Comment by PythonicAlpha

Don't think, that in Germany the situation is that much better. We might not have those agreements in the contracts, since in Germany there are (luckily) many regulations what can be put into contracts. But the German law has also some specialties: For example, when you make an invention in your free time, even when it has nothing to do with your current job, you must first ask your employer, if he wants to buy the invention, if you want or not.