To my knowledge, this is not possible in LISP.
The only way I am aware of to retrieve this information is to use the getTabSelected() function of ObjectArx.
FWIW -
I too know of no way of doing this from LISP natively, however, the .NET API exposes the bool Layout.TabSelected Property, which could be utilized to extend LISP via custom LispFunction Method.
As a quick example, consider this pseudo-named, custom LayoutListSelected function:
Attached to this post is an Autoloader .bundle which supports 2012-2014 natively, but the ./Contents/Windows/2010/ assembly can be NETLOADed into 2010 & 2011 as well, as it has been compiled to .NET 3.5 framework (for those still using pre-Autoloader 2010 Database versions)... Simply download, unblock, and unzip to ..\ApplicationPlugins\, and start AutoCAD.
[Edit] - Autodesk forums would not allow me to upload the attached Autoloader .bundle as a .ZIP, so I've added a .TXT file extension, which seems to have worked... Simply remove this prior to unzipping.
... And for those, like me, that would prefer to compile themselves, here's the source code (C#):
using Autodesk.AutoCAD.Runtime;
using Autodesk.AutoCAD.ApplicationServices;
using Autodesk.AutoCAD.DatabaseServices;
using Autodesk.AutoCAD.EditorInput;
using System.Collections.Generic;
[assembly: CommandClass(typeof(BlackBox.AutoCAD.LayoutListSelected.Commands))]
namespace BlackBox.AutoCAD.LayoutListSelected
{
class Commands
{
[LispFunction("LayoutListSelected")]
public ResultBuffer LayoutListSelected(ResultBuffer args)
{
if (args != null)
throw new TooManyArgsException();
Document doc = Application.DocumentManager.MdiActiveDocument;
Database db = doc.Database;
//Editor ed = doc.Editor;
//LayoutManager layoutMgr = LayoutManager.Current;
List<string> layouts = new List<string>();
ResultBuffer res = new ResultBuffer();
using (Transaction tr = db.TransactionManager.StartTransaction())
{
DBDictionary layoutDic =
(DBDictionary)tr.GetObject(db.LayoutDictionaryId, OpenMode.ForRead, false);
foreach (DBDictionaryEntry entry in layoutDic)
{
Layout layout =
(Layout)tr.GetObject(entry.Value, OpenMode.ForRead);
string layoutName = layout.LayoutName;
if (layout.TabSelected)
layouts.Add(layoutName);
}
tr.Commit();
}
layouts.Remove("Model");
if (0 < layouts.Count)
{
layouts.Sort();
foreach (string layoutName in layouts)
{
res.Add(new TypedValue(5005, layoutName));
}
return res;
}
else
return null;
}
}
// Special thanks to Gile for his LispException classes:
class LispException : System.Exception
{
public LispException(string msg) : base(msg) { }
}
class TooFewArgsException : LispException
{
public TooFewArgsException() : base("too few arguments") { }
}
class TooManyArgsException : LispException
{
public TooManyArgsException() : base("too many arguments") { }
}
class ArgumentTypeException : LispException
{
public ArgumentTypeException(string s, TypedValue tv)
: base(string.Format(
"invalid argument type: {0}: {1}",
s, tv.TypeCode == (int)LispDataType.Nil ? "nil" : tv.Value))
{ }
}
}
@JoistDetailer wrote:
That looks like it will work. I appreciate your response and effort!
However, you lost me when you said to "download, unblock, and unzip to .." - what do you mean by "unblock"?? Please pardon my ignorance...I'm not familiar with the Autoloader or dotNet.
No worries; this was just a quick example. 
- Download the attached file (above).
- If you're using Windows 7, you'll probably need to right click the downloaded file, choose properties, and then hit the unblock button, followed by ok. If not using Windows 7 (i.e., XP, etc.), disregard.
- Change .ZIP.TXT to just .ZIP file extension.
- Unzip
If you're using 2012 or newer:
- Simply move the resultant ..\BlackBox Layout List Selected.bundle\ folder to %AppData%\Autodesk\ApplicationPlugins\ folder, and start AutoCAD. That's it (hooray Autoloader!). Lemon squeezy.
if you're using 2011 or 2010:
- Copy the ..\BlackBox Layout List Selected.bundle\Contents\Windows\2010\bbox_LayoutListSelected18.dll file to any location on your local disk where you have write permission (or to a similar network folder if Acad.Exe.Config has LoadFromRemoteSources XmlAttribute enabled?), and then from within your session of AutoCAD use the NETLOAD Command to load.
- If you like this, and want it to be loaded for you at startup, let me know, and we can either add to your Acad.lsp (if you have write permission?), or set you up a registry loader which will do the same.
Now, if you're using 2009 or older, let me know... I'll have to see if this API feature (the TabSelected Property) was exposed to .NET 3.0 Framework, etc. and attempt to provide you an additional asembly, etc.
It sounds like a lot if you're not already familiar, but this is really quite simple once you've done it... Hope this makes (more?) sense now.
Cheers
