An exclamatory sentence that begins with the infinitive phrase

@KDog posted:

(a)  She shook her head. “I guess none of those cute kids will ever become printers now, will they? Gee, I hope they don’t stop reading and writing! Andto think of it happening in front of such an interested audience! Oh, I feel just terrible about it.”

Hi, KDog—As Ray's post suggests, this use of an exclamative "(And) to think . . . " infinitival clause is a common, formulaic exclamation of surprise or dismay in English. Here are some examples from the COCA corpus:

• "So eye opening . And to think it's happening here in America."
• "Moses, Moses, Moses. Moses . And to think that I was stupid enough to trust you. "
• "Skip it, Linda. And to think I wanted to live with the three of you in a beautiful Miami bungalow with wicker furniture and bright floral patterns."
• "You've converted me . And to think I avoided it for three years. Those silly little love songs soured me."
• "You made being special sound so good . And to think I was going to follow you to the end of the universe."
• Never would have guessed that . And to think we almost lost him. Well, it all worked out."

@KDog posted:

I'm also wondering how "it" and "happening" are right behind a prepostion "of" like the underlined phrase. I think "happening" is a gerund because of the preposition "of" but I don't understand how "it" can be in front of "happening" like that. I guess "it" is a subject of "happening" semantically but I don't know my reasoning is right.

Yes, "it" is the subject of "happening." The meaning is the same as it would be if "it" were in the possessive: "to think of its happening . . . !" One formal term for the construction with the accusative pronoun rather than the possessive is the "Acc-ing construction." (Ray has described the same construction using jargon from X-bar syntax.)  You can Google "Acc-ing construction" if you like. Historically, the construction was controversial. Fowler called it the "fused participle" and thought it was bad, but he was mistaken. It's perfectly normal.

Ray and David, I want to express my sincere gratitude for your kind response. Learning something new always feels great, and thanks to both of you, I have gained a new understanding.