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

[John Baboval <baboval@spineless.org>]

On 11/7/2013 8:46 AM, Gerd Hoffmann wrote:
>    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.

I think the best thing for me to do at this point is to just start 
implementing with multiple QemuConsole, then, and post again when I have 
a better idea of what it ends up looking like. I'll keep you posted.

>
> cheers,
>    Gerd
>
>