1.83 class joint

Class joint is a super-class for all line-like graphical classes that may have arrows at either or both ends of the line. Currently it has the following subclasses:

• class line Straight line-segment
• class arc Part of an ellipse (or circle).
• class path Line through a number of control-points. May be smooth (interpolated) or a series of straight line-segments.
• class bezier_curve Smooth curve leaving joint<-start in the direction of a control-point to joint<-end arriving from the direction of a contol-point.

  Class joint defines all methods that deal with attaching and deleting arrows at the start or end of the line. Despite the name, the joint->arrows related to a joint need not be instances of class arrow. Instead, they may be instances of any subclass of class graphical, provided the class inplements the joint->points method compliant to arrow->points. This allows the definition of new arrow like objects and attaching them to the tips of line-like objects

  See joint->arrows, joint->first_arrow and joint->second_arrow. See also class arrow.

  See also

  class arrow

1.83.1 Instance variables

joint <- first_arrow: graphical*

Arrow object at the start-point of the joint. If @nil, no arrow is displayed. Default (simple) arrows are normally attached using joint->arrows.

Any graphical implementing joint->points compliant to arrow->points can be used as an arrow head. If the joint is changed, it's graphical->compute method will send joint->points to the arrow object and recompute the bounding box of the joint. Similar, graphical->redraw will draw invoke the graphical->redraw method of the arrow(s).

joint <- second_arrow: graphical*

Arrow object at the end-point of the joint. If @nil, no arrow is displayed.

1.83.2 Send methods

joint ->arrows: arrows={none,first,second,both}

Inherits description from: joint<-arrows

joint ->initialise: x=[int], y=[int], width=[int], height=[int], arrows=[{none,first,second,both}]

For an application programmer it is not useful to make instances of class joint directly. See line->initialise, arc->initialise and path->initialise.

1.83.3 Get methods

joint <-arrows: -> arrows={none,first,second,both}

The joint<->arrows method provides a simple interface to joint->first_arrow and joint->second_arrow. If it attaches arrows the new arrow is created using joint<-default_arrow.

joint <-default_arrow: -> graphical

Create a default arrow (new(arrow)), see arrow->initialise. This method is called by joint->arrows. Intended to be redefined for making lines with different arrow styles.