program Psysmenu;
uses
  Forms,
  Sysmenu in '\SYSMENU.PAS' {Form1};

{$R *.RES}
begin
  Application.CreateForm(TForm1, Form1);
  Application.Run;
end.

unit Sysmenu;

interface
uses
  SysUtils, WinTypes, WinProcs, Messages, Classes, 
  Graphics, Controls,Forms, Dialogs;
type
  TForm1 = class(TForm)
        procedure FormCreate(Sender: TObject);
  private
      procedure  user_sysmenu(var msg:twmmenuselect);
                               message wm_syscommand;

  public
        { Public declarations }
  end;
var
  Form1: TForm1;
implementation
{$R *.DFM}

procedure  TForm1.user_sysmenu(var msg:TWMMENUSELECT);
begin
   if msg.iditem=100 then
      showmessage('     響應系統選單!')
      { 也 可 以setwindowpos()來實現處於最前端功能}
   else
      inherited;     { 作預設處理,必須呼叫這一過程}
end;

procedure TForm1.FormCreate(Sender: TObject);
   var hmenu:integer;
begin
   hmenu:=getsystemmenu(handle,false);
   {獲取系統選單控制代碼}
   appendmenu(hmenu,MF_SEPARATOR,0,nil);
   appendmenu(hmenu,MF_STRING,100,'加入系統選單');
   {加入使用者選單}
end;
end.

//出錯的主要原因是:缺少一句程式碼   message wm_syscommand;  

//這句程式碼的主要作用是：A window receives this message when the user chooses a commond from the window menu.

//而如果註釋了inherited ,則所有系統選單都不能用。