Forwarding Single X Window to Multiple Displays

Peter Hutterer peter.hutterer at
Tue Apr 28 15:32:18 PDT 2009

On Tue, Apr 28, 2009 at 12:48:04PM -0400, Smith, Richard G  wrote:
> I am investigating the possibility of forwarding the display of an
> X-Window to more than one destination. I know that the DISPLAY
> environment variable can be set to forward the display/control of a
> window to another location. Is it possible to forward a single display
> to more than one destination, one being the master with control, and the
> other a slave (display-only) display? We are building a networked
> aircraft crew trainer where each station is a single machine. There are
> modes of operation where more than one crew station needs to see a
> shared common display. I was hoping to run a single instance of the
> shared application on a server and forward the display to multiple
> destinations.

It's easy to write an app that displays the same window on multiple displays
at once. All you need is multiple XOpenDisplay() calls and then you just
treat both windows like two completely separate windows (which means you
handle redrawing on both separately, etc.).

It's not easy at all however replicates the output on another display without
that application's support. There's many details in the protocol that make
this task hard and you're likely to run into a wall at some point where you
just can't get further with reasonable effort.


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