Currently, among the other options, GtkJustification contains GTK_JUSTIFY_LEFT and GTK_JUSTIFY_RIGHT. Would it not be better to rename them to GTK_JUSTIFY_START and GTK_JUSTIFY_END? I am implementing a widget in which the "direction" (GtkTextDirection) can be changed, and in the case of GTK_TEXT_DIR_RTL together with GTK_JUSTIFY_START things would be aligned to the right, whereas making things aligned to the right using GTK_JUSTIFY_LEFT would be very counterintuitive.
―madmurphy