Gtk.TextView.prototype.get_window

function get_window(win:Gtk.TextWindowType):Gdk.Window {
    // Gjs wrapper for gtk_text_view_get_window()
}

Retrieves the Gdk.Window corresponding to an area of the text view; possible windows include the overall widget window, child windows on the left, right, top, bottom, and the window that displays the text buffer. Windows are null and nonexistent if their width or height is 0, and are nonexistent before the widget has been realized.