Re: [Qemu-devel] Question on QEMU's VNC Server hextile implementation

[Anthony Liguori]

Yaniv Kaul wrote:
> According to the RFB protocol, section 6.6.4 (hextile encoding), regarding the 
> 'ForegroundSpecified' bit, it says: 'If this bit is set then the 
> SubrectsColoured bit must be zero.'.
> It doesn't seem QEMU's VNC server does that. In fact, it looks like both bits 
> are set.
> I've verified against a different VNC server, and I didn't see this happening.
> (it may be a Wireshark dissector bug, of course).
>   

Yes, this definitely goes against the wording in the specification.  
It's also wasting bits on the wire.  I'll work up a patch on Monday.

I checked the real vnc client to make sure it handles this combination 
and it does.  I think the reason the spec forbids this is that a 
SubrectsColoured invalidates the foreground color.  Having the two is 
therefore not a useful combination because the foreground color won't 
actually be used for anything.

We do invalidate the foreground color correctly but we're just sending 
out useless data so removing it's a good idea.  Thanks for catching this!

Regards,

Anthony Liguori

> TIA,
> Y.
>
>
>