type
  TfrmModal = class(TForm)
    Edit1: TEdit;
  private
    { Private declarations }
    procedure WMSysCommand(var Msg: TWMSysCommand); message WM_SYSCOMMAND;

...

procedure TfrmModal.WMSysCommand(var Msg: TWMSysCommand);
begin
  if Msg.CmdType = SC_MINIMIZE then
    Application.Minimize
  else 
    inherited;
end;

i. 任务栏唤起时，对话框直接显示出来，然后才是主窗体从任务栏上动画出来。

ii. 显示出来后，焦点没有落在它身上，需要点击下主窗体触发，焦点才会移到它上面。

type
  TfrmModal = class(TForm)
    Edit1: TEdit;
  private
    { Private declarations }
    procedure WMSysCommand(var Msg: TWMSysCommand); message WM_SYSCOMMAND;
    procedure WMShowWindow(var Msg: TWMShowWindow); message WM_SHOWWINDOW;

...

procedure TfrmModal.WMShowWindow(var Msg: TWMShowWindow);
begin
  inherited;
  if Self.WindowState = wsMinimized then
  begin
    Self.WindowState := wsNormal;
    Application.BringToFront;
  end;
end;

procedure TfrmModal.WMSysCommand(var Msg: TWMSysCommand);
begin
  inherited;
  if Msg.CmdType = SC_MINIMIZE then
    Application.Minimize;
end;