If you're just going to sit there doing nothing, at least do nothing correctly

Summary

There may be times where you need to make an API do nothing. It’s important to have it do nothing in the correct way. For example, Windows has an extensive printing infrastructure. But that infrastructure does not exist on Xbox. What should happen if an app tries to print on an Xbox? Well, the wrong thing to do is to have the printing functions throw a Not­Supported­Exception. The app that the user installed on the Xbox was probably tested primarily, if not exclusively, on a PC, where printing is always available. When run on an Xbox, the exception will probably go unhandled, and the app will crash. Even if the app tried to catch the exception, it would probably display a message like “Oops. That went badly. Call support and provide this incident code.” A better design for “supporting” printing on Xbox is to have the printing functions succeed, but report that there are no printers installed. With this behavior, when the app tries to print, it will ask the user to select a printer, and show an empty list. The user realizes, “Oh, there are no printers,” and cancels the printing request. To deal with apps that get fancy and say “Oh, you have no printers installed, let me help you install one,” the function for installing a printer can return immediately with a result code that means “The user cancelled the operation.” The idea here is to have the printing functions all behave in a manner perfectly consistent with printing being fully supported, yet mysteriously there is never a printer to print to. Now, you probably also want to add a function to check whether printing even works at all. Apps can use this function to hide the Print button from their UI if they are running on a system that doesn’t support printing at all. But naïve apps that assume that printing works will still behave in a reasonable manner: You’re just on a system that doesn’t have any printers and all attempts to install a printer are ineffective. The name we use to describe this “do nothing” behavi...