const
 WM_MouseEnter = $B013;
 WM_MouseLeave = $B014;
type
 TfrmMain = class(TForm)
  .
  .
 Timer1: TTimer;
 procedure Timer1Timer(Sender: TObject);
 protected
 procedure WMMouseEnter(var Msg: TMessage); message WM_MouseEnter;
 end;
implementation
{$R *.dfm}
procedure TfrmMain.WMMouseEnter(var Msg: TMessage);
begin
 if(Top<0) then
 begin
 Top := 0;
 //为保证下拉窗体后呈现在最前面
 SetWindowPos(Handle,HWND_TOPMOST,0,0,0,0,SWP_NOMOVE or SWP_NOSIZE);
 //将窗体推到最前
 SetWindowPos(Handle,HWND_NOTOPMOST,0,0,0,0,SWP_NOMOVE or SWP_NOSIZE);
 //然后取消窗体最前
 end;
 Timer1.Enabled := True;
end;
//依赖定时器定时检查鼠标是否还在窗体范围内，
//这样此能避免因为快速移动鼠标而丢失MOUSELEAVE事件
procedure TfrmMain.Timer1Timer(Sender: TObject);
var
 rc:TRECT;
 pt:TPOINT;
begin
 GetWindowRect(self.Handle,rc); //取窗体的矩形区域
 GetCursorPos(pt); //取得当前鼠标所在位置
 if(not PtInRect(rc,pt)) then //如果鼠标不在窗体范围内
 begin
  if(Top = 0) then
  //如果目前窗体正吸附在屏幕上沿，则上移隐藏窗体
  begin
   Top := 0-Height+2;
  end;
  Timer1.Enabled := False; //窗体隐藏后定时器关闭
  SetWindowPos(Handle,HWND_TOPMOST,0,0,0,0,SWP_NOMOVE or SWP_NOSIZE);
  //将窗体推到最前
 end;
end;