Gtk.TextIter.prototype.backward_to_tag_toggle

function backward_to_tag_toggle(tag:Gtk.TextTag):Boolean {
    // Gjs wrapper for gtk_text_iter_backward_to_tag_toggle()
}

Moves backward to the next toggle (on or off) of the Gtk.TextTag tag, or to the next toggle of any tag if tag is null. If no matching tag toggles are found, returns false, otherwise true. Does not return toggles located at iter, only toggles before iter. Sets iter to the location of the toggle, or the start of the buffer if no toggle is found.