Updating the C:GPath Function

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 directoryTutorialVisualLISPLesson6 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 set
          ;; 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 "
    The 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 set
    q      ;; 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 "
    Function cancelled.")
      ) ;_ end of if
      (princ "
    Incomplete 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 "
    Type 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.

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