The level of granularity for the font selection.
Depending on this value, the pango.font_description.FontDescription that is returned by gtk.font_dialog_button.FontDialogButton.getFontDesc will have more or less fields set.
Select a font family
Select a font face (i.e. a family and a style)
Select a font (i.e. a face with a size, and possibly font variations)
Select a font and font features
The level of granularity for the font selection.
Depending on this value, the pango.font_description.FontDescription that is returned by gtk.font_dialog_button.FontDialogButton.getFontDesc will have more or less fields set.