By: Frank Zander
At: Contract CADD Group
Website: http://www.contractcaddgroup.com/
Email: frank.zander@contractcaddgroup.com
Phone: (604) 591-1140

This article explores the AutoCAD r14.01 version of VBA.   The topics covered include; what is VBA, why one would want to use VBA in AutoCAD, how to setup/access AutoCAD r14.01's VBA, how an object (line, circle, etc) is described by AutoCAD's VBA object model, how Forms and controls on Forms act as VBA objects. For the curious, I have created a small visibility program using VBA with AutoCAD 14.01. This article was written for the non-programmer and hopefully the instructions will entice the non-programmer to try a hand at creating a simple visibility VBA  program. For those who do not want to type in the code used in this article, the visibility program is available for downloading at: http://www.contractcaddgroup.com/download/hideshow.zip

Visual Basic for Applications (VBA) allows Visual Basic (VB) programmers to work in a familiar Visual Basic environment. Those not familiar with the Visual Basic environment will find that the interface is easy to use and straight forward.

Three reasons:

1. Speed

To quote Autodesk -- "VBA is fast. VBA is hosted by AutoCAD and doesn't have the associated overhead of calling out to a separate process. In internal benchmarks, VBA is significantly faster than AutoLISP® or Visual Basic running as a separate application. The execution speed is very close to a compiled C++ ObjectARX DLL-based extension." Programs created with Visual Basic for Applications execute faster than programs created outside of an application. For example, a VBA program will run faster than the same code setup as a standalone VB executable (exe) program.

2. Ease of use.

Visual Basic/VBA interface is easy to learn and use. VBA-enabled programs (e.g. Word 97, Office 97 Excel 97, AutoCAD 14.01, Visio Technical, IntelliCAD, etc) allow the user to learn and program in the same Visual Basic environment.

3. Universality

VBA has become broadly accepted as the Windows-based customization tool of choice. The VBA interface resembles Visual Basic 5 (VB5). AutoCAD users only need to learn one programming environment (VBA) to be able to program with VB in all VBA enabled programs. The VBA editor included AutoCAD uses the same programming environment used in Office 97 applications. LISP only works in a handful of CADD programs (e.g. AutoCAD, IntelliCAD, Cadkey), Lisp is clunky, as well as hard to learn.

With Visual Basic, the programmer creates a user interface by adding controls from the Toolbox to a Form. To create a push button only requires a selection of the button control in the Toolbox and drawing/placing the control on a Form. It is very easy to create a Form that looks the way it will be used as a program. Buttons to push, Text boxes for entry, Option lists, etc, are a breeze to create, size, and change. The ability to rapidly create a prototype interface for a new program is stunning to say the least. Also, the resulting Form can be saved and imported into any Windows VBA-enabled program.

To use VBA for AutoCAD requires AutoCAD r14.01. If you do not have the 14.01 version see your local Autodesk dealer for details on how to obtain the r14.01 update. When installing or updating to AutoCAD r14.01 also select the install VBA option (default on Typical and Custom installation settings).

To start the VBA editor for a new project inside of AutoCAD do the following:

1. From the pull down menu select: Tools | Macro | Visual Basic Editor

Or at the command prompt type: VBAide

Or for AutoCAD 2000: ALT + F11

 

 



 

To load an existing VBA project into AutoCAD do the following:

1. From the pull down menu select: Tools | Macro | Load Project…

Or at the command prompt type: VBALOAD

VBA uses Objects to work within documents. VBA describes everything within an AutoCAD drawing (lines, circles, arcs, text, etc) as an Object. Every Object in a drawing then has properties. A line within the current drawing in model space has a color property that would be described as Thisdrawing.ModelSpace.lineobject.color . A full listing and graphical representation of the AutoCAD Object model as well as Methods, Properties, Constants, VBA events and example code — can be accessed in AutoCAD from the online help (press F1 help) as shown below.

 Every object (button, textbox, combobox, etc) on a Form becomes a sub-object of the Form. For example the Off button text on the Visibility form could be described as frmVisibility.cmdHideObjects.Caption = "Off"

In planning this article, I wanted to demonstrate a simple program that would be useful to all AutoCAD users and not be specific to one discipline (e.g. Mechanical, Structural, or Architectural, etc.). I also wanted to create a very simple program that would be easy for the non-programmer to create and understand. Hopefully I have achieved this with the Visibility program. The Visibility program allows the user to select any drawing entity in AutoCAD and make the object(s) selected non-visible and later make the non-visible objects Visible. Say you are working on a very-crowed drawing and only need a few of the existing lines (circles, blocks etc.) to work on. Traditionally one would turn off layers and only work with the remaining layers displayed. But what if you need to work on several layers and need some of the drawing entities on those layers not to show? Hmm… One could erase the unwanted drawing entities, draw the required information and then OOPS the erased entities back into the drawing. However, what happens if you forget to OOPS the erased entities back into the drawing before saving and exiting the drawing? Or what happens if you erase more entities after your original erase? Well we all know those answers… You loose your erased objects. But what if I told you that one of the modifiable object properties of any AutoCAD object is its Visibility? Yes, you can make objects non-visible! And then at any time make the non-visible objects visible! So irrespective of drawing layer settings, anything you can select with the Visibility program, will make the individual selected entities (objects) non-visible. Think of it as having an OBJECT freeze / thaw command. Other uses of the Visibility program could include embedding non-displaying copyright information, or creating non-displaying reference geometry for future reference.

Creating the Visibility Form:

1. At the AutoCAD command prompt type: VBAide
2. From the VBAide pull down menus select Insert | UserForm.
3. Press F4 to go to the properties-UserForm1 window.
4. Change the (name) field from UserForm1 to frmVisibility
5. Change the Caption field from UserForm1 to Visibility
6. Press F5 to check out your new form and how it will display in AutoCAD.
7. Press the X in the top right hand corner to close the form.

Creating the Off Button on the Visibility Form:

1. From the VBAide pull down menus select View | Toolbox
2. Press the command button in the Toolbox controls.



 

3. Draw the command button (make a window) on the visibility form (frmVisibility)
4. Press F4 to go to the properties-CommandButton1 window.
5. Change the (name) field from CommandButton1 to cmdHideObjects
6. Change the Caption field from cmdHideObjects to Off  
7. Press F5 to check out your form and new Off button to see how it will display in AutoCAD.
8. Press the X in the top right hand corner to close the form.

Saving your project:

1. From the VBAide pull down menus select File | Save
2. Save this project as visibility.dvb

• Note if you save this project as PROJECT.DVB in your AutoCAD directory, it will automatically load for each AutoCAD session.

Creating the On button for the Visibility Form:

1. Press the command button in the Toolbox controls.
2. Draw the command button (make a window) on the visibility form (frmVisibility)
3. Press F4 to go to the properties-CommandButton1 window
4. Change the (name) field from CommandButton1 to cmdShow
5. Change the Caption field from cmdShow to On
6. Press F5 to check out your form and new On button to see how it will display in AutoCAD.
7. Press the X in the top right hand corner to close the form.

Creating the Exit button for the Visibility Form:

1. Press the command button in the Toolbox controls.
2. Draw the command button (make a window) on the visibility form (frmVisibility)
3. Press F4 to go to the properties-CommandButton1 window
4. Change the (name) field from CommandButton1 to cmdExit
5. Change the Caption field from cmdExit to Exit
6. Press F5 to check out your form and new Exit button to see how it will display in AutoCAD.
7. Press the X in the top right hand corner to close the form.

Creating the click event on the Exit button:

• So far the command button is in location and shows "Exit", but does nothing. Why? You have not assigned an event to the command button. What is an event? An event is what happens when a user changes something or interacts with a program. The event you want to monitor is when the user clicks the Exit button. In the VBA ide window Double click the Exit command button quickly. Notice that VBA Form Object view window changes to a View Code window. Also notice that you are presented with the code following:

Private Sub cmdExit_Click()

End Sub

In between Private Sub and End Sub is where you write code… Add the code Unload Me between Private Sub cmdExit_Click() and End Sub as shown in the example code in The Code for the Visibility program. Now when the Visibility form is displayed in AutoCAD, the Exit button will unload the Visibility Form. Add comments to you program to make it easier to understand. By placing a ' in front of the comments, the VBA editor will ignore anything with a ' in front of it and automatically turn it green…

 To create the click events for the Off button see Private Sub cmdHideObjects_Click() as shown below in The Code for the Visibility program.
 To create the click events for the On button see Private Sub cmdShow_Click() as shown below in The Code for the Visibility program.

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