bopomofo tone marks

Vasil Stanev

Hi,
do bopomofo glyphs allow for tone attachment?

"It is important to understand that bopomofo tone marks are not combining characters. They are regular spacing characters that are stored after the sequence of bopomofo letters that make up a syllable."

John Hudson

Where is the quote from? If accurate, it suggests that bopomofo uses spacing characters to indicate tone, rather than marks, so do not require attachment. This is similar to some other systems I have seen for transcribing Chinese languages.

John Savard

I question the quote, since I thought that when National Alphabet characters are written vertically, the tone marks are still on their right, not below them, which would seem to mean they are being combined.

Belleve Invis

Wikipedia should have good images:
https://zh.wikipedia.org/wiki/%E6%B3%A8%E9%9F%B3%E7%AC%A6%E8%99%9F
The tone marks do not combine with the base character.