active window

A window manager is system software that controls the placement and appearance of windows within a windowing system in a graphical user interface. Most window managers are designed to help provide a desktop environment. They work in conjunction with the underlying graphical system that provides required functionality—support for graphics hardware, pointing devices, and a keyboard—and are often written and created using a widget toolkit.

Few window managers are designed with a clear distinction between the windowing system and the window manager. Every graphical user interface based on a windows metaphor has some form of window management. In practice, the elements of this functionality vary greatly. Elements usually associated with window managers allow the user to open, close, minimize, maximize, move, resize, and keep track of running windows, including window decorators. Many window managers also come with various utilities and features such as task bars, program launchers, docks to facilitate halving or quartering windows on screen, workspaces for grouping windows, desktop icons, wallpaper, an ability to keep select windows in foreground, the ability to "roll up" windows to show only their title bars, to cascade windows, to stack windows into a grid, to group windows of the same program in the task bar in order to save space, and optional multi-row taskbars.

History

In 1973, the Xerox Alto became the first computer shipped with a working WIMP GUI. It used a stacking window manager that allowed overlapping windows. However, this was so far ahead of its time that its design paradigm would not become widely adopted until more than a decade later. While it is unclear if Microsoft Windows contains designs copied from Apple's classic Mac OS, it is clear that neither was the first to produce a GUI using stacking windows. In the early 1980s, the Xerox Star, successor to the Alto, used tiling for most main application windows, and used overlapping only for dialogue boxes, removing most of the need for stacking.

Mac OS was one of the earliest commercially successful examples of a GUI that used a sort of stacking window management via QuickDraw. Currently macOS uses a somewhat more advanced window manager that has supported compositing since Mac OS X 10.0, and was updated in Mac OS X 10.2 to support hardware accelerated compositing via the Quartz Compositor.

GEM 1.1 was a window manager that supported the desktop metaphor, and used stacking, allowing all windows to overlap. It was released in the early 1980s. GEM is famous for having been included as the main GUI used on the Atari ST, which ran Atari TOS, and was also a popular GUI for MS-DOS prior to the widespread use of Microsoft Windows. As a result of a lawsuit by Apple, GEM was forced to remove the stacking capabilities, making it a tiling window manager.

During the mid-1980s, Amiga OS contained an early example of a compositing window manager called ''Intuition'' (one of the low-level libraries of AmigaOS, which was present in Amiga system ROMs), capable of recognizing which windows or portions of them were covered, and which windows were in the foreground and fully visible, so it could draw only parts of the screen that required refresh. Additionally, Intuition supported compositing. 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 blits using the system's hardware blitter 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.

Intuition also anticipated the choices of the user by recognizing the position of the pointer floating over other elements of the screen (title bars of windows, their close and resizing gadgets, whole icons), and thus it was capable of granting nearly a zero-wait state experience to the use of the Workbench window manager.

Noteworthy to mention is the fact that Workbench was the only window manager that eventually inspired an entire family of descendant and successors: Ambient in MorphOS, Zune/Wanderer in AROS, Workbench NG (New Generation in AmigaOS 4.0 and 4.1). Workbench 4.1 was enhanced by 2D vector interface powered by Cairo libraries, and presenting a modern Porter-Duff 3D based Compositing Engine.

In 1988, Presentation Manager became the default shell in OS/2, which, in its first version, only used a command line interface (CLI). IBM and Microsoft designed OS/2 as a successor to DOS and Windows for DOS. After the success of Windows 3.10, however, Microsoft abandoned the project in favor of Windows. After that, the Microsoft project for a future OS/2 version 3 became Windows NT, and IBM made a complete redesign of the shell of OS/2, substituting the Presentation Manager of OS/2 1.x for the object-oriented Workplace Shell that made its debut in OS/2 2.0.

Examples

X window managers

On systems using the X window system, there is a clear distinction between the window manager and the windowing system. Strictly speaking, an X window manager does not directly interact with video hardware, mice, or keyboards – that is the responsibility of the display server.

Users of the X Window System have the ability to easily use many different window managers – Metacity, used in GNOME 2, and KWin, used in KDE Plasma Workspaces