Showing Modeless Form with Help of PerDocumentClass

Sometimes, we want to provide UI as modeless form that floats on top of AutoCAD, presenting useful information to user and allowing user to still interact with either AutoCAD or the UI. However, if the data to be presented is document specific, the modeless form has to be updated/refreshed whenever the active document in AutoCAD changes.

I wrote an article on this topic a few years ago, where 2 approaches were described: using singleton form instance, or multiple form instances. If the data used in the UI is document specific, using singleton form would require UI refreshing, which in turn may require lengthy data re-collecting/re-loading. In that article, the multiple-form approach relies on non-static CommandMethod call to instantiate the CommandClass per document, so that the UI can be member of the CommandClass and be created somehow automatically.

However, to make AutoCAD plug-in code cleaner, more modular, one may not want to put document specific data models and/or UI components directly in a CommandClass. Also, per-document CommandClass is only instantiated when a non-static CommandMethod is called. So, what if you want the per-document data available before a non-static CommandMethod is called against each document?

In this article, I demonstrate how to take advantage of PerDocumentClassAttribute class, introduced by AutoCAD 2015, to show modeless form easily with document specific data.

Firstly, Kean Wamsley had posted 2 articles about "PerDocumentClassAttribute" here and here. One may want to read them first before following me further here.

Here is a PerDocumentClass that holds some data for each document opened in AutoCAD and holds an UI (a modeless form) to allow user to view/edit the per-document data:

using System;
using Autodesk.AutoCAD.ApplicationServices;
using Autodesk.AutoCAD.Runtime;
using CadApp = Autodesk.AutoCAD.ApplicationServices.Application;
 
[assembly: PerDocumentClass(typeof(PerDocModelessForm.MyDocData))]
 
namespace PerDocModelessForm
{
    public class MyDocData : IDisposable
    {
        private const string USERDATA_KEY = "My_PER_DOC_DATA";
 
        public string UserName { private set; get; }
        public string DrawingName { private set; get; }
        public string DwgNote1 { internal set; get; }
        public string DwgNote2 { internal set; get; }
        public MyDocDataView DataView { private set; get; }
        public bool WasShown { internal set; get; }
 
        private IntPtr _dwgPointer = IntPtr.Zero;
        private bool _saved = false;
        private Document _dwg = null;
 
        public MyDocData(Document dwg)
        {
            _dwg = dwg;
            DwgNote1 = "";
            DwgNote2 = "";
            UserName = CadApp.GetSystemVariable("LOGINNAME").ToString();
            DrawingName = dwg.Name;
            DataView = new MyDocDataView(this);
 
            _dwgPointer = dwg.UnmanagedObject;
            _saved = false;
 
            dwg.UserData.Add(USERDATA_KEY, this);
 
            // Update DrawingName property if file is saved to a new file name
            dwg.Database.SaveComplete += (o, e) =>
            {
                if (e.FileName.ToUpper()!=DrawingName.ToUpper())
                {
                    DrawingName = e.FileName;
                }
            };
 
            // Show the view when document is activated, if
            // the view was shown when the document was activate prevuoisly
            CadApp.DocumentManager.DocumentActivated += (o, e) =>
            {
                if (e.Document.UnmanagedObject == _dwgPointer)
                {
                    if (WasShown)
                    {
                        DataView.Visible = true;
                    }
                }
            };
 
            // Hide the data view if the document is deactivated
            CadApp.DocumentManager.DocumentToBeDeactivated += (o, e) =>
            {
                if (e.Document.UnmanagedObject == _dwgPointer)
                {
                    if (DataView.Visible)
                    {
                        WasShown = true;
                        DataView.Visible = false;
                    }
                }
            };
 
            // Save myDocData to somewhere
            CadApp.DocumentManager.DocumentToBeDestroyed += (o, e) =>
            {
                var doc = e.Document;
                if (doc.UnmanagedObject == _dwg.UnmanagedObject)
                {
                    var data = doc.UserData[USERDATA_KEY] as MyDocData;
                    SaveDwgNotes(data);
                }
            };
        }
 
        public static MyDocData Create(Document dwg)
        {
            return new MyDocData(dwg);
        }
 
        public static void ShowDocData(Document dwg)
        {
            var data = dwg.UserData[USERDATA_KEY] as MyDocData;
            CadApp.ShowModelessDialog(CadApp.MainWindow.Handle, data.DataView, true);
        }
 
        public void Dispose()
        {
            if (DataView!=null)
            {
                DataView.Dispose();
            }
        }
 
        #region private methods
 
        private void SaveDwgNotes(MyDocData data)
        {
            if (!data._saved)
            {
                System.Windows.Forms.MessageBox.Show(
                    "Saving drawing note data to somewhere...",
                    "Per Document Data in \"" + System.IO.Path.GetFileName(_dwg.Name) + "\"...",
                    System.Windows.Forms.MessageBoxButtons.OK,
                    System.Windows.Forms.MessageBoxIcon.Information);
 
                //To DO: save drawing note data to somewhere
 
 
                data._saved = true;
            }
        }
 
        #endregion
    }
}

Here is the command that allows user to view/edit data for each document:

using Autodesk.AutoCAD.Runtime;
using CadApp = Autodesk.AutoCAD.ApplicationServices.Application;
 
[assembly: CommandClass(typeof(PerDocModelessForm.MyCommands))]
 
namespace PerDocModelessForm
{
    public class MyCommands
    {
        [CommandMethod("ShowData")]
        public static void RunCommandA()
        {
            var dwg = CadApp.DocumentManager.MdiActiveDocument;
            MyDocData.ShowDocData(dwg);
        }
    }
}

This video clip shows the code in action

Some Thought

PerDocumentClass greatly simplifies the process of creating and cleaning "per-document" data in AutoCAD - a multiple document application: the class is instantiated to each existing open document when the .NET assembly, where the PerDocumentClass is defined, is loaded and to each newly opened document.

Using PerDocumentClass would make data segregation in the principle of "separate-concerns" much easier. My code here shows how multiple modeless forms are used for documents in AutoCAD with each only being associated to specific document.

In this example of using modeless form, I use Windows Form. Using WPF window would be the same. Using PaletteSet for each document is doable in the same way, but might not be desirable, because PaletteSet is designed to run at application level, as an UI (pallete) container, especially if a GUID is used to instantiate a PaletteSet, and AutoCAD remembers a PaletteSet based on its GUID per-application.

Download source code here.

Custom Command Showing Or Not Showing Dialog Box - 2 of 2

This is the second post on the topic of showing or not showing dialog box within custom command execution. The part 1 is here.

While an AutoCAD operation started with a command often needs to deal with files, thus needs file path/name to be inputted into the operation process with File Open/Save dialog box or at command line, even more often, the operation needs other data inputs than file path/name. Depending on the data input requirements, dialog box is used as more user-friendly UI and better input quality control means. However, in order to make a command script-able, a version of the same command often exists that collects all inputs from command line. The convention is to prefix "-" the regular command name as that command's command-line-only version. So, when we do create our own custom command with CommandMethod class, we should also try to follow this convention, if we want our custom command to be script-able.

Below is the code example:

[CommandMethod("DoThis")]
[CommandMethod("-DoThis")]
[CommandMethod("DiaDoThis")]
public static void DoSomething()
{
    var dwg = CadApp.DocumentManager.MdiActiveDocument;
    var ed = dwg.Editor;
 
    var cmd = CadApp.GetSystemVariable("CMDNAMES").ToString().ToUpper();
    var showDialog = !cmd.StartsWith("-") && !cmd.StartsWith("DIA");
 
    var userInput = showDialog ?
        GetInputFromDialog() :
        GetInputFromCommandLine();
 
    string msg;
    if (userInput=="YES")
        msg = $"The command proceeded {(showDialog?"with dialog box input":"with command line input")}.";
    else
        msg = $"The command cancelled {(showDialog ? "with dialog box input" : "with command line input")}.";
 
    CadApp.ShowAlertDialog(msg);
}
 
private static string GetInputFromDialog()
{
    var msg = "The process needs you to answer:\n\n" +
        "YES to continue\n" +
        "NO to caancel\n\n" +
        "Do you want to continue?";
    var res = System.Windows.Forms.MessageBox.Show(
        msg, "My Dialog Box",
        System.Windows.Forms.MessageBoxButtons.YesNo,
        System.Windows.Forms.MessageBoxIcon.Question,
        System.Windows.Forms.MessageBoxDefaultButton.Button1);
 
    return res == System.Windows.Forms.DialogResult.Yes ? "YES" : "NO";
}
 
private static string GetInputFromCommandLine()
{
    var ed = CadApp.DocumentManager.MdiActiveDocument.Editor;
    var input = "NO";
 
    var opt = new PromptKeywordOptions(
        "\nContinue the process?");
    opt.AppendKeywordsToMessage = true;
    opt.Keywords.Add("Yes");
    opt.Keywords.Add("No");
    opt.Keywords.Default = "Yes";
 
    var res = ed.GetKeywords(opt);
    if (res.Status== PromptStatus.OK)
    {
        input = res.StringResult.ToUpper();
    }
 
    return input;
}

The code is really simple, where I just used a message box, as a dialog box, to collect user input, but the interesting part is the multiple CommandMethodAttribute used to decorate the same methods as multiple custom commands. And notice that I also prefixed one of the command name with "Dia", implying it is dialog box version of the command, instead of prefixing the command with "-". This is just meant to show how I can use the different command name to run different version of the command, dialog box version, or command line version.

See this video clip for the code in action.

Custom Command Showing Or Not Showing Dialog Box - 1 of 2

Most AutoCAD users should know that toggle system variable "FILEDIA" would change AutoCAD built-in command behaviour, if the command needs user to supply valid file path/name during the command execution: either showing a Open/Save file dialog box for user to select file path/name, or asking user to enter file path/name at command line. The command line input is especially important, because it makes the command script-able (that is, the command can be included in a list of script macro with file path/name supplied, so that the script executing would not be interrupted by File Open/Save dialog box, waiting for user input).

Also, some AutoCAD built-in commands show dialog boxes other then File Open/Save dialog box. By AutoCAD convention, if we execute these command with prefix "-", the command would execute its command-line version for user inputs, if the command does have a command-line version.

When we do our custom AutoCAD programming, we should try our best to follow these AutoCAD convention to make our custom command script-able, whenever it is possible and/or necessary.

This post discusses making custom command showing/not showing File Open/Save dialog box, according to system variable "FILEDIA" value.

It turned out, it is rather easy, in terms of writing code, as shown below.

[CommandMethod("MyCmd")]
public static void RunMyCommand()
{
    var dwg = CadApp.DocumentManager.MdiActiveDocument;
    var ed = dwg.Editor;
 
    try
    {
        var fDia = Convert.ToInt32(CadApp.GetSystemVariable("FILEDIA"));
        var fileName = GetFileNameFromEditor(ed, fDia);
 
        if (string.IsNullOrEmpty(fileName))
        {
            CadApp.ShowAlertDialog("Command is cancelled.");
        }
        else
        {
            CadApp.ShowAlertDialog($"Command carries on with drawing:\n\n{fileName}");
 
            // Continue the execution with the valid file name, 
            // such as read the DWG file into side database
        }
    }
    catch (System.Exception ex)
    {
        ed.WriteMessage("\nError:\n{0}.", ex.Message);
    }
    finally
    {
        Autodesk.AutoCAD.Internal.Utils.PostCommandPrompt();
    }
}
 
private static string GetFileNameFromEditor(Editor ed, int fileDia)
{
    while (true)
    {
        var opt = new PromptOpenFileOptions("\nOpen a drawing file");
        opt.DialogCaption = "Open Drawing";
        opt.Filter = "AutoCAD Drawing *.dwg|*.dwg";
        if (ed.Document.IsNamedDrawing)
        {
            opt.InitialDirectory = System.IO.Path.GetDirectoryName(ed.Document.Name);
        }

        opt.PreferCommandLine = fileDia == 0;
 
        var res = ed.GetFileNameForOpen(opt);
        if (res.Status == PromptStatus.OK)
        {
            var valid = true;
 
            if (opt.PreferCommandLine)
            {
                if (!System.IO.File.Exists(res.StringResult))
                {
                    ed.WriteMessage(
                        $"\nFile not found:\n{res.StringResult}!");
                    valid = false;
                }
            }
 
            if (valid)
            {
                return res.StringResult;
            }
        }
        else
        {
            return "";
        }
    }
}

As the code shows, simply use Editor.GetFileNameForOpen[Save] in conjunction with PromptOpen[Save]FileOption does the trick: simply setting PreferCommandLine property of the PromptFileOptions class to False/True makes Editor.GetFileNameForOpen[Save]() method to either show File Open/Save dialog box, or ask user to enter file path/name at command line. In my code, if the file path/name is to be entered at command line, the code needs to valid the entered file path/name to make sure the file existence (for opening, of course. If it is for saving, creating necessary folder, prompt saving overwriting is warranted in following code).

See this video clip showing how the code works.

Change Width of DBText/AttributeReference - Part Three: Real Time Change

In 2 previous posts (here and here), the situation I tried to deal with is to fit a string of text into a limited space, such as a table's field with given width.

Obviously, besides shrinking the text string's width by reducing its WidthFactor, user can also rephrase the word/characters of the text string to reduce the width while keeping the meaning of the text. This way, the text would be presented visually the same (i.e. in the same WidthFactor).

With DBText, since it can be edited in place, so, user can change the wording of the text and see if the text would fit into the space while typing. But the the case of AttributeReference, the user can only either edit it in attribute editing dialog box, or in Properties window. For the former, when the attribute in edited in the dialog box, the real change occurs with the typing, which is good, because you can see if the text's width exceeds out of the allowed space at real time. For the latter, use can only see the change when the editing is completed (the focus leaves the edited field in Properties window).

After doing previous 2 posts, I thought why not doing one more article on changing text/attribute at real time by giving user chances of either changing text string's wording, or WidthFactor. The other reason of writing once more on this topic is that I have not seen sample code on the net about real time change of text entity while typing.

Here is the code of CommandClass RealTimeTextEditor:

using Autodesk.AutoCAD.Runtime;
using Autodesk.AutoCAD.ApplicationServices;
using Autodesk.AutoCAD.DatabaseServices;
using Autodesk.AutoCAD.EditorInput;
using CadApp = Autodesk.AutoCAD.ApplicationServices.Application;
 
[assembly: CommandClass(typeof(RealTimeTextEdit.RealTimeTextEditor))]
 
namespace RealTimeTextEdit
{
    public class RealTimeTextEditor
    {
        private Document _dwg;
        private string _defaultTarget = "Text";
        
        public RealTimeTextEditor()
        {
            SelectedId = ObjectId.Null;
            OriginalWidthFactor = 1.0;
            OriginalText = "";
            _dwg = CadApp.DocumentManager.MdiActiveDocument;
        }
 
        #region properties
 
        internal ObjectId SelectedId { private set; get; }
        internal string OriginalText { private set; get; }
        internal double OriginalWidthFactor { private set; get; }
 
        #endregion
 
        #region public methods
 
        [CommandMethod("MyTextEdit")]
        public void EditText()
        {
            while(true)
            {
                var target = SelectEditTarget(_defaultTarget);
                if (!string.IsNullOrEmpty(target))
                {
                    _defaultTarget = target;
 
                    ObjectId textId = ObjectId.Null;
                    if (_defaultTarget=="Text")
                    {
                        textId = SelectTextEntity();
                    }
                    else
                    {
                        textId = SelectAttributeEntity();
                    }
 
                    if (!textId.IsNull)
                    {
                        GetTextInformation(textId);
                        DoEditWork();
                    }
                }
                else
                {
                    break;
                }
            }
 
            _dwg.Editor.WriteMessage("\n");
        }
 
        #endregion
 
        #region private methods
 
        private string SelectEditTarget(string defaultTarget)
        {
            var target = "";
 
            var opt = new PromptKeywordOptions(
                "\nEdit Text or Attribute?");
            opt.AppendKeywordsToMessage = true;
            opt.Keywords.Add("Text");
            opt.Keywords.Add("Attribute");
            opt.Keywords.Add("eXit");
            opt.Keywords.Default = defaultTarget;
 
            var res = _dwg.Editor.GetKeywords(opt);
            if (res.Status== PromptStatus.OK)
            {
                if (res.StringResult!="eXit")
                {
                    return res.StringResult;
                }
            }
 
            return target;
        }
 
        private ObjectId SelectTextEntity()
        {
            ObjectId textId = ObjectId.Null;
 
            var opt = new PromptEntityOptions(
                "\nSelect a TEXT entity:");
            opt.SetRejectMessage(
                "\nInvalid selection: not a TEXT entity!");
            opt.AddAllowedClass(typeof(DBText), true);
 
            var res = _dwg.Editor.GetEntity(opt);
            if (res.Status== PromptStatus.OK)
            {
                textId = res.ObjectId;
            }
 
            return textId;
        }
 
        private ObjectId SelectAttributeEntity()
        {
            ObjectId attId = ObjectId.Null;
 
            while (true)
            {
                var opt = new PromptNestedEntityOptions(
                    "\nSelect an Attribute in block:");
                opt.AllowNone = false;
 
                var res = _dwg.Editor.GetNestedEntity(opt);
                if (res.Status == PromptStatus.OK)
                {
                    if (res.ObjectId.ObjectClass.DxfName.ToUpper() == "ATTRIB")
                    {
                        attId = res.ObjectId;
                    }
                    else
                    {
                        _dwg.Editor.WriteMessage(
                            "\nInvalid selection: not an attribue in block!");
                    }
                }
                else
                {
                    break;
                }
 
                if (!attId.IsNull) break;
            }
 
            return attId;
        }
 
        private void GetTextInformation(ObjectId textId)
        {
            using (var tran = _dwg.TransactionManager.StartTransaction())
            {
                var txt = (DBText)tran.GetObject(textId, OpenMode.ForRead);
                OriginalText = txt.TextString;
                OriginalWidthFactor = txt.WidthFactor;
                SelectedId = textId;
                tran.Commit();
            }
        }
 
        private void DoEditWork()
        {
            using (var dlg = new dlgTextBox(this))
            {
                dlg.TextStringChanged += (o, e) =>
                  {
                      UpdateTextEntity(e.TextString);
                  };
 
                dlg.TextWidthFactorChanged += (o, e) =>
                {
                    UpdateTextEntity(e.WidthFactor);
                };
 
                dlg.Left = 50;
                dlg.Top = 50;
 
                var res = CadApp.ShowModalDialog(CadApp.MainWindow.Handle, dlg, false);
 
                if (res== System.Windows.Forms.DialogResult.Cancel)
                {
                    //restore the originals
                    UpdateTextEntity(OriginalText);
                    UpdateTextEntity(OriginalWidthFactor);
                }
            }
        }
 
        private void UpdateTextEntity(string textString)
        {
            using (var tran = _dwg.TransactionManager.StartTransaction())
            {
                var txt = (DBText)tran.GetObject(SelectedId, OpenMode.ForWrite);
                txt.TextString = textString;
                tran.Commit();
            }
            _dwg.Editor.UpdateScreen();
        }
 
        private void UpdateTextEntity(double widthFactor)
        {
            using (var tran = _dwg.TransactionManager.StartTransaction())
            {
                var txt = (DBText)tran.GetObject(SelectedId, OpenMode.ForWrite);
                txt.WidthFactor = widthFactor;
                tran.Commit();
            }
            _dwg.Editor.UpdateScreen();
        }
 
        #endregion
    }
}

I need UI as a modal dialog box where user can re-typing text string, or change WidthFactor. It looks like this:

Here the dialog box' code behind:

using System;
using System.Windows.Forms;
 
using Autodesk.AutoCAD.DatabaseServices;
 
namespace RealTimeTextEdit
{
    public partial class dlgTextBox : Form
    {
        private RealTimeTextEditor _tool = null;
        private ObjectId _textId = ObjectId.Null;
        private bool _setText = false;
 
        internal dlgTextBox()
        {
            InitializeComponent();
        }
 
        internal dlgTextBox(RealTimeTextEditor tool):this()
        {
            _tool = tool;
        }
 
        internal event TextStringChangedEventHandler TextStringChanged;
        internal event TextWidthFactorChangedEventHandler TextWidthFactorChanged;
 
        internal bool Undo { private set; get; }
 
        #region private methods
 
        private void ShowSelected()
        {
            if (!_tool.SelectedId.IsNull)
            {
                _setText = true;
                _textId = _tool.SelectedId;
                txtOld.Text = _tool.OriginalText;
                txtNew.Text = _tool.OriginalText;
                txtNew.Enabled = true;
                txtFactor.Text = _tool.OriginalWidthFactor.ToString("#0.00");
                udFactor.Value = Convert.ToDecimal(_tool.OriginalWidthFactor);
                btnUndo.Enabled = false;
                _setText = false;
            }
        }
 
        #endregion
 
        private void txtNew_TextChanged(object sender, EventArgs e)
        {
            if (_setText) return;
 
            btnUndo.Enabled = true;
            TextStringChanged?.Invoke(
                this, 
                new TextStringChangedEventArgs(txtNew.Text));
        }
 
        private void udFactor_ValueChanged(object sender, EventArgs e)
        {
            if (_setText) return;
 
            btnUndo.Enabled = true;
            TextWidthFactorChanged?.Invoke(
                this, 
                new TextWidthFactorChangedEventArgs(Convert.ToDouble(udFactor.Value)));
        }
 
        private void btnUndo_Click(object sender, EventArgs e)
        {
            this.DialogResult = DialogResult.Cancel;
        }
 
        private void btnClose_Click(object sender, EventArgs e)
        {
            this.DialogResult = DialogResult.OK;
        }
 
        private void dlgTextBox_Load(object sender, EventArgs e)
        {
            ShowSelected();
        }
    }
 
    internal class TextStringChangedEventArgs : EventArgs
    {
        internal string TextString { private set; get; }
        internal TextStringChangedEventArgs(string textString)
        {
            TextString = textString;
        }
    }
 
    internal delegate void TextStringChangedEventHandler(
        object sender, TextStringChangedEventArgs e);
 
    internal class TextWidthFactorChangedEventArgs : EventArgs
    {
        internal double WidthFactor { private set; get; }
        internal TextWidthFactorChangedEventArgs(double widthFactor)
        {
            WidthFactor = widthFactor;
        }
    }
 
    internal delegate void TextWidthFactorChangedEventHandler(
        object sender, TextWidthFactorChangedEventArgs e);
}

As the code shows, the real-time change to the target DBText/AttributeReference is triggered by the UI firing event TextStringChanged and TextWidthFactorChanged. The event handlers (highlighted in red) make the actual change.

See this video that shows the code in action.

It is worth pointing out: in the CommandClass RealTimeTextEditor I use non-static method as the CommandMethod, which means for each Document this command is used, a class instance is created by AutoCAD, so that the user's previous choice of editing target (Text, or Attribute), which is asked at beginning of the command execution, is the default choice (default keyword in the GetKeyword() call). The video clip shows this effect in its last portion.

Note:
Most of my posts come with video clips that show how the code run in AutoCAD. Until this post, I have always used Jing from TechSmith with free video host at screencast.com (thanks for the free stuff!). However, TechSmith recently announced their policy change that from now on, they would only keep video clips for one year for free Jing version user. So, starting from this post, I stopped using free Jing to generate screen capture video. Instead, I use OBS Studio to record screen as MP4 files and store and share them from my Google drive. I'll try to collect all the video clips used in my posts into my Google drive and update the links in the old posts as soon as possible before they are removed from screencast.com (hopefully I can find enough time before the deadline in September :-().

Change Width of DBText/AttributeReference by Its WidthFactor - Part Two: Drag-Fitting

In previous post, I showed the code to automatically adjust DBText's width to fit into a given space by reducing DBText's WidthFactor. Then I thought why not give user another handy way to adjust DBText's width: simply drag the DBText entity to desired width, much similar to AutoCAD's built-in dragging to scale an entity (but in this case, only width of DBText entity is "scaled").

Now that I am talking about dragging entities, I could derive my process from Jig class, or just build my own "Jig" style process with Transient graphics. I decided to go with the latter.

Here is the code:

using System;
 
using Autodesk.AutoCAD.ApplicationServices;
using Autodesk.AutoCAD.DatabaseServices;
using Autodesk.AutoCAD.Geometry;
using Autodesk.AutoCAD.EditorInput;
using Autodesk.AutoCAD.GraphicsInterface;
using CadApp = Autodesk.AutoCAD.ApplicationServices.Application;
 
namespace FitAttributeWidth
{
    public class TextWidthDragger
    {
        private Document _dwg;
        private Editor _ed;
        private ObjectId _txtId = ObjectId.Null;
        private double _factor = 1.0;
        private double _width = 0.0;
        private DBText _textDrawable = null;
        private Point3d _basePoint;
 
        private TransientManager _tsManager = TransientManager.CurrentTransientManager;
 
 
        public TextWidthDragger()
        {
            
        }
 
        public void DragTextEntity()
        {
            _dwg = CadApp.DocumentManager.MdiActiveDocument;
            _ed = _dwg.Editor;
 
            var entId = SelectDragTarget();
            if (entId.IsNull)
            {
                _ed.WriteMessage("\n*Cancel*\n");
                return;
            }
 
            DragDBText(_dwg, entId);
        }
 
        public void DragDBText(Document dwg, ObjectId txtId)
        {
            _dwg = dwg;
            _ed = dwg.Editor;
            _txtId = txtId;
 
            DoTextDrag();
        }
 
        #region private methods: select DBText or AttributeReference
 
        private ObjectId SelectDragTarget()
        {
            var entId = ObjectId.Null;
 
            var opt = new PromptKeywordOptions(
                "\nSelect a Text or an Attribute in block:");
            opt.AppendKeywordsToMessage = true;
            opt.Keywords.Add("Text");
            opt.Keywords.Add("Attribute");
            opt.Keywords.Default = "Text";
 
            var res = _ed.GetKeywords(opt);
            if (res.Status== PromptStatus.OK)
            {
                if (res.StringResult == "Text")
                    entId = SelectDBText();
                else
                    entId = SelectAttribute();
            }
 
            return entId;
        }
 
        private ObjectId SelectDBText()
        {
            var txtId = ObjectId.Null;
 
            var opt = new PromptEntityOptions(
                "\nSelect a Text entity:");
            opt.SetRejectMessage("\nInvalid selection: not a text entity!");
            opt.AddAllowedClass(typeof(DBText), true);
 
            var res = _ed.GetEntity(opt);
            if (res.Status== PromptStatus.OK)
            {
                txtId = res.ObjectId;
            }
 
            return txtId;
        }
 
        private ObjectId SelectAttribute()
        {
            var attId = ObjectId.Null;
 
            while (true)
            {
                var opt = new PromptNestedEntityOptions(
                    "\nSelect an Attribute in block:");
                opt.AllowNone = false;
 
                var res = _ed.GetNestedEntity(opt);
                if (res.Status == PromptStatus.OK)
                {
                    if (res.ObjectId.ObjectClass.DxfName.ToUpper() == "ATTRIB")
                    {
                        attId = res.ObjectId;
                    }
                    else
                    {
                        _ed.WriteMessage(
                            "\nInvalid selection: not an attribue in block!");
                    }
                }
                else
                {
                    break;
                }
 
                if (!attId.IsNull) break;
            }
 
            return attId;
        }
 
        #endregion
 
        #region private methods
 
        private void DoTextDrag()
        {
            using (var tran = _dwg.TransactionManager.StartTransaction())
            {
                var target = (DBText)tran.GetObject(_txtId, OpenMode.ForRead);
                _factor = target.WidthFactor;
                _width = GetTextWidth(target) / _factor;
                _basePoint = target.Position;
 
                bool dragOk = false;
                try
                {
                    _textDrawable = (DBText)target.Clone();
                    _textDrawable.ColorIndex = 2;
 
                    _ed.PointMonitor += Editor_PointMonitor;
 
                    var dist = GetDistance();
                    if (dist!=double.MinValue)
                    {
                        _factor = dist / _width;
                        target.UpgradeOpen();
                        target.WidthFactor = _factor;
                    }
                }
                finally
                {
                    ClearTransients();
                    _textDrawable.Dispose();
                    _ed.PointMonitor -= Editor_PointMonitor;
                }
 
                if (dragOk && _factor!=target.WidthFactor)
                {
                    target.UpgradeOpen();
                    target.WidthFactor = _factor;
                }
 
                tran.Commit();
            }
        }
 
        private double GetTextWidth(DBText txt)
        {
            var ext = txt.GeometricExtents;
            return Math.Abs(ext.MaxPoint.X - ext.MinPoint.X);
        }
 
        private void Editor_PointMonitor(object sender, PointMonitorEventArgs e)
        {
            ClearTransients();
 
            var dist = e.Context.RawPoint.DistanceTo(_basePoint);
            _factor = dist / _width;
 
            e.AppendToolTipText($"Width scale factor: {_factor}");
 
            _textDrawable.WidthFactor = _factor;
 
            AddTransients();
        }
 
        private void AddTransients()
        {
            _tsManager.AddTransient(
                _textDrawable, 
                TransientDrawingMode.Highlight, 
                128, 
                new IntegerCollection());
        }
 
        private void ClearTransients()
        {
            _tsManager.EraseTransient(_textDrawable, new IntegerCollection());
        }
 
        private double GetDistance()
        {
            var opt = new PromptDistanceOptions(
                "\nSet text entity width scale factor:");
            opt.AllowZero = false;
            opt.AllowNegative = false;
            opt.AllowArbitraryInput = false;
            opt.AllowNone = false;
            opt.UseBasePoint = true;
            opt.BasePoint = _basePoint;
            opt.UseDashedLine = true;
 
            var res = _ed.GetDistance(opt);
            if (res.Status == PromptStatus.OK)
                return res.Value;
            else
                return double.MinValue;
        }
 
        #endregion
    }
}

Here is the command to run it:

[CommandMethod("DragTextWidth")]
public static void DragTextWidth()
{
    var dwg = CadApp.DocumentManager.MdiActiveDocument;
    var ed = dwg.Editor;
 
    try
    {
        var dragger = new TextWidthDragger();
        dragger.DragTextEntity();
    }
    catch (System.Exception ex)
    {
        ed.WriteMessage("\nError:\n{0}.", ex.Message);
    }
    finally
    {
        Autodesk.AutoCAD.Internal.Utils.PostCommandPrompt();
    }
}

Again, as mentioned in previous post, for simplicity, when calculate entity's width I assume the DBText/AttributeReference entity is placed horizontally. The code also tries to show the DBText's WidthFactor dynamically as tooltip when the DBText entity is dragged. However, since the tooltip thing is handled in PointMonitor event in the simplest way, the tooltip only shows when mouse cursor stays not moving. It might be possible to use the same or similar approach showed in this post to make a good tooltip to show changing WidthFactor while dragging. Again, for the simplicity of this post, I decide not spend time on this for now.

See this video clip showing how the code works.