Documentation bug
Section: GDK Reference manual, "Windows" section
"The windowing system will NORMALLY fill a window with its background when the
window is obscured then exposed, ..."

Correct version:
The windowing system DOES fill a window with its background under these
conditions ...
The windowing system DOES NOT fill a window with its background under these
conditions ...

Other information:
How useful is it to use the word "normally" in a functions documentation? Its
like using the words "sometimes" or "occaisionally" or "if you're very very lucky".

I would have thought its the windowing systems responsibility to ALWAYS fill a
window with its background when the window is obscured then exposed, and if it
does not do this its a gtk+ bug.
However, if there are any special exceptions they should be clearly documented.