[Xen-devel] Re: vnc client, 16 bit, strange colors when viewing a PV guest

["Daniel P. Berrange" <berrange@xxxxxxxxxx>]

On Tue, Feb 26, 2008 at 10:06:13AM -0700, Pat Campbell wrote:
> 
> Using tightVNC, the colors are messed up when viewing a PV guest running
> on a 3.2 hypervisor from a client system with a 16 bit deep display.
> virt-manager --> viewer works OK.
> Standalone virt-viewer and other VNC clients have bad colors.  
> 
> This problem is new with Xen 3.2 and the qemu xenfb code.
> 
> As a short term fix I added a second macro in tools/ioemu/hw/xenfb.c to
> munge the colors from 32 bit  to 16 bit based on an algorithm used by
> RealVNC.  Patch I used is attached, not suggesting it be merged.
> 
> Is anybody else seeing this problem?
> 
> By the way, while looking at the original macro I think the last shift
> for blue should of used BRS instead if GRS.  ( Changing that did not
> make the colors better. )

Yes, clearly that last  GRS is bogus & should have been BRS.

>         int col;                                                        \
>         for (col = x ; col < w ; col++) {                               \
>             *dst = (((*src >> RRS) & RM) << RLS) |                      \
>                 (((*src >> GRS) & GM) << GLS) |                         \
> -                (((*src >> GRS) & BM) << BLS);                          \
> +               (((*src >> BRS) & BM) << BLS);                          \
>             src++;                                                      \
>             dst++;                                                      \
>         }                                                               \
>     }

Note that there is also a colour shift problem in GTK-VNC (used by
virt-viewer & virt-manager) - you need latest GTK-VNC from the source
repo to get the fix.  So you may have been seeing a cobmo of 2 bugs

Dan.
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