The ICCCM allows window managers to implement additional window states, which will appear to clients as substates of NormalState and IconicState. Two commonly met examples are Maximized and Shaded. A window manager may implement these as proper substates of NormalState and IconicState, or it may treat them as independent flags, allowing e.g. a maximized window to be iconified and to re-appear as maximized upon de-iconification.

The WM_TRANSIENT_FOR hint of the ICCCM allows clients to specify that a toplevel window may be closed before the client finishes. A typical example of a transient window is a dialog. Some dialogs can be open for a long time, while the user continues to work in the main window. Other dialogs have to be closed before the user can continue to work in the main window. This property is called modality. While clients can implement modal windows in an ICCCM compliant way using the globally active input model, some window managers offer support for handling modality.

The window manager may offer to arrange the managed windows on a desktop that is larger than the root window. The screen functions as a viewport on this large desktop. Different policies regarding the positioning of the viewport on the desktop can be implemented: The window manager may only allow the viewport position to change in increments of the screen size (paging) or it may allow arbitrary positions (scrolling).

To fulfill the ICCCM principle that clients should behave the same regardless whether a window manager is running or not, window managers which implement large desktops must interpret all client-provided geometries with respect to the current viewport.

A window manager which implements a large desktop typically offers a way for the user to make certain windows 'stick to the glass', i.e. these windows will stay at the same position on the screen when the viewport is moved.

Most X servers have only a single screen. The window manager may virtualize this resource and offer multiple so-called 'virtual desktops', of which only one can be shown on the screen at a time. There is some variation among the features of virtual desktop implementations. There may be a fixed number of desktops, or new ones may be created dynamically. The size of the desktops may be fixed or variable. If the desktops are larger than the root window, their viewports (see Section 2.3, “Large Desktops”) may be independent or forced to be at the same position.

A window manager which implements virtual desktops generally offers a way for the user to move clients between desktops. Clients may be allowed to occupy more than one desktop simultaneously.

A pager offers a different UI for window management tasks. It shows a miniature view of the desktop(s) representing managed windows by small rectangles and allows the user to initiate various window manager actions by manipulating these representations. Typically offered actions are activation (see Section 2.8, “Activation”), moving, restacking, iconification, maximization and closing. On a large desktop, the pager may offer a way to move the viewport. On virtual desktops, the pager may offer ways to move windows between desktops and to change the current desktop.

A taskbar offers another UI for window management tasks. It typically represents client windows as a list of buttons labelled with the window titles and possibly icons. Pressing a button initiates a window manager action on the represented window, typical actions being activation and iconification. In environments with a taskbar, icons are often considered inappropriate, since the iconified windows are already represented in the taskbar.

In the X world, activating a window means to give it the input focus. This may not be possible if the window is unmapped, because it is on a different desktop. Thus, activating a window may involve additional steps like moving it to the current desktop (or changing to the desktop the window is on), deiconifying it or raising it.

Some window managers display some form of animation when (de-)iconifying a window. This may be a line drawing connecting the corners of the window with the corners of the icon or the window may be opaquely moved and resized on some trajectory joining the window location and the icon location.

Window-in-window MDI is a multiple document interface known from MS Windows platforms. Programs employing it have a single top-level window which contains a workspace which contains the subwindows for the open documents. These subwindows are decorated with window manager frames and can be manipulated within their parent window just like ordinary top-level windows on the root window.

Override-redirect windows are ignored by traditional window managers, but not by compositing managers. Compositing managers are responsible for painting all windows to the screen, including override-redirect windows.

To enable compositing managers to decorate override-redirect window properly, for example by making them translucent or by changing the shape of the windows, this spec allows clients to set properties on override-redirect windows indicating the function of the windows.

Some window managers keep the toplevel windows not in a single linear stack, but subdivide the stack into several layers. There is a lot of variation among the features of layered stacking order implementations. The number of layers may or may not be fixed. The layer of a toplevel window may be explicit and directly modifiable or derived from other properties of the window, e.g. the type of the window. The stacking order may or may not be strict, i.e. not allow the user to raise or lower windows beyond their layer.

This spec tries to address the following issues:

This spec doesn't cover any of the following:

The window manager is supposed to be in charge of window management policy, so that there is consistent behavior on the user's screen no matter who wrote the clients.

The spec offers a lot of external control about window manager actions. This is intended mainly to allow pagers, taskbars and similar window manager UIs to be implemented as separate clients. "Ordinary" clients shouldn't use these except maybe in response to a direct user request (i.e. setting a config option to start maximized or specifying a -desk n command line argument).