[winswitch] Update for Xpra running Wireshark in Docker container

[Antoine Martin]

(snip)
> I followed the exact steps in
> https://xpra.org/trac/wiki/Encryption/SSL and still have the issue. I
> have lots of these log entries, but will retry with a trusted
> certificate. One thing I found out is, that when I open the HTML5 client
> in a Browser it is asking for a client certificate. I do have client
> certificates installed, but don’t want to use them and click on cancel.
> Could it be, that client certificates are causing this error?
That's odd, a default SSL configuration does not require any client
certificates.
Most browsers will just reject self-signed server certificates, though
some will allow them when connection to "localhost".

(snip)
>>> I tested this on a local computer with more or less unlimited
>>> bandwidth. I tried to modify the encoding settings via xpra.conf, but
>>> it seems they had no effect. I checked the information at
>>> https://xpra.org/trac/wiki/Encodings/Debugging
>>> <https://xpra.org/trac/wiki/Encodings/Debugging> but I wasn’t able to
>>> fix this myself. Are there any hints for high quality encoding?
>> The best way would be to just add a new hint so we map wireshark to a
>> "text" mode:
>> https://xpra.org/trac/browser/xpra/trunk/src/content-type
>> https://xpra.org/trac/browser/xpra/trunk/src/content-type/50_class.conf
>>
>> Alternatively, you should be able to get pixel perfect screen updates
>> just by increasing the "min-quality" parameter.
> 
> I added a hint for Wireshark to be mapped to text mode and the quality
> is perfect now.
> Even if a lot of packages are analyzed, only approx.
> 500KB/s of bandwidth are used to deliver the updates to the client! Can
> we add Wireshark to the official 50_class.conf or should I just do it
> for my docker deployment?
Please submit the change so that other xpra users can benefit.

This applies to all the applications I do not have time to test.
We should be able to grow those hint files though crowdsourcing.

> I still get a lot of DPI errors, even when connecting with devices with
> lower resolutions on Linux:
> 2019-10-14 08:30:02,461 DPI set to 20 x 21 (wanted 96 x 96)
> 2019-10-14 08:30:02,463  you may experience scaling problems, such as
> huge or small fonts, etc
> 2019-10-14 08:30:02,463  to fix this issue, try the dpi switch, or use a
> patched Xorg dummy driver
> 2019-10-14 08:30:02,485 sent updated screen size to 1 client: 1664x896
> (max 8192x4096)
There were no patched dummy driver "xserver-xorg-video-dummy" packages
for Debian "bullseye" yet.
I have just pushed some DEBs to the stable repository. Try updating your
system and it should install over the default one. (untested)
This should solve your DPI problems.
Alternatively, you could switch to Xvfb.

Bear in mind that development distributions like Debian Testing often
have ABI breakage before their release. So this build may break at some
point in the future. If it does, let me know and I'll push another rebuild.

> I tried to manually set dpi=96 in the xpra.conf but that didn’t seem to
> have an effect. I checked the information about Xdummy
> here https://xpra.org/trac/wiki/Xdummy but it seems that is already used
> by default. Output of "cat /usr/local/etc/xpra/conf.d/55_server_x11.conf
> | tail -n1“:
> # Selecting virtual X server:
> xvfb = /usr/lib/xorg/Xorg -noreset -novtswitch -nolisten tcp +extension
> GLX +extension RANDR +extension RENDER -auth $XAUTHORITY -logfile
> ${XPRA_LOG_DIR}/Xorg.${DISPLAY}.log -configdir
> ${XDG_RUNTIME_DIR}/xpra/xorg.conf.d/$PID -config /etc/xpra/xorg.conf
> 
> How can I verify if all required packages are installed and how do I
> solve the DPI issues?
If you followed the installation instructions, you should have all the
default packages installed already.

Cheers,
Antoine

> 
> Thanks again for your great support
> Florian