X2Go Bug report logs - #1633
New clipboard issue in Libreoffice with X2Go

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From: Ulrich Sibiller <ulrich.sibiller@gmail.com>
Date: Wed, 26 Mar 2025 22:55:36 +0100
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Subject: Re: [X2Go-Dev] Bug#1633: Bug#1633: New clipboard issue in Libreoffice
 with X2Go
To: Jens Reyer <jens.reyer@leberrohstoffe.com>, 1633@bugs.x2go.org
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thanks, review will take some time....

Uli

On Tue, Mar 25, 2025 at 12:00 PM Jens Reyer
<jens.reyer@leberrohstoffe.com> wrote:
>
> Hi
>
> sorry for the late reply. I made my answers inline:
>
>
> Ulrich Sibiller <ulrich.sibiller@gmail.com> hat am 17. März 2025 um 21:35 geschrieben:
>
> Hello again,
>
> I had a look at the logfile. It's been a while since I worked on the
> clipboard code. But I _think_ there are a few things you should test:
>
> restrict clipboard to text only: add X2GO_NXAGENT_DEFAULT_OPTIONS+="
> -textclipboard" to /etc/x2go/x2goagent.options on the server side and
> start a NEW session (no reconnect). Does that help?
>
> No, same behavior.
>
> But I kept this setting for all further tests.
>
>
> not sure what exactly you have been doing while creating the sessionlog. But I can seen "caja" on the server side requesting clipboard.
> Please try to run a session without caja (which is a file manager,
> unclear what it does with selections).
>
> See new session.log without any caja mention, from a client with twm/xterm to a session with twm on the server. There I started xterm, then did a "libreoffice --calc /home/localadmin/test.ods" and did several ctrl+c ctrl+v in that calc document.
>
>
> it _looks_ like something on the client side is requesting theclipboard when you are doing your tests. The question is what program
> is doing that. If possible run a few programs on the client side,
> preferably only a very simple session (fvwm twm or so) and an xterm.
> Run x2goclient from there.
> To find out what program on the client side is requesting the
> clipboard you can check the server log file for lines like this:
> nxagentHandleSelectionRequestFromXServer: Received
> SelectionRequestEvent from real server: selection [529][CLIPBOARD]
> target [469][TARGETS] requestor
> [display[nx,options=/tmp/.x2go-localadmin/C-localadmin-50-1742211621_stDMATE_dp24/options:50.0]/0xe09e31]
> destination [386][GDK_SELECTION] time [13640727]. The bold number is
> the requestor. You can check that with xwininfo -id <number> on the
> client.
>
> The bold marking went missing, so I just  tested all ids.
>
> From client mate to server twm I always get "No such window ...", e.g.
>
> me@client:~$ xwininfo -id 531
> X Error: 9: Bad Drawable
> Request Major code: 14
> ResourceID in failed request: 0x213
> Serial number of failed request: 3
> xwininfo: error: No such window with id 0x213.
>
>
> Then I tested from the twm/xterm client to a twm/xterm session on the server, see the attached Bug1633_nxagentHandleSelectionRequestFromXServer.log
>
>
>
> there's an option to include the clipboard content (or rather thedata being transferred) in the session log in DEBUG mode. This helps
> in identifying what stage we are in. Change #undef
> PRINT_CLIPBOARD_CONTENT_ON_DEBUG to #define and recompile
>
> Done, see new session.log.
>
>
> while at it you could also try to change the timeout for theclipboard transfer. I hardcoded 5s when I wrote all this and it was ok
> for me ever since. But YMMV. #define CONVERSION_TIMEOUT 5000. In your
> log I see errors like this "nxagentConvertSelection: got new request
> before timeout expired on previous request, notifying failure to
> client [20] (addr [0x557c39ea2f40] PID [18630] Cmd
> [/usr/lib/libreoffice/program/soffice.bin])". This means that the
> previous clipboard-related communication has not finished when soffice
> starts another request which then is denied. So this indicates that
> some answer from the client side is still due. I suspect that this
> answer is never sent so your diagnosis that every second paste is
> working might in fact resemble a 5s pattern. Meaning: you can only
> successfully paste every 5s, but not quicker. So I suggest to decrease
> the timeout to 2s or so and see if that makes a difference for you.
> One thing here is strange here, though: Doing a copy in soffice on the
> server side makes soffice the clipboard owner. So while you are
> working inside soffice there should be no communication to the client
> that awaits any answer. Which again leads me to the suspicion that
> there's some clipboard manager involved.
>
> First I tried waiting for 15 seconds after copying: this does NOT help.
>
> Then I recompiled with #define CONVERSION_TIMEOUT 2000, same behavior, see new session.log
>
>
> x11 clipboard transfers are size restricted. That means that biggerselections are to be transferred to the requestor in multiple packets.
> nx does not support this currently, so you are restricted to 256kB. Is
> it possible that your selection is bigger than that?
>
> No, its always just a few characters.
>
>
>
> I also see SelectionClear requests from the client side. Which alsoindicates there's something dealing with clipboard on the client side.
>
> I still see SelectionClear in the new twm/xterm to twm/xterm session.log, but I'm not sure which side they are from.
>
>
>
> I played around with these tools:https://github.com/phillbush/xcliputils Using xclipowner -w you can
> watch if the clipboard owner changes. Run that on the client and then
> do clipboard stuff in libreoffice on the server. The owner as printed
> by xclipowner should never change except for the first time. If it
> does we have another indication of a clipboard-manager-in-the-middle
> attack ;-)
>
> From client Mate to server twm a successful ctrl+c results in
>
> 0x03C0016A
>
> and a failed ctrl+c results in a
>
> 0x00000000
> 0x03C0016A
>
>
> From twm/xterm client to a twm/xterm session on the server both failed and successful ctrl+c results in
>
> 0x00E0016A
>
>
> Thanks and greets
>
> _______________________________________________
> x2go-dev mailing list
> x2go-dev@lists.x2go.org
> https://lists.x2go.org/listinfo/x2go-dev

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