XScreenSaver

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XScreenSaver
Xscreensaver xmatrix.png
XScreenSaver-demo and the XMatrix hack
Original author(s) Jamie Zawinski
Developer(s) Jamie Zawinski
Initial release17 August 1992;28 years ago (1992-08-17)
Stable release
6.0 / April 2, 2021;3 months ago (2021-04-02) [1]
Repository github.com/Zygo/xscreensaver
Written in ANSI C, X11, OpenGL
Operating system Unix, macOS, iOS, Android
Type Screensaver
License MIT License [2]
Website jwz.org/xscreensaver/
Xscreensaver "GLMatrix" Screensaver

XScreenSaver is a free and open-source collection of 240+ [3] screensavers for Unix, macOS, iOS and Android operating systems. It was created by Jamie Zawinski in 1992 and is still maintained by him, with new releases coming out several times a year. [4]

Contents

Platforms

The free software and open-source Unix-like operating systems running the X Window System (such as Linux and FreeBSD) use XScreenSaver almost exclusively.[ citation needed ] On those systems, there are several packages: one for the screen-saving and locking framework, and two or more for the display modes, divided somewhat arbitrarily. [5]

On Macintosh systems, XScreenSaver works with the built-in macOS screen saver.

On iOS systems, XScreenSaver is a stand-alone app that can run any of the hacks full-screen.

On Android systems, the XScreenSaver display modes work either as normal screen savers (which Android sometimes refers to as "Daydreams") or as live wallpapers.

There is no official version for Microsoft Windows, and the developer discourages anyone from porting it. The author considers Microsoft to be "a company with vicious, predatory, anti-competitive business practices" [6] and says that, as one of the original authors of Netscape Navigator, he holds a "personal grudge" against Microsoft because of its behavior during the First Browser War.

Software Architecture

The XScreenSaver daemon is responsible for detecting idle-ness, blanking and locking the screen, and launching the display modes. The display modes (termed "hacks" from the historical usage "display hack") are each stand-alone programs.

This is an important security feature, in that the display modes are sandboxed into a separate process from the screen locking framework. This means that a programming error in one of the graphical display modes cannot compromise the screen locker itself (e.g., a crash in a display mode will not unlock the screen).

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.

For historical and portability reasons, the included hacks are all written in ANSI C. About half of them use the X11 API, and about half use the OpenGL 1.3 API.

Rather than forking the code-base and re-writing the hacks to target different platforms, XScreenSaver contains a number of compatibility layers.

Security

In addition to sandboxing the display modes, the XScreenSaver daemon links with as few libraries as possible. In particular, it does not link against GUI frameworks like GTK or KDE, but uses only raw Xlib for rendering the unlock dialog box.

In recent years, some Linux distributions have begun using the gnome-screensaver or kscreensaver screen-blanking frameworks by default instead of the framework included with XScreenSaver. [9] In 2011, gnome-screensaver was forked as both mate-screensaver and cinnamon-screensaver. Earlier versions of these frameworks still depended upon the XScreenSaver collection of screen savers, which is over 90% of the package. [10] However, in 2011, gnome-screensaver version 3 dropped support for screensavers completely, supporting only simple screen blanking, [11] and as of 2018, Linux Mint's cinnamon-screensaver 4.0.8 no longer supports the XScreenSaver hacks. [12]

Those Linux distributions that have replaced XScreenSaver with other screen-locking frameworks have suffered notable security problems. 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. [13] [14] [15] [16] [17] [18] [19]

In 2004, Zawinski had written about the architectural decisions made in XScreenSaver with the goal of avoiding this very class of bug, [20] leading him to quip in 2015, "If you are not running XScreenSaver on Linux, then it is safe to assume that your screen does not lock." [21]

Display Modes

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.

Though many of the newer hacks take full advantage of the power of modern computers, the age of the project means that some of the older hacks may look dated to modern eyes, as they were originally written for much less powerful computers.

Examples of hacks include: [3]

Some of the included hacks are very similar to demo effects created by the demoscene:

See also

XScreenSaver was featured in Sleep Mode: The Art of the Screensaver, [22] a gallery exhibition curated by Rafaël Rozendaal at Rotterdam's Het Nieuwe Instituut in 2017.

Commons-logo.svg Media related to XScreenSaver at Wikimedia Commons

Related Research Articles

Jamie Zawinski, commonly known as jwz, is an American impresario, computer programmer, and blogger. He is best known for his role in the creation of Netscape Navigator, Netscape Mail, Lucid Emacs, Mozilla.org, and XScreenSaver. He is also the proprietor of DNA Lounge, a nightclub and live music venue in San Francisco.

Xfce Desktop environment

Xfce or XFCE is a free and open-source desktop environment for Unix-like operating systems.

In computing, cross-platform software is computer software that is implemented on multiple computing platforms. Cross-platform software may be divided into two types; one requires individual building or compilation for each platform that it supports, and the other one can be directly run on any platform without special preparation, e.g., software written in an interpreted language or pre-compiled portable bytecode for which the interpreters or run-time packages are common or standard components of all platforms.

Screensaver Computer program that blanks the screen or fills it with moving images

A screensaver is a computer program that blanks the screen or fills it with moving images or patterns when the computer has been idle for a long time. The original purpose of screensavers was to prevent phosphor burn-in on CRT, plasma and OLED computer monitors. Though modern monitors are not susceptible to this issue, screensavers are still used for other purposes. Screensavers are often set up to offer a basic layer of security, by requiring a password to re-access the device. Some screensavers use the otherwise unused computer resources to do useful work, such as processing for distributed computing projects.

OpenGL ES Subset of the OpenGL API for embedded systems

OpenGL for Embedded Systems is a subset of the OpenGL computer graphics rendering application programming interface (API) for rendering 2D and 3D computer graphics such as those used by video games, typically hardware-accelerated using a graphics processing unit (GPU). It is designed for embedded systems like smartphones, tablet computers, video game consoles and PDAs. OpenGL ES is the "most widely deployed 3D graphics API in history".

Maemo Mobile operating system

Maemo is a software platform originally developed by Nokia, now developed by the community, for smartphones and Internet tablets. The platform comprises both the Maemo operating system and SDK. Maemo played a key role in Nokia's strategy to compete with Apple and Android, and that strategy failed for complex, institutional and strategic reasons.

A compositing window manager, or compositor, is a window manager that provides applications with an off-screen buffer for each window. The window manager composites the window buffers into an image representing the screen and writes the result into the display memory.

GNOME Screensaver

Up until GNOME 3.5, GNOME Screensaver was the GNOME project's official screen blanking and locking framework. With the release of GNOME 3.5.5, screen locking functionality became a function of GDM and GNOME Shell by default.

Clutter is a GObject-based graphics library for creating hardware-accelerated user interfaces. Clutter is an OpenGL-based 'interactive canvas' library and does not contain any graphical control elements. It relies upon OpenGL (1.4+) or OpenGL ES for rendering,. It also supports media playback using GStreamer and 2D graphics rendering using Cairo.

ShiVa3D is a 3D game engine with a graphical editor designed to create applications and video games for desktop PCs, the web, game consoles and mobile devices. Games made with ShiVa can be exported to over 20 target platforms, with new export targets being added regularly.

Wayland (display server protocol) Computer display server protocol

Wayland is a communication protocol that specifies the communication between a display server and its clients, as well as a C library implementation of that protocol. A display server using the Wayland protocol is called a Wayland compositor, because it additionally performs the task of a compositing window manager.

Mono (software) Computer software project

Mono is a free and open-source .NET Framework-compatible software framework. Originally by Ximian, it was later acquired by Novell, and is now being led by Xamarin, a subsidiary of Microsoft and the .NET Foundation. Mono can be run on many software systems.

Cinnamon (desktop environment) Desktop environment

Cinnamon is a free and open-source desktop environment for the X Window System that derives from GNOME 3 but follows traditional desktop metaphor conventions. Cinnamon is the principal desktop environment of the Linux Mint distribution and is available as an optional desktop for other Linux distributions and other Unix-like operating systems as well.

FireMonkey

FireMonkey is a cross-platform GUI framework developed by Embarcadero Technologies for use in Delphi or C++Builder, using C++ or Object Pascal to build cross platform applications for Windows, macOS, iOS, and Android. A 3rd party library, FMX Linux, enables the building of FireMonkey applications on Linux.

A lock screen is a computer user interface element used by various operating systems. They regulate immediate access to a device by requiring that the user perform a certain action in order to receive access, such as entering a password, using a certain button combination, or performing a certain gesture using a device's touchscreen. There are various authentication methods to get past the lock screen, with the most popular and common ones being personal identification numbers (PINs), the Android pattern lock, and biometrics.

mpv (media player)

mpv is free and open-source media player software based on MPlayer, mplayer2 and FFmpeg. It runs on several operating systems, including the Unix-like operating systems and the non-Unix Microsoft Windows, along with having an Android port called mpv-android. It is cross-platform, running on ARM, PowerPC, x86/IA-32, x86-64, and MIPS architecture.

3D Maze screensaver

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References

  1. "Changelog" . Retrieved 3 April 2021.
  2. "Debian XScreenSaver copyright list". 24 December 2020. Retrieved 24 December 2020.
  3. 1 2 "List of screen savers included in the XScreenSaver collection". 8 December 2020. Retrieved 24 December 2020.
  4. "XScreenSaver release history". 8 December 2020. Retrieved 24 December 2020.
  5. "Debian XScreenSaver package list". 24 December 2020. Retrieved 24 December 2020.
  6. "XScreenSaver: Windows Version". www.jwz.org. Retrieved 24 December 2020.
  7. 1 2 "jwz.org blog post about the iOS port". 19 June 2012. Retrieved 24 December 2020.
  8. "jwz.org blog post about the Android port". 23 May 2016. Retrieved 24 December 2020.
  9. "XScreenSaver FAQ regarding KDE/Gnome" . Retrieved 24 December 2020.
  10. "XScreenSaver source code distribution". 8 December 2020. Retrieved 24 December 2020.
  11. Campagna, Giovanni (21 March 2011). "Re: What is the status of the screensaver in GNOME3?". gnome-shell (Mailing list).
  12. "Linux Mint 19.1 Announcement". 20 December 2018. Retrieved 24 December 2020.
  13. "Gnome-Screensaver Key Flood". 16 April 2014. Retrieved 24 December 2020.
  14. "Cinnamon-Screensaver Key Flood". 22 August 2014. Retrieved 24 December 2020.
  15. "CVE-2014-1949, Cinnamon-Screensaver Lock Bypass". 16 January 2015. Retrieved 24 December 2020.
  16. "Mandriva Security Advisory MDVSA-2015:162". 29 March 2015. Retrieved 24 December 2020.
  17. "CVE-2015-7496, Hold ESC to unlock Gnome-session GDM". 24 November 2015. Retrieved 18 January 2021.
  18. "CVE-2019-3010, Privilege Escalation in Oracle Solaris XScreenSaver fork". 23 October 2019. Retrieved 24 December 2020.
  19. "Cinnamon-screensaver lock by-pass via the virtual keyboard". 15 January 2021. Retrieved 15 January 2021.
  20. "XScreenSaver: On Toolkit Dialogs". 19 October 2004. Retrieved 24 December 2020.
  21. "jwz.org blog post about Gnome security bugs". 4 April 2015. Retrieved 24 December 2020.
  22. "Sleep Mode: The Art of the Screensaver: Jamie Zawinski Interview". 27 January 2017. Retrieved 24 December 2020.