-y + <-height
```
@see line->orientation
line->points: start_x=[int], start_y=[int], end_x=[int], end_y=[int] Set ->start from the first X-Y couple and ->end from the second. Any default value leaves the corresponding line parameter unchanged. See also graphical ->set.

@see line->start_x @see line->start_y @see line->end_y @see line->end_x @see line->start @see line->end
line->second_arrow: graphical* @see line-second_arrow @see class arrow
line->start: point Inherits description from: line<-end

@see line->points
line->start_x: int Inherits description from: line<-start_x

@see line->points
line->start_y: int Inherits description from: line<-start_x

@see line->points

line<-angle: origin=[point] -> degrees=real Return the angle of the line with the positive X-axe in degrees counter clockwise.
line<-distance: to=graphical|point|event, segment=[bool] -> int If the argument is a point object, this method computes the distance to the the infinitely extended line (if segment is @default or @off) or the line segment if segment is @on.

If the argument is an event object, act as above using the position of the event in the coordinate space of the <-device.

If the argument is a graphical objects, it invokes area <-distance: area using the areas of both graphicals.

See also ->in_event_area.
line<-start: -> point
line<-end: -> point Unlike normal graphicals, lines are in general not specified using their <-width and <-height but using <-start and <-end.

@see line<-start
line<-intersection: with=line -> point Return a new point object describing the intersection point of both infinitely extended lines. Fails if the lines are parallel.
line<-length: -> int Distance between the points <-start and <-end. See also point <-distance.