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?