(In reply to Martin Gräßlin from comment #11)
I'd say two groups of behavior:
* might change during life time of window (e.g. maximize)
* might not change during life time of window (e.g. quick help)
And I'm not sure whether the same rules would apply. For a disabled
maximized I'd expect
Thank you for calling me in, Thomas!
If a button in a UI becomes temporarily unavailable because of some
situation-specific circumstances, it should be disabled and get a
tooltip explaining these circumstances.
The buttons in window decorations, however, are usually not temporarily
unavailable.
