[wxMac] wxTreebook issue

[H]

While there have been several posts about treebooks, I remembered 
another one:
When compiling the wxTreebook sample on the Mac (OSX) the tree and the 
data windows overlap. It seems to be that the size calculation of the 
tree window does not work because the size to display the tree in the 
tree window is anyway not large enough.
The same happens when I change in my own program from a standard 
notebook to a wxTreebook.
I compiled the treebook sample of version 2.8.0.

Hartwig