Windowing system

Source: Wikipedia, the free encyclopedia.
window decoration is either drawn by the window manager
or by the client. The drawing of the content is the task of the client.

In

pointer) paradigm for a user interface
.

Each currently running

tiling interface where they are not allowed to overlap. Usually a window decoration is drawn around each window. The programming of both the window decoration and of available widgets inside of the window, which are graphical elements for direct user interaction, such as sliders, buttons, etc., is eased and simplified through the use of widget toolkits
.

Technical details

The main component of any windowing system is usually called the

communications protocol, which is usually called display server protocol, the display server being the mediator between the clients and the user. It receives all the input from the kernel, that the kernel receives from all attached input devices, such as keyboard, pointing devices, or touchscreen and transmits it to the correct client. The display server is also responsible for the output of the clients to the computer monitor. The output of sound is usually not managed by the display server, but the sound volume is usually handled through GUI applets and it is the display server who decides which applications are on top. A windowing system enables the computer user to work with several programs at the same time. Each program presents its GUI in its own window, which is generally a rectangular area of the screen.[citation needed
]

From a programmer's point of view, a windowing system implements graphical primitives. For example: rendering fonts or drawing a line on the screen. It provides an abstraction of the graphics hardware for use by higher-level elements of the graphical interface such as a window manager.[citation needed]

A display server protocol can be network capable or even network transparent, facilitating the implementation of thin clients.[citation needed]

Display server

window decorations
, but compositing window managers do more.

A display server or window server is a program whose primary task is to coordinate the input and output of its clients to and from the rest of the operating system, the hardware, and each other. The display server communicates with its clients over the display server protocol, a

communications protocol
, which can be network-transparent or simply network-capable.

The display server is a key component in any graphical user interface, specifically the windowing system.

The server/client relationship of a standalone display server is somewhat counterintuitive in that a "server" is usually thought of as a large, remote machine, whereas a standalone "display server" is a small local system, with most clients being executed on a larger central machine. The explanation is that a display server provides the services of a display and input devices.

Display server communications protocols

X11

Main articles: X Window System core protocol and X Window System
The X.Org Server communicates with its clients, e.g. Amarok, over the X11 protocol.
X Window System logo
X Window System logo

One example of a display server is the

KMS driver. The component writes the data into the framebuffer and content of the framebuffer is transmitted to the connected screen and displayed. X relies on GLX
.

One of the implementations of display server concept is

Mutter or KWin
.

Notable examples of display servers implementing the X11 display server protocol are X.Org Server, XFree86, XQuartz and Cygwin/X, while client libraries implementing the X11 display server protocol are Xlib and XCB.

Wayland

Main article: Wayland (protocol)
The Wayland display server protocol
Wayland logo
Wayland logo

Display servers that implement the Wayland display server protocol are called

Weston, Mutter, KWin or Enlightenment
.

Wayland compositors communicate with Wayland clients over the

rendering API. The display server still gets to decide which window is on top and thus visible to the user and also still is responsible for passing data regarding to input devices from evdev
to its clients.

Wayland is used to a certain degree in some Linux desktop distributions, such as

Fedora. It is also well suited for mobile computing and has been adopted, for example, by the smartphone- and tablet-focused projects Tizen, Sailfish OS and AsteroidOS
.

An implementation of Wayland is available under the MIT License, the libwayland-client and libwayland-server libraries.

There is an ongoing effort to add Wayland support to ChromeOS.[2]

Mir

Main article: Mir (software)

The

Ubuntu
. As of 2017, it has been replaced with the Wayland display server for desktop editions of Ubuntu.

There are implementations of the Mir display server, the libmir-server and the libmir-client libraries available under the

GPLv3
.

Windowing systems with APIs

SurfaceFlinger

Google developed a display server called SurfaceFlinger[3] for Android (another Linux kernel-based operating system primarily for mobile devices):

Everything in Android is rendered to a "surface"; "surfaces" are produced by applications and placed into a queue that is managed by SurfaceFlinger.[4][5]

Yet another Android-specific solution is "Gralloc". Gralloc handles device memory i.e. it does allocation, arbitration, it handles synchronization via Android/Linux fence file descriptors. Gralloc competes with other solutions like e.g. Mesa's

Generic Buffer Management (GBM) or Nvidia's EGLStreams. The Gralloc hardware abstraction layer (HAL)
is used to allocate the buffers that underlie "surfaces".

For compositing in Android, Surfaces are sent to SurfaceFlinger, which uses OpenGL ES to do the compositing.

Hardware Composer HAL (HWC) was introduced in Android 3.0 and has evolved steadily over the years. Its primary purpose is to determine the most efficient way to composite buffers with the available hardware. As a HAL, its implementation is device-specific and usually done by the display hardware OEM.

Quartz Compositor

For Apple's macOS family of operating systems, Quartz Compositor fulfils the tasks of a display server and of a window manager in the windowing system.

Desktop Window Manager

For Microsoft Windows, from Windows Vista onward, Desktop Window Manager enables the use of hardware acceleration to render the graphical user interface. It was originally created to enable portions of the new "Windows Aero" user experience, which allowed for effects such as transparency, 3D window switching and more. It is also included with Windows Server 2008, but requires the "Desktop Experience" feature and compatible graphics drivers to be installed. From Windows 8 onwards DWM can't be disabled and is software rendered if no suitable graphics card is installed.

List of windowing systems

For Unix-like operating systems

For Windows NT-family operating systems

Web windowing systems

Other

Some systems such as

Microsoft Windows (XP, 9x and earlier), the classic Mac OS (version 9 and earlier), and Palm OS, contain a windowing system which is integrated with the OS.[citation needed
]

See also

References

  1. ISBN 9780824727178
    . Retrieved 8 June 2017.
  2. ^ "Ozone Overview". Retrieved 2017-08-20.
  3. ^ "Android system architecture" (PDF). Archived from the original (PDF) on 2016-04-08.
  4. ^ "Android Developer: Surface".
  5. ^ "Android Developer: SurfaceFlinger and Hardware Composer".
  6. ^ "HP Windows/9000 User's Manual" (PDF). Hewlett Packard. April 1988. Retrieved 2021-10-26.
  7. ^ "Andrew: A Distributed Personal Computing Environment" (PDF). Communications of the ACM. 29 (3). March 1986.
  8. S2CID 11138733
    .
  9. ^ "Chilton::INF::Window Management". www.chilton-computing.org.uk. Retrieved 2023-04-11.
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