[fpc-pascal]About "callbacks method" of a class

[mili]

Hello, everybody

  I am using gtk2forpascal. I want to program as follows:
>>>>>
TButton = class(Tobject)
  private
    FButton:PGtkWidget;
  public
    constructor Create;
    destructor  Destroy;
    procedure   Callback_OnClick(widget:PGtkWidget; data:Object); cdecl;
end;//TButton

constructor TButton.Create;
begin
  inherited Create;
  FButton:=gtk_button_new_with_label('Click Me!');
  gtk_widget_show(FButton);
  g_signal_connect(G_OBJECT(FButton),'clicked',
    TGCALLBACK(@Callback_OnClick),self);
  ...
end;//TButton.Create

procedure TButton.Callback_OnClick(widget:PGtkWidget; data:Object); cdecl;
begin
  ......
end;//TButton.Callback_OnClick
<<<<<

But I can't comiler this program. When I connect the signal with a subroutine 
which is not a method, the compilation works. Can anybody confirm me that: In 
class definition, We can't use "@MethodName" and in one method there's no way 
to directly connect a signal with another method in the same class? In short, 
is there "callbacks method"?


And another problem, I found the following code style in Lazarus project 
sources:
>>>>>
procedure TSomeClass.FuncName(...);
  procedure FuncNameEmbeded(...);
  begin
    .....
  end;//FuncNameEmbeded
begin
end;//TSomeClass.FuncName
<<<<<

I know it's "nested procedure". But the information from fpc documentations is 
too little. can you tell me more about it? Why the following code can compile 
but will run with "Access violation"?
>>>>>
procedure TSomeClass.FuncName(...);
  procedure FuncNameEmbeded(...);
  begin
    .....
    writeln(FValue);//Here FValue is a member (Integer) of TSomecalss
    .....
  end;//FuncNameEmbeded
begin
end;//TSomeClass.FuncName
<<<<<

Thanks,
Yours,
mili