I felt a little disappointed and was about to leave when somethin_英语解答

I felt a little disappointed and was about to leave when something there attracted my attention.
这题为什么不用before?这句是啥意思啊?

人气：221 ℃　时间：2020-03-26 06:27:47

解答

我有点儿失望.正当我准备离开时,有人进入了我的视线(吸引了我的注意)
be about to do.when...
是固定搭配,表示"正准备做...,...发生了."