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Wednesday 10th of March 2010

Window Manager

A window manager is computer 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 windowing system which provides required functionality such as 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 clear distinction between the windowing system and the window manager. Every graphical operating system which uses a windows metaphor has some form of window management, however in practice the elements of this functionality vary greatly. The elements usually associated with window managers are those which 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 docks, task bars, program launchers, desktop icons, and wallpaper.

 

Types of window managers

Window managers are often divided into three classes, which describe how windows are drawn and updated.

  1. Compositing Window Managers
    Compositing window managers allow all windows to be created and drawn separately and then put together and displayed in various 2D and 3D environments. This allows for a great deal of variety in interface look and feel, and for the presence of advanced 2D and 3D visual effects.

    Mac OS X was the first operating system to be packaged with a Compositing window manager.
  2. Stacking window managers
    All window managers that have overlapping windows and are not compositing window managers are stacking window managers, although it is possible that not all use exactly the same methodologies. Stacking window managers allow windows to overlap by drawing background windows first, which is referred to as painter's algorithm. Changes sometimes require all windows to be re-stacked or repainted which usually involves redrawing every window. However to bring a background window to the front usually only requires that one window to be redrawn, since background windows may have bits of other windows painted over them effectively erasing the areas that are covered.
  3. Tiling window manager
    Tiling window managers paint all windows on-screen by placing them side by side or above and below each other, so that no window ever covers another. Microsoft Windows 1.0 used tiling, and a variety of tiling window managers for Linux/UNIX are available.
 

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