Compositing Manager
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A compositing manager, or compositor, is software that provides applications with an off-screen
buffer Buffer may refer to: Science * Buffer gas, an inert or nonflammable gas * Buffer solution, a solution used to prevent changes in pH * Lysis buffer, in cell biology * Metal ion buffer * Mineral redox buffer, in geology Technology and engineeri ...
for each window, then composites these window buffers into an image representing the screen and writes the result into the display memory. A compositing window manager is a
window manager A window manager is system software that controls the placement and appearance of window (computing), windows within a windowing system in a graphical user interface. Most window managers are designed to help provide a desktop environment. They ...
that is also a compositing manager. Compositing managers may perform additional processing on buffered windows, applying 2D and 3D animated effects such as blending,
fading In wireless communications, fading is the variation of signal attenuation over variables like time, geographical position, and radio frequency. Fading is often modeled as a random process. In wireless systems, fading may either be due to mul ...
,
scaling Scaling may refer to: Science and technology Mathematics and physics * Scaling (geometry), a linear transformation that enlarges or diminishes objects * Scale invariance, a feature of objects or laws that do not change if scales of length, energ ...
,
rotation Rotation or rotational/rotary motion is the circular movement of an object around a central line, known as an ''axis of rotation''. A plane figure can rotate in either a clockwise or counterclockwise sense around a perpendicular axis intersect ...
,
duplication Duplication, duplicate, and duplicator may refer to: Biology and genetics * Gene duplication, a process which can result in free mutation * Chromosomal duplication, which can cause Bloom and Rett syndrome * Polyploidy, a phenomenon also known ...
, bending and contortion, shuffling, blurring, redirecting applications, and
translating Translation is the communication of the meaning of a source-language text by means of an equivalent target-language text. The English language draws a terminological distinction (which does not exist in every language) between ''transla ...
windows into one of a number of
displays A display device is an output device for presentation of information in visual or tactile form (the latter used for example in tactile electronic displays for blind people). When the input information that is supplied has an electrical signal ...
and
virtual desktop In computing, a virtual desktop is a term used with respect to user interfaces, usually within the WIMP (computing), WIMP paradigm, to describe ways in which the virtual space of a computer's desktop environment is expanded beyond the physical ...
s. Computer graphics technology allows for visual effects to be rendered in real time such as
drop shadow In graphic design and computer graphics, a drop shadow is a visual effect consisting of a drawing element which looks like the shadow of an object, giving the impression that the object is raised above the objects behind it. The drop shadow is of ...
s, live previews, and complex animation. Since the screen is
double buffered In computer science, multiple buffering is the use of more than one buffer to hold a block of data, so that a " reader" will see a complete (though perhaps old) version of the data instead of a partially updated version of the data being created b ...
, it does not flicker during updates. The most commonly used compositing managers and compositing window managers include: * for
Linux Linux ( ) is a family of open source Unix-like operating systems based on the Linux kernel, an kernel (operating system), operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically package manager, pac ...
,
BSD The Berkeley Software Distribution (BSD), also known as Berkeley Unix or BSD Unix, is a discontinued Unix operating system developed and distributed by the Computer Systems Research Group (CSRG) at the University of California, Berkeley, beginni ...
,
Hurd GNU Hurd is a collection of microkernel servers written as part of GNU, for the GNU Mach microkernel. It has been under development since 1990 by the GNU Project of the Free Software Foundation, designed as a replacement for the Unix kernel, and ...
and
OpenSolaris OpenSolaris () is a discontinued open-source computer operating system for SPARC and x86 based systems, created by Sun Microsystems and based on Solaris. Its development began in the mid 2000s and ended in 2010. OpenSolaris was developed as ...
using the
X Window System The X Window System (X11, or simply X) is a windowing system for bitmap displays, common on Unix-like operating systems. X originated as part of Project Athena at Massachusetts Institute of Technology (MIT) in 1984. The X protocol has been at ...
: The '
X server X server may refer to: * a display server for the X Window System * X.Org Server, the X.Org Foundation's display server for the X Window System * HPE Integrity Superdome X Server, a line of HPE Integrity Servers HPE Integrity Servers is a ser ...
' traditionally performs compositing from numerous networked sources at high speed but stylistic preferences may require compositing duties to be performed by a co-compositor with varying effects on visual qualities, capabilities and performance factors. Some examples are
Compiz Compiz () is a compositing window manager for the X Window System, using 3D graphics hardware to create fast compositing desktop effects for window management. Effects, such as a minimization animation or a cube workspace, are implemented as loa ...
,
KWin KWin is a window manager for the X Window System and a Wayland (display server protocol)#Wayland compositors, Wayland compositor. It is released as a part of KDE Plasma, for which it is the default window manager. KWin can also be used on its o ...
,
Xfwm Xfce or XFCE (pronounced as four individual letters, ) is a free and open-source desktop environment for Linux and other Unix-like operating systems. Xfce aims to be fast and lightweight while still visually appealing and easy to use. The deskt ...
,
Enlightenment Enlightenment or enlighten may refer to: Age of Enlightenment * Age of Enlightenment, period in Western intellectual history from the late 17th to late 18th century, centered in France but also encompassing (alphabetically by country or culture): ...
, Muffin (compositing window manager for Cinnamon DE), and Mutter compositing window managers and the xcompmgr and
picom Picom is a lightweight standalone compositor created for the X Window System. It is a fork of compton, created because compton wasn't being actively maintained; compton is, in turn, a fork of xcompmgr-dana, forked from xcompmgr. Configuration P ...
compositors; * for Linux and BSD using Wayland: the
Weston Weston may refer to: Places Australia * Weston, Australian Capital Territory, a suburb of Canberra * Weston, New South Wales * Weston Creek, a residential district of Canberra * Weston Park, Canberra, a park Canada * Weston, Nova Scotia * W ...
, KWin, and Mutter compositing window managers; * for
Windows Windows is a Product lining, product line of Proprietary software, proprietary graphical user interface, graphical operating systems developed and marketed by Microsoft. It is grouped into families and subfamilies that cater to particular sec ...
: the
Desktop Window Manager Desktop Window Manager (DWM, previously Desktop Compositing Engine or DCE in builds of pre-reset Windows Longhorn) is the compositing window manager in Microsoft Windows since Windows Vista that enables the use of hardware acceleration to render ...
; and * for
macOS macOS, previously OS X and originally Mac OS X, is a Unix, Unix-based operating system developed and marketed by Apple Inc., Apple since 2001. It is the current operating system for Apple's Mac (computer), Mac computers. With ...
: the
Quartz Compositor Quartz Compositor is the display server (and at the same time the compositing window manager) in macOS. It is responsible for presenting and maintaining rasterized, rendered graphics from the rest of the Core Graphics framework and other ren ...
.


Contrast with stacking window managers

The
window manager A window manager is system software that controls the placement and appearance of window (computing), windows within a windowing system in a graphical user interface. Most window managers are designed to help provide a desktop environment. They ...
sends each window a
message A message is a unit of communication that conveys information from a sender to a receiver. It can be transmitted through various forms, such as spoken or written words, signals, or electronic data, and can range from simple instructions to co ...
to repaint itself when needed. Windows may overlap. When a window in front is moved, it can reveal an area of a window behind that was previously concealed. Window managers are broadly categorised by their strategy for causing that newly revealed area to be displayed to the user. In the "stacking" strategy, the window manager tells the back window to repaint itself. In the "compositing" strategy, the window manager maintains an off-screen memory buffer containing the full appearance of each window, including the back window. With a stacking manager, the repainting process can become corrupted when a program that is slow, unresponsive or buggy does not respond to messages in a timely manner. A malicious program can cause the system to appear unstable by simply neglecting to repaint its window. Then, one or more of the following conditions may result: * a clipped window does not repaint uncovered regions, resulting in either blank spaces or a "trail" left behind from another window * portions of windows (such as decorative drop shadows) are left behind and not properly painted over * the mouse pointer is corrupted * the entire screen freezes until the program either responds or is terminated With a compositing manager, if a window stops repainting itself when requested by the window manager, its last repaint will remain displayed and the window might be dimmed. Often, the title changes to reflect the status of the window as unresponsive. A program may prevent its window from being moved or unmapped, but generally will not cause repainting problems.


History

One of the first systems with a compositing windowing system was the Commodore
Amiga Amiga is a family of personal computers produced by Commodore International, Commodore from 1985 until the company's bankruptcy in 1994, with production by others afterward. The original model is one of a number of mid-1980s computers with 16-b ...
, released in 1985. Applications could first request a region of memory outside the current display region for use as bitmap. The Amiga windowing system would then use a series of
bit blit Bit blit (also written BITBLT, BIT BLT, BitBLT, Bit BLT, Bit Blt etc., which stands for ''bit block transfer'') is a data operation commonly used in computer graphics in which several bitmaps are combined into one using a ''boolean function''. Th ...
s using the system's hardware
blitter A blitter is a circuit, sometimes as a coprocessor or a logic block on a microprocessor, dedicated to the rapid movement and modification of data within a computer's memory. A blitter can copy large quantities of data from one memory area to a ...
to build a composite of these applications' bitmaps - along with buttons and sliders - in display memory, without requiring these applications to redraw any of their bitmaps. On March 24, 2001,
Mac OS X v10.0 Mac OS X 10.0 (code named Cheetah) is the first major release of macOS, Apple's desktop and server operating system. It was released on March 24, 2001, for a price of $129 after a public beta. Mac OS X was Apple's successor to the classic Ma ...
became the first mainstream
operating system An operating system (OS) is system software that manages computer hardware and software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for ...
to feature software-based 3D compositing and effects, provided by its
Quartz Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The Atom, atoms are linked in a continuous framework of SiO4 silicon–oxygen Tetrahedral molecular geometry, tetrahedra, with each oxygen being shared between two tet ...
component. With the release of Mac OS X v10.2 and
Quartz Extreme Quartz Compositor is the display server (and at the same time the compositing window manager) in macOS. It is responsible for presenting and maintaining rasterized, rendered graphics from the rest of the Core Graphics framework and other ren ...
, the job of compositing could move to dedicated
graphics hardware Graphics hardware is computer hardware that generates computer graphics and allows them to be shown on a display, usually using a graphics card (video card) in combination with a device driver to create the images on the screen. Types Grap ...
. In 2003
Sun Microsystems Sun Microsystems, Inc., often known as Sun for short, was an American technology company that existed from 1982 to 2010 which developed and sold computers, computer components, software, and information technology services. Sun contributed sig ...
demonstrated an ambitious 3D graphics system called
Project Looking Glass Project Looking Glass is a now inactive free software project under the GNU General Public License, GPL to create an innovative Graphical user interface#Three-dimensional user interfaces, 3D desktop environment for Linux, Solaris (operating sy ...
to layer on top of its Swing toolkit. It was first shown at the 2003 LinuxWorld Expo. Although Apple threatened to sue Sun for breach of
intellectual-property Intellectual property (IP) is a category of property that includes intangible creations of the human intellect. There are many types of intellectual property, and some countries recognize more than others. The best-known types are patents, co ...
rights, other window managers have implemented some of the functionality in Looking Glass. By 2006 development was discontinued by Sun, whose primary business was transitioning from graphically oriented
Unix workstation A workstation is a special computer designed for technical or computational science, scientific applications. Intended primarily to be used by a single user, they are commonly connected to a local area network and run multi-user operating syste ...
s to selling
enterprise Enterprise (or the archaic spelling Enterprize) may refer to: Business and economics Brands and enterprises * Enterprise GP Holdings, an energy holding company * Enterprise plc, a UK civil engineering and maintenance company * Enterpris ...
mainframes. Microsoft first presented the Desktop Window Manager in Project Longhorn to the 2003
Windows Hardware Engineering Conference The Windows Hardware Engineering Community (WinHEC) is a series of technical conferences and workshops, where Microsoft elaborates on its hardware plans for Windows devices. The WinHEC from 1992 to 2008, which stood for Windows Hardware Engineeri ...
, demonstrating wobbly windows. Severe delays in the development of Longhorn caused
Microsoft Microsoft Corporation is an American multinational corporation and technology company, technology conglomerate headquartered in Redmond, Washington. Founded in 1975, the company became influential in the History of personal computers#The ear ...
not to debut its 3D-compositing window-manager until the release of
Windows Vista Windows Vista is a major release of the Windows NT operating system developed by Microsoft. It was the direct successor to Windows XP, released five years earlier, which was then the longest time span between successive releases of Microsoft W ...
in January 2007. Implementing compositing under the
X Window System The X Window System (X11, or simply X) is a windowing system for bitmap displays, common on Unix-like operating systems. X originated as part of Project Athena at Massachusetts Institute of Technology (MIT) in 1984. The X protocol has been at ...
required some redesign, which took place incrementally.
Metacity Metacity (pronounced ) was the default window manager used by the GNOME 2 desktop environment until it was replaced by Mutter in GNOME 3. It is still used by GNOME Flashback, a session for GNOME 3 that provides a similar user experience to the ...
2.8.4 was released in August 2004. However, the first widely publicized compositing window manager for X was
Xfwm Xfce or XFCE (pronounced as four individual letters, ) is a free and open-source desktop environment for Linux and other Unix-like operating systems. Xfce aims to be fast and lightweight while still visually appealing and easy to use. The deskt ...
, released in January 2005. On 26 January 2005
Compiz Compiz () is a compositing window manager for the X Window System, using 3D graphics hardware to create fast compositing desktop effects for window management. Effects, such as a minimization animation or a cube workspace, are implemented as loa ...
was released, introducing fully accelerated 3D-compositing to the Linux platform.
KDE KDE is an international free software community that develops free and open-source software. As a central development hub, it provides tools and resources that enable collaborative work on its projects. Its products include the KDE Plasma gra ...
's
KWin KWin is a window manager for the X Window System and a Wayland (display server protocol)#Wayland compositors, Wayland compositor. It is released as a part of KDE Plasma, for which it is the default window manager. KWin can also be used on its o ...
also supports compositing.


Compositing and 3D effects in operating systems

In compositing, 3D effects could be applied on windows to provide 3D desktop effects. Modern compositing window managers use 3D hardware acceleration. Compositing window manager software communicates with graphics hardware via programming interfaces such as
OpenGL OpenGL (Open Graphics Library) is a Language-independent specification, cross-language, cross-platform application programming interface (API) for rendering 2D computer graphics, 2D and 3D computer graphics, 3D vector graphics. The API is typic ...
or
Direct3D Direct3D is a graphics application programming interface (API) for Microsoft Windows. Part of DirectX, Direct3D is used to render three-dimensional graphics in applications where performance is important, such as games. Direct3D uses hardware ...
. The earliest widespread implementations using this technique were released for the Mac in Mac OS X 10.2, and for Linux in a
Luminocity Luminosity is an absolute measure of radiated electromagnetic energy per unit time, and is synonymous with the radiant power emitted by a light-emitting object. In astronomy, luminosity is the total amount of electromagnetic energy emitted per ...
prototype. Currently, window managers using OpenGL include Compiz, KWin, and the Quartz Compositor, while Desktop Window Manager currently uses DirectX 9. OpenGL is still not fully supported in hardware, so performance of OpenGL-based compositing should continue to improve as hardware improves.


X11 and Wayland

Stacking window managers running on the
X Window System The X Window System (X11, or simply X) is a windowing system for bitmap displays, common on Unix-like operating systems. X originated as part of Project Athena at Massachusetts Institute of Technology (MIT) in 1984. The X protocol has been at ...
(X11) required a chroma keying or green screening
extension Extension, extend or extended may refer to: Mathematics Logic or set theory * Axiom of extensionality * Extensible cardinal * Extension (model theory) * Extension (proof theory) * Extension (predicate logic), the set of tuples of values that ...
. Compositing was introduced by way of the
Composite Extension The Composite Extension of the X Window System The X Window System (X11, or simply X) is a windowing system for bitmap displays, common on Unix-like operating systems. X originated as part of Project Athena at Massachusetts Institute of Techn ...
. Compositing managers use hardware acceleration through this extension, if available. Under X11, the ability to do full 3D-accelerated compositing required fundamental changes to the window system protocol in order to use hardware acceleration. Originally, a number of modified X11 implementations designed around
OpenGL OpenGL (Open Graphics Library) is a Language-independent specification, cross-language, cross-platform application programming interface (API) for rendering 2D computer graphics, 2D and 3D computer graphics, 3D vector graphics. The API is typic ...
began to appear, including Xgl. The introduction of
AIGLX Accelerated Indirect GLX ("AIGLX") is an Open-source software, open source project founded by Red Hat and the Fedora (operating system), Fedora community, led by Kristian Høgsberg, to allow accelerated indirect GLX rendering capabilities to t ...
would eliminate the need to use Xgl, and allow window managers to do 3D accelerated compositing on a standard X server, while still allowing for direct rendering. Currently,
NVIDIA Nvidia Corporation ( ) is an American multinational corporation and technology company headquartered in Santa Clara, California, and incorporated in Delaware. Founded in 1993 by Jensen Huang (president and CEO), Chris Malachowsky, and Curti ...
,
Intel Intel Corporation is an American multinational corporation and technology company headquartered in Santa Clara, California, and Delaware General Corporation Law, incorporated in Delaware. Intel designs, manufactures, and sells computer compo ...
, and ATI cards support AIGLX. Compiz introduced a cube effect, which allows the user to see up to 6 virtual desktops at once. Each desktop is converted into a surface texture of the cube, which can be rotated at will. Compiz displays a wide array of 2D and 3D effects and has relatively low hardware requirements. In 2012, Compiz was included in
Ubuntu Ubuntu ( ) is a Linux distribution based on Debian and composed primarily of free and open-source software. Developed by the British company Canonical (company), Canonical and a community of contributors under a Meritocracy, meritocratic gover ...
Linux, and was enabled automatically when supported hardware and drivers were available and the user had not selected 2D Mode. Mutter (Metacity + Clutter) has replaced Metacity as the default window manager for
GNOME A gnome () is a mythological creature and diminutive spirit in Renaissance magic and alchemy, introduced by Paracelsus in the 16th century and widely adopted by authors, including those of modern fantasy literature. They are typically depict ...
. It is featured in the
GNOME Shell GNOME Shell is the graphical shell of the GNOME desktop environment starting with version 3, which was released on April 6, 2011. It provides basic functions like launching applications and switching between windows. GNOME Shell replaced GN ...
component of GNOME 3.0. It uses the display engine Clutter, which has been ported to all major operating systems,
netbooks A netbook is a small-sized laptop computer; they were primarily sold from 2007 until around 2013, designed mostly as a means of accessing the Internet and being significantly less expensive than regular-sized laptops. At their inception in l ...
and
smartphones A smartphone is a mobile phone with advanced computing capabilities. It typically has a touchscreen interface, allowing users to access a wide range of applications and services, such as web browsing, email, and social media, as well as mult ...
. Since version 4, KDE's window manager
KWin KWin is a window manager for the X Window System and a Wayland (display server protocol)#Wayland compositors, Wayland compositor. It is released as a part of KDE Plasma, for which it is the default window manager. KWin can also be used on its o ...
has compositing capabilities. KWin features much of the same functionality also present in
Compiz Compiz () is a compositing window manager for the X Window System, using 3D graphics hardware to create fast compositing desktop effects for window management. Effects, such as a minimization animation or a cube workspace, are implemented as loa ...
. With the Wayland protocol, a compositing window manager is also a display server; there is no display server separate from the window manager. The combined window manager/display server is called a
Wayland compositor 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 composito ...
.
Weston Weston may refer to: Places Australia * Weston, Australian Capital Territory, a suburb of Canberra * Weston, New South Wales * Weston Creek, a residential district of Canberra * Weston Park, Canberra, a park Canada * Weston, Nova Scotia * W ...
is a reference implementation of a Wayland compositor; KWin and Mutter are also Wayland compositors as well as being X11 compositing window managers.


Java

Project Looking Glass was a window manager combining 3D rendering and the cross-platform
Java Java is one of the Greater Sunda Islands in Indonesia. It is bordered by the Indian Ocean to the south and the Java Sea (a part of Pacific Ocean) to the north. With a population of 156.9 million people (including Madura) in mid 2024, proje ...
programming language. It is now inactive and released under the
GNU General Public License The GNU General Public Licenses (GNU GPL or simply GPL) are a series of widely used free software licenses, or ''copyleft'' licenses, that guarantee end users the freedom to run, study, share, or modify the software. The GPL was the first ...
. The
Granular Linux Granular, or Granular Linux, was a Linux distribution targeted at the common desktop users. Granular was based on PCLinuxOS and came as an installable live CD. The CD version of Granular featured two desktop environments – KDE and a developmen ...
live CD distribution includes Looking Glass as an optional window manager. In the aftermath of it being discontinued, some of its features, such as cover switching and thumbnail live previews, have found their way onto other window managers. Its more original features included window tilting, two-sided window frames and
parallax scroll Parallax scrolling is a technique in computer graphics where background images move past the camera more slowly than foreground images, creating an illusion of depth in a 2D scene of distance. The technique grew out of the multiplane camera tec ...
ing backgrounds.


AmigaOS 4 and MorphOS

While they are able to run on 3D-capable hardware, AmigaOS 4 and MorphOS are designed to run on old
legacy Legacy or Legacies may refer to: Arts and entertainment Comics * " Batman: Legacy", a 1996 Batman storyline * '' DC Universe: Legacies'', a comic book series from DC Comics * ''Legacy'', a 1999 quarterly series from Antarctic Press * ''Legacy ...
Amiga computers, starting with the
Amiga 1200 The Amiga 1200, or A1200 (code-named " Channel Z"), is a personal computer in the Amiga computer family released by Commodore International, aimed at the home computer market. It was launched on October 21, 1992, at a base price of £399 in the ...
. As such, their window managers have mostly planar rendering capabilities that include composite layering, alpha blending, gradients, high resolution and multiple desktops ("screens") that can partially clip one another.


Microsoft Windows

While the window manager in Windows 2000 does perform compositing, it does not perform transformations such as a per-pixel alpha. Few commercial applications took advantage of alpha blending;
freeware Freeware is software, often proprietary, that is distributed at no monetary cost to the end user. There is no agreed-upon set of rights, license, or EULA that defines ''freeware'' unambiguously; every publisher defines its own rules for the free ...
programs were among the first to experiment with it, albeit through optional settings. Compositing was introduced with
Desktop Window Manager Desktop Window Manager (DWM, previously Desktop Compositing Engine or DCE in builds of pre-reset Windows Longhorn) is the compositing window manager in Microsoft Windows since Windows Vista that enables the use of hardware acceleration to render ...
in
Windows Vista Windows Vista is a major release of the Windows NT operating system developed by Microsoft. It was the direct successor to Windows XP, released five years earlier, which was then the longest time span between successive releases of Microsoft W ...
. Windows Vista and Windows 7 allow the user to disable Desktop Window Manager by selecting the Windows Basic appearance settings. In addition, it is automatically disabled by Windows in order to perform
hardware overlay In computing, hardware overlay, a type of video overlay, provides a method of rendering an image to a display screen with a dedicated memory buffer inside computer video hardware. The technique aims to improve the display of a fast-moving video i ...
through the Overlay Mixer Filter.


Usability and eye candy

The compositing approach makes it easier to implement a number of features that make the user interface more accessible, simpler to use or with eye candy elements.


Magnifiers

Vector graphics Vector graphics are a form of computer graphics in which visual images are created directly from geometric shapes defined on a Cartesian plane, such as points, lines, curves and polygons. The associated mechanisms may include vector displ ...
, such as
TrueType TrueType is an Computer font#Outline fonts, outline font standardization, standard developed by Apple Inc., Apple in the late 1980s as a competitor to Adobe Inc., Adobe's PostScript fonts#Type 1, Type 1 fonts used in PostScript. It has become the ...
fonts and 3D-accelerated elements, can be expanded without degradation (usually due to
aliasing In signal processing and related disciplines, aliasing is a phenomenon that a reconstructed signal from samples of the original signal contains low frequency components that are not present in the original one. This is caused when, in the ori ...
). A
screen magnifier A screen magnifier is software that interfaces with a computer's graphical output to present enlarged screen content. By enlarging part (or all) of a screen, people with visual impairments can better see words and images. This type of assistive te ...
enlarges an area of the screen, making portions of text easier to read – whether to prevent
eye strain Eye strain, also medically termed as asthenopia (), is a common eye condition characterized by nonspecific symptom, non-specific symptoms such as fatigue, pain in or around the eyes, blurred vision, headache, and occasional diplopia, double vis ...
, for the
visually impaired Visual or vision impairment (VI or VIP) is the partial or total inability of visual perception. In the absence of treatment such as corrective eyewear, assistive devices, and medical treatment, visual impairment may cause the individual difficul ...
, or simply at a distance.
Zoom Zoom may refer to: Arts, entertainment and media Film * ''Zoom'' (2006 film), starring Tim Allen * ''Zoom'' (2015 film), a Canada-Brazil film by Pedro Morelli * ''Zoom'' (2016 Kannada film), a Kannada film * ''Zoom'' (2016 Sinhala film), a Sr ...
effects such as the fish eye magnifier and zoom desktop effects provide this functionality.


Live preview

A preview of a window can be displayed in a pop-up
thumbnail Thumbnails are reduced-size versions of pictures or videos, used to help in recognizing and organizing them, serving the same role for images as a normal text index does for words. In the age of digital images, visual search engines and image-o ...
when the user hovers its associated
taskbar The taskbar is a graphical user interface element that has been part of Microsoft Windows since Windows 95, displaying and facilitating switching between running computer program, programs. The taskbar and the associated Start menu, Start Menu were ...
button. This allows the user to identify and manage several concurrently running programs.


Window switching

Windows with similar names and icons tend to cause confusion, especially when their title bars overlap; the position of every such window on the taskbar has to be memorized. When there are many open windows in this manner, the user often has to resort to trial and error—clicking each taskbar button one-by-one—before proceeding. Window switching allows one to quickly preview several windows at once by temporarily rearranging them against a decorative background. After a selection is made, the windows are then restored to their original arrangement. Selection begins when the user either enters a hotkey combination, moves the mouse pointer to a hotspot on the screen, or, in some situations, uses the mouse's
scroll wheel A scroll wheel is a wheel used for scrolling. The term usually refers to such wheels found on computer mouse, computer mice (where they can also be called a mouse wheel). It is often made of hard plastic with a rubbery surface, centred around a ...
. Items are navigated using the keyboard or mouse. An item is selected by either releasing the hotkey, hitting the Enter key or clicking on it with the mouse.


Flip switching

The flip switcher is an enhancement to the
Alt-Tab is the common name for a keyboard shortcut that has been in Microsoft Windows since Windows 1.0 (1985). This shortcut switches between application-level windows without using the mouse; hence it was named ''Task Switcher'' (''Flip'' in Windows ...
switching feature. Running windows are arranged into a stack – similar to a flip-style selector in a 1950s
jukebox A jukebox is a partially automated music-playing device, usually a coin-operated machine, that plays a user-selected song from a self-contained media library. Traditional jukeboxes contain records, compact discs, or digital files, and allow user ...
, or a
Rolodex A Rolodex is a rotating card file device used to store a contact list. Its name, a portmanteau of the words "rolling" and "index", has become somewhat genericized for any personal organizer performing this function, or as a metonym for a total a ...
. In some systems, the user can press Alt-Shift-Tab to navigate backwards. Visual transitions are applied to each item while navigating. Common implementations of flip switching include
Flip 3D Windows Aero (a backronym for ''Authentic, Energetic, Reflective, and Open'') is the design language introduced in the Microsoft Windows Vista operating system in 2006. The changes introduced by Windows Aero encompassed many elements of the Windo ...
in Windows and Shift Switcher in Compiz.


Cover switching

Cover switching is like flip switching with a few, mostly visual, differences. Instead of one stack with the selection at the top, two symmetrical stacks are shown with the current selection front and center (similar to the window tilting feature in Looking Glass).
Cover Flow Cover Flow is an animated, three-dimensional graphical user interface element that was integrated within the Macintosh Finder and other Apple Inc. products for visually flipping through snapshots of documents, website bookmarks, album artwork, ...
is an implementation of cover switching in macOS. More recent versions use blurring to de-emphasize non-selected items. Cover Flow has also been implemented in other software published by
Apple An apple is a round, edible fruit produced by an apple tree (''Malus'' spp.). Fruit trees of the orchard or domestic apple (''Malus domestica''), the most widely grown in the genus, are agriculture, cultivated worldwide. The tree originated ...
such as
iTunes iTunes is a media player, media library, and mobile device management (MDM) utility developed by Apple. It is used to purchase, play, download and organize digital multimedia on personal computers running the macOS and Windows operating s ...
. This is also referred to as "flick-book view."


Ring switching

Ring switching is like flip switching, except the windows move in a circle, with the current selection in front, usually at the bottom. Most compositing window managers include this feature out of the box, and third-party applications, such a
3d-desktop
are also available.


Grouping

The user can group windows together, such that only one window at a time is visible in each group. In Compiz, the window frame is flipped to indicate when the active window in its group has been changed.


Exposé

macOS displays a preview of every window on the screen by tiling them. Other systems with similar functionality (Microsoft Windows, Compiz, KWin, third-party applications) are referred to as Exposé clones. The hotkey to activate Exposé is not Alt-Tab, but rather F3.


Mission Control

Mac OS X 10.7 combines several other compositing features developed by Apple—such as Exposé,
Dashboard A dashboard (also called dash, instrument panel or IP, or fascia) is a control panel (engineering), control panel set within the central console of a vehicle, boat, or cockpit of an aircraft or spacecraft. Usually located directly ahead of the ...
, and Spaces—into a larger program called
Mission Control A mission control center (MCC, sometimes called a flight control center or operations center) is a facility that manages space flights, usually from the point of launch until landing or the end of the mission. It is part of the ground segment ...
.


Widget engines

On macOS, "widgets" (single-purpose
applet In computing, an applet is any small application that performs one specific task that runs within the scope of a dedicated widget engine or a larger program, often as a plug-in. The term is frequently used to refer to a Java applet, a program ...
s) such as a clock, note pad, and calculator can appear by pressing a
hotkey In computing, a keyboard shortcut (also hotkey/hot key or key binding) is a software-based assignment of an action to one or more keys on a computer keyboard. Most operating systems and applications come with a default set of keyboard shortcu ...
. Widget engines speed work by keeping commonly used widgets accessible while unobtrusive. They are handled by the Dashboard program in macOS. Compiz starts with a blank Widget Layer, allowing the user to add applications by clicking on them. A variety of widgets are supported, including
Screenlets Screenlets is the name of both a set of independently developed widget applications and the widget engine which runs them. The engine runs primarily on X11-based compositing window managers, most notably with Compiz on Linux. Development Until ...
,
gDesklets gDesklets is a GNOME program which provides the architecture for small applets ( desktop widgets) to be placed on top of the user's desktop. It is comparable to other desktop widget programs. The applets placed on the desktop are meant to be q ...
and
SuperKaramba SuperKaramba is a tool, a so-called widget engine, that allows the creation of functionality enhancement modules (desktop widgets) on the KDE desktop. The desktop widgets are usually embedded directly into the background and do not disturb the n ...
. Windows Vista provides
gadgets A gadget is a mechanical device or any ingenious article. Gadgets are sometimes referred to as '' gizmos''. History The etymology of the word is disputed. The word first appears as reference to an 18th-century tool in glassmaking that was dev ...
that the user can place on the
Windows Sidebar Windows Desktop Gadgets (called Windows Sidebar in Windows Vista) is a discontinued widget engine for Microsoft Gadgets. Desktop Gadgets have been replaced by Windows 10 Taskbar Widgets. It was introduced with Windows Vista, in which it features ...
(Sidebar gadgets), a
Windows Live Windows Live is a discontinued brand name for a set of web services and software products developed by Microsoft as part of its software-as-a-service platform. Chief components under the brand name included web services (all of which were exposed ...
start page A home page (or homepage) is the main web page of a website. Usually, the home page is located at the root of the website's domain or subdomain. For example, if the domain is example.com, the home page is likely located at the URL www.exampl ...
(Web gadgets), or an external display, such as the user's mobile phone ( SideShow gadgets). The Windows Sidebar was a visible partition in Windows Vista, and was eliminated in Windows 7, along with Sidebar gadgets which were changed to
Desktop Gadgets Microsoft Gadgets are lightweight single-purpose applications, or software widgets, that can sit on a Microsoft Windows user's computer desktop, or are hosted on a web page. According to Microsoft, it will be possible for the different types of g ...
.


Transitions and other effects

Before compositing window managers were developed, windows would instantly jump in and out of view, which is incongruent with the interface metaphor (and with a physical
office An office is a space where the employees of an organization perform Business administration, administrative Work (human activity), work in order to support and realize the various goals of the organization. The word "office" may also denote a po ...
setting). Some systems like the
Classic Mac OS Mac OS (originally System Software; retronym: Classic Mac OS) is the series of operating systems developed for the Mac (computer), Macintosh family of personal computers by Apple Computer, Inc. from 1984 to 2001, starting with System 1 and end ...
avoided this issue with ZoomRects, animating the windows outline "zooming" toward its final position. But on most systems, the sudden appearance and disappearance of
GUI Gui or GUI may refer to: People Surname * Gui (surname), an ancient Chinese surname, ''xing'' * Bernard Gui (1261 or 1262–1331), inquisitor of the Dominican Order * Luigi Gui (1914–2010), Italian politician * Gui Minhai (born 1964), Ch ...
elements may seem confusing or even chaotic to inexperienced users. Visual transitions provide context and help distinguish the causal relationships of GUI elements. Instead of just disappearing, a window may fade away, or visibly shrink to the taskbar. A pull-down menu that has been clicked may smoothly radiate outward from the menu bar, making it easier to determine its origin and purpose. Gradual and natural transitions may be especially helpful for elderly or visually impaired users who notice changes to the screen more slowly and with less clarity. For example, an inexperienced user may impulsively click on a menu that was activated by accident, causing him or her to lose work. The short delay necessary to display a visual transition may give the user enough time to make a conscious decision, and avoid such mistakes.


User interface façades

Metisse Metisse is a 2.5D X window manager with many features that set it apart from the traditional 3D "cube" workspace. Windows can be turned three-dimensionally in any direction, enabling the user to fit more windows onto a screen, and they can be sc ...
implements user interface façades, a system that provides users with simple ways to adapt, reconfigure, and recombine existing graphical interfaces, through the use of direct manipulation techniques.


List of compositing window managers


3Dwm
a three-dimensional workspace manager and general-purpose platform for 3D user interfaces. As of June 2006 this project is inactive. *
Desktop Window Manager Desktop Window Manager (DWM, previously Desktop Compositing Engine or DCE in builds of pre-reset Windows Longhorn) is the compositing window manager in Microsoft Windows since Windows Vista that enables the use of hardware acceleration to render ...
and the
Windows Aero Windows Aero (a backronym for ''Authentic, Energetic, Reflective, and Open'') is the design language introduced in the Microsoft Windows Vista operating system in 2006. The changes introduced by Windows Aero encompassed many elements of the Windo ...
theme on Windows *
Quartz Compositor Quartz Compositor is the display server (and at the same time the compositing window manager) in macOS. It is responsible for presenting and maintaining rasterized, rendered graphics from the rest of the Core Graphics framework and other ren ...
on macOS *
Compiz Compiz () is a compositing window manager for the X Window System, using 3D graphics hardware to create fast compositing desktop effects for window management. Effects, such as a minimization animation or a cube workspace, are implemented as loa ...
*
Marco Marco may refer to: People Given name * Marco (actor) (born 1977), South Korean model and actor Surname * Georg Marco (1863–1923), Romanian chess player of German origin * Jindřich Marco (1921–2000), Czechoslovak photographer and numismat ...
*
KWin KWin is a window manager for the X Window System and a Wayland (display server protocol)#Wayland compositors, Wayland compositor. It is released as a part of KDE Plasma, for which it is the default window manager. KWin can also be used on its o ...
(since version 3.3) * Mutter *
Xfwm Xfce or XFCE (pronounced as four individual letters, ) is a free and open-source desktop environment for Linux and other Unix-like operating systems. Xfce aims to be fast and lightweight while still visually appealing and easy to use. The deskt ...
from within
Xfce Xfce or XFCE (pronounced as four individual letters, ) is a Free and open-source software, free and open-source desktop environment for Linux and other Unix-like operating systems. Xfce aims to be fast and Lightweight software, lightweight whil ...
(since version 4.2) *
Metisse Metisse is a 2.5D X window manager with many features that set it apart from the traditional 3D "cube" workspace. Windows can be turned three-dimensionally in any direction, enabling the user to fit more windows onto a screen, and they can be sc ...
*
Mir ''Mir'' (, ; ) was a space station operated in low Earth orbit from 1986 to 2001, first by the Soviet Union and later by the Russia, Russian Federation. ''Mir'' was the first modular space station and was assembled in orbit from 1986 to ...
(since version 1.0)


List of standalone compositing managers


xcompmgr
€”a minimal alternative to Compiz
Compton
€“a bug-fixed fork of dcompmgr, which is a fork of xcompmgr. (Not maintained since 2017.)
Picom
a lightweight compositor for X11. It is a fork of Compton.
Cairo Compmgr
(Cairo Composite Manager)—a compositing add-on for existing window managers. It uses
Cairo Cairo ( ; , ) is the Capital city, capital and largest city of Egypt and the Cairo Governorate, being home to more than 10 million people. It is also part of the List of urban agglomerations in Africa, largest urban agglomeration in Africa, L ...
, a vector graphics library also used in
GTK+ GTK (formerly GIMP ToolKit and GTK+) is a free software cross-platform widget toolkit for creating graphical user interfaces (GUIs). It is licensed under the terms of the GNU Lesser General Public License, allowing both free and proprietary s ...
.
Unagi Compositing Manager
€”a compositing manager which can be used along with an existing window manager. It uses the
XCB XCB (''X protocol C-language Binding'') is a library implementing the client side of the X11 display server protocol. XCB is written in the C programming language and distributed under the MIT License. The project was started in 2001 by Ba ...
library. (Not maintained since 2014.) * MCompositor—used on
MeeGo MeeGo is a discontinued Linux distribution hosted by the Linux Foundation, using source code from the operating systems Moblin (produced by Intel) and Maemo (produced by Nokia). MeeGo was primarily targeted at mobile devices and information app ...
handsets.


Operating systems with compositing window managers

* Mac OS X 10.0 and later * any
Unix-like A Unix-like (sometimes referred to as UN*X, *nix or *NIX) operating system is one that behaves in a manner similar to a Unix system, although not necessarily conforming to or being certified to any version of the Single UNIX Specification. A Uni ...
OS using
XOrg X.Org Server is the free and open-source implementation of the X Window System (X11) display server stewarded by the X.Org Foundation. Implementations of the client-side X Window System protocol exist in the form of ''X11 libraries'', which ...
/
AIGLX Accelerated Indirect GLX ("AIGLX") is an Open-source software, open source project founded by Red Hat and the Fedora (operating system), Fedora community, led by Kristian Høgsberg, to allow accelerated indirect GLX rendering capabilities to t ...
or Xgl * AmigaOS 4 *
MorphOS MorphOS is an AmigaOS-like operating system designed for Power and PowerPC based computers. The core, based on the Quark microkernel, is proprietary, although several libraries and other parts are open source, such as the Ambient desktop. The p ...
2.0 and later * Windows Vista and later


See also

*
Window manager A window manager is system software that controls the placement and appearance of window (computing), windows within a windowing system in a graphical user interface. Most window managers are designed to help provide a desktop environment. They ...
*
Tiling window manager In computing, a tiling window manager is a window manager with the organization of the screen often dependant on mathematical formulas to organise the windows into a non-overlapping frame. This is opposed to the more common approach used by stac ...
*
Stacking window manager A stacking window manager (also called floating window manager) is a window manager that draws and allows windows to overlap, without using a compositing algorithm. All window managers that allow the overlapping of windows but are not compositing ...
*
Re-parenting window manager A re-parenting window manager is an X Window System window manager that adopts all other windows. In the X Window System, every window has a parent window, which may be either the root window or another window. Windows that are children of the root ...
*
Retained mode Retained mode in computer graphics is a major pattern of API design in graphics libraries, in which * the graphics library, instead of the client, retains the scene (complete object model of the rendering primitives) to be rendered and * th ...
*
Zooming user interface In computing, a zooming user interface or zoomable user interface (ZUI, pronounced zoo-ee) is a type of graphical user interface (GUI) where users can change the scale of the viewed area in order to see more detail or less, and browse through ...
*
Computer graphics Computer graphics deals with generating images and art with the aid of computers. Computer graphics is a core technology in digital photography, film, video games, digital art, cell phone and computer displays, and many specialized applications. ...


References


External links

* * * * * * * * {{DEFAULTSORT:Compositing Window Manager Graphical user interfaces *