Tries to ensure that there is a window-system native window for this
GdkWindow. This may fail in some situations, returning FALSE.
Offscreen window and children of them can never have native windows.
Some backends may not support native child windows.
Since 2.18
Tries to ensure that there is a window-system native window for this GdkWindow. This may fail in some situations, returning FALSE. Offscreen window and children of them can never have native windows. Some backends may not support native child windows. Since 2.18