how do i remove white background in node inside virtual TVirtualStringTree?

[drama22]

i tried to use TargetCanvas.Brush.Style := bsClear; inside BeforeCellPaint still node have white back ground here is the full code

Delphi-Quellcode:

procedure TForm2.VTs1BeforeCellPaint(Sender: TBaseVirtualTree;
  TargetCanvas: TCanvas; Node: PVirtualNode; Column: TColumnIndex;
  CellPaintMode: TVTCellPaintMode; CellRect: TRect; var ContentRect: TRect);
begin
TargetCanvas.Brush.Style := bsClear;
TargetCanvas.FillRect(CellRect);
end;