How can a non-admin program cover your entire screen with a window?



  • This year, since many students are online, College Board (the company that administers AP Exams in the US, along with the SAT) recently released its Digital Testing App. Once installed, and going through a setup, it allows you to go through a test demo to mirror the actual test conditions. However, once you do, it covers your entire screen and prevents you from ALT+TAB to another window. The "select window" UI still shows up, but if you actually try to switch, the Testing App window still remains.

    This ability could make sense if the program was given administrator privileges on install (like Respondus Lockdown Browser, I believe), but the Testing App wasn't, and yet still could. This could just be a trick like just a really big window, but I'm not completely sure. Could anyone shed some light on this and how could they do this?



  • Fullscreen is easy: The vast majority of video games, for example, do it. I don't know if Windows has a dedicated API call for this, but if it doesn't, it's easy to fake: Just make a screen-sized window with the "Always on Top" attribute and no window decorations.

    Disabling ALT+TAB is harder, but there are a number of options: for example, the accessibility toolkit lets you intercept arbitrary keystrokes. The only key combination that no application can disable is CTRL+ALT+DELETE.



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