Can you help translating this very small C++ component to Delphi?

Question

I\'m translating the following C++ component to Delphi:

http://borland.newsgroups.archived.at/public.delphi.vcl.components.using.win32/200708/0708225318.html

Answer 1

@Steve's answer works fine, but with a simple adding you can create an actual line seperator between two items.

procedure WndProc(var Message: TMessage); override;
procedure ListWndProc(var Message: TMessage);
procedure DrawItem(Index: Integer; Rect: TRect;
  State: TOwnerDrawState); override;

Change the last part of DrawItem to:

if( not Boolean(Items.Objects[Index]) ) then
  Canvas.TextOut(Rect.Left + 3, Rect.Top + (((Rect.Bottom - Rect.Top) div 2) -
    (Canvas.TextHeight('Wg') div 2)), Items.Strings[Index])
else
begin
  Canvas.Pen.Color := clSilver;
  Canvas.Pen.Width := 1;
  Canvas.Pen.Style := psSolid;
  Canvas.MoveTo(Rect.Left + 3, Rect.Top + ((Rect.Bottom - Rect.Top) div 2));
  Canvas.LineTo(Rect.Right - 3, Rect.Top + ((Rect.Bottom - Rect.Top) div 2));
end;

It helps me alot when I can see how the class can be used. So for others I added an example on how to use it:

uses
  Forms, o_comboboxplus;

var
 fComboPlus: TComboBoxPlus;

begin
  fComboPlus := TComboBoxPlus.Create(Form1);
  with(fComboPlus) do
  begin
    Parent := Form1;
    Left := 10;
    Top := 10;
    Items.Add('Test1');
    Items.Add('Test2');
    Items.Add('Test3');
    Items.Add('Test4');
    Enabled[2] := false;    //'Test3' will become a line seperator
  end;
end;

Answer 2

It's after midnight I'm tired - sorry about my stupidity. It's working with the following modifications:

procedure WndProc(var Message: TMessage); override;
procedure ListWndProc(var Message: TMessage);
procedure DrawItem(Index: Integer; Rect: TRect;
  State: TOwnerDrawState); override;

(add two overrides and take out the virtual)

The last thing to sort out is not to let the combobox close up if the disabled item is selected without keyboard keys!