AutoLISP Tutorial: Batch Layer On/Off

Welcome to the Batch Layer On/Off AutoLISP Tutorial. In this comprehensive guide, we’ll delve into the world of AutoCAD customization, exploring a unique script designed to toggle the visibility of multiple layers simultaneously. Whether you’re a seasoned AutoCAD professional or a beginner looking to expand your skills, understanding this program can greatly enhance your productivity. As we break down the code step-by-step, you’ll gain insight into both the logic and functionality behind this powerful tool.

By the end of this tutorial, you’ll not only have a functional command at your disposal, but you’ll also have broadened your understanding of AutoLISP programming. Let’s embark on this learning journey together!

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AutoLISP program that toggles the visibility of multiple layers

In this tutorial, we’ll break down a simple AutoLISP program that toggles the visibility of multiple layers in an AutoCAD drawing.

(defun C:BLAYONOFF (/ sset layers i layname layobj)
; Get all layers in the drawing
(setq layers (tblnext “LAYER” T))
(while layers
(setq laylist (cons (cdr (assoc 2 layers)) laylist))
(setq layers (tblnext “LAYER”))
)

; Prompt user to select layers from the list
(setq sset (ssget “X” ‘((-4 . “<OR”) (list 8 laylist) (-4 . “OR>”))))

; If nothing selected, exit
(if (null sset)
(progn
(princ “\nNo layers selected.”)
(exit)
)
)

; Toggle visibility of selected layers
(setq i 0)
(repeat (sslength sset)
(setq layname (cdr (assoc 8 (entget (ssname sset i)))))
(setq layobj (tblobjname “LAYER” layname))
(if (vla-get-IsFrozen (vla-item (vla-get-layers (vla-get-activedocument (vlax-get-acad-object)))) layname))
(vla-put-isfrozen layobj :vlax-false)
(vla-put-isfrozen layobj :vlax-true)
)
(setq i (1+ i))
)

(princ “\nVisibility of selected layers toggled.”)
(princ)
)

(princ “\nType BLAYONOFF to start the command.”)
(princ)

Once you’ve added this code to your AutoCAD environment, you can run it by typing BLAYONOFF at the command line. The program will display a list of all layers in the drawing. After you select the desired layers, the program will toggle their visibility.

Note: Always backup your work before using custom scripts or commands, as unforeseen issues might arise.

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Let’s explore it step by step:

1. Code Setup:

(defun C:BLAYONOFF (/ sset layers i layname layobj)

• defun: This is the function definition in LISP. Every LISP command starts with it.
• C:BLAYONOFF: The function name. It’s what you’ll type into AutoCAD to execute the command.
• /: The slash indicates the start of local variables declaration.
• sset, layers, i, layname, layobj: These are local variables.

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2. Gather All Layers:

(setq layers (tblnext “LAYER” T))
(while layers
(setq laylist (cons (cdr (assoc 2 layers)) laylist))
(setq layers (tblnext “LAYER”))
)

• tblnext: Function retrieves the next table entry in the drawing database. We’re looking for “LAYER” entries.
• The while loop iterates through all the layers in the drawing.
• (cdr (assoc 2 layers)): Retrieves the layer name.
• cons: Adds the layer name to the laylist.

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3. User Selection:

(setq sset (ssget “X” ‘((-4 . “<OR”) (list 8 laylist) (-4 . “OR>”))))

• ssget: Used to select objects in AutoCAD.
• "X": Allows for extended selection criteria.
• The list construction ((-4 . "<OR") (list 8 laylist) (-4 . "OR>")) is a filter. It allows the user to select objects based on layer names stored in laylist.

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4. Check User Selection:

(if (null sset)
(progn
(princ “\nNo layers selected.”)
(exit)
)
)

• Checks if the user hasn’t selected anything.
• progn: Groups multiple expressions.
• If no layers are selected, it prints a message and exits.

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5. Toggle Visibility:

(setq i 0)
(repeat (sslength sset)
(setq layname (cdr (assoc 8 (entget (ssname sset i)))))
(setq layobj (tblobjname “LAYER” layname))
(if (vla-get-IsFrozen (vla-item (vla-get-layers (vla-get-activedocument (vlax-get-acad-object)))) layname))
(vla-put-isfrozen layobj :vlax-false)
(vla-put-isfrozen layobj :vlax-true)
)
(setq i (1+ i))
)

• Iterates over all selected layers.
• ssname: Gets the i-th selected object.
• entget: Retrieves object data.
• tblobjname: Gets the LAYER object for a given layer name.
• Uses VLA functions (Visual LISP functions) to check if a layer is frozen.
• vla-get-IsFrozen: Checks if a layer is frozen.
• vla-put-isfrozen: Toggles layer visibility.

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6. Completion Message:

(princ “\nVisibility of selected layers toggled.”)
(princ)
)

• Once the layers are toggled, it prints a confirmation message.

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7. Command Initialization:

(princ “\nType BLAYONOFF to start the command.”)
(princ)

• Notifies the user how to start the command once the LISP is loaded.

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