Obviously, the method Highlight() of AttributeReference, although being derived from Entity, has its own overridden implementation, so that it behaves the same as its owner, the BlockReference.
Now that AttributeReference.Highlight() does not work, I thought looking into Overrule could lead to easy solution.
Naturally, I turned to HighlightOverrule first, which I posted an article about it a few years ago here. However, seeing the code in that article, I realize that it will not work, because the code still need to call AttributeReference.Highlight() inside the overridden Overrule's Hightlight() method.
As alternative, I tried to use DrawableOverrule. In this try, I successfully made AttributeRefernce being drawn in different colors (thus, a sort of "highlighting"). However, I have difficulties to make the attribute text showing in the way being highlighted in AutoCAD.
Nevertheless, using DrawableOverrule is a viable solution to "highlight" attribute. Since I have found a even better solution, I am not going to show the DrawableOverrule for attribute in this article (maybe later, if I can manage a bit time).
The solution I post here is to use Transient Graphics. The code is rather simple and does not need much explanation.
Here is the class called AttributeHighlighter:
1 using System;
2 using System.Collections.Generic;
3 using System.Linq;
4 using Autodesk.AutoCAD.DatabaseServices;
5 using Autodesk.AutoCAD.Geometry;
6 using Autodesk.AutoCAD.GraphicsInterface;
7
8 namespace HighlightAttribute
9 {
10 public class AttributeHighlighter : IDisposable
11 {
12 private TransientManager _tManager =
13 TransientManager.CurrentTransientManager;
14 private List<Drawable> _entities = new List<Drawable>();
15
16 public void Dispose()
17 {
18 DisposeDrawables();
19 }
20
21 public void Highlight(IEnumerable<ObjectId> blkIds)
22 {
23 DisposeDrawables();
24
25 CollectDrawables(blkIds);
26
27 foreach (var ent in _entities)
28 {
29 _tManager.AddTransient(
30 ent,
31 TransientDrawingMode.Highlight,
32 128,
33 new IntegerCollection());
34 }
35 }
36
37 public void Unhighlight()
38 {
39 _tManager.EraseTransients(
40 TransientDrawingMode.Highlight,
41 128,
42 new IntegerCollection());
43 }
44
45 private void DisposeDrawables()
46 {
47 foreach (var ent in _entities)
48 {
49 ent.Dispose();
50 }
51
52 _entities.Clear();
53 }
54
55 private void CollectDrawables(IEnumerable<ObjectId> ids)
56 {
57 Database db = ids.First().Database;
58 using (var tran = db.TransactionManager.StartTransaction())
59 {
60 foreach (var id in ids)
61 {
62 BlockReference bref =
63 tran.GetObject(id, OpenMode.ForRead)
64 as BlockReference;
65
66 if (bref == null) continue;
67
68 foreach (ObjectId attId in bref.AttributeCollection)
69 {
70 AttributeReference att = (AttributeReference)
71 tran.GetObject(attId, OpenMode.ForRead);
72
73 _entities.Add(att.Clone() as Drawable);
74 }
75 }
76
77 tran.Commit();
78 }
79 }
80 }
81 }
Then here is the command to use AttributeHighlighter:
1 using System.Collections.Generic;
2 using Autodesk.AutoCAD.ApplicationServices;
3 using Autodesk.AutoCAD.DatabaseServices;
4 using Autodesk.AutoCAD.Runtime;
5 using Autodesk.AutoCAD.EditorInput;
6 using CadApp = Autodesk.AutoCAD.ApplicationServices.Application;
7
8 [assembly: CommandClass(typeof(HighlightAttribute.Commands))]
9
10 namespace HighlightAttribute
11 {
12 public class Commands
13 {
14 [CommandMethod("MyAtt")]
15 public static void SetAttHighlight()
16 {
17 Document dwg = CadApp.DocumentManager.MdiActiveDocument;
18 Editor ed = dwg.Editor;
19
20 IEnumerable<ObjectId> ids = SelectAllBlocks(ed);
21 if (ids != null)
22 {
23 using (AttributeHighlighter hl = new AttributeHighlighter())
24 {
25 hl.Highlight(ids);
26 ed.UpdateScreen();
27 ed.GetString("\nPress any key to continue...");
28 hl.Unhighlight();
29 ed.UpdateScreen();
30 }
31 }
32
33 Autodesk.AutoCAD.Internal.Utils.PostCommandPrompt();
34 }
35
36 private static IEnumerable<ObjectId> SelectAllBlocks(Editor ed)
37 {
38 TypedValue[] vals = new TypedValue[]
39 {
40 new TypedValue((int)DxfCode.Start,"INSERT")
41 };
42
43 PromptSelectionResult res = ed.SelectAll(new SelectionFilter(vals));
44 if (res.Status == PromptStatus.OK)
45 return res.Value.GetObjectIds();
46 else
47 return null;
48 }
49 }
50 }
What the command does is select all blocks, which have attributes, and pass the selected blocks' ObjectId to AttributeHighlighter, which searches through all the blocks and create a set of clones of all attributes and uses these cloned attributes to draw Transient Graphics (highlight) on top of the attributes. To user's eye, it looks like the attributes are highlighted. See this short video clip.