code: func (v *TextView) GetVisibleRect() *gdk.Rectangle {
  	var rect C.GdkRectangle
  	C.gtk_text_view_get_visible_rect(v.native(), &rect)
  	return gdk.WrapRectangle(uintptr(unsafe.Pointer(&rect)))
  }
docs: // GetVisibleRect is a wrapper around gtk_text_view_get_visible_rect().