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Xephyr - X server outputting to a window on a pre-existing X display


Xephyr [:display] [option ...]


Xephyr is a kdrive server that outputs to a window on a pre-existing "host" X display. Think Xnest but with support for modern extensions like composite, damage and randr.

Unlike Xnest which is an X proxy, i.e. limited to the capabilities of the host X server, Xephyr is a real X server which uses the host X server window as "framebuffer" via fast SHM XImages.

It also has support for "visually" debugging what the server is painting.


-screen widthxheight
sets the screen size.
-parent id
uses exiting window id . If a -screen argument follows a -parent argument, this screen is embedded into the given window.
set 'cursor acceleration': The host's cursor is reused. This is only really there to aid debugging by avoiding server paints for the cursor. Performance improvement is negligible.


Send a SIGUSR1 to the server (e.g. pkill -USR1 Xephyr) to toggle the debugging mode. In this mode red rectangles are painted to screen areas getting painted before painting the actual content. The delay between this can be altered by setting a XEPHYR_PAUSE env var to a value in micro seconds.