Re: [Qemu-devel] [PATCH 1/1] vnc: Add support for color map

["Denis V. Lunev" <den@openvz.org>]

On 05/24/2016 05:19 PM, Denis V. Lunev wrote:
> From: Alexander Graf <agraf@suse.de>
>
> Our current VNC code does not handle color maps (aka non-true-color) at all
> and aborts if a client requests them. There are 2 major issues with this:
>
>   1) A VNC viewer on an 8-bit X11 system may request color maps
>   2) RealVNC _always_ starts requesting color maps, then moves on to full color
>
> In order to support these 2 use cases, let's just create a fake color map
> that covers exactly our normal true color 8 bit color space. That way we don't
> lose anything over a client that wants true color.
>
> Reported-by: Sascha Wehnert <swehnert@suse.com>
> Signed-off-by: Alexander Graf <agraf@suse.de>
>
> Actually this is a very old patch originally submitted in 2013 by
> Alexander. The situation is still the same with RealVNC, it does not
> connect by default to QEMU VNC. The problem is that this client is
> really popular. This is better to be kludged.
>
> Signed-off-by: Pavel Butsykin <pbutsykin@virtuozzo.com>
> Signed-off-by: Denis V. Lunev <den@openvz.org>
> CC: Gerd Hoffmann <kraxel@redhat.com>
> CC: Paolo Bonzini <pbonzini@redhat.com>
> ---
>   ui/vnc.c | 33 +++++++++++++++++++++++++++++++--
>   1 file changed, 31 insertions(+), 2 deletions(-)
>
> diff --git a/ui/vnc.c b/ui/vnc.c
> index d2ebf1f..ddd01fd 100644
> --- a/ui/vnc.c
> +++ b/ui/vnc.c
> @@ -2094,6 +2094,24 @@ static void set_pixel_conversion(VncState *vs)
>       }
>   }
>   
> +static void send_color_map(VncState *vs)
> +{
> +    int i;
> +
> +    vnc_write_u8(vs, VNC_MSG_SERVER_SET_COLOUR_MAP_ENTRIES);
> +    vnc_write_u8(vs,  0);    /* padding     */
> +    vnc_write_u16(vs, 0);    /* first color */
> +    vnc_write_u16(vs, 256);  /* # of colors */
> +
> +    for (i = 0; i < 256; i++) {
> +        PixelFormat *pf = &vs->client_pf;
> +
> +        vnc_write_u16(vs, (((i >> pf->rshift) & pf->rmax) << (16 - pf->rbits)));
> +        vnc_write_u16(vs, (((i >> pf->gshift) & pf->gmax) << (16 - pf->gbits)));
> +        vnc_write_u16(vs, (((i >> pf->bshift) & pf->bmax) << (16 - pf->bbits)));
> +    }
> +}
> +
>   static void set_pixel_format(VncState *vs,
>                                int bits_per_pixel, int depth,
>                                int big_endian_flag, int true_color_flag,
> @@ -2101,8 +2119,15 @@ static void set_pixel_format(VncState *vs,
>                                int red_shift, int green_shift, int blue_shift)
>   {
>       if (!true_color_flag) {
> -        vnc_client_error(vs);
> -        return;
> +        /* Expose a reasonable default 256 color map */
> +        bits_per_pixel = 8;
> +        depth = 8;
> +        red_max = 7;
> +        green_max = 7;
> +        blue_max = 3;
> +        red_shift = 0;
> +        green_shift = 3;
> +        blue_shift = 6;
>       }
>   
>       switch (bits_per_pixel) {
> @@ -2132,6 +2157,10 @@ static void set_pixel_format(VncState *vs,
>       vs->client_pf.depth = bits_per_pixel == 32 ? 24 : bits_per_pixel;
>       vs->client_be = big_endian_flag;
>   
> +    if (!true_color_flag) {
> +        send_color_map(vs);
> +    }
> +
>       set_pixel_conversion(vs);
>   
>       graphic_hw_invalidate(vs->vd->dcl.con);
ping