Comment 13 for bug 769644

Thanks, jmarsden. OK, I did the following:

    $ xwininfo -root
    xwininfo: Window id: 0xbb (the root window) (has no name)
    [...]

    $ xev -id 0xbb
    [...]
    [ Type "lxpanelctl run" in another terminal ]

    ClientMessage event, serial 16, synthetic YES, window 0xbb,
        message_type 0x1dd (_LXPANEL_CMD), format 8

    [...]

This means, the X event "_LXPANEL_CMD" is indeed sent by lxpanelctl and received by the root window.
However,

    $ xwininfo
     xwininfo: Please select the window about which you
              would like information by clicking the
              mouse in that window.
    [ Mouse Click on the lxpanel ]
      xwininfo: Window id: 0x120001f "panel"
    [...]

    $ xev -id 0x120001f
    [ Type "lxpanelctl run" in another terminal ]
    [ No further output ]

This means, the X event never reaches the lxpanel.

I suppose, there is a configuration file somewhere defining which events are hand on to which windows. Can anyone give a hint?

(Or am I totally on the wrong path? I do not have any experience with debugging X / window managers etc. Maybe I should inspect something else... Any suggestions?)