Class

Summary

A pinboard-object that draws itself as an arrow, which can switch dynamically from double-headed to single-headed.

Package

capi

Superclasses

arrow-pinboard-object

Initargs

:double-head-predicate

A function determining whether a single or double arrowhead is drawn.

Description

double-head-predicate should be a function of two arguments returning a boolean value. The first argument is the output pane on which the arrow pinboard object is drawn. The second argument is the arrow pinboard object itself.

double-head-predicate should return a true value if the arrow is to be double-headed, and nil if a single-headed arrow should be drawn. It is called each time the arrow object is redrawn.

Example

(defvar *doublep* t)

(let ((dhr 

       (capi:contain 

        (make-instance

         'capi:pinboard-layout

         :description

         (list

          (make-instance 

           'capi:double-headed-arrow-pinboard-object

           :double-head-predicate

           #'(lambda (x y) *doublep*)

           :start-x 5 :start-y 5 :end-x 95 :end-y 95)

          (make-instance 

           'capi:double-headed-arrow-pinboard-object

           :double-head-predicate

           #'(lambda (x y) *doublep*)

           :head-direction :backwards

            :start-x 5 :start-y 95 :end-x 95 :end-y 5)))

        :visible-min-width 100

        :visible-min-height 100)))

  (dotimes (x 10)

    (sleep 1)

    (setq *doublep* (not *doublep*))

    (mapcar 'capi:redraw-pinboard-object 

            (capi:layout-description dhr))))

See also

Creating graphical objects