Hello.

In TWinControl.Destroy there is code:

  while n > 0 do
  begin
    Control := Controls[n - 1];
    Remove(Control);   <--
     ...
    Control.Parent := nil; <--
    n := ControlCount;
  end;

In Remove() which is non-virtual:

procedure TWinControl.Remove(AControl : TControl);
begin
  if AControl  nil then
  begin
    ...
    AControl.FParent := nil;
    ...
  end;
end;
So, first there is AControl.FParent := nil, then there is
Control.Parent := nil. There is one too many.

Also, the first assignment is directly to variable bypassing virtual SetParent. The other uses property which calls SetParent but it doesn't do anything because Parent is already =nil.

Is it correct that Control.Parent can be removed? And which should be the correct version of assignment: using FParent or Parent?

That one was not needed any more. I removed it.

FParent is correct.

Mattias

2011/5/23 Mattias Gaertner :

OK. Thanks!