[X2Go-User] Failing to resume session

[Michael DePaulo]

(Resending this email because I accidentally CC'd lists.berlios.de).

Hi Stephane,

I need to look into this more. I'll do so over the next few days.

On Fri, Jun 6, 2014 at 5:49 AM, Stephane Mutz
<stephane.mutz at blinksight.com> wrote:
> Hi Michael,
>
> I confirm the effect of the -nowgl option.
>
> I changed the setting on my windows client and could
> not resume the session anymore from it while I can when
> I remove the option.
>
> I created a new session after setting the -nowgl setting and
> could resume it from my linux client.

1st, note that "WGL" is VcXsrv's (and Cygwin X11's) equivalent of
nx-libs/x2goagent and X.org's "GLX". Both WGL and GLX are opengl
support.
"-nowgl" disables WGL.

2nd, I am a little confused. Under the github link, the X2Go user
stated that disabling WGL fixed the issue. However, you are stating
that enabling WGL fixes the issue.
Note that I am thinking that whenever you run X2Go Client (or
standalone VcXsrv) on a system that doesn't support OpenGL (including
a windows desktop over RDP), then WGL is disabled automatically.

> Can you explain the effect of the -extension XFIXES, -extension GLX
> and -nolisten tcp just so that I know what to set properly?

You can read about the 3 options here. This is the x2goserver version
4.0.1.15 version of the file:
http://code.x2go.org/gitweb?p=x2goserver.git;a=blob;f=x2goserver/etc/x2goagent.options;h=32005ffd57dece7bf191fda1d74c9f1aa127b514;hb=c0ec55f91ff6449ce07800829a4d1331abbbb740

Basically the 2 options:
-extension XFIXES
-extension GLX
Disable the X11 protocol extensions "XFIXES" and "GLX". Disabling both
extensions maximizes compatibility with applications. If it turns out
that enabling 1 or 2 of these X11 extensions (by putting a "+" instead
of a "-" at the beginning) fixes compatibility with an application
that you use, only then should you enable 1 or 2 of them.

The option:
-nolisten tcp
Is important for security. Unless you have an application that depends
on it, or you specifically want to export your X11 display instead of
using X11 forwarding over SSH, you definitely SHOULD have that option
set. You can read more here:
http://superuser.com/questions/560532/what-is-the-nolisten-tcp-parameter-for-x

> Do you still want me to file the bug report?
>
> Regards, Stephane.

Yes, please do so.

Note that external X server settings you are using.

I have observed the issue even when you using the internal X server,
so I will add details about that as I investigate.

-Mike#2

On Fri, Jun 6, 2014 at 5:49 AM, Stephane Mutz
<stephane.mutz at blinksight.com> wrote:
> Hi Michael,
>
> I confirm the effect of the -nowgl option.
>
> I changed the setting on my windows client and could
> not resume the session anymore from it while I can when
> I remove the option.
>
> I created a new session after setting the -nowgl setting and
> could resume it from my linux client.
>
> Can you explain the effect of the -extension XFIXES, -extension GLX
> and -nolisten tcp just so that I know what to set properly?
>
> Do you still want me to file the bug report?
>
> Regards, Stephane.
>
>
>
> On 05/06/2014 16:30, Michael DePaulo wrote:
>
> It might be.  It might also be related to VcXsrv's WGL option.
>
> Unless something comes up,  I'll investigate tonight.
>
> Sent from my Android Smartphone
> On Jun 5, 2014 9:47 AM, "Stephane Mutz" <stephane.mutz at blinksight.com>
> wrote:
>>
>> Hello Michael,
>>
>> Could it be related to the settings of:
>> -extension XFIXES
>> -extension GLX
>>
>> Those were always obscure for me and I noticed
>> a discrepency between my home computer and work computer.
>>
>> Also I realised I'm missing -nolisten tcp. Should I add it?
>>
>> I don't think any of these config settings have changed recently though.
>> The appearance of the problem seems more related to an update on either
>> side
>> but I can't be sure.
>>
>> I'll post the bug report tonight.
>>
>> Thanks for the pointer to the workaround. I can't test it right now
>> but I'll give it a try as soon as I can.
>>
>> Regards, Stephane.
>>
>>
>> On 05/06/2014 15:22, Michael DePaulo wrote:
>>>
>>> On Thu, Jun 5, 2014 at 4:07 AM, Stephane Mutz
>>> <stephane.mutz at blinksight.com> wrote:
>>>>
>>>> Hello,
>>>>
>>>> Since a few weeks, I can't resume a session that was created
>>>> at work from my home computer. When I connect and select
>>>> the session to resume, I get an error popup:
>>>>
>>>> Failed to restore all the required visuals.
>>>>
>>>> Can't resume the NX session on this display.
>>>>
>>>> This setup was working for months so I assume it is due to an
>>>> update.
>>>> At home, I'm using a Linux Mint with 4.0.2.0 X2GO client.
>>>> At work, the client is running on Windows7 (version 4.0.2.0 as well).
>>>>
>>>> Any clue about what could be causing the problem?
>>>>
>>>> Regards, Stephane.
>>>
>>> Hi Stephane,
>>>
>>> I have seen this error myself. Could you please submit a bug report
>>> for package "x2goclient"?
>>> http://wiki.x2go.org/doku.php/wiki:bugs
>>>
>>> I will look into it further. It looks like some people have identified
>>> a fix or workaround:
>>> https://github.com/stowler/imagingcore/issues/16
>>>
>>> Also, FYI, this was discussed previously:
>>> https://lists.berlios.de/pipermail/x2go-user/2014-April/002201.html
>>>
>>> -Mike#2
>>
>>
>
>