[NTG-context] Is there a replacement for \tracechinesetrue in mkiv?

Hi, I wrote some CJK vertical typesetting macros in mkii a long time ago and I want to adopt it to mkiv. Sadly the \iftracechinese is gone. Can I still draw boxes of each glyph to see if they are aligned in my way? Drawing a line in the background is so not cool. -- Best Regards Chen