[libvirt PATCH 0/3] Enable copy/paste for vnc displays

[Daniel P. Berrangé]

On Wed, Mar 23, 2022 at 12:01:19PM +0400, Marc-André Lureau wrote:
> Hi
> 
> On Wed, Mar 23, 2022 at 12:47 AM Jonathon Jongsma <jjongsma at redhat.com> wrote:
> >
> > This patch series enables support for the qemu-vdagent character device which
> > enables copy/paste support between guest and client when using vnc graphics.
> >
> > The guest must be configured with something like the following:
> >
> >     <channel type='qemu-vdagent'>
> >       <source clipboard='on' mouse='on'/>
> >       <target type='virtio' name='com.redhat.spice.0'/>
> >     </channel>
> >
> > Copy/paste sync requires a vnc client that has support for copy/paste commands.
> > Currently virt-viewer does not work, but the version of tigervnc provided by
> > fedora (executable name 'vncviewer') does work.
> >
> > More details about this device on Gerd's blog:
> > https://www.kraxel.org/blog/2021/05/qemu-cut-paste/
> >
> > OPEN QUESTIONS:
> >
> > - I'm not fully convinced that the `<source>` element is the right place for
> >   the new `clipboard` / `mouse` configuration options, but I'm not sure that
> >   adding a new xml element to the `<channel>` is the right approach either.
> >   Suggestions welcome.
> 
> I am not convinced <channel> is appropriate either for -chardev
> qemu-vdagent. That's why in my dbus display series it's an
> implementation detail
> (https://patchew.org/Libvirt/20211222194345.766352-1-marcandre.lureau@redhat.com/20211222194345.766352-13-marcandre.lureau@redhat.com/),
> and it's not exposed to the domain XML directly. However I realize
> that my approach is probably broken, as it looks like I totally missed
> the associated virtserialport! :)
> 
> As you say "source" is strange to put those extra channel options too.
> 
> And the only really valid associated device is a virtserialport of
> name "com.redhat.spice.0", so what's the point in exposing that detail
> to the user?

At the QEMU level we have one serial port with chardv

  -chardev qemu-vdagent,id=ch1,name=vdagent,clipboard=on
  -device virtio-serial-pci \
  -device virtserialport,chardev=ch1,id=ch1,name=com.redhat.spice.0


but IIUC, we can have multiple frontends - ie both VNC and DBus
display, and in that case the clipboard=on property on the
chardev will apply to both VNC & DBus displays. We can't
control clipboard independantly for the displays, so it is
right to put the control in the XML for the <channel> for
both VNC and DBus.

With regards,
Daniel
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