TControl = class(TComponent) 
  private 
    FLeft: Integer; 
    FTop: Integer; 
    FVisible: Boolean; 
    FOnClick: TNotifyEvent; 
    {中间代码太长，省略，具体请看Delphi源代码} 
  protected     
    procedure Click; dynamic; 
    property OnClick: TNotifyEvent read FOnClick write FOnClick stored IsOnClickStored;     
    {中间代码太长，省略，具体请看Delphi源代码} 
  public 
    constructor Create(AOwner: TComponent); override; 
    destructor Destroy; override; 
    property Visible: Boolean read FVisible write SetVisible stored IsVisibleStored default True;   
    {中间代码太长，省略，具体请看Delphi源代码} 
  published 
    property Left: Integer read FLeft write SetLeft; 
    property Top: Integer read FTop write SetTop; 
    property Width: Integer read FWidth write SetWidth; 
    property Height: Integer read FHeight write SetHeight; 
    property Cursor: TCursor read FCursor write SetCursor default crDefault; 
    property Hint: string read FHint write FHint stored IsHintStored; 
    property HelpType: THelpType read FHelpType write FHelpType default htContext; 
    property HelpKeyword: String read FHelpKeyword write SetHelpKeyword stored IsHelpContextStored; 
    property HelpContext: THelpContext read FHelpContext write SetHelpContext stored IsHelpContextStored default 0; 
end; 

type 
  TLineTo = class(TGraphicControl) 
  {省略····} 
  published 
    property Visible; 
  end; 

type 
  TLineTo = class(TGraphicControl) 
  {省略······} 
  published 
    property OnClick; 
  end; 

type 
  TLineTo = class(TGraphicControl) 
  protected     
    procedure Click; override; 
  end; 
implementation 
procedure TLineTo.Click; 
begin 
  inherited Click;   {执行标准处理，包括调用事件处理过程} 
end; 

unit LineTo; 
 
interface 
 
uses 
  SysUtils, Classes, Controls, Dialogs; 
 
type 
  TLineTo = class(TGraphicControl) 
  private 
    FPenWidth: Integer; 
    procedure SetPenWidth(Value: Integer); 
  protected 
    procedure Paint; override; 
    procedure Click; override; 
  public 
    constructor Create(AOwner: TComponent); override; 
    destructor Destroy; override; 
  published 
    property PenWidth: Integer read FPenWidth write SetPenWidth default 1; {如果值是1的话就不写进窗体DFM文件，节省空间} 
    property Visible; 
    property OnClick; 
  end; 
 
procedure Register; 
 
implementation 
 
procedure Register; 
begin 
  RegisterComponents('Samples', [TLineTo]); 
end; 
 
constructor TLineTo.Create(Aowner: TComponent); 
begin 
  inherited Create(AOwner); 
  {一些字段可以在这里初始化} 
  FPenWidth := 1; 
end; 
 
destructor TLineTo.Destroy; 
begin 
  {一些资源可以在这里释放} 
  inherited Destroy; 
end; 
 
procedure TLineTo.Paint; 
begin 
  with Canvas do 
  begin 
    MoveTo(0, 0); 
    LineTo(Self.Width, Self.Height); 
  end; 
end; 
 
procedure TLineTo.Click; 
begin 
  inherited Click; {执行标准处理，包括调用事件处理过程} 
  ShowMessage('画线控件 V1.0 by 无幻');   {需要uses Dialogs} 
end; 
 
procedure TLineTo.SetPenWidth(Value: Integer); 
begin 
  if FPenWidth <> Value then 
  begin 
    FPenWidth := Value; 
    Canvas.Pen.Width := FPenWidth; 
    Invalidate; 
  end; 
end; 
end. 

procedure TForm1.lnt1Click(Sender: TObject); 
begin 
  ShowMessage('你点击了TLineTo控件'); 
end;