Re: [Qemu-devel] Multi-head support RFC

[Gerd Hoffmann <kraxel@redhat.com>]

  Hi,

> As far as the EDID is concerned, there can only be one EDID for a 
> display+hw pair, or the guest won't know what to do. In my use-case, I 
> simply pass real EDIDs through, and create a full-screen window for each 
> real monitor.

Ok, makes sense.

> If you wanted to have two UIs displaying the same 
> DisplaySurface, the EDID would have to come from one of them, and the 
> other would have to clip, or scale.

Yes.

> > Why not?  That is exactly my plan.  Just have the virtual graphic card
> > call graphic_console_init() multiple times, once for each display
> > connector it has.
> >
> > Do you see fundamental issues with that approach?
> Currently only one QemuConsole is active at a time, so that would have 
> to change....

That isn't mandatory any more.  It is still the default behavior of a
DisplayChangeListener to follow the active_console, for compatibility
reasons.  SDL and VNC still behave that way.

You can explicitly bind a DisplayChangeListener to a QemuConsole though,
by setting DisplayChangeListener->con before calling
register_displaychangelistener().

gtk binds to QemuConsole #0.

spice creates a display channel per (graphical) console.  Each display
channel has a DisplayChangeListener instance, and each
DisplayChangeListener is linked to a different QemuConsole.

For your UI you probably want follow the spice model.  Have a
DisplayChangeListener for each physical monitor of the host, have a
fixed QemuConsole bound to each DisplayChangeListener.
DisplayChangeListeners can come and go at runtime just fine, so you
should be able to create/destroy them on monitor plug/unplug events on
the host.

cheers,
  Gerd