Screen cracked by thin line after exposure to sun

Today was a hot day and I was working with my MacBook Pro w/ Touch Bar on my lap (directly exposed to the sun) when I suddenly saw a thin line cracking the screen into two halves.

I couldn't believe my eyes. Nothing fell onto the screen, nothing touched it or scratched it; the MacBook was simply sitting on my lap. I attached some photos below. It's weird but the left-hand side of the screen is somewhat darker now.

Does this fall under the limited warranty offered by Apple? I don't have Apple Care. If it doesn't, how much would it cost me to repair it?