How can the Stack Exchange app indicate that code blocks are tappable?

Question

In case you're unaware, there's now an official Stack Exchange Android app. With it comes some new behaviour for code blocks: you can tap them to pop them out and view them in a sorta-full screen view.

If a code block is especially wide, it's cut off and can't be scrolled around. You have to pop up the code block this way to scroll around and view the whole thing. This is useful, but it comes with a usability problem I'll get into further down.

Here's a couple of screenshots. Left is a code block; right is the same code block popped up and scrolled over a little.

The problem is: this is confusing to people using the app, because they don't expect that this is possible and nothing actually communicates that they can do it. Plenty of users have simply assumed there is no way to view code snippets that get cut off. I've written a request about this on Meta Stack Overflow (which these screenshots are from).

How can the Stack Exchange app communicate that these code blocks can be tapped?

Answer 1

A full-screen icon floating in the bottom right or top right margin will do just fine.

This is the place where 90% of all movie players have it too. And a lot of lightboxes mimic this. If you care for big well-known sites, Youtube has it on videos, and so does Facebook (images).

It's generally a square with a small arrow in it, a bunch of corners, or maybe some arrows pointing all directions.

Here's a quick mockup just to get the idea across, I'm sure you can improve on this when it comes to style, positioning, etc.

Maybe make it look more clickable by making it look like the app. Another quicky:

You could easily come up with a minimize icon as well for when the app hits full-screen.

Alternatively

Alternatively, you could just add a link. Be it a word or a button, inside or outside the area, that says "full screen", "expand", "maximize" or the like.

Disclaimer: I've only installed it today and played around with it for like 5 minutes, so it's hard for me to give you a definitive fitting answer. Whatever the choice, just think about what pattern would fit best with the rest of the app.