[Lazarus] Purpose of TControl.UpdateRolesForForm?

[Vincent Snijders]

2011/10/9 Hans-Peter Diettrich <DrDiettrich1 at aol.com>:
> This method is called by a form, when its Default or Cancel control changes.
> But why do the affected controls receive no hint about their new role?
>
> What's the intended purpose of this method?
>
> If it is used (overridden) only in TCustomButton, the (there) interesting
> information could be passed in added arguments.
>
> TControl.ActiveDefaultControlChanged is much more informative, but I suspect
> an bug in the TCustomForm implementation - NewControl is always Nil.
>
> Can somebody explain, or simplify the current mess in the LCL?

See also:
http://bugs.freepascal.org/view.php?id=20443

Vincent