[Qt-interest] possible to detect if a widget in a dock is visible?

[Paul Miller]

I have some widgets in a dock that do some expensive things, 
performance-wise. I would only like it do these computations when the 
dock is actually visible (not when it is undocked, not when it is 
obscured by another dock).

I note that QWidget::isVisible() is TRUE even if the widget really isn't.

Is this possible to do?