Would be nice if QWindow provided an isFullscreen() like QWidget does

New feature/API extension request:

While porting a desktop app built on Qt4.8 QDeclarativeView to Qt5.2 QQuickView, I noticed the lack of an isFullscreen() method on QQuickView.

It'd be nice if QWindow derived gui module components had ready access to such a method. Is it possible to add such a method?

It's not yet clear to me whether things like the MacOS10.8 fullscreen button affect Qt's window state in such a way that this info is available by checking window state bits (if it is, all the more reason to add an isFullscreen; if it isn't... well I assume that might have something to do with why there isn't an isFullscreen provided).

A particular use case where such a method is useful is a hotkey which toggles between fullscreen and "normal" window modes. I used to use an 'f' key for this and users were used to it; telling them to use 'f' for fullscreen and something else for normal (Esc, 'n' for normal, 'w' for window) doesn't work because they're too used to bashing on 'f'. But implementing toggle relies on being able to obtain accurate knowledge re fullscreen state, and this also needs to be aware of any externally triggered switch to fullscreen (e.g via the MacOS10.8 window decoration).

A similar argument might be made for adding isMaximised/isMinimised but I've never found those useful myself.