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AutoCAD

Bug Watch: Dynamic Input that Isn't and Two Kinds of Broken Objects

11 Jan, 2006 By: Steve Johnson Cadalyst

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AutoCAD 2006's Dynamic Input is great as long as you are a bit slow, the object that Autodesk forgot, Undo still misbehaving and tanks for the memories.

Not So Dynamic After All (2006 to 2006 SP1)
Perhaps the most obvious new AutoCAD 2006 feature is Dynamic Input. Instead of entering commands at the Command prompt, you enter them at your cursor location. Unfortunately, this potentially excellent feature needs work. The first disappointment is when Dynamic Input is turned on, it effectively disables the Command prompt as an input mechanism. What you type is not echoed to the Command prompt as you type it. It appears eventually after you enter your input, but by then it's too late.

The nice thing about the good old Command prompt is that you know exactly where it is. If you want to check your typing, you know where to look. With Dynamic Input, you have to search because it's in a different place each time. The slight pause and extra mental effort involved may seem trivial, but don't underestimate it in terms of productivity. Let's hope AutoCAD 2007 provides the option of having input echoed at the Command prompt as it's typed.

That's more of a wish list item than a bug, but what really kills Dynamic Input for me is a performance issue that I consider bad enough to call a bug. If you're a keyboard-heavy user, when AutoCAD prompts for a point, you may quickly type in an object snap followed by the space bar. Do that in AutoCAD 2006 and AutoCAD seems to stick. What happened is that you typed too fast for AutoCAD and it left your space behind.

Let's not get hung up about whether this is the most efficient way of picking object snap points in AutoCAD. The point is that if you type E N D [Space] when AutoCAD's asking for a point, you have a right to expect it to use the end point object snap, not to get stuck. The same issue applies to other typed and mouse inputs. Quickly type in a two letter command alias (such as TR for Trim), and immediately right-click for Enter. With Dynamic Input on, soon AutoCAD ignores the second of your two letters and gives you the wrong command (such as T for Mtext instead of TR for Trim). Try the same thing with Dynamic Input off, and you will get much better results.

Workaround: One thing Autodesk got right was the ease of adjusting the Dynamic Input settings. You can easily turn them on and off with a single click on the DYN button in AutoCAD's system tray, and a right-click on that button gives you access to the settings that exercise finer control over it. Try turning off the Dynamic Input settings one by one and try out AutoCAD until it reacts fast enough for you.

Ruined Rtext (2006 to 2006 SP1)
Since AutoCAD 2000, AutoCAD has incorporated a special kind of text object, thanks to the Express tools. The Rtext object provided a variable kind of text, long before fields were introduced. Rtext can either use DIESEL expressions or can point to an external text file. Rtext still mostly works in AutoCAD 2006 from a user's point of view. The only hint of something wrong is that when you select an Rtext object, the Properties palette does not identify the object type, but instead leaves the object type blank. From a programmer's point of view, things are more serious. ActiveX access to Rtext is completely broken. Enter the following LISP code and select an Rtext object when prompted.

(vlax-ename->vla-object (car (entsel)))

In earlier AutoCAD releases, this code will return an AutoCAD object as expected, like this:

#<VLA-OBJECT IAcadEntity 050f3074>

In AutoCAD 2006, this generates an error, like this:

; error: Automation Error. Description was not provided.

Why should you care? Even if you've never created Rtext objects of your own and don't write programs, this can still bite you. If you ever use drawings created by people other than yourself and if they were created in the past six years, they could contain Rtext. If you use any program or utility that processes objects and uses ActiveX (e.g., Visual LISP, Visual Basic), it will crash as soon as it gets to an Rtext object.

Workaround: None known.

Underhanded Undo Revisited
In September 2003 and January 2004, I mentioned problems with AutoCAD 2004 undoing things it shouldn't. I thought those problems were behind us, but it seems they are not. The problem persists of AutoCAD performing a random number of undo steps, even when no undo was requested. This seems to be triggered by hitting the Esc key, particularly in the Mtext editor. If you have any information that might help track down this persistent little critter, please let me know steve.johnson@cadalyst.com.

Now For Something Remarkably Similar -- The Sequel
In May 2005 I suggested that it's a bad idea to leave an aquarium with a base made of wire-reinforced glass out in the sun because it causes cracks. This month, some further advice. If you do have an aquarium with cracks in it, don't try to save a few bucks by letting your local aquarium supplier seal it with silicon and place another sheet of glass over the top of the cracked pane. Either dismantle the whole aquarium and rebuild it with uncracked panes or buy a new aquarium. It is cheaper and more convenient than the alternative.

What alternative? The one that involves discovering a very wet floor six months later, catching dozens of fish and finding temporary alternative accommodation for them, finding somewhere to put a lot of plants, rocks and wet gravel, and then having to buy and set up a new aquarium anyway. No prizes will be awarded for guessing how I learned about this one.