Contraction of ～てるのか

Question

伸ばしてんのか？髪。。。

I was under the impression that the て form followed by ん was a contraction of ～てるの. However, in this sentence we have a のか following it. The のか sounds like it's supposed to nominalize and question the previous phrase, though I'm not sure how that works, even having read a few past posts on the subject.

My attempt at translation is:

You're growing it out? Your hair?

I don't see any pondering going on there, though, so I'm not confident.

Edit

伸ばしてのか？

Seems basically the same to me at this point, which may help explain my confusion.

Answer 1

There may be certain dialects where it is otherwise, but ～ているの, in the most colloquial standard Japanese, contracts to ～てんの, not simply ～てん, on its own. Before certain だ it can contract a little further: in colloquial speech, 何をしているのだ can appear as 何してんだ. That may be the source of your confusion. I guarantee you, you will never hear 伸ばしてのか？ People simply do not say it.

Also, are you familiar with the ～のだ construction? The の here was probably originally a nominalizer, but over time it grew into its own thing. ～のだ offers an explanation; ～のか asks for one (besides when ～のだ is paired with a question word like 何, in which case ～のか would sound rhetorical). That is a very simplified explanation; it might be better to look into it yourself.