Support for remote desktop systems

Andrew Wedgbury andrew.wedgbury at
Thu Aug 8 07:50:25 PDT 2013

Hi Daniel,

----- Original Message -----
> From: "Daniel Stone" <daniel at>
> To: "Andrew Wedgbury" <andrew.wedgbury at>
> Cc: wayland-devel at
> Sent: Tuesday, 6 August, 2013 5:46:44 PM
> Subject: Re: Support for remote desktop systems
> Hi Andrew,
> Nice to hear from you. :)
> Unfortunately, the pretty blunt answer is that it's not the kind of
> interface we're intending to support at the moment.  There are two
> primary reasons behind this: the first is that by design, we tend to
> put things like this in private, compositor-led, protocol.  So, when
> you go to take a screenshot in Weston, the compositor spawns a client
> which is then given a private interface - specifically for
> screenshots
> - that no other client can see.  From this, the compositor would need
> at least some involvement.
> The second, which is a little more serious, is that the buffer
> handling is totally abstract and not specified by the Wayland
> protocol
> itself.  wl_buffer objects (which are not really transportable
> between
> clients) can be created by the EGL stack, or SHM buffers, or, or, or.
> There's not much getting around this, without the compositor being
> the
> one to map the buffers into userspace and pull the content out.  This
> is pretty much what the extant RDP compositor backend already does,
> as
> I see you've noticed.
> We're hoping that Weston, which has a pretty strong plugin
> architecture, will serve as the base for many environments, so with
> any luck targeting that will give you good reach.  The RDP compositor
> backend, and screenshot/videocast clients should be able to serve as
> a
> pretty good example of how to go about it.
> Sorry to disappoint ...

Thanks for the information. We'll concentrate on Weston for now then.

Very interesting looking at the screenshot/videocast example. As you say, Weston spawns the screenshot app, which is allowed access to a private interface which it uses to obtain the screenshot. Not sure whether you'd want Weston to launch a VNC server in this way though, it seems like the user should have a bit more control over this, but there does need to be some mechanism to control access to the private interface it would need to use.

BTW, is there any reason the video recorder works differently? - it writes the capture file directly from within Weston rather than go via an external app. Just curious.

Andrew Wedgbury <andrew.wedgbury at>

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