How do you know when it just isn't going to work anymore?

I sat down for lunch yesterday with uncertainty. Even though he had happily ran to the door, Foodie Baby had rubbed his eyes a couple of times on the way to the restaurant.
He happily sat in his highchair, drank water from his sippy and took our offerings of tomatoes to keep him happy (and enjoyed being doused with juice, as I forgot to throw the bib on him before he bit into a juicy cherry tomato half.)
Then, it went downhill.
He chugged from the sippy, then threw it to the floor.
"Uohh" (new word).
His ever-faithful Chuck truck made a few rounds before it too went on the floor.
Then, by the time I got my soup, It had turned into only playing on my lap. Then he wanted down.
Nothing was working.
We ended up pulling the highchair in the quiet dining room (considering other conversations were about babies, no one was minding) and putting him in a chair.
He didn't want his fried rice, he poked at it, took a couple bites, then cried.
Q quick reprieve was made when a food pouch was pulled and he sucked on pureed pears, peas and green beans for a couple of minutes.
Kicked the glass window.
Rubbed his hands all over the glass window.
During a fit I whisked him away to have a talk. First he got to take out a few wiggles on the patio (a better choice for future excursions)
" Are you still hungry?"
Nod.
"Would you like to go finish your lunch?"
Nod.
"OK. but you have to sit nicely and eat your lunch so we can sit with Grandma."
Nod.
I'm sure many people know what a toddler's word can be worth.
Another walk outside with grandma let me scarf down my yellow curry and finish my soup.
A few minutes later, well, he was gone for good.
I checked all over and surveyed the damage. Surprisingly little food on the floor, pouch cap on the floor, long smears on the sparkling glass.
I threw down some money and left, forgetting the fried-rice-to-go I had the waiter package.
because darn it, it's good. He would eat it another day.
The waiter chased me down with the bag as I found Foodie Baby and my mom, who had wandered down the street in his apparent elation.
And then he feel asleep instantly in the car seat.

Yes, Foodie Baby, I guess, I think (this is my first kid, y'all) may be hitting the age where going to lunch is no longer a casual thing. Carefully orchestrated around naps, or food taken to go may be my theme.
We have one more try coming up tomorrow, a little later than I wanted but still earlier than my last lunch.
We shall see.