It was such a boring movie that I fell asleep while watching it.

问题描述:

It was such a boring movie that I fell asleep while watching it.
为什么while 后面接的是watching it,ing形式,而不是从句谓语watch呢?
while不是连词吗?怎么不链接从句呢?

省略了I was吧?while I was waching it.
表达正在看的时候睡着了.