なっている when does it mean resultant state, and when does it refer to progression?


> バスに乗っている間に眠くなっている

Take for example the sentence above. My question is about when なっている appears
with adjectives/verbs such as 暑い、眠い、寒い、酷い (i.e. adjectives/verbs unlike 死ぬ)
and that also have a time duration included e.g. バスに乗っている間に. When does なっている
indicate a resultant state and not progression?




Overall, I don't think there is any way to hard and fast way to tell from
grammar. You have to judge from context and common usages.

In the example you gave, it seems a bit vague what (although the usage of 間 to
me indicates a change, not a resultant state), so I did a google search and
found this paragraph ([here](http://www.o-daira.jp/childhood.html)):

[code]

    保育所が終わって帰ってくると、いつも亡くなった祖父がバス停まで迎えに来てくれていました。
    バスに乗っている間に眠くなっていることが多くて、帰りは祖父に背負ってもらい帰ることもありました
    
[/code]

Having more context makes this much clearer for me, and now I can tell what is
going on. I feel this case expresses that the speaker "got sleepy" while on
the bus, and then was in a sleepy "state" when getting off the bus, so I would
say it is sort of a mix of the two. I would translate the second sentence
above as follows:

[code]

    There were many times when I got sleepy while riding the bus, and there were even times when my grandfather would carry me home.
    
[/code]

Here is simpler example where context can help distinguish between the two
meanings:

[code]

    最近、だんだん暑くなってきてるね。  [pretty clearly 'progressive' meaning, i.e. active change in temperature]
    暑くなってる。  [could be either progressive, or state]
    暑い           [if you want to talk about simple state, this is the most common way]
    
[/code]

