NetWM

Extended Window Manager Hints, a.k.a. NetWM, is an X Window System standard for the communication between window managers and applications. It builds on the functionality of the Inter-Client Communication Conventions Manual for the mediation of access to shared X resources, like the screen and the input focus. Applications request access, while the window manager grants or denies it. Communication occurs via X properties and client messages.
The EWMH is a comprehensive set of protocols to implement a desktop environment. It defines both required and optional protocols. The window manager may choose to implement virtual desktops or a layered stacking order, but if it does, then the EWMH defines how this is communicated.

Protocol overview

All EWMH protocol identifiers start with the five letter
prefix _NET_.

Root window properties

The WM must update a set of properties on the root window:
; _NET_SUPPORTED : lists all the EWMH protocols supported by this WM.
; _NET_CLIENT_LIST : lists all application windows managed by this WM.
; _NET_NUMBER_OF_DESKTOPS : indicates the number of virtual desktops.
; _NET_DESKTOP_GEOMETRY : defines the common size of all desktops.
; _NET_DESKTOP_VIEWPORT : defines the top left corner of each desktop.
; _NET_CURRENT_DESKTOP : gives the index of the current desktop.
; _NET_DESKTOP_NAMES : lists the names of all virtual desktops.
; _NET_ACTIVE_WINDOW : gives the currently active window.
; _NET_WORKAREA : contains a geometry for each desktop.
; _NET_SUPPORTING_WM_CHECK : gives the window of the active WM.
; _NET_VIRTUAL_ROOTS : if the WM supports virtual root windows.
; _NET_DESKTOP_LAYOUT : shows the layout of the active pager.
; _NET_SHOWING_DESKTOP : is 1 for "showing the desktop" mode.

Client messages

An application may send client messages to a window manager:
; _NET_WM_STATE : to change the state of an application window.
; _NET_ACTIVE_WINDOW : to activate an application window.
; _NET_SHOWING_DESKTOP : toggles display of application windows.
; _NET_CLOSE_WINDOW : to close an application window.
; _NET_WM_MOVERESIZE : to interactively resize an application window.
; _NET_MOVERESIZE_WINDOW : to immediately resize an application window.
; _NET_REQUEST_FRAME_EXTENTS : consults frame border dimensions.
; _NET_WM_FULLSCREEN_MONITORS : defines the monitors for a fullscreen window.

If the WM supports window stacking:
; _NET_RESTACK_WINDOW : asks to change the stacking order for a window.

If the WM supports virtual desktops:
; _NET_CURRENT_DESKTOP : changes the current desktop.
; _NET_NUMBER_OF_DESKTOPS : changes the number of desktops.

A WM may choose to ignore these messages:
; _NET_DESKTOP_GEOMETRY : changes the dimension of all desktops.
; _NET_DESKTOP_VIEWPORT : changes the viewport for the current desktop.

Window properties

The EWMH defines these application window properties:
; _NET_WM_NAME : the title of the window.
; _NET_WM_VISIBLE_NAME : the window title as shown by the WM.
; _NET_WM_ICON_NAME : the title of the icon.
; _NET_WM_VISIBLE_ICON_NAME : the icon title as shown by the WM.
; _NET_WM_DESKTOP : the desktop the window is in.
; _NET_WM_WINDOW_TYPE : the functional type of the window.
; _NET_WM_STATE : the current window state.
; _NET_WM_ALLOWED_ACTIONS : a list of supported user operations.
; _NET_WM_STRUT : if the window wishes to reserve space at the edge.
; _NET_WM_STRUT_PARTIAL : reserved space details at the screen edge.
; _NET_WM_ICON_GEOMETRY : the geometry of a possible icon.
; _NET_WM_ICON : an array of possible icons for the client.
; _NET_WM_PID : the process ID of the client owning this window.
; _NET_WM_HANDLED_ICONS : whether a pager provides icons.
; _NET_WM_USER_TIME : time of last user activity in this window.
; _NET_WM_USER_TIME_WINDOW : the window which shows user activity.
; _NET_FRAME_EXTENTS : the left, right, top and bottom frame sizes.
; _NET_WM_OPAQUE_REGION : which window regions are fully opaque.
; _NET_WM_BYPASS_COMPOSITOR : requests that the window is uncomposited.

Window states

The ICCCM defines only three distinct states a window can be in:
# Withdrawn,
# Normal,
# Iconic.
In addition it supports an Urgent flag
to request user attention.

The EWMH defines thirteen window state flags:
* Above: show the window above others,
* Below: show the window below others,
* DemandsAttention: same as the urgent flag,
* Focused: the window has input focus,
* Fullscreen: show the window fullscreen,
* Hidden: the window is unmapped,
* MaximizedHorizontal: the window is stretched horizontally,
* MaximizedVertical: the window is stretched vertically,
* Modal: the window is a modal popup,
* Shaded: the window is rolled up,
* SkipPager: the window should not be shown on a pager,
* SkipTaskbar: the window should be ignored by a taskbar,
* Sticky: the window should be shown on all virtual desktops.

Additional protocols

; _NET_WM_PING : a WM can use this to test if a client is alive.
; _NET_WM_SYNC_REQUEST : for synchronizing repaints when resizing.
; _NET_WM_FULL_PLACEMENT : the WM will handle any window placement.

List of window managers that support Extended Window Manager Hints

Tiling and dynamic window managers

* aewm
* awesome
* bspwm
* echinus
* goomwwm
* herbstluftwm
* i3
* LeftWM
* ''Notion''
* Qtile
* spectrwm
* subtle
* Wingo
* wmii
* xmonad (needs to be turned on in the config)

Stacking window managers

* Blackbox
* Compiz
* CTWM (as of 4.0.0)
* edewm
* Fluxbox
* FVWM (via a plugin prior to v2.4 and native support from v2.5)
* IceWM
* JWM
* KWin
* Metacity
* Marco
* Openbox

Other window managers

* Enlightenment (E16 and E17)
* evilwm
* interfacewm
* matchbox
* Sawfish (not completely)
* wmfs
* Xfwmxfwm4 standards
/ref>

Notes and references

External links

*
The Window Manager Specification Project
at freedesktop.org

Extended Window Manager Hints Support For FVWM

{{XWinSys

Freedesktop.org
X Window System