This command configures the layout of the Single Logical screen feature. Its first argument is the number of screens to use. It must be followed by exactly this number of screen-spec arguments. Each of these can be written either in standard X geometry format: "<width>x<height>+<x>+<y>" or as a space separated list of numbers: "x y width height". Both ways of describing screens can be mixed in a single command. All four numbers must be supplied. The x and y values specify the origin of the screen in relation to the global screen's origin while width and height specify the size of the screen in pixels. No checks are done if the geometries make sense, so it is possible to define overlapping screens (with random results) or screens that are not visible at all.

XineramaSlsScreens 3 \
  512x768+0+0 512x300+512+0 512 300 512 468
XineramaSls On
XineramaPrimaryScreen 1
Xinerama On