Specifies the kind of crossing for GdkEventCrossing.
See the X11 protocol specification of LeaveNotify for full details of crossing event generation.
The window is entered from an ancestor or left towards an ancestor.
The pointer moves between an ancestor and an inferior of the window.
The window is entered from an inferior or left towards an inferior.
The window is entered from or left towards a window which
is neither an ancestor nor an inferior.
The pointer moves between two windows which are not ancestors of
each other and the window is part of the ancestor chain
between one of these windows and their least common ancestor.