XScreenSaver
Encyclopedia
XScreenSaver is a collection of about two hundred free screensaver
s for Unix
and Mac OS X
computers. It was created by Jamie Zawinski
in 1992 and is still maintained by him.
The free software
and open source
Unix-like
operating systems running the X Window System
(such as Linux
and FreeBSD
) use XScreenSaver almost exclusively. On those systems, there are two parts to XScreenSaver: the collection of screen savers; and the framework for blanking and locking the screen.
In recent years, some of the Linux distributions have begun using the gnome-screensaver
or kscreensaver screen-blanking frameworks by default instead of the framework included with XScreenSaver. They still depend on the XScreenSaver collection of screen savers, which is over 90% of the package.
On Macintosh
systems, XScreenSaver works with the usual Apple screen saver framework, and X11
is unneeded.
XScreenSaver is released under the terms of the X11 License.
") are each stand-alone programs invoked by the xscreensaver daemon. In this way, 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 portability, the included hacks are all written in C
, using libX11 and/or OpenGL
1.3.
An important feature of the xscreensaver daemon's design is 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 un-lock the screen).
On Unix systems, running the hacks from the command line will cause them to open their own non-full-screen window.
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.
Popular hacks include:
Some of the included hacks are very similar to demo effect
s created by the demoscene
:
Screensaver
A screensaver is a type of computer program initially designed to prevent phosphor burn-in on CRT and plasma computer monitors by blanking the screen or filling it with moving images or patterns when the computer is not in use...
s for Unix
Unix-like
A Unix-like operating system is one that behaves in a manner similar to a Unix system, while not necessarily conforming to or being certified to any version of the Single UNIX Specification....
and Mac OS X
Mac OS X
Mac OS X is a series of Unix-based operating systems and graphical user interfaces developed, marketed, and sold by Apple Inc. Since 2002, has been included with all new Macintosh computer systems...
computers. It was created by Jamie Zawinski
Jamie Zawinski
Jamie Zawinski , commonly known as jwz, is a former professional American computer programmer responsible for significant contributions to the free software projects Mozilla and XEmacs, and early versions of the Netscape Navigator web browser...
in 1992 and is still maintained by him.
The free software
Free software
Free software, software libre or libre software is software that can be used, studied, and modified without restriction, and which can be copied and redistributed in modified or unmodified form either without restriction, or with restrictions that only ensure that further recipients can also do...
and open source
Open source
The term open source describes practices in production and development that promote access to the end product's source materials. Some consider open source a philosophy, others consider it a pragmatic methodology...
Unix-like
Unix-like
A Unix-like operating system is one that behaves in a manner similar to a Unix system, while not necessarily conforming to or being certified to any version of the Single UNIX Specification....
operating systems running the X Window System
X Window System
The X window system is a computer software system and network protocol that provides a basis for graphical user interfaces and rich input device capability for networked computers...
(such as Linux
Linux
Linux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds...
and FreeBSD
FreeBSD
FreeBSD is a free Unix-like operating system descended from AT&T UNIX via BSD UNIX. Although for legal reasons FreeBSD cannot be called “UNIX”, as the direct descendant of BSD UNIX , FreeBSD’s internals and system APIs are UNIX-compliant...
) use XScreenSaver almost exclusively. On those systems, there are two parts to XScreenSaver: the collection of screen savers; and the framework for blanking and locking the screen.
In recent years, some of the Linux distributions have begun using the gnome-screensaver
Gnome-screensaver
gnome-screensaver is the GNOME project's official screen blanking and locking framework. On some GNOME-based Linux distributions, it is used instead of the framework that is a part of XScreenSaver....
or kscreensaver screen-blanking frameworks by default instead of the framework included with XScreenSaver. They still depend on the XScreenSaver collection of screen savers, which is over 90% of the package.
On Macintosh
Macintosh
The Macintosh , or Mac, is a series of several lines of personal computers designed, developed, and marketed by Apple Inc. The first Macintosh was introduced by Apple's then-chairman Steve Jobs on January 24, 1984; it was the first commercially successful personal computer to feature a mouse and a...
systems, XScreenSaver works with the usual Apple screen saver framework, and X11
X Window System
The X window system is a computer software system and network protocol that provides a basis for graphical user interfaces and rich input device capability for networked computers...
is unneeded.
XScreenSaver is released under the terms of the X11 License.
Architecture
One reason for XScreenSaver's popularity is the modularity of its design, which makes it easy to add new display modes. The display modes (termed "hacks" from the historical usage "display hackDisplay hack
A display hack is a computer program with similar purpose to a kaleidoscope: to make pretty pictures . Famous display hacks include munching squares and smoking clover. Some display hacks can be also implemented by creating text files which contain numerous escape sequences for a text terminal to...
") are each stand-alone programs invoked by the xscreensaver daemon. In this way, 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 portability, the included hacks are all written in C
C (programming language)
C is a general-purpose computer programming language developed between 1969 and 1973 by Dennis Ritchie at the Bell Telephone Laboratories for use with the Unix operating system....
, using libX11 and/or OpenGL
OpenGL
OpenGL is a standard specification defining a cross-language, cross-platform API for writing applications that produce 2D and 3D computer graphics. The interface consists of over 250 different function calls which can be used to draw complex three-dimensional scenes from simple primitives. OpenGL...
1.3.
An important feature of the xscreensaver daemon's design is that the display modes are sandboxed
Sandbox (computer security)
In computer security, a sandbox is a security mechanism for separating running programs. It is often used to execute untested code, or untrusted programs from unverified third-parties, suppliers, untrusted users and untrusted websites....
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 un-lock the screen).
On Unix systems, running the hacks from the command line will cause them to open their own non-full-screen window.
Hacks
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.
Popular hacks include:
- Atlantis – an OpenGLOpenGLOpenGL is a standard specification defining a cross-language, cross-platform API for writing applications that produce 2D and 3D computer graphics. The interface consists of over 250 different function calls which can be used to draw complex three-dimensional scenes from simple primitives. OpenGL...
animation showing whaleWhaleWhale is the common name for various marine mammals of the order Cetacea. The term whale sometimes refers to all cetaceans, but more often it excludes dolphins and porpoises, which belong to suborder Odontoceti . This suborder also includes the sperm whale, killer whale, pilot whale, and beluga...
s and dolphinDolphinDolphins are marine mammals that are closely related to whales and porpoises. There are almost forty species of dolphin in 17 genera. They vary in size from and , up to and . They are found worldwide, mostly in the shallower seas of the continental shelves, and are carnivores, mostly eating...
s. - BSOD – shows fake fatal screen of death variants from many computer systems, including Microsoft WindowsMicrosoft WindowsMicrosoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...
Blue Screen of DeathBlue Screen of DeathTo forse a BSOD Open regedit.exe,Then search: HKLM\SYSTEM\CurrentControlSet\services\i8042prt\ParametersThen make a new DWORD called "CrashOnCtrlScroll" And set the value to 1....
, a Linux kernel panicKernel panicA kernel panic is an action taken by an operating system upon detecting an internal fatal error from which it cannot safely recover. The term is largely specific to Unix and Unix-like systems; for Microsoft Windows operating systems the equivalent term is "Bug check" .The kernel routines that...
, a DarwinDarwin (operating system)Darwin is an open source POSIX-compliant computer operating system released by Apple Inc. in 2000. It is composed of code developed by Apple, as well as code derived from NeXTSTEP, BSD, and other free software projects....
crash, an AmigaAmigaThe Amiga is a family of personal computers that was sold by Commodore in the 1980s and 1990s. The first model was launched in 1985 as a high-end home computer and became popular for its graphical, audio and multi-tasking abilities...
"Guru MeditationGuru MeditationGuru Meditation is an error notice displayed by early versions of the Commodore Amiga computer when they crashed. It is analogous to the "Blue Screen Of Death" in Microsoft Windows operating systems.- Description :...
" error, a sad Mac, and more. - Apple2 – simulates an Apple IIApple IIThe Apple II is an 8-bit home computer, one of the first highly successful mass-produced microcomputer products, designed primarily by Steve Wozniak, manufactured by Apple Computer and introduced in 1977...
computer, showing a user entering a simple BASICBASICBASIC is a family of general-purpose, high-level programming languages whose design philosophy emphasizes ease of use - the name is an acronym from Beginner's All-purpose Symbolic Instruction Code....
program and running it. When run from the command-line, it is a fully functional terminal emulatorTerminal emulatorA terminal emulator, terminal application, term, or tty for short, is a program that emulates a video terminal within some other display architecture....
(as is Phosphor.) - Barcode – a number of coloured barcodeBarcodeA barcode is an optical machine-readable representation of data, which shows data about the object to which it attaches. Originally barcodes represented data by varying the widths and spacings of parallel lines, and may be referred to as linear or 1 dimensional . Later they evolved into rectangles,...
s scroll across the screen. - Flow – a 3D display of strange attractors.
- Flying toasters – 3D toasters fly around, inspired by the classic After Dark screensaver.
- Gears – an OpenGL animation of intermeshing gearGearA gear is a rotating machine part having cut teeth, or cogs, which mesh with another toothed part in order to transmit torque. Two or more gears working in tandem are called a transmission and can produce a mechanical advantage through a gear ratio and thus may be considered a simple machine....
s and planetary gears. - GLMatrix – an OpenGL animation similar to the "digital rainMatrix digital rainMatrix digital rain, Matrix code or sometimes green rain, is the computer code featured in the Matrix series. The falling green code is a way of representing the activity of the virtual reality environment of the Matrix on screen. All three Matrix movies, as well as the spin-off The Animatrix...
" title sequence seen in the Matrix trilogy. - Molecule – an OpenGL animation showing space-fillingSpace-filling modelIn chemistry a space-filling model, also known as calotte model, is a type of three-dimensional molecular model where the atoms are represented by spheres whose radii are proportional to the radii of the atoms and whose center-to-center distances are proportional to the distances between the atomic...
or ball-and-stickBall-and-stick modelIn chemistry, the ball-and-stick model is a molecular model of a chemical substance which is to display both the three-dimensional position of the atoms and the bonds between them...
models of a series of common drugs and other molecules. - Penrose – tiles the screen aperiodically with coloured Penrose tiles.
- Spotlight – puts a moving spotlight across the desktop in the style of the James BondJames BondJames Bond, code name 007, is a fictional character created in 1953 by writer Ian Fleming, who featured him in twelve novels and two short story collections. There have been a six other authors who wrote authorised Bond novels or novelizations after Fleming's death in 1964: Kingsley Amis,...
film opening sequences. - Sproingies – an animation in the style of the video game Q*bert.
- Webcollage – creates collages out of random images found on the Web.
- XPlanet – draws planetPlanetA planet is a celestial body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and has cleared its neighbouring region of planetesimals.The term planet is ancient, with ties to history, science,...
s and other celestial bodies that update in real time. - XMatrix – animations similar to the "digital rainMatrix digital rainMatrix digital rain, Matrix code or sometimes green rain, is the computer code featured in the Matrix series. The falling green code is a way of representing the activity of the virtual reality environment of the Matrix on screen. All three Matrix movies, as well as the spin-off The Animatrix...
" sequence seen in the Matrix trilogy.
Some of the included hacks are very similar to demo effect
Demo effect
Demo effects are computer-based real-time visual effects found in demos created by the demoscene.The main purpose of demo effects in demos is to show off the skills of the programmer...
s created by the demoscene
Demoscene
The demoscene is a computer art subculture that specializes in producing demos, which are non-interactive audio-visual presentations that run in real-time on a computer...
:
- Boing – based on the 1984 program regarded as the first Amiga demo ever, showing the bouncing red and white ball.
- Bumps – an implementation of full-screen 2D bumpmapping.
- MetaBallsMetaballsMetaballs are, in computer graphics, organic-looking n-dimensional objects. The technique for rendering metaballs was invented by Jim Blinn in the early 1980s....
– another common demo effect. - Moire2 – moving interference circlesMoiré patternIn physics, a moiré pattern is an interference pattern created, for example, when two grids are overlaid at an angle, or when they have slightly different mesh sizes.- Etymology :...
similar to those common in older Amiga demos. - ShadeBobs – another effect common in older Amiga demos.
- XFlame – the filter-based fire effect, also known as flame effect.