case $THIS_SUB_DEPENDS in
GTK) echo "GTK support requested, forcing gtk+2 dependency." &&
     depends gtk+2 '--enable-gtk'
     ;;
GTK3) echo "GTK3 support requested, forcing gtk+3 dependency." &&
     depends gtk+3 '--enable-gtk3'
     ;;
*) echo unknown sub-depends!!! ; return 1 ;;
esac

.