Small Q (no issue): ListView inplace editor bounds and selection

[d7_2_laz]

(On Windows x64, Lazarus 2.0.12):
It's only aesthetics, but i'm wondering if it's possible to make the inplace editor for ListView to appear just like as in Delphi: the bounds of the inplace editor field are autosized here to the Length of the text. In Laz. it's determined by the boundaries of the column cell; the edit field does fill the whole cell.
TreeVuew EditNode similar.

I guess it's not done by the API, as for example such has no effect:

Code: Pascal  [Select][+][-]

1. hEdit := ListView_GetEditControl(Handle);
2. SendMessage(hEdit, EM_SETMARGINS, 1,MAKELONG(15,0));
3. PostMessage(hEdit, EM_SETSEL, 0, myLength);  // defiine lenght of the selection marker

Not a big thing, but maybe somebody does know if it's possible to influence that.

[d7_2_laz]

I add a screenshot about what i would like to achieve (behavious similar to windows explorer)

[ASerge]

the bounds of the inplace editor field are autosized here to the Length of the text

If you really want to, you can take a chance:

Code: Pascal  [Select][+][-]

1. unit Unit1;
2.  
3. {$mode objfpc}{$H+}
4.  
5. interface
6.  
7. uses
8.   Classes, SysUtils, Forms, Controls, ComCtrls;
9.  
10. type
11.   TForm1 = class(TForm)
12.     ListView1: TListView;
13.     procedure FormCreate(Sender: TObject);
14.   end;
15.  
16. var
17.   Form1: TForm1;
18.  
19. implementation
20.  
21. {$R *.lfm}
22.  
23. uses LMessages;
24.  
25. type
26.   TMyListViewEditor = class(TCustomListViewEditor)
27.   protected
28.     procedure WMSetFocus(var Message: TLMSetFocus); message LM_SETFOCUS;
29.   end;
30.  
31.   TOpenListView = class helper for TListView
32.     function GetEditor: TCustomListViewEditor;
33.   end;
34.  
35.   TCustomListViewEmulator = class(TWinControl)
36.   private
37.     FEditor: TCustomListViewEditor;
38.   end;
39.  
40. // Caution: no check
41. // Use only for descendants of Instance class without new members
42. procedure ChangeClassForInstance(Instance: TObject; NewClass: TClass);
43. begin
44.   TClass(Pointer(Instance)^) := NewClass;
45. end;
46.  
47. procedure TForm1.FormCreate(Sender: TObject);
48. begin
49.   ChangeClassForInstance(ListView1.GetEditor, TMyListViewEditor);
50. end;
51.  
52. function TOpenListView.GetEditor: TCustomListViewEditor;
53. begin
54.   {$WARNING Very unsafe code}
55.   // Two unsafe assumes
56.   // 1. FEditor is the first field in TCustomListView (TListView)
57.   // 2. The compiler arranges the fields in the order of declaration
58.   Result := TCustomListViewEmulator(Pointer(Self)).FEditor;
59. end;
60.  
61. procedure TMyListViewEditor.WMSetFocus(var Message: TLMSetFocus);
62. const
63.   CExtensionForWidth = 6;
64. var
65.   W: Integer;
66. begin
67.   W := (Owner as TListView).Canvas.TextWidth(Text);
68.   if Width > W + CExtensionForWidth then
69.     Width := W + CExtensionForWidth;
70.   inherited;
71. end;
72.  
73. end.

[d7_2_laz]

Hello ASerge, thank you!
Applied the helper functions to a custom listview and indeed it works, but (my agreement here) i doubt if it's worthy to go such a hacky bridge.

Would it be (complementary or alternatively) cost such an effort too to simply restrict the initial selecion of an edit field content to a portion of it?
Like in the screenshot: mark only a file name as selected, not it's extenson?
As an SendMessage EM_SETSEL (with a lenght parameter) won't work here.
An approach for that would be simplier or would it be based on the same technique?

[d7_2_laz]

Just for interest:
Within the TMyListViewEditor.WMSetFocus it would work:
...
PostMessage(Handle, EM_SETSEL, 0, 9);   // Example only

(of course nobody wants to embed business logic within TMyListViewEditor.WMSetFocus. But by principle it's possible though)

[d7_2_laz]

Better to do:
within TMyCustomListView.Editing something lke:
...
  hEdit := (TListView(Self)).GetEditor.Handle;
  PostMessage(hEdit, EM_SETSEL, 0, ln);

Will work