I saw this photo on bored panda. I’ve never thought about building in a pop-up table. It would be great for a paper plate with sandwiches and I would include a cut out for a coke can.
It’s a simple concept. I’m looking at benches that I can buy and modify. Cut out the center and reuse the slats for the table top. Reenforce the cut edges of the bench with a cleat.
The x-brace will take some experimenting. So it can be lifted up and locked in place.
Looks like a fun and creative project.
Hey, that’s actually a really neat idea! I like it.
I’m thinking the scissor mechanism necessary for a LaZBoy type foot rest would be difficult
I may use Aluminum bar stock for the x-brace. I found a source online that sells it in various thickness. 0.1875" x 1.5" should work. Thats 3/16. I don’t really need 1/4.
A friend has a drill press and other machine tools.
I ordered a bench yesterday. Can’t start work until mid September when its cooler.
I want to see how this turns out.
The picture details gives me confidence. One side of the X is loosely bolted to the frame. The other side travels in a angled slot. There’s probably a roller that slides in the groove.
I think I can replicate it. After the third or fourth try. 
I’m persistent when the job requires it.
I used to get in trouble for taking stuff apart to see how it works. My dad helped me and I eventually learned to tear stuff down and get it back together.
I am unsure of calculating the length of the legs. So the table lowers evenly with the bench. I may have to experiment with cardboard.
Pretty clever.
I would add piece of wood on each side of the floating legs (parallel to the length of the bench) to keep the floating leg from popping out of the channel.
I’ll keep that in mind.