Sentences starting with 'Would that...' [closed]

While reading a book, I'm stumbling on a special construct which I didn't seem to have encountered before where author starts her sentences with "Would that...".

Here are several examples:

The water starts the day again, resetting her senses. Would that it were so easy to turn time on and off like this, to start yesterday again such that it would not end in this bizarre new reality.

She clasps her hands on her lap to hide a splat of paint on her shirt. Would that she had changed into nicer clothes before leaving the house this morning.

"You are safe," she tells the kids. "It's going to be all right now." She wants them to believe this. Would that she could also.

Can someone please explain what the above construct means and if that is proper English usage?

Thank you in advance.

“Would that” is simply a synonym for “I wish that” or “I regret that.” If you look at the New Oxford American Dictionary definition of would, it says “Expressing a wish or regret.” It also mentions how it is a literary usage of the word “would,” meaning it is correct grammar usage. However, it is not a common use of the word “would,” so it is difficult grammatical construct to understand.