Virtualtreeview - Controls auf Nodes

[Baltenweck]

Hallo zusammen,

auf den Nodes eines TVirtualStringTree's möchte ich ein Panel darstellen.
Hier mal das Testprogramm (lazerus):

Delphi-Quellcode:

unit Unit1;

{$mode DELPHI}

interface

uses
  Classes, SysUtils, FileUtil, VirtualTrees, Forms, Controls, Graphics, Dialogs,
  StdCtrls,ExtCtrls;

type
 
  TForm1 = class(TForm)
    Button1: TButton;
    Panel1: TPanel;
    VST: TVirtualStringTree;
    procedure Button1Click(Sender: TObject);
    procedure FormClose(Sender: TObject; var CloseAction: TCloseAction);
    procedure FormCreate(Sender: TObject);
    procedure VSTAfterCellPaint(Sender: TBaseVirtualTree;
      TargetCanvas: TCanvas; Node: PVirtualNode; Column: TColumnIndex;
      const CellRect: TRect);
  private
    { private declarations }
  public
    { public declarations }
  end;

type
  PTreeData = ^TTreeData;
  TTreeData = record
    NodeName : String;  // Eindeutige Bezeichnung
    Panel : TPanel;
  end;

var
  Form1: TForm1;
  Node : PVirtualNode;
  Data: PTreeData;

implementation

{$R *.lfm}

procedure TForm1.FormCreate(Sender: TObject);
begin
  VST.NodeDataSize:=SizeOf(TTreeData);
  VST.DefaultNodeHeight:=50;
end;

procedure TForm1.VSTAfterCellPaint(Sender: TBaseVirtualTree;
  TargetCanvas: TCanvas; Node: PVirtualNode; Column: TColumnIndex;
  const CellRect: TRect);
begin
  Data := VST.GetNodeData(Node);
  If Assigned(Data) Then begin
    Data^.Panel.Left:=20;
    Data^.Panel.Width:=CellRect.Right-CellRect.Left-Data^.Panel.Left;
    Data^.Panel.Top:=CellRect.Top;
    Data^.Panel.Height:=CellRect.Bottom-CellRect.Top;
  end;
end;

procedure TForm1.FormClose(Sender: TObject; var CloseAction: TCloseAction);
begin
  VST.Free;
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
  Node := VST.AddChild(nil);
  If VST.AbsoluteIndex(Node) > -1 then begin
    Data := VST.GetNodeData(Node);
    Data^.NodeName:='Nodename';
    Data^.Panel:= TPanel.Create(nil);
    Data^.Panel.Parent := VST;
    Data^.Panel.Left := 40;
    Data^.Panel.Top := 0;
    Data^.Panel.Width := 50;
    Data^.Panel.Height := VST.DefaultNodeHeight;
    Data^.Panel.Anchors := [akTop,akLeft];
    Data^.Panel.BorderWidth := 0;
    Data^.Panel.Autosize:=True;
    Data^.Panel.Color:=clRed;
    Data^.Panel.Visible:=True;
  end;
end;

end.

Die Frage ist: Warum wird das Panel nicht angezeigt
Wäre für Denkanstöße sehr Dankbar !!

Gruß
Patrick