CAD tip # 13529:

Question CAD
% platform category

How to redefine the behavior of a standard AutoCAD command?

If you want to change or extend the behavior of a standard AutoCAD command, you can use several methods. Let's take an example of UNISOLATEOBJECTS (unisolate objects). We want AutoCAD to regenerate the active viewport after the isolation is lifted. We can use one of the following methods:

Menu editing.
If you usually invoke the command from menu or from a ribbon or via a keyboard shortcut, just modify its definition in the menu (the CUI command) - e.g., instead of calling ^C^C_unisolateobjects here, use and save the user menu macro ^C^C_unisolateobjects;_regen
Redefinition.
Using the _UNDEFINE command, you can "unlearn" an internal AutoCAD command and replace its behavior with a custom command definition of the same name. You can provide the redefinition using, for example, a LISP macro. Add a command redefinition function to an automatically loaded .LSP file (e.g. ACADDOC.LSP):
```
(command "_UNDEFINE" "_UNISOLATEOBJECTS")
(defun C:UNISOLATEOBJECTS()
 (command "._UNISOLATEOBJECTS")
 (princ " and regen")
 (command "_REGEN")
 (princ)
)
```

Reactor.
A reactor is a way to add automatic responses to an event in AutoCAD. This can be, for example, a command completion event (commandEnded). Again, add the following reactor definition to any .LSP file you load automatically:

(vl-load-com)
(defun MY_Unisolate (reac com)
  (if (wcmatch (strcase (car com)) "UNISOLATE*")
    (vla-regen (vla-get-activedocument (vlax-get-acad-object)) acActiveViewport)
  )
)
(setq *UNISOReactor
 (vlr-command-reactor
     "Unisolate reactor"
     '((:vlr-commandEnded . MY_Unisolate)))
 )
)

You can also use the first option in AutoCAD LT. The second one can be used also in AutoCAD Web.

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* CAD

8.11.2022 25125×

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applies to: AutoCAD · AutoCAD LT · AutoCAD Architecture · AutoCAD Mechanical · AutoCAD Plant 3D · AutoCAD Map 3D · Civil 3D 3D ·

See also:
Tip 10763:	How to block specific AutoCAD commands?
Tip 8802:	How to turn off the Exchange Apps in AutoCAD 2013?
Tip 7897:	How to control BLIPMODE and SCREENMENU in AutoCAD 2012?
Tip 4452:	Compare AutoCAD and AutoCAD LT - what are the key differences?
Tip 4241:	How to lock given AutoCAD variables from editing?

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