There is a number of window management features or behaviours which are
not specified in the ICCCM, but are commonly met in modern Window Managers and Desktop Environments.
ICCCM
の中では定義されていないが、
一般に今日のウィンドウマネージャやデスクトップ環境において見られる
ウィンドウ管理ための多くの機能や振舞がある。
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.
Maximization is a very old feature of Window Managers. There was even a ZoomedState
in early ICCCM drafts. Maximizing a window should give it as much of the
screen area as possible (this may not be the full screen area, but only
a smaller 'workarea', since the Window Manager may have reserved certain areas for other
windows). A Window Manager is expected to remember the geometry of a maximized window
and restore it upon de-maximization. Modern Window Managers typically allow separate
horizontal and vertical maximization.
With the introduction of the Xinerama extension in X11 R6.4, maximization
has become more involved. Xinerama allows a screen to span multiple
monitors in a freely configurable geometry. In such a setting, maximizing
a window would ideally not grow it to fill the whole screen, but only the
monitor it is shown on. There are of course borderline cases for windows
crossing monitor boundaries, and 'real' maximization to the full screen may
sometimes be useful.
Some Desktop Environments offer shading (also known as rollup) as an alternative to
iconfication. A shaded window typically shows only the titlebar, the client
window is hidden, thus shading is not useful for windows which are not
decorated with a titlebar.
The Window Manager _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 to change the viewport
position 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 wether 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.
There are two options for implementing a large desktop: The first is to
keep the managed windows (or, if reparenting, their frames) as children
of the root window. Moving the viewport is achieved by moving all managed
windows in the opposite direction.
The second alternative is to reparent all managed windows to a dedicated
large window (somewhat inappropriately called a 'virtual root'). Moving
the viewport is then achieved by moving the virtual root in the opposite
direction.
Both alternatives are completely ICCCM compliant, although the second one
may be somewhat problematic for clients trying to figure out the Window Manager decorations
around their toplevel windows and for clients trying to draw background
images on the root window.
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
the section called 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.
There are at least two options for implementing virtual desktops.
The first is to use multiple virtual roots (see
the section called Implementation note
) and change the current
desktop by manipulating the stacking order of the virtual roots. This is
completely ICCCM compliant, but has the issues outlined in
the section called Implementation note
The second option is to keep all managed windows as children of the root
window and unmap the frames of those which are not on the current desktop.
This puts the clients in an undefined ICCCM state, since they are unviewable,
but not iconic. In practice, this seems to cause no problems and the ICCCM
compliant alternative to iconify all clients on non-current desktops (without
showing their icons) is clearly not acceptable.
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
the section called 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.
This spec tries to address the following issues:
Allow clients to influence their initial state with respect
to maximization, shading, stickyness, desktop.
Improve the Window Managers ability to vary window
decorations by allowing clients to hint the Window Manager about the type
of their windows.
Enable pagers and taskbars to be implemented as separate
clients and allow them to work with any compliant Window Manager.
This spec doesn't cover any of the following:
Other IPC mechanisms like ICE or Corba.
Window Manager configuration.
Window Manager documentation.
Geometry between desktops.
Clients appearing on a proper subset of desktops.
Window-in-window MDI.
The Window Manager is supposed to be in charge of window management
policy, so that there is consistent behaviour 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 cmdline
argument).
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