Comment 8 for bug 1305586

Andrea,

That's why I've written "some"...
Basically it happens for the windows that don't emit a NotifyGrab event to the server.
And the problem is that X doesn't guarantee that this happens when a grab is set.

So, while in some cases (like the gnome-keyring box) we can still get an NotifyWhileGrabbed event that is enough for us to know that it's grabbing, in other ones (like vbox), there's not much other way than trying to grab/ungrab the root window to check if the screen is already grabbed or not. :(