X window manager

From Free net encyclopedia

An X window manager is software that controls the placement and appearance of windows under the X Window System, a graphical user interface mainly used on Unix-like systems.

Unlike the Apple Macintosh and Microsoft Windows platforms, which have historically provided a vendor-controlled, fixed set of ways to control how windows and panes display on a screen, and how the user may interact with them, window management for the X Window System was deliberately kept separate from the software providing the graphical display. The user can choose between various third-party window managers, which differ from one another in several ways, including:

customizability of appearance and functionality:
- textual menus used to start programs and/or change options
- docks and other graphical ways to start programs
- multiple desktops and virtual desktops (desktops larger than the physical monitor size), and pagers to switch between them
consumption of memory and other system resources
degree of integration with a desktop environment, which provides a more complete interface to the operating system, and provides a range of integrated utilities and applications.

Alternative shells for Microsoft Windows have also emerged. For example, LiteStep can replace the user interface on Windows 95, 98, or NT with an Afterstep style. OS/2 ships with Presentation Manager as the default shell, but third party sources can supply alternatives.

1 How window managers work
2 Popular window managers for X
3 Other window managers for X
4 See also
5 External links

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How window managers work

When a window manager is running, some kind of interaction between the X server and its clients is redirected through the window manager. In particular, whenever an attempt to show a new window is made, this request is redirected to the window manager, which decides the initial position of the window. Additionally, most modern window manager are reparenting, which usually lead to a banner being placed at the top of the window and a decorative frame being drawn around the window. These two elements are controlled by the window manager rather than the program. Therefore, when the user clicks or drags these elements, it is the window manager that takes the appropriate actions (such as moving or resizing the window).

Window managers are also responsible for icons. Indeed, icons do not exist at the X Window core protocol level. When the user requests a window to be iconified, the window manager unmaps it (makes it non-visible) and takes the appropriate actions to show an icon in its place. Some window managers do not support icons.

While the main aim of window manager is, as suggested by its name, to manage the windows, many window managers have additional features such as handling mouse clicks in the root window, present panes and other visual elements, handling some keystrokes (e.g., Alt-F4 may iconify a window), deciding which application to run at start-up, etc.

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