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 paint‐ ing.
The server accepts all the standard options of Xserver(1) and the fol‐ lowing additional options: -screen widthxheight sets the screen size. -parent id uses existing window id . If a -screen argument follows a -parent argument, this screen is embedded into the given win‐ dow. -host-cursor 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. -resizeable Allow the Xephyr window to be resized, even if not embedded into a parent window. By default, the Xephyr window has a fixed size. -no-host-grab Disable grabbing the keyboard and mouse.
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 ar‐ eas getting painted before painting the actual content. The delay be‐ tween this can be altered by setting a XEPHYR_PAUSE env var to a value in micro seconds.
• Rotated displays are currently updated via full blits. This is slower than a normal orientated display. Debug mode will therefore not be of much use rotated. • The '-host-cursor' cursor is static in its appearance. • The build gets a warning about 'nanosleep'. I think the various '-D' build flags are causing this. I haven't figured as yet how to work round it. It doesn't appear to break anything however. • Keyboard handling is basic but works. • Mouse button 5 probably won't work.