4 Choices

4.3 Graph panes

Here is a simple example of a graph pane. It draws a small rooted tree:

(contain 
 (make-instance
  'graph-pane
  :roots '(1)
  :children-function 
  #'(lambda (x)
      (when (< x 8)
       (list (* 2 x) (1+ (* 2 x))))))) 

Figure 4.6 A graph pane

The graph pane is supplied with a:children-function which it uses to calculate the children of the root node, and from those children it continues to calculate more children until the termination condition is reached. For more details of this, see the CAPI Reference Manual.

You can associate selection, retraction, extension, and action callbacks with any or all elements of a graph. Here is a simple graph pane that has an action callback on its nodes.

First, define the following four callback functions:

(defun test-action-callback (&rest args)
            (capi:display-message "Action"))

(defun test-selection-callback (&rest args)
            (capi:display-message "Selection"))

(defun test-extend-callback (&rest args)
            (capi:display-message "Extend"))

(defun test-retract-callback (&rest args)
            (capi:display-message "Retract"))

(contain
   (make-instance
      'graph-pane 
      :interaction :extended-selection
      :roots '(1)
      :children-function
       #'(lambda (x)
            (when (< x 8)
                  (list (* 2 x) (1+ (* 2 x)))))
      :action-callback 'test-action-callback
      :selection-callback 'test-selection-callback
      :extend-callback 'test-extend-callback
      :retract-callback 'test-retract-callback))

The extension callback function is called when the selection is extended by middle clicking on another node (thus selecting it too).

The retract callback function is called whenever an already selected node is deselected.

The action callback function is called whenever an action is performed on a node (that is, whenever it is double clicked on).

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