Need help documenting Text alignment

[Valentin Villenave]

Greetings,

I'm having a hard time trying to properly document the markup
alignment properties, can anyone give me a hand?

It takes place here:
http://kainhofer.com/~lilypond/Documentation/user/lilypond/Text-alignment.html

- \center-align works differently from \right-align, does it?

- what's the difference between \center-align and \column?

- what is \dir-column for?

- what is \hcenter for? is it like \hcenter-in without padding?

- what are \halign and \general-align for?

- does \hspace take vertical space as well?

- is \null equivalent to \hspace #0?

- what's is \pad-x for? (difference with the other pad-* commands?)

I'd welcome examples too -- if any of you has enough time to help me.

Cheers,
Valentin