focus problem on wxCocoa

[Buzz]

Hi,

I have a little focus problem on wxCOCOA 3.0.1 : I wanted to set te
background color of a wxDialog.
So I put a wxPanel that fills the entire dialog, changed the color of this
panel, and put my controls on this panel.
But when I do so, I cannot tell the dialog which field should have the
focus when the dialog opens. SetFocus doesn't work, unless I do it after
the dialog is shown (which
-AFAIK- would not be possible with modal dialogs).

If I remove the wxPanel, everything's back to normal, SetFocus works
normally.

Am I doing something wrong, or did I hit some small bug ?

I tested this on wxCOCOA 3.0.1, wxGTK and wxMSW, and the issue is only
present on OSX.
And I think this problem was already present on version 2.9.5.

I prepared an example based on the minimal sample, opening the very same
wxDialog, with or without wxPanel.

Any clue would be appreciated..
Michel.