mode
Determines the way GtkLevelBar
interprets the value properties to draw the level fill area.
Specifically, when the value is %GTK_LEVEL_BAR_MODE_CONTINUOUS, GtkLevelBar
will draw a single block representing the current value in that area; when the value is %GTK_LEVEL_BAR_MODE_DISCRETE, the widget will draw a succession of separate blocks filling the draw area, with the number of blocks being equal to the units separating the integral roundings of property@Gtk.LevelBar:min-value and property@Gtk.LevelBar:max-value.