[Pkg-lxde-maintainers] Bug#855025: I'm also seeing the reported issue

[Keith A. Bare II]

I believe I also ran across this issue tonight, working on building a dev
VM for a project.

>From .xsession-errors / the VNC server log:

...
** Message: main.vala:102: Session is LXDE
** Message: main.vala:103: DE is LXDE
** Message: main.vala:134: log directory:
/scratch/kbare/.cache/lxsession/LXDE
** Message: main.vala:135: log path:
/scratch/kbare/.cache/lxsession/LXDE/run.log

And then the LXDE/run.log:

...
** Message: app.vala:130: lxpanel exit with this type of exit: 139
** Message: app.vala:148: Exit not normal, try to reload
** Message: app.vala:76: Launching lxpanel
process 19874: arguments to dbus_message_new_method_call() were incorrect,
assertion "path != NULL" failed in file ../../../dbus/dbus-message.c line
1367.
This is normally a bug in some application using the D-Bus library.
** Message: x-terminal-emulator has very limited support, consider choose
another terminal

** (light-locker:19874): WARNING **: screensaver already running in this
session
** Message: app.vala:130: lxpanel exit with this type of exit: 139
** Message: app.vala:148: Exit not normal, try to reload
...
** Message: app.vala:130: lxpanel exit with this type of exit: 139
** Message: app.vala:148: Exit not normal, try to reload
** Message: app.vala:156: Application crashed too much, stop reloading

Collected core files, and the crashing thread's backtrace matches:

(gdb) bt
#0  0x000055d7311c8c90 in task_button_window_focus_changed
(button=0x55d7321901b0 [TaskButton], win=0x0) at task-button.c:1668
#1  0x00007fab4ecf1d15 in panel_icon_grid_forall (container=<optimized
out>, include_internals=<optimized out>, callback=0x55d7311c8c60
<task_button_window_focus_changed>, callback_data=0x0) at icon-grid.c:1081
#2  0x000055d7311c4e0d in taskbar_net_active_window (tb=0x55d7321fe640,
widget=<optimized out>) at launchtaskbar.c:2284
#3  0x000055d7311c5403 in taskbar_net_active_window (tb=0x55d7321fe640,
widget=0x0) at launchtaskbar.c:2279
#4  0x000055d7311c5403 in launchtaskbar_constructor_task
(ltbp=ltbp at entry=0x55d7321fe640)
at launchtaskbar.c:1059
#5  0x000055d7311c5605 in _launchtaskbar_constructor (panel=0x55d7320b14a0
[PanelToplevel], settings=0x55d732154f40, mode=<optimized out>) at
launchtaskbar.c:1159
#6  0x00007fab4ecf9275 in lxpanel_add_plugin (p=p at entry=0x55d7320b14a0
[PanelToplevel], name=0x55d732154240 "taskbar", cfg=cfg at entry=0x55d732154e40,
at=at at entry=-1) at plugin.c:542
#7  0x00007fab4ecf6bc2 in panel_parse_plugin (cfg=0x55d732154e40,
p=0x55d7320b14a0 [PanelToplevel]) at panel.c:1593
#8  0x00007fab4ecf6bc2 in panel_start_gui (panel=panel at entry=0x55d7320b14a0
[PanelToplevel], list=list at entry=0x7fab3c003f80) at panel.c:1691
#9  0x00007fab4ecf75fb in panel_start (p=0x55d7320b14a0 [PanelToplevel]) at
panel.c:1992
#10 0x00007fab4ecf75fb in panel_new (config_file=<optimized out>,
config_name=<optimized out>) at panel.c:2014
#11 0x000055d7311bfc1b in _start_panels_from_dir (panel_dir=0x55d7321493c0
"/etc/xdg/lxpanel/LXDE/panels") at main.c:415
#12 0x000055d7311bdd16 in start_all_panels () at main.c:440
#13 0x000055d7311bdd16 in main (argc=<optimized out>, argv=<optimized out>,
env=0x7ffcb135ace8) at main.c:568

Trying to figure out what might be going on, I did a Google search for
"taskbar_net_active_window", and found this discussion of window manager
hints.

https://standards.freedesktop.org/wm-spec/wm-spec-latest.html#idm140200472702304

    > The window ID of the currently active window or None if no window has
the focus.

I'm guessing maybe the problem is, since no VNC client has connected,
there's no active Window, i.e., the None case, and lxpanel isn't handling
that properly.

One thing that I've noticed that's kind of weird, is I do get the lxpanel
the first time after I delete all of the .cache .config and .local
directories.  I think it's because clipit makes a pop-up asking if I want
to save the clipboard to a file--which creates and activates a window,
making the win parameter non-NULL.

Another tricky thing is if you connect to the VNC server fast enough, while
the session is still doing its reload attempts, you also end up getting the
panel.

In any case, I'll try Sebastian's patch.

--Keith Bare
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