11.3.3 An example pinboard object

To create your own pinboard objects, the class drawn-pinboard-object is provided, which is a pinboard-object that accepts a display-callback to display itself. The following example creates a new subclass of drawn-pinboard-object that displays an ellipse.

(defun draw-ellipse-pane (gp pane

                             x y

                             width height)

  (with-geometry pane

    (let ((x-radius

           (1- (floor %width% 2)))

          (y-radius

           (1- (floor %height% 2))))

      (gp:draw-ellipse 

       gp

       (1+ (+ %x% x-radius))

       (1+ (+ %y% y-radius))

       x-radius y-radius

       :filled t

       :foreground 

       (if (> x-radius y-radius) 

           :red 

         :yellow)))))

(defclass ellipse-pane

     (drawn-pinboard-object)

  ()

  (:default-initargs

   :display-callback 'draw-ellipse-pane

   :visible-min-width 50

   :visible-min-height 50))

(contain

 (make-instance 'ellipse-pane)

 :best-width 200

 :best-height 100)

Figure 11.7 An ellipse-pane class

The with-geometry macro is used to set the size and position, or geometry, of the ellipse drawn by the draw-ellipse-pane function. The fill color depends on the radii of the ellipse - try resizing the window to see this. See the LispWorks CAPI Reference Manual for more details of drawn-pinboard-object .

Now that you have a new ellipse-pane class, you can create instances of them and place them inside layouts. For instance, the example below creates nine ellipse panes and place them in a three by three grid.

(contain

 (make-instance

  'grid-layout

  :description

  (loop for i below 9

        collect

        (make-instance 'ellipse-pane))

  :columns 3)

 :best-width 300

 :best-height 400)

Figure 11.8 Nine ellipse-pane instances in a layout