[Lazarus] repaint method on Darwin/Carbon

[dmitry boyarintsev]

> rather than Application.ProcessMessages;
>
> On Win32 and GTK2/Linux this works perfectly, but on Carbon it won't repaint anything until the
> application can service its message queue.
>
> Is this expected behaviour or an inherent in the toolkit?

Mac OS X allows to draw only on Paint event (generated by OS), you
can't draw in any other event (i.e. buttonclick, timer etc..).
You must update controls using Application.ProcessMessages.

Thanks,
Dmitry