VCL控件透明

  TestPanel = class(Tpanel)
  public
    procedure Paint; override;
  end;
  
 procedure TestPanel.Paint;
var
  R: TRect;
begin
  inherited;
  R := ClientRect;
  DrawParentBackground(Self, Canvas.Handle, @R, True);  //透明 不透明则  DrawParentBackground(Self, Canvas.Handle)
end;

procedure DrawParentBackground(Control: TControl; DC: HDC; R: PRect = nil;
  bDrawErasebkgnd: Boolean = False);
var
  LastOrigin: TPoint;
begin
  GetWindowOrgEx(DC, LastOrigin);
  Control.Parent.Perform(WM_ERASEBKGND, Integer(DC), Integer(DC));
  Control.Parent.Perform(WM_PAINT, Integer(DC), Integer(DC));
  SetWindowOrgEx(DC, LastOrigin.X, LastOrigin.Y, nil);
end;


// 测试DEMO
procedure TForm1.Button1Click(Sender: TObject);
var
  T1: TestPanel;
begin
  T1 := TestPanel.Create(Self);
  T1.Left := 100;
  T1.Caption := 'dd';
  T1.Parent := Self;
end;