AutoCAD

AutoCAD Slips with Its Grips (Bug Watch AutoCAD Tutorial)

1 Jul, 2008 By: Steve Johnson

Grip goofs galore, and how to crash AutoCAD by picking OK.


AutoCAD 2004 introduced the GRIPOBJLIMIT system variable, which allows you to restrict the circumstances under which AutoCAD displays grips on preselected objects. If this is set to zero, AutoCAD always displays grips when objects are preselected, as long as grips are actually turned on. If it is set to a nonzero value, AutoCAD displays no grips when the number of selected objects exceeds the value of GRIPOBJLIMIT. The default value is 100, so AutoCAD will display grips if you select one to 100 objects, and no grips if you select 101 or more.

The idea is that if you're selecting a very large number of objects, you're unlikely to be doing so for the purposes of grip editing, so omitting the grips speeds things up and makes the objects more visible. What's wrong with that? Nothing, in theory, but there are just a few things that don't quite work properly.

Bad Add (2004 to 2005)
Assuming GRIPOBJLIMIT is set to 100, if you select 100 objects and then add some more to take you over the limit, what happens? It depends on the release. In AutoCAD 2006 and later, things work properly. As long as you keep adding objects, the grips are displayed when 100 or fewer objects are selected and suppressed when 101 or more are selected. AutoCAD 2004 and 2005 are less well behaved. If the first selection action picks up 100 objects or less, grips will always be displayed. So if you first select one object and then another 10,000, grips will be displayed on 10,001 objects despite the limit supposedly being 100.

Workaround: None known.

Don't Go Back, You'll Lose Your Grip (2004 to 2009)
If GRIPOBJLIMIT is set to 100, what happens if you select more than 100 objects and then remove some of them from the selection set by holding down the Shift key? You might expect grips to reappear when there are fewer than 100 objects selected, but this does not happen. The grip visibility does not change when you remove objects from the selection set.

Workaround: None known.

Limitless Grips (2004 to 2009)
Let's say GRIPOBJLIMIT is set to 100 and you select 10,000 objects. The grips are suppressed, as expected. Now use one of AutoCAD's controls to change the properties of the selected objects. For example, use the Layer toolbar control to move the objects to a different layer. The objects will correctly change properties, but then the objects are incorrectly festooned with grips.

Workaround: None known.

Grip Lock (2009)
To see this bug, first set the PICKADD system variable to 0. This is equivalent to turning on the toggle Use SHIFT to Add to Selection in the Selection tab of the Options dialog box. What this means is that when selecting objects, if you want the next selection to add to the existing selection rather than replacing it, you need to hold down the Shift key. This method of working is preferred by some users and is consistent with selection methods in other software, including Windows Explorer.

Now turn off PICKADD and see the bug in action. First, we have to persuade AutoCAD to display grips on a large number of objects (e.g., several thousand). You can do this by setting GRIPOBJLIMIT to 0, or you could follow the steps described above for the Limitless Grips bug. Now let's say you want to clear the selection set to do something else. You could hit Esc, or you could do as Help for PICKADD states, "To clear a selection set quickly, draw a selection window in a blank area of the drawing." If you do the former, AutoCAD clears the grips quite quickly. If you do the latter, AutoCAD locks up, or at least appears to. I find that AutoCAD returns to the land of the living after a delay of between 30 seconds and two minutes, but other people have found that AutoCAD stays locked.

Workaround: None known other than training yourself to hit Esc to clear the selection set instead of working the way you're used to. You can reduce the delay somewhat by zooming in before picking so fewer grips are visible on screen, but the apparent lock-up is still very intrusive.

Crashing Is Bad, OK? (2009)
If you have AutoCAD 2009's Ribbon turned on, when you create or edit mtext, the ribbon usually changes to provide you with the controls you need to edit mtext. If the ribbon is off, a toolbar-style interface is provided instead. You can force AutoCAD to use this interface by setting the MTEXTTOOLBAR system variable, or by changing the setting from within the ribbon as shown here.

figure
Turning on the mtext editing toolbar interface from the Ribbon.

If you do use this interface, beware. If you pick in the Oblique Angle, Tracking, or Width Factor edit boxes and then pick the OK button, AutoCAD crashes.

figure
Crashing AutoCAD in two easy steps.

Workaround: None known other than "Don't do that" or avoiding this interface by using the ribbon.


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Lynn Allen

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