const
  LeftTextIndent = 20;

// OnDrawText
procedure TForm1.VirtualTreeDrawText(Sender: TBaseVirtualTree; TargetCanvas: TCanvas; Node: PVirtualNode; Column: TColumnIndex;
  const Text: string; const CellRect: TRect; var DefaultDraw: Boolean);
var
  R: TRect;
  DrawFormat: Cardinal;
begin
  DefaultDraw := False;

  R := CellRect;
  R.Left := R.Left + LeftTextIndent;
  // this needs to be improved; ideal would be if the DrawFormat would be passed
  // from the TCustomVirtualStringTree.DoTextDrawing method to this event
  DrawFormat := DT_NOPREFIX or DT_VCENTER or DT_SINGLELINE;
  DrawTextW(TargetCanvas.Handle, PWideChar(Text), Length(Text), R, DrawFormat);
end;

// OnMeasureTextWidth
procedure TForm1.VirtualTreeMeasureTextWidth(Sender: TBaseVirtualTree; TargetCanvas: TCanvas; Node: PVirtualNode; Column: TColumnIndex;
  const Text: string; var Extent: Integer);
begin
  Extent := Extent + LeftTextIndent;
end;