compiz team mailing list archive

[Greg Merchan <940603@xxxxxxxxxxxxxxxxxx>]

>From what I've read in the comments, it looks like this is similar to a
problem that arose years ago with the "system tray" as it was called.
(The name "system tray" came from the "systray.exe" process on MS
Windows which provided some icons for what was officially known as the
notification area.)

The old system tray in GNOME, following KDE's model, would occasionally
fail to display icons in the tray; instead they were framed by the
window manager—sawfish or sawmill at the time. It didn't always happen.
It was unpredictable.

The root of the problem was a race condition. KDE's protocol required a
commitment (unspecified, as I recall) from the window manager to not try
to manage windows somehow marked for the system tray. Applications would
map the window, the window manager would ignore it, and the system tray
would reparent it. GNOME's implementation did not include the window
manager commitment. Applications would map the window and both the
window manager and the system tray would try to reparent it. The outcome
was determined by whichever process won the race to reparent.

The subsequent freedesktop.org system tray protocol eliminated the race
condition by not mapping the window destined for it before the
reparenting was complete. Instead of mapping, clients were expected to
send a ClientMessage to the tray. After that the XEMBED protocol took
over.

It sounds like chromium is mapping when it should not be mapping.
Searching through the code right now I've seen at least two places where
they call XMapWindow during initialization of some objects. I must be
missing something because I haven't found embedding. (But I just started
minutes ago.)

-- 
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https://bugs.launchpad.net/bugs/940603

Title:
  white box randomly shows up at top left corner blocking applications
  from using stuff under it

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