The font for this test case is the same as in MORX–2. When rendering the string OBCD1, we set the end of the marked glyph sequence to B; then we change it to C; finally, to D. However, we never set the start of the marked glyph sequence. If your rendering engine is correctly implemented, it should implicitly start the marked glyph range at the beginning of the string, and move the O after the D when executing the rearrangement for 1.