GTK+ applications can request a dark theme variant. In order to
make other applications - namely window managers using GTK+ for
themeing - aware of this choice, GTK+ uses this function to
export the requested theme variant as _GTK_THEME_VARIANT property
on toplevel windows.
Note that this property is automatically updated by GTK+, so this
function should only be used by applications which do not use GTK+
to create toplevel windows.
GTK+ applications can request a dark theme variant. In order to make other applications - namely window managers using GTK+ for themeing - aware of this choice, GTK+ uses this function to export the requested theme variant as _GTK_THEME_VARIANT property on toplevel windows. Note that this property is automatically updated by GTK+, so this function should only be used by applications which do not use GTK+ to create toplevel windows.