Updating the C:GPath Function

Update the C:GPath function by adding reactor creation logic.

To add reactor creation logic to C:GPath

  1. Replace your version of gpmain.lsp with the updated version shown below. Copy this code from the <AutoCAD directory>\Tutorial\VisualLISP\Lesson6 directory:
    (defun C:GPath (/
      (setvar "OSMODE" 0)			;; Turn off object snaps
    ;; Lesson 6 adds a stubbed-out command reactor to AutoCAD
      ;; However, it would be undesirable to react to every
      ;; drawing of a circle should the COMMAND tile creation
      ;; method be chosen by the user.  So, disable the 
      ;; *commandReactor* in case it exists. 
    (if *commandReactor*
    	(setq *commandReactor* nil)
    	(vlr-remove-all :VLR-Command-Reactor)
      ;; Ask the user for input: first for path location and
      ;; direction, then for path parameters.  Continue only if you
      ;; have valid input.  Store the data in gp_PathData.
      (if (setq gp_PathData (gp:getPointInput))
    	(if (setq gp_dialogResults
    		 (cdr (assoc 40 gp_PathData))
    		 ) ;_ end of gp:getDialogInput
    	) ;_ end of setq
    	;; Now take the results of gp:getPointInput and append this to
    	;; the added information supplied by gp:getDialogInput
    	(setq gp_PathData (append gp_PathData gp_DialogResults))
    	;; At this point, you have all the input from the user
    	;; Draw the outline, storing the resulting polyline "pointer"
    	;; in the variable called PolylineName
    	(setq PolylineName (gp:drawOutline gp_PathData))
    	;; Next, it is time to draw the tiles within the boundary.
    	;; The gp_tileList contains a list of the object pointers for
    	;; the tiles.  By counting up the number of points (using the
    	;; length function), we can print out the results of how many
    	;; tiles were drawn.
    	(princ "\nThe path required ")
    		(setq tileList (gp:Calculate-and-Draw-Tiles gp_PathData))
    	) ;_ end of length
    	) ;_ end of princ
    	(princ " tiles.")
    ;; Add the list of pointers to the tiles (returned by
    	;; gp:Calculate-and-Draw-Tiles) to gp_PathData. This will
    	;; be stored in the reactor data for the reactor attached 
    	;; to the boundary polyline.  With this data, the polyline
    	;; "knows" what tiles (circles) belong to it.
    	(setq gp_PathData
    		 (append (list (cons 100 tileList))
    					; all the tiles
    		 ) ;_ end of append
    	) ;_ end of setq
    ;; Before we attach reactor data to an object, let's look at
    	;; the function vlr-object-reactor
    	;; vlr-object-reactor has the following arguments:
    	;;  (vlr-object-reactor owner's data callbacks)
    	;; The callbacks Argument is a list comprised
    	;; '(event_name . callback_function)
    	;; For this exercise we will use all arguments
    	;; associated with vlr-object-reactor
    	;; These reactor functions will execute only if
    	;; the polyline in PolylineName is modified or erased
    	;; The first argument for vlr-object-reactor is
    	;; the "Owner's List" argument.  This is where to
    	;; place the object to be associated with the
    	;; reactor.  In this case, it is the vlaObject
    	;; stored in PolylineName.
    	(list PolylineName)
    	;; The second argument contains the data for the path
    	;; The third argument is the list of specific reactor
    	;; types that we are interested in using
    		;; reactor that is called upon modification of the object
    		(:vlr-modified . gp:outline-changed)
    		;; reactor that is called upon erasure of the object
    		(:vlr-erased . gp:outline-erased)
    	) ;_ end of vlr-object-reactor
    	;; Next, register a command reactor to adjust the polyline
    	;; when the changing command is finished
    	(if (not *commandReactor*)
    	(setq *commandReactor*
    		 nil		; No data is associated with the command reactor
    			 (:vlr-commandWillStart . gp:command-will-start)
    			 (:vlr-commandEnded . gp:command-ended)
    		 ) ;_ end of vlr-command-reactor
     ;; The following code removes all reactors when the drawing is
     ;; closed. This is extremely important!!!!!!!!!
     ;; Without this notification, AutoCAD may crash upon exiting!
     (if (not *DrawingReactor*)
    	(setq *DrawingReactor*
    		 nil		; No data is associated with the drawing reactor
    		 '((:vlr-beginClose . gp:clean-all-reactors)
    		 ) ;_ end of vlr-DWG-reactor
    	) ;_ end of progn
    	(princ "\nFunction cancelled.")
    	) ;_ end of if
    	(princ "\nIncomplete information to draw a boundary.")
      ) ;_ end of if
      (princ)			 ; exit quietly
    ) ;_ end of defun
    ;;; Display a message to let the user know the command name.
    (princ "\nType GPATH to draw a garden path.")
  2. Review the code modifications and comments describing what each new statement does. This tutorial shows all modified code in boldface.