“Decorations” are the features the window manager adds to a toplevel
This function sets the traditional Motif window manager hints that tell the
window manager which decorations you would like your window to have.
Usually you should use
gtk_window_set_decorated() on a
GtkWindow instead of
using the GDK function directly.
decorations argument is the logical OR of the fields in
GdkWMDecoration enumeration. If #GDK_DECOR_ALL is included in the
mask, the other bits indicate which decorations should be turned off.
If #GDK_DECOR_ALL is not included, then the other bits indicate
which decorations should be turned on.
Most window managers honor a decorations hint of 0 to disable all decorations, but very few honor all possible combinations of bits.
Decoration hint mask.