Fvwm supports the Xinerama extension of newer X servers which is similar to multi head support (multiple
screens) but allows one to move windows between screens. If Xinerama support has been compiled into fvwm, it
is used whenever fvwm runs on an X server that supports and uses multiple screens via Xinerama. Without this
option, the whole desktop is treated as one big screen. For example, menus might pop up right between two
screens. The EdgeResistance option of the Style command command allows for specifying an explicit resistance
value for moving windows over the screen edge between two Xinerama screens. Xinerama support can be enabled
or disabled on the fly or from the configuration file with the Xinerama command. Many modules and commands
work nicely with Xinerama displays.

Whenever a geometry in the usual X format can be supplied, fvwm’s Xinerama extension allows for specifying a
screen in addition to the geometry (or even the screen alone). To do this, a ‘@’ is added to the end of the
geometry string followed by either the screen number or a letter. A number is taken as the number of the
Xinerama screen to be used (as configured in the X server). The letter can be one of ‘g’ for the global
screen (the rectangle that encloses all Xinerama screens), ‘p’ for the primary screen (see below), ‘c’ for
the current screen (the one that currently contains the pointer). If the X server does not support Xinerama
or only one screen is used, the screen bit is ignored.

Style * IconBox 64×300-0-0@p

Xinerama support can be configured to use a primary screen. Fvwm can be configured to place new windows and
icons on this screen. The primary screen is screen 0 by default but can be changed with the
XineramaPrimaryScreen command.

Xinerama support was designed to work out of the box with the same configuration file that would work on a
single screen. It may not perform very well if the involved screens use different screen resolutions. In
this situation, windows may get stuck in the portion of the whole desktop that belongs to neither screen.
When this happens, the windows or icons can be retrieved with the command

All MoveToScreen

that can be entered in an FvwmConsole window or with FvwmCommand.

For multi-screen implementations other than Xinerama, such as Single Logical Screen, it is possible to
simulate a Xinerama configuration if the total screen seen by fvwm is made up of equal sized monitors in a
rectangular grid. The commands XineramaSls, XineramaSlsSize and XineramaSlsScreens are used to configure
this feature.