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:feedback function in dragging-output-record

I am using CLIM 1.0 - Genera 8.1.1 and want to limit the movement
of an output record as I drag it with the mouse.  I want to constrain
it to move only in the y-direction and between y-min and y-max values
which bracket the initial y-position.

DRAGGING-NODE causes the "node" to move only in the y-direction (between
y-min & y-max), regardless of the mouse's x-location -- but the erasing of 
the output-record does not erase properly unless the mouse stays on the "y-axis"
[its (- current-x initial-x) remaining 0].

==> Will Taylor
..
(dragging-output-record pane node-output-record :repaint nil :finish-on-release t
		       	:feedback #'DRAGGING-NODE)
..

(defun DRAGGING-NODE (output-record stream initial-x initial-y current-x current-y mode)
  "feedback function of dragging-output-record for dragging a node between its parent
   and its children"
  (let* ((node *drag-node*) (delta-y nil)
	 (editor-pane (editor-pane *evolutionary-tree-frame*))
	 (current-tree (current-tree editor-pane))
	 (time-factor (time-factor current-tree))
	 (y-min (- initial-y 20)) (y-max (+ initial-y 20)) (y-limit 0))
      (case mode
	(:draw
	  (setf (node-y node) current-y)
	  (setf delta-y (- current-y *node-y-position*))
	  (incf (node-pixel-branch-length node) delta-y)
	  (setf *branch-length* (truncate (node-pixel-branch-length node) time-factor))
	  (if (< current-y y-min)
	      (setf y-limit (- y-min current-y)))
	  (if (> current-y y-max)
	      (setf y-limit (- y-max current-y)))
	  (multiple-value-bind (x-offset y-offset)
	      (convert-from-relative-to-absolute-coordinates
		stream output-record)
	    ;; force node to move only in the y-direction
	    (replay-1 output-record stream nil (- x-offset (- current-x initial-x))
		      (+ y-offset y-limit)))
	  (setf *node-y-position* current-y))
	(:erase
	  (erase-output-record output-record stream)))))
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