Re: [PATCH] vnc: drop vnc_colordepth() call.

[Laszlo Ersek <lersek@redhat.com>]

Hi Gerd,

On 01/22/21 09:55, Gerd Hoffmann wrote:
> With gtk-vnc (which supports VNC_FEATURE_WMVI) this results in
> sending a VNC_ENCODING_WMVi message to the client.  Which in turn
> seems to make gtk-vnc respond with another non-incremental update
> request.  Hello endless loop ...
>
> Drop the call.
>
> Fixes: 9e1632ad07ca ("vnc: move initialization to framebuffer_update_request")
> Reported-by: Laszlo Ersek <lersek@redhat.com>
> Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
> ---
>  ui/vnc.c | 1 -
>  1 file changed, 1 deletion(-)
>
> diff --git a/ui/vnc.c b/ui/vnc.c
> index d429bfee5a65..0a3e2f4aa98c 100644
> --- a/ui/vnc.c
> +++ b/ui/vnc.c
> @@ -2041,7 +2041,6 @@ static void framebuffer_update_request(VncState *vs, int incremental,
>      } else {
>          vs->update = VNC_STATE_UPDATE_FORCE;
>          vnc_set_area_dirty(vs->dirty, vs->vd, x, y, w, h);
> -        vnc_colordepth(vs);
>          vnc_desktop_resize(vs);
>          vnc_led_state_change(vs);
>          vnc_cursor_define(vs);
>

while this patch has some effect, it does not fix the issue.

* With the gvncviewer binary I mentioned before, there is no change in
behavior -- initial screen shown, no updates then, and finally
connection dropped:

> Connected to server
> Remote desktop size changed to 800x480
> Connection initialized
> Error: Failed to flush data
> Disconnected from server

* With virt-manager, there is a before-after difference: the screen is
now *flashing*, between actual content and a black void. Meanwhile the
VNC client is still spinning.

* If I pass "--gtk-vnc-debug" to "gvncviewer", the following log snippet
keeps repeating:

> src/vncconnection.c Emit main context 8
> src/vncconnection.c Re-requesting framebuffer update at 0,0 size 640x480, incremental 0
> src/vncconnection.c Num rects 1
> src/vncconnection.c FramebufferUpdate type=-223 area (640x480) at location 0,0
> src/vncconnection.c Desktop resize w=640 h=480
> src/vncconnection.c Emit main context 5
> src/vncdisplay.c Framebuffer size / format unchanged, skipping recreate
> src/vncconnection.c Requesting framebuffer update at 0,0 size 640x480, incremental 0
> src/vncconnection.c Num rects 1
> src/vncconnection.c FramebufferUpdate type=-261 area (1x1) at location 0,0
> src/vncconnection.c LED state: 0

Thanks
Laszlo