[TUHS] [groff] How to show all hyphenation points?

[Doug McIlroy]

> I have a vague intuition right now that the hyphenation decisions
> ...
> should be accessible without having to invoke the output driver.

Would't that require some way to detect a hyphenation event?
Offhand, I can't think of a way to do that.

But if you know in advance what word's hyphenation is in
question, you could switch environments, use the .ll 1u 
trick in a diversion, and base your decision on the result.

Doug