drawable (Imlib2::Context)

    /*
     * Get the current X11 Drawable.
     *
     * Note: This method is not available unless Imlib2-Ruby was compiled
     * with X11 support.  You can check the constant Imlib2::X11_SUPPORT to
     * see if X11 support is available.
     *
     * Examples:
     *   drawable = context.get_drawable
     *   drawable = context.drawable
     *
     */
    static VALUE ctx_drawable(VALUE self) {