XScreenSaver is a free and open-source collection of 240+[3] screensavers for Unix, macOS, iOS and Android operating systems.

This is an important security feature, in that the display modes are sandboxed into a separate process from the screen locking framework.

It also means that a third-party screen saver can be written in any language or with any graphics library, so long as it is capable of rendering onto an externally provided window.

Those other frameworks have a history of security bugs that allow the screen to be un-locked without a password, e.g., by simply holding a key down until the locker crashes.

"[21] The included hacks are highly varied, ranging from simple 2D psychedelia, to 3D demonstrations of complex mathematical principles, to simulations of other computer systems, to re-creations of artifacts and effects from movies.