When compositor is turned on in xfwm4, xfce4 panel is displayed with <1 opacity. When systray lies on this panel, it also has the same opacity. However, some of the icons, sometimes, gets to display rectangle holes, having a opacity larger than 0 but smaller than 1. It should not be the problem of program this icons belong to, because sometimes, icon1 is displayed abnormally while icon2 is ok, but sometimes icon2 is displayed abnormally while icon1 is ok. A screenshot is available at http://www.geocities.com/cao_yiqun/images/bug.png . There the icon displayed abnormally is gaim icon, lying at the rightmost. Reproducible: Sometimes Steps to Reproduce: 1. Turn compositor on in xfwm4 2. Start a few programs having systray icons 3. There it is Actual Results: Some icons are displayed abnormally, without any image but a rectangle hole. Expected Results: Icons should be displayed normally, as the launcher icons.
Yes, I have no idea what causes this, unfortunately. The expose handling of XEMBED clients seems to be a bit broken. Possibly we need to check the XEMBED specification and the GtkPlug/GtkSocket implementation to find out what is happening. If someone has a clue about this, I'd be happy with any extra information I can get.
I am also experiencing this behaviour, although when I force a redraw, by setting autohide for instance, the panel is redrawn correctly.
This bug is too old, a lot regarding this issue has been changed (xfwm4, panel, system tray). So I'm closing it. Please create a new bug if this problem exists in trunk.