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AutoCAD

A Cure for Disappearing Dialog Boxes

6 Aug, 2006 By: Steve Johnson

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Cadalyst's own bug doctor diagnoses and treats CMDDIA-related ailments in AutoCAD

Editor's note: AutoCAD's CMDDIA is a troublesome topic that surfaces from time-to-time in Cadalyst editors' e-mail in boxes and in Cadalyst Discussion Forums. What is it and how do you fix related problems? Read on for answers from our Bug Watch columnist, Steve Johnson.

If you're in the habit of reading AutoCAD-related newsgroups and forums, sooner or later you will see someone ask for help because his or her AutoCAD dialog boxes no longer appear. Typically, you will then see someone else suggest setting the FILEDIA or CMDDIA system variable to 1. The first suggestion will help as long as it is only AutoCAD's File dialog boxes that have gone missing. It will have no effect on any dialog box that is not prompting for a file. The second suggestion is unlikely to help in any recent AutoCAD release.

There is some confusion about CMDDIA, and a few misconceptions are flying around. Let's see if I can clear things up.

What is CMDDIA?
The CMDDIA system variable was introduced by AutoCAD Release 12 in 1992 and has been there ever since. It stands for CoMmanD DIAlog, and its basic function is to determine whether certain commands use dialog boxes or command-line prompts. That concept has now largely been replaced by commands that are available with and without leading hyphens. For example, the Insert command issues a dialog box but the -Insert command does not.

The Help documentation for CMDDIA vanished in AutoCAD 2000. It returned in AutoCAD 2006, but with a uselessly vague description. It was rewritten in AutoCAD 2007 to make the description at least partially useful, but is still incomplete. Documented or not, CMDDIA has been there and doing something for the past ten releases. But what?

What Does It Affect?
When it was first introduced, setting CMDDIA to 0 affected the following things:

• The Plot command's dialog box was suppressed.
• External database command dialog boxes were suppressed (for example, Asesqled).
• Dimension command text entry prompt sequences were different.

The Release 13 dimension overhaul removed CMDDIA's influence from some dimensioning commands. AutoCAD 2000 killed the ASE database commands and overhauled the Plot dialog box, removing them from the above list. Exactly what was left for CMDDIA to affect from AutoCAD 2000 onward?

• Express Tools Layer Manager. The Lman command started respecting CMDDIA in AutoCAD 2000. It still issues Command-line prompts in AutoCAD 2007 when CMDDIA is set to 0.
• Dimedit New, Dim Newtext, Leader and Qleader commands. When CMDDIA is set to 0, Command-line prompts are used for text entry rather than the Mtext dialog box.

It is worth noting that setting CMDDIA to 0 works correctly with the Leader command, but not Qleader. It has caused Qleader to issue a misleading prompt since AutoCAD 2000. I wrote this one up as "Qleader Quirk" in Bug Watch April 2004. Qleader actually works fine as long as you ignore what it tells you. This bug still exists in AutoCAD 2007.

What Does Work
If CMDDIA no longer determines whether the Plot command invokes a series of prompts rather than a dialog box, what does? The following things have worked over the years:

• Releases 12 to 14: Set CMDDIA to 0 before entering the Plot command or use LISP -- for example, (command "_.PLOT").
• AutoCAD 2000 to 2007: Enter the -Plot command with a leading hyphen or use LISP -- for example, (command "_.PLOT") or (command "_.-PLOT").

In Release 14 and later, to force AutoCAD to use the dialog box version of the Plot command when called from LISP, you can just call the (initdia) function first:

   (initdia)
   (command "_.PLOT")

One last note about suppressing Plot dialog boxes: The PLQUIET system variable was introduced by AutoCAD 2000, but not as a replacement for CMDDIA. It has no effect on the main Plot dialog box, but setting it to 1 will prevent the appearance of supplementary warning and error dialog boxes.