Can you verify whether the WAYLAND_DISPLAY environment variable is set in the TurboVNC session?  That could be the cause.  If you started the TurboVNC session from a shell in the local (Wayland) session, then the TurboVNC session may have picked up the WAYLAND_DISPLAY environment variable, and that may have caused certain applications running in the TurboVNC session to display to the local (Wayland) session rather than to the TurboVNC (X11) session.

Try unsetting WAYLAND_DISPLAY when you run the applications in the TurboVNC session, e.g.

    WAYLAND_DISPLAY= gcalculator

If that fixes the problem, then I can modify xstartup.turbovnc and make it unset that environment variable automatically.


On 1/16/24 2:22 PM, Torsten Kupke wrote:

Hi DRC,

unfortunately I have to proceed this thread. When working locally again on the machine running the TVNC server 3.1 on Ubuntu 22.04, I detected, that some windows of applications provided with Ubuntu (at least the calculator and the system log) and started from within the locally running TVNC client are still overlaid on the native desktop. When the client is in fullscreen mode, they are completely hidden and become only visible, when the client leaves the fullscreen mode. And then again I can see the only icon residing on the desktop (called "Home") twice with a small diagonal offset between both. However, inside the TVNC client window that icon is visible a third time (which is expected in this case).

Very annoying is the fact, that mostly (sometimes there are exceptions) it is not possble to activate those windows by simply clicking into them. Instead I have to click onto the icon representing those windows in the dock bar to be able to work with them. And then, when I want to proceed my work inside the TVNC client, I have to click onto its icon in the dock bar of the local session. Simply clicking into the TVNC client instead does nothing. I think, this behaviour has to do with the overlaid desktop. So my question would be, whether it's possible to avoid displaying it and showing those application windows only inside the TVNC client, when started inside (as it was under Ubuntu 18.04).

Apart from this, when I start those applications from within the TVNC client running on my home PC, I can see their windows also in fullscreen mode.

BR

tkansgar

Am 05.01.2024 um 00:41 schrieb 'DRC' via TurboVNC User Discussion/Support:
For completeness, I discovered a workaround to the issue, which is passing '-listen local' to /opt/TurboVNC/bin/vncserver. Apparently GDM will not stomp on Display :1 if TurboVNC is listening on both the abstract and pathname Unix domain sockets associated with that display.  Passing '-listen local' causes TurboVNC to listen on the abstract UDS.  Note, however, that there are security concerns with abstract UDSs, so maybe not a good idea on production systems.

On Tuesday, January 2, 2024 at 9:42:46 PM UTC-5 DRC wrote:

    Oof.  Apparently I already filed the issue as a bug against RHEL,
    and Red Hat rejected it.

    https://bugzilla.redhat.com/show_bug.cgi?id=1673793

    But since the issue also occurs in Ubuntu, maybe I should've
    filed it against GDM.

    (I realize that the issue is resolved from your POV.  I am just
    updating this thread in case someone finds it via Google. 
    Apparently I answer so many bug reports that I can't remember the
    ones I myself filed two years ago, so the person who finds this
    thread via Google may be me.)

    On 1/2/24 6:29 PM, DRC wrote:

    I don't know why the issue occurred in the first place, then,
    unless for some reason your employer also disabled Wayland in
    /etc/gdm3/custom.conf.  Regardless, I'm glad you were able to
    find a workaround for your particular use case.  I did notice
    that, on my Rocky Linux 8 box, the greeter always starts Xorg on
    Display :0 regardless of the value of WaylandEnable.  Maybe
    Ubuntu 22 can behave that way as well, under certain circumstances.


    On 1/2/24 3:16 PM, Torsten Kupke wrote:

    Hi DRC,

    for me this issue is resolved in the meanwhile. I managed the
    relevant files on the remote host to start TuboVNC's X Server
    for display :2 and therefore with port 5902. And for both
    TuboVNC viewers (on the remote host too and on my Windows PC at
    home) I did the same. That works perfectly. So I wouldn't need
    an improvement regarding this.

    And no, I don't use VirtualGL. The remote host is my
    workstation (owned by my employer), where I do my daily work.
    For my job I have no need to use OpenGL (or VirtualGL).

    But I have some other new issues with TuboVNC, which I will
    report in the next days (when I have some time to write the
    mail(s)).

    BR

    transgar

    Am 02.01.2024 um 20:45 schrieb 'DRC' via TurboVNC User
    Discussion/Support:
    Further information regarding this issue:

    With the default GDM configuration, there is no X server
    active on the login screen, because the GDM greeter is using
    Wayland.  When you log in, either Xwayland or Xorg (depending
    on whether you chose a Wayland or an Xorg session) is started
    on Display :0, so there is no possibility of a conflict with
    TurboVNC.  However, if you use vglserver_config in VirtualGL
    to configure the host for use with VirtualGL's GLX back end,
    vglserver_config will disable Wayland in GDM. That causes the
    GDM greeter to use Xorg rather than Wayland, and the greeter's
    Xorg instance listens on Display :0.  Thus, VirtualGL can use
    the greeter's X server to access the GPU while the host is
    sitting at the login prompt.

    On hosts configured thusly (with WaylandEnable=false in GDM's
    custom.conf file), a conflict occurs if you start a TurboVNC
    session while the host is sitting at the login prompt, then
    you log in locally.  When you start a TurboVNC session while
    the host is sitting at the login prompt, TurboVNC (rightfully)
    chooses Display :1 for the session, because nothing is using
    the resources associated with Display :1. However, if you then
    log in locally, GDM starts a second Xorg instance for the
    local session (so as not to conflict with the greeter's Xorg
    instance.)  GDM indiscriminately chooses Display :1 for the
    local session without checking whether something else is
    already using the resources associated with Display :1.  Thus,
    it effectively stomps all over the TurboVNC session that is
    listening on Display :1.  That causes the problems that you
    observed.

    I can (and will) make the vncserver script more robust, in the
    sense that it will check whether an abstract socket for a
    display number is in use before deciding to use that display
    number. However, GDM needs to do likewise.

    The only apparent workarounds for this are:

    1. If you have used vglserver_config to configure a host for
    use with VirtualGL's GLX back end, then be very cautious when
    logging in locally.  That is true irrespective of TurboVNC,
    because logging in locally on such a host will cause GDM to
    suspend the greeter's X server, which has the effect of
    causing any applications currently running with VirtualGL to
    freeze.  Use '/opt/TurboVNC/bin/vncserver -list' to ensure
    that no TurboVNC sessions are listening on :1 before you log
    in locally, and avoid local logins if at all possible.

    2. Comment out 'WaylandEnable=false' in /etc/gdm3/custom.conf,
    and restart GDM.  This is not true of all modern Linux
    systems, but with Ubuntu 22 at least, GDM will continue to
    start an Xorg instance at the login prompt even though the
    greeter is using Wayland.  You can set VGL_DISPLAY=:1024 to
    use that Xorg instance as a 3D X server with VirtualGL's GLX
    back end.

    I'm also going to investigate whether it might be possible for
    VirtualGL to play more nicely with Wayland on modern Linux
    distributions.

    On Tuesday, December 19, 2023 at 1:40:38 PM UTC-5 DRC wrote:

        No, by deleting /tmp/.X11-unix/X1, I was able to exactly
        reproduce the
        issue you reported with the Session Manager. That error
        occurred when
        the Session Manager tried to start a new TurboVNC session
        through SSH.
        In order for Port=5901 to have any effect, it would either
        have to be
        specified in the default TurboVNC connection info file
        (~/.vnc/default.turbovnc), or it would have to be
        specified in another
        connection info file (either a TightVNC-compatible
        connection info file,
        which has a .vnc extension, or a TurboVNC connection info
        file, which
        has a .turbovnc extension) that you pass to the TurboVNC
        Viewer on the
        command line.  Otherwise, the mere existence of such a
        connection info
        file on the machine wouldn't matter.  Also, the error
        occurred prior to
        the TurboVNC Viewer attempting to establish the RFB
        connection with the
        TurboVNC Server, so the viewer had not yet used the value
        of the Port
        parameter.

        DRC

        On 12/19/23 12:40 PM, Torsten Kupke wrote:
        > Hi CRC,
        >
        > Am 19.12.2023 um 16:41 schrieb 'DRC' via TurboVNC User
        > Discussion/Support:
        >> Apparently something happened that caused
        /tmp/.X11-unix/X1 to be
        >> deleted, so the vncserver script didn't know that the
        primary X
        >> server was using Display :1, and it tried to use that
        display number
        >> itself.
        >
        > Maybe I have another explantion for this: I have a .vnc
        file stored on
        > that machine specifying "port=5901". I think, the viewer
        found this
        > file and therefore tried to connect to the XServer :1.
        Could this be
        > the case? So if :1 now is in use by the native XServer,
        I simply would
        > have to specify "port=5902" in my .vnc file. Can you
        agree? Would this
        > solve my issue?
        >
        > However, I'm on Christmas vacation now. So I will need a
        proper
        > solution not before 2nd of Jan. '24.
        >
        > Merry Christmas and a happy new year for you and all
        other readers!
        >
        > tkansgar
        >

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